Sinanthropus

Jianshi--Earliest Extra-African Hominin, Further Evidence of Late Occurring Lufengpithecus or Fossil Orangutan?

2010-08-18T19:52:00.000-07:00

Liu et al. (2010) have recently published a study of three supposedly hominin teeth from the Longgudong cave site in Jianshi county, Hubei. The teeth augment the sample of 4 hominin-like teeth collected in and around Jianshi in the 1970s that were initially attributed to an australopithecine (Gao 1975). The assessment by Liu et al. (2010) supplements the report in the 2004 monograph on Jianshi (Zheng 2004) published as the first in a series commissioned as part of the State Key Project of the 9th Five Year Plan – Origin of Early Humans and Environmental Background. The 2004 monograph is a comprehensive study of the geology, stratigraphy and paleontology of the fossil bearing site. In it the three hominin-like teeth, collected in 2000, were assigned to the Javanese genus and species Meganthropus paleojavanicus, based primarily on metric criteria.

The Jianshi site is further distinguished by the presence of a relatively large number of Gigantopithecus blacki teeth (28 in toto) and an extensive and diagnostic mammalian fauna. Study of the micro- and macro-mammalian fossils indicates a biochronological age slightly younger than the Longgupo site at Wushan, Chongqing (former Sichuan) or the Gigantopithecus cave site at Liucheng, Guangxi. Paleomagnetic research, however, suggests that the hominin-like material falls below the Reunion Normal Polarity Event or in excess of 2.15 mya. As such the Jianshi specimens would represent the earliest record of an extra-African human presence in all of Eurasia.

I recently reposted an essay written over a decade ago, derived from my 1994 Dissertation, which suggested that the original Jianshi molars could be favorably compared to fossil orangutan teeth previously collected in South China and Java. I have also written extensively on the Longgupo mandibular fragment and shown how it is compatible with an attribution to Lufengpithecus. Russ Ciochon, who along with Huang Wanpo, et al. (1995), originally described the Longgupo specimen as an early hominin, has since backtracked and conceded its non-hominin nature (Ciochon 2009). Given the possibility that the new Jianshi specimens may be mimicking a hominin morphotype I think it is essential to compare the new specimens not only to other hominins known from Africa, Europe and Asia, as has been done by Liu et al. (2010), but with other hominoids, including Lufengpithecus, known from southern China and Southeast Asia. In this regard Schwartz et al. (1994, 1995) published a study of hominoid dental remains from a variety of Pleistocene age sites in Vietnam. These included teeth ascribed to Gigantopithecus, Homo and Pongo. Amongst these teeth are some attributed to a new species, Pongo hooijeri, described as,

“Description and Diagnosis: Larger than most subspecies of fossil and living Pongo pygmaeus (see figs. 9-11), but differs from all known populations of P. pygmaeus in lacking significant crenulation on the occlusal surfaces of the molars and upper premolars, and on the basins of the lower premolars. Incisors are not known. Molar cusp disposition similar to that of P. pygmaeus, but the cusps themselves are puffier and more rounded occlusally as well as on their external slopes. The occlusal surfaces are thus more poorly defined, and the occlusal basins are more constricted. Discussion: The characters of the molars listed above distinguish these teeth very markedly from those of Pongo pygmaeus, and give them a very distinctive "gestalt." While it does appear that this new form belongs in the same general clade as the extant orangutan, it is by no means clear on the basis of current evidence that the two are very closely related. Pending better material, we feel a conservative interpretation is most appropriate, and have thus allocated this dentally distinctive primate to its own species of Pongo. It may well turn out, however, that the relationship between the two species is more distant than this implies, and it is possible that a separate generic designation for hooijeri will ultimately be warranted.”

Unfortunately only the holotype specimen, a lower M2, is figured. In its overall appearance it looks remarkably similar to M2’s from Lufeng and is analogous in features to the M1 from Longgupo. Its description and analysis is also consistent with previously known Lufengpithecus.

The two recently described molars from Jianshi, one upper and one lower, are extremely well worn and lack most diagnostic surface features. They, as well as the original set of four molars described from Jianshi, are relatively large but fall within the upper range of variation of the Lufeng sample of hominoid molars. In this regard the Longgupo specimen falls within the lower range of variation. Therefore in terms of dental metrics there is no reason to dismiss the Jianshi and Longgupo remains as potentially members of a single highly dimorphic species such as seen in Lufengpithecus.

Liu et al. (2010) use a bevy of geometric morphometric techniques to tease apart shape discriminations to sort the Jianshi teeth relative to a variety of hominin samples. In a cursory comparison of the new Jianshi molars with homologous teeth in Schwartz et als study it appears that the sort of comparisons made by Liu et al. (2010) should also be done with non-hominin taxa from contiguous regions of East and Southeast Asia.

Additionally, the Mohui and Chuifeng Cave sites in the Bubing Basin of southern Guangxi have produced an abundant early Pleistocene fauna with, respectively, 16 and 92 teeth assigned to Gigantopithecus blacki. Another set (n=17) of smaller teeth from Mohui have been tentatively assigned to Hominoidea (gen. et sp. indet.)(Wang et al. 2007). These are said to include molars similar to those from the Longgupo mandibular fragment (Huang et al., 1995). Wang et al. go on to say that this Mohui sample does not strongly resemble Pongo remains found in Wuyun Cave and other sites in China. In addition Chuifeng Cave has produced "24 relatively large teeth, with high crowned molars and a simple occlusal pattern, (that) differ from the low crowned and wrinkled molars of Pongo, as well as the very large teeth of G. blacki. These teeth are provisionally assigned to Hominoidea gen. et sp. indet." (Wang 2009) Unfortunately neither the Mohui nor Chuifeng specimens are figured in the pertinent articles. Another similar molar specimen has been reported from Sanhe Cave in Chongzuo, Guangxi (Jin et al. 2009). Given the fact that non-hominin, non-pongine teeth that have been mistaken for specimens of Homo are now found widespread throughout southern China and northern Vietnam, the possibility must be entertained that the Jianshi teeth also represent a non-hominin taxon.

Zhao et al. (2009) describe and discuss a set of orangutan-like teeth from the early Late Pleistocene (~110 kya) site of Mulanshan, Guangxi. They review similar specimens collected from throughout southern China and from Chinese drugstores since the 1930s. They reach similar conclusions as have others, that there are two distinct morphs within the sample. Specimens that are morphologically similar, but larger than, extant and subfossil orangutans from Indonesia (see also Wang et al. 2009) and those that are less crenulated with smoother, less complex occlusal surfaces. These latter specimens are said to be similar to Lufengpithecus but on average somewhat larger. Zhao et al. go on to say that there are also specimens within the Lufeng and Yuanmou hypodigms of Lufengpithecus that are similar to the more crenualted specimens collected from Pleistocene sites in southern China and northern Vietnam. They conclude that "In the absence of the skull and postcranial bones, it is difficult to establish new genus or species based on Pleistocene orangutan-like isolated teeth."

Thus, there are a number of possibilities, none of which are, as of yet, conclusive.

1. All the specimens discussed above including the Jianshi molars are variants of one or more species or subspecies of orangutan.

2. The specimens can be divided between a Pleistocene descendant of Lufengpithecus, fossil forms of Pongo or a previously unidentified "mystery ape".

3. Some of the specimens can be allocated to an early form of hominin, the rest to Pongo or some other combination of the above.

Below are some visual comparisons of relevant specimens:

Tham Hai Cave Upper RM1 or M2 (reversed)

"Immediately adjacent to Tham Khuyen, this cave was excavated toward the end of 1964 by a joint Vietnamese-German (DDR) team. Dating is uncertain, but the site is thought to be approximately contemporaneous with Tham Khuyen. A single tooth was attributed to Homo erectus (Cuong (sic) Nguyen, 1985). This is a relatively large upper right molar (BL width 15.41 mm; MDlength 13.47 mm), which is heavily worn. It almost certainly belongs to the "Morph 2" category of Schwartz et al. (1994), described below as a new species of Pongo." (Schwartz et al. 1995).

To the left is an upper right molar of Lufengpithecus hudienensis recovered from the Yuanmou Basin of Yunnan. The Yuanmou sites are dated between 7-8 mya. Note the similarity of the Yuanmou specimen's occlusal outline to the specimen of Homo erectus from Zhoukoudian (ZKD) shown below (specimens are not to scale).


Occlusal views of UM1s a) Jianshi b) Australopithecus c) ZKD H. erectus d) Sangiran H.erectus e) modern Chinese

Right Lower M1 or M2 (TK 65/123), Right Lower M1 or M2 (Jianshi PA 1277), Longgupo Right Lower M1 (not to scale).

Original Jianshi lower molars compared to Pongo lower molar from Tham Khuyen Cave Vietnam (center). Note median placement of longitudinal fissure and alignment of transverse fissures in all specimens (not to scale).

Original Jianshi lower molars compared to Lufengpithecus hudienensis from Yuanmou Basin, Yunnan and a specimen from Mohui originally described as "hominid" (not to scale).

Given the ambiguous nature of hominoid dentitions from the Mio-Plio-Pleistocene of East Asia the issues discussed above cannot be resolved until more diagnostic material is recovered.

Literature cited:

Ciochon, R. The mystery ape of Pleistocene Asia. 2009, Nature, 459:910-911.

Etler, DA. The Chinese Hominidae: New Finds, New Interpretations. 1994, PhD. Dissertation, University of California, Berkeley.

Etler, DA. Mystery ape: other fossils suggest that it's no mystery at all. 2009, Nature 460:684.

Etler, DA., Crummett, TL., Wolpoff, MH. Longgupo: Early Homo colonizer or Late Pliocene Lufengpithecus survivor in South China? 2001, Hum Evol. 16:1-12.

Gao, J. Australopithecine teeth associated with Gigantopithecus. Vertebrata PalAsiatica, 1975, 13(2):81-88.

Huang, W., Ciochon, R., Gu, Y., Larick, R., Fang, Q., Schwarcz, H., Yonge, C., de Vos, J. and Rink, W. Early Homo and associated artifacts from Asia. Nature, 1995, 378:275-78.

Jin, C., Qin D., Pan W., Tang Z., Liu, J., Wang, Y., Deng C., Zhang, Y., Dong, W., and Tong, H. A newly discovered Gigantopithecus fauna from Sanhe Cave, Chongzuo, Guangxi, South China, Chinese Science Bulletin, 2009, 54(5):788-797.

Liu W, Clarke R, Xing S. Geometric morphometric analysis of the early Pleistocene hominin teeth from Jianshi, Hubei Province, China. Sci China Earth Sci, 2010, 53: 1141–1152.

Schwartz, J. H., Vu, T. L., Nguyen, L. C., Le, T. K., and Tattersall, I. A diverse hominoid fauna from the late middle Pleistocene breccia cave of Tham Khuyen, Socialist Republic of Vietnam, 1994, Anthropologica Papers of the American Museum of Natural History, 73:1-11.

Schwartz, J. H., Vu, T. L., Nguyen, L. C., Le, T. K. A review of the Pleistocene hominoid fauna of the Socialist Republic of Vietnam (excluding Hylobatidae). Anthropological Papers of the American Museum of Natural History, 1995, 76:1-23.

Wang, W. New discoveries of Gigantopithecus blacki teeth from Chuifeng Cave in the Bubing Basin, Guangxi, south China. Journal of Human Evolution, 2009, 57:229–240.

Wang, W., Potts, R., Hou, Y., Chen, Y., Wu, H., Yuan B., and Huang, W. Early Pleistocene hominid teeth recovered in Mohui cave in Bubing Basin, Guangxi, South China, 2005, Chinese Science Bulletin, 50(23):2777—2782.

Wang, CB., Zhao, L., Jin, C., Hu, Y. and Wang, CS. Quantitative study of Pleistocene fossil orangutan teeth from China and their taxonomic significance. 2009, Acta Anthropologica Sinica 28(2):192-200.

Wang, W., Potts, R., Yuan, B., Huang, W., Cheng H., Edwards, R. L., Ditchfield, P. Sequence of mammalian fossils, including hominoid teeth, from the Bubing Basin caves, South China, 2007, Journal of Human Evolution 52:370-379.

Zhao, L., Wang, C., Jin, C., Qin, D. and Pan, W. Fossil Orangutan-like hominoid teeth from late Pleistocene human site of Mulanshan cave in Chongzuo of Guangxi and implications on taxonomy and evolution of orangutan, 2009, Chinese Sci Bull, 54: 3924―3930.

Zheng S H. Jianshi Hominid Site. Beijing: Science Press, 2004, 1–412.

Zhou, G. Supplementary notes on the baby skull of Sivapithecus yunnanensis -- with discussions on "Wushan Man." Memoirs of Beijing Natural History Museum, 1999, 58:111-123.

Its time to sink the genus Australopithecus redux

2010-08-11T13:23:00.000-07:00

Back in June I posted a comment on the implications of the discovery of "Kadanuumuu (Big Man) and Karabo" the partial skeletons of Australopithecus afarensis at Woranso-Mille in Ethiopia and A. sediba from Malapa in South Africa. The point I was trying to make was that new discoveries at both ends of the Australopithecine lineage were blurring the distinction between the genera Australpithecus and Homo. The Homo-like features of the Woranso-Mille skeleton suggested that the time separating the primitive looking Ardipithecus ramidus from Woranso-Mille's ancestor A. anamensis was too short to accommodate the degree of morphological change that had occurred between them. On the other end of the timescale the recently described A. sediba has been attributed to early Homo by some because of the amount of morphological overlap (particularly dental) between the two.

Now we have a new report in Nature by McPherron et al. that shows that A. afarenis was a potential stone tool user by ~3.4 mya. This further muddies the water regarding what it is that differentiates Australopithecus from Homo. The Woranso-Mille skeleton mitigates the role of body size and proportions in distinguishing the two from one another. A. sediba minimizes the differences in tooth size, form and function between the two. H. floresiensis, if accepted as a valid hominin species, demolishes the brain size Rubicon separating Australopithecus from Homo. And now we have the last bastion of Homo, stone tool use, falling by the wayside. What is left to distinguish the genus Australopithecus from Homo?

As I previously argued the sinking of Australopithecus into Homo, as a subgenus, seems eminently reasonable, if not now mandatory.

The abstract of the Nature article follows:

The oldest direct evidence of stone tool manufacture comes from Gona (Ethiopia) and dates to between 2.6 and 2.5 million years (Myr) ago1. At the nearby Bouri site several cut-marked bones also show stone tool use approximately 2.5 Myr ago2. Here we report stone-tool-inflicted marks on bones found during recent survey work in Dikika, Ethiopia, a research area close to Gona and Bouri. On the basis of low-power microscopic and environmental scanning electron microscope observations, these bones show unambiguous stone-tool cut marks for flesh removal and percussion marks for marrow access. The bones derive from the Sidi Hakoma Member of the Hadar Formation. Established 40Ar–39Ar dates on the tuffs that bracket this member constrain the finds to between 3.42 and 3.24 Myrago, and stratigraphic scaling between these units and other geological evidence indicate that they are older than 3.39 Myr ago. Our discovery extends by approximately 800,000 years the antiquity of stone tools and of stone-tool-assisted consumption of ungulates by hominins; furthermore, this behaviour can now be attributed to Australopithecus afarensis.

Either A. afarensis should be revised to H. afarensis or the possibility must be entertained that the Woranso-Mille individual and the maker of the stone tool cut marks at Dikika represent a new previously unknown species of Homo (perhaps H. antiquus Ferguson 1984) that lived contemporaneously with A. afarensis.

Will the real “H. floresiensis” please stand-up?

2010-07-27T21:47:00.000-07:00

Well, I’m going to go off the deep end this time with what some may consider an outrageous proposal. Visions of giant rats dancing in my head have led me back to meditations on the enigmatic “hobbit.” Could the beloved “hobbit” aka “Homo floresiensis” actually be a descendant of Lufengpithecus? The edifice I will build is most likely a house of cards, but venues such as this allow for flights of fancy, if not fantasy.

Back in 2006 I posted an approving comment on Gary Richard's take down of Homo floresiensis. He had written a well-reasoned refutation of the idea that H. floresiensis was a distinct species descended from some form of archaic human. He instead argued that the population being sampled were insularly dwarfed modern humans. In the interim the study of the post-cranial anatomy of H. floresiensis, in particular its wrist and ankle, have convinced most informed observers that the so-called hobbit is in actuality a distinct archaic hominan species and not an insularly dwarfed population of H. sapiens or some congenitally deformed modern human of small stature. Its wrist and ankle are so archaic looking that comparisons have been made with the extant chimpanzee, as well as australopiths. Other aspects of its anatomy such as its hip, shoulder and limb proportions also hearken back to early hominans such as Australopithecus or H. habilis. The suggestion that H. floresiensis is descended from an early African hominan that dispersed into Southeast Asia nearly 2 mya is thus taken seriously by many paleoanthropologists.

There is, however, another possibility. There are cryptozoological tales from throughout Southeast Asia that refer to an elusive, small bipedal orangutan-like creature called Orang Pendek in Sumatra and Ebu Gogo on the island of Flores. Much speculation has equated H. floresiensis with these diminutive cryptohumanoids. There are also tales of giant bipedal orangutans that have recently resurfaced. Crompton et al. have published on aboreal bipedality in extant orangutans as a model for the origin of terrestrial bipedalism in early hominans. Descriptions of the orang pendek and the similar ebu gogo, tell of a small, dark furred, short legged, terrestrial biped that walks with an inverted heel. Its upper torso is said to be very powerful, its mouth compact, its eyes set wide apart and its nose distinctly humanoid. While not a perfect match with H. floresiensis the similarities are such that speculation has run rampant regarding their identity with one another.

The orang pendek has traditionally been thought of as a small relative of the orangutan. There is, however, another potential hominoid in the vicinity. Although extinct it is thought by some, myself included, to have survived into the early Pleistocene of southern China (where fossil orangutan teeth are numerous). This is Lufengpithecus, the so-called mystery ape of Mio-Pliocene China. According to research I’ve reviewed in this blog, Lufengpithecus had many traits long thought to be diagnostic of early hominans. It has been variously identified as a stem hominoid, a primitive pongine, a basal hominine or an early hominan. Given its close proximity, persistence in the fossil record, and mix of characteristics Lufengpithecus is a good candidate for the ancestor of the orang pendek and similar Southeast Asian cryptoids. And if the orang pendek/ebu gogo is synonymized with the “hobbit” logic dictates that the latter's ancestry can be traced to Lufengpithecus as well. This would suggest that the “hobbit” may actually be a faux or pseudo-human that evolved in parallel with us “true” humans. A very interesting proposition indeed, and one that would necessitate a new genus name for the species, perhaps something along the lines of Microanthropus floresiensis.

H. floresiensis vs Lufengpithecus proximal femora

To left: dorsal view H. floresiensis - Lufengpithecus

To right: ventral view H. floresiensis - Lufengpithecus

Late Miocene Hominoids: Back to the Future

2010-07-27T00:54:00.000-07:00

The discovery of a 7 million year old hominoid tooth in Bulgaria may not sound like much but it could be a “big deal.” For one, it demonstrates that late Miocene (Turolian) apes persisted in Europe much later than previously thought. The Turkish ape, Ouranopithecus turkae, with a biochronological age of 8.7–7.4 mya and fossil hominoids from Yunnan attributed to Lufengpithecus, dated between 6-11 mya, also last well into the Turolian. It is also during the Turolian that purported basal hominans (i.e. Sahelanthropus) begin to appear in the African fossil record.

Ouranopithecus, a well-known late Miocene European hominoid, has been identified as a hominine (a member of the African ape/human clade) by many paleoanthropologists. Based on evidence recently reviewed at this blog many Chinese paleoanthropologists now recognize Lufengpithecus to, likewise, be a stem hominine. What the new Bulgarian tooth demonstrates is that the radiation of these purported stem hominines extended both in time and space to a much greater extent than once thought.

The question has arisen, however, as to whether these potential hominines could be direct human (hominan) ancestors. If Sahelanthropus, at 7 mya, is accepted as a hominan, there is no biochronological reason not to accept the others as well. Biogeography should not enter into the picture either, as primates are known to disperse as readily as any other order of mammals. As I have attempted to show in these posts many, if not all, the cranial and post-cranial features used to diagnose early hominans (aka hominins) in Africa have been identified in Lufengpithecus. Both Ouranopithecus and Lufengpithecus represent fossil lineages that extent back to 10-11 mya. The same may be demonstrated in Africa for the lineage represented by Sahelanthropus and Orrorin. Thus purported hominans, i.e. direct human ancestors, may be documented in the fossil record at time scales and across continental areas equivalent to those proposed in the 1960s and 70s for Ramapithecus.

Well, then, it may be asked, what of the molecular clock? Geneticists have long argued for a late divergence of chimpanzees and humans between 4-6 mya. Human paleontologists, however, have recently wanted to push this divergence further back in time to accommodate the likes of Sahelanthropus. The increasingly dense and diagnostic late Miocene hominoid fossil record may thus force us to either acknowledge an early divergence hypothesis for hominan origins or accept the fact that stem hominines (i.e. the ancestors of the extant African apes and humans) were indistinguishable from early hominans. The poster child for this latter hypothesis may be Ardipithecus.

The implications of either of these hypotheses are quite significant. If an early divergence hypothesis for hominan origins on the order of 12 mya is accepted, the molecular clock would need to be recalibrated. This is in keeping with those who suggest that primate origins can be traced back to the Cretaceous on the order of 80+ mya. For instance, If we double the divergence time of apes and humans from 4-6 mya to 8-12 mya we should also double the dates for the origins of anatomically modern Homo sapiens and their “Out of Africa” dispersal. Thus, the common ancestor of Neanderthals and H. sapiens would be on the order of 0.8-1.2 mya rather than 0.4-0.6 mya, AMHS would have originated 400 kya rather than 200 kya, and the “Out of Africa” dispersal would have begun 120-140 kya rather than 60-70 kya. These revised dates are actually more in keeping with the emerging human fossil record than the dates now commonly accepted. The second hypothesis, that the common ancestor of extant hominines was more hominan than not, would overturn the conventional wisdom that human ancestors are uniquely derived relative to our shared ancestor with the African apes. Of course it can always be argued that none of the evidence presented here has any direct relevance to the question of human evolution, that late Miocene Eurasian apes with hominan-like traits have nothing to do with the origins of the African apes or humans. Any similarities they share with hominines or hominans, for that matter, are just examples of homoplasy, i.e. parallel evolution. I've argued that hypothesis and it's implications in a previous post. For the sake of clarity let me reiterate the three alternative hypotheses regarding late Miocene hominoids.

1. Late Miocene Eurasian apes, with features that have been favorably compared with hominans (i.e. direct human ancestors and their collateral kin), are in fact early members of the human clade. This would entail an early divergence of the African apes and humans perhaps as long as 12 mya.

2. Late Miocene Eurasian apes, with features that have been favorably compared with hominans, are actually stem hominines (African ape/human ancestors either direct or collateral). This would mean that nearly all the features currently used to identify members of the human clade, such as cranial and post-cranial adaptations for some form of post-facultative, pre-obligate, habitual bipedalism are to be found in the last common ancestor (LCA) of the African apes and humans. Hence, given the constraints of the late divergence hypothesis of human origins (i.e. the LCA of chimpanzees and humans lived 4-6 mya), the likes of Sahelanthropus, Orrorin and Ardipithecus would be very close or identical to the the LCA of the African ape/human clade.

3. Late Miocene Eurasian apes, with features that have been favorably compared with hominans, are either early pongines or stem hominoids that evolved adaptations for bipedalism and other hominan-like traits in parallel with our African ancestors, suggesting that features that have long been thought to distinguish the human lineage from other hominoids are not so unique after all.

All three of these hypotheses are heterodox as they challenge the prevailing orthodoxy that the human lineage emerged from a bunch of jungle dwelling African apes who had never left their continental homeland and that human-like adaptations for bipedalism were unique to ouirselves amongst the hominoids. In other words all those late Miocene Eurasian apes were nothing but an interesting but ultimately futile evolutionary sideshow. Any so-called hominan-like traits they possessed have been over-interpreted, misinterpreted or simply don't exist.

This position is epitomized by Cartmill and Smith (2009) who have this to say about the late Miocene Eurasian apes:

All these supposed orangutan relatives are of approximately the same age (late Miocene, around 10 Mya). Because they all resemble Pongo, albeit in different ways and to different degrees, they all have been placed in the orangutan family Pongidae by some authorities. But if Sivapithecus and its relatives are pongids, then the arm-swinging adaptations shared by the living apes must have evolved at least three separate times: once for orangutans, once for gibbons, and once for hominids. It seems equally likely that orangutan-like facial morphology evolved twice – once in the orang lineage, and convergently in the ancestry of Sivapithecus. We provisionally interpret Sivapityhecus and most of the other Miocene pseudo-orangutans as comprising an extinct family of specialized proconsuloids, the Sugrivapithecidae. However, Khorapithecusmay may prove to be a true member of the orangutan family.

Cartmill, M. and F. Smith. 2009. The Human Lineage, Wiley-Blackwell.

This scenario seems far-fetched to me, as I would expect adaptations for arm-swinging locomotion to be a common parallelism in suspensory hominoids, while the autapomorphic facial features of orangutans seem to be much less adaptive, and as a consequence, may have much greater phylogenetic weight. Nevertheless it highlights the prevailing notion that early human evolution occurred in Africa and Africa alone and that any attempt to look father afield is misguided.

“The giant rat of Sumatra, a story for which the world is not yet prepared.”

2010-07-26T14:37:00.000-07:00

Well Sir Arthur Conan Doyle had it right. Even he may have been daunted by a recent discovery on the neighboring island of Timor. Imagine a fully grown raccoon weighing between 10-15 lbs. Now morph it into a rat of similar weight and size. What you have envisioned is a new species of rat that lived on the Indonesian island until it went extinct about 2000 years ago. As humans have lived on Timor since at least 40,000 ya there's no question that these giant rats graced the palate of many a Timoran. The largest rats alive today are found in the Philippines and weigh a mere 5 lbs at most. Read more about it at Science Daily.

The Timor rat is to the left, the common black rat to the right.

A Late Miocene (Turolian) Hominoid from Bulgaria

2010-07-25T22:53:00.000-07:00

The Paleontological Museum in Assenovgrad, Bulgaria, a branch of the NMNH – Sofia recently announced the discovery of a Late Miocene (Turolian) hominoid in South Bulgaria (Chirpan District). The discovery, the first of its kind in Bulgaria, was the result of intensive paleontological field work that has led to the identification of a number of Late Miocene fossil localities. The recovery of over 30,000 fossils lays a firm foundation for the study of Miocene faunas and paleoenvironments in Bulgaria. Given Bulgaria’s proximity to Late Miocene hominoid discoveries in Greece and Turkey the search for fossil apes was given top priority. The new find consists of a single upper fourth premolar resembling Ouranopithecus. A preliminary report is given by the Bulgarian Science Academy.

Of most significance is the specimen's age, estimated to be ~ 7 mya. This is later than any previously discovered European hominoid and coeval with Lufengpithecus from Yunnan in China. This suggests that Eurasian hominoids survived later and were more widespread than once thought. How this relates to the emergence of hominans is at present unknown.

Some Interesting Comparisons

2010-07-24T20:09:00.000-07:00

Here are side-by-side comparisons of the Butterfly Ridge Child (Lufengpithecus hudienensis)(YV0999)(7-8 mya) and the Dikika Child (Australopithecus afarensis)(3.3 mya)(above) and YV0999, the Taung Child (A. africanus)(~2.5 mya) and The Hadar juvenile (A. afarensis)(3.2 mya)(below). I've taken some liberties with the Dikika and Taung specimens by photographically removing the bone enmeshed in matrix and the endocast, respectively, to highlight the portions of the face that are comparable to the Yuanmou specimen. Interestingly all are about the same dental age. There are clearly some similarities here.

Hudieliangzi Dikika

Hudieliangzi A. africanus Taung

A. afarensis 333-105

The Juvenile Hominoid from Butterfly Ridge

2010-07-24T17:37:00.000-07:00

Over the last month I've been reviewing the study of Lufengpithecus lufengensis recently published by Xu and Lu (2008). It is the 3rd publication in the ponderous sounding series of monographs entitled "State Key Project of the 9th Five Year Plan -- Origin of Early Humans and Environmental Background." The 2nd monograph in the series deals with a number of sites in the Yuanmou Basin of Yunnan that have produced prolific fossil hominoids. Long thought to be younger than Lufeng, these sites are now known to be somewhat older, between 7-8 mya. Lufeng has been dated perhaps a million years younger. The most important hominoid fossil excavated from the Yuanmou basin is a little heralded juvenile skull which is finally described in detail in the recent monograph (Qi and Dong 2004).

There has been considerable terminological confusion surrounding the hominoid remains from Yuanmou. Some consider them conspecific with the poorly known and somewhat older material from Kaiyuan (Harrison et al., 2002), and they've been subsequently dubbed L. keiyuanensis (the difference in spelling is due to the romanization method employed in China during the 1950s when the site was first discovered). He (1997) in an initial review of the Yuanmou hominoids, attributes the remains to a new hominoid species, L. yuanmouensis. The consensus seems to be building, however, that the proper scientific name, based on nomenclatural precedence, should be L. hudienensis (Qi et al., 2006). This is a very poetic name as it's derived from the fossil bearing locality in the Yuanmou Basin that produced many hominoid fossils called Hudieliangzi, which translated means Butterfly (hudie) Ridge (liangzi). The hominoid bearing localities in the Yuanmou Basin have yielded hundreds of isolated teeth, several upper and lower jaw fragments with teeth intact and a single post-cranial bone (phalanx). The localities and the taxonomy of the hominoid remains are reviewed by Harrison et al. (2002) and Qi et al. (2006). The most important specimen from Butterfly Ridge is, however, the face and palate of a young juvenile hominoid that is the same dental age as the famous Taung Baby from South Africa which launched the careers of both Raymond Dart and Australopithecus africanus.

YV0999

Discovered in 1988 the specimen (YV0999) is beautifully preserved and extremely informative. It was originally briefly described by Zhang Xingyong et al. (1988) and reported on by CK Ho (1990). The juvenile has a dental age of ~3 years and is directly comparable to the A. afarensis juvenile A.L. 333-105 from Hadar, the Dikika child and the Taung child. In brief it has a mix of Asian ape/pongine and African ape/hominine traits with the largest number and most phylogentically significant falling on the hominine side of the ledger. Below is a translation of the description and analysis of the specimen as given in the monograph.

The only cranial specimen of a fossil hominoid from the Yuanmou basin is the juvenile skull YV0999. The specimen preserves a relatively complete face and a portion of the frontal bone. The areas immediately above the orbits match and can be pieced together. Most of the frontal squama is broken away but a portion of the frontal that extends to the coronal suture is preserved on the left side. There are 10 adult upper jaw fragments but they only give a small amount of information regarding the anatomy of the adult hominoid skull. We compare the juvenile skulls of orangutans, chimpanzees, gorillas and australopiths of roughly the same developmental age. A comparison of the characteristics of YV0999 follows:

(1) The temporal line and sagittal crest. The temporal line on the skull of Lufengpithecus hudienensis is poorly expressed. There is a weak projection of the temporal line arising on the left zygomatic process at the lateral margin of the orbit. In chimpanzees and gorillas, the temporal lines are well developed; in orangutans the development of the temporal line is weak. There is an obvious temporal line in the juvenile skull of Lufengpithecus lufengensis (PA828). It is also evident in the skull of human children. The starting location and characteristics of the temporal line in the Taung skull are similar to the Yuanmou specimen. The temporal line in YV0999 is most similar to the condition in orangutans. In the course of human evolution, the temporal ridge gradually evolved into the form of the temporal line, which is due to the expansion of skull and cranial vault and the increased weakening of the temporalis muscle, the bone does not require a high ridge for the attachment of a strong temporal muscle. The expansion of the skull also provides a large attachment surface for the temporalis muscle.

(2) Supraorbital ridge and supraorbital sulcus. The supraorbital ridge is very weak, and the frontal bone is continuous with the slightly elevated supraorbital portion of the bone surface. There is no supraorbital sulcus, the bone surface is smooth. In the orangutan the supraorbital region has a thin ridge-like projection. This forms a well expressed superaorbital ridge in adults. It is very much like the supraorbital ridge in the Sivapithecus GSP1500 skull, which lacks a supraorbital sulcus. Chimpanzees and gorillas have an obvious supraorbital ridge and sulcus. In the two juvenile Australopithecus skulls the supraorbital ridge and sulcus are not well-expressed. YV0999 differs from the modern apes and is most similar to Australopithecus.

(3) Glabellar region. Relatively broad and flat forehead. While observing the juvenile L. hudienensis skull we discovered that it had bubble-shaped holes in the glabella cavity, which was suspected development of the frontal sinus. Orangutans have a very narrow and shallow concave area between the eyebrows, with no development of a frontal sinus. Chimpanzees and gorillas have a glabellar area that is significantly elevated, and there is a very large frontal sinus. The two australopithecines have a relatively protruding glabellar region. It is broad with a very large frontal sinus. Lufengpithecus has a broad but deeply concave glabellar region with a developed and obvious frontal, sinus. CT scan results also confirmed the presence of frontal sinus. There is a great difference between YV0999 and orangutans.

(4) Interorbital region, comparatively broad, close to that seen in the African apes much broader than in orangutans (see Table 2.30). The interorbital region in the Taung skull is also relatively broad. The Inter-orbital region width in juvenile human skull is also larger. YV0999 and orangutans differ significantly.

(5) Lateral side of the orbits. Broad and flat surface anterolaterally, the lateral margin has a marginal tubercle, it rises in an arc. In this point YV0999 is most similar to the orangutan. In the chimpanzee and gorilla the lateral side of the orbit is relatively narrow and swollen. This area in Australopithecus is also arched.

(6) Position of the lacrimal fossa. In YV0999 it is positioned relatively high, its shape is relatively broad. The position of the posterior lacrimal crest is also somewhat high but not very sharp. In orangutans the lacrimal fossa is positioned relatively low but is relatively broad in shape. The posterior lacrimal crest is positioned very low. In chimpanzees and gorillas the lacrimal fossa and posterior lacrimal crest are positioned relatively high. In gorillas the lacrimal fossa is relatively broad and the posterior lacrimal crest is not that sharp, but in chimpanzees the lacrimal fossa is relatively narrow and the posterior lacrimal crest is tall and sharp and clearly projects. In YV0999 the position of the lacrimal fossa is more similar to that of the African apes.

(7) Orbital shape. Height is slightly greater than width, approximately elliptical in shape, the inner half of the superior margin of the orbit is relatively flat, the lower margin and lateral margins are relatively sharp. The shape of the orangutan’s orbits and its relatively sharp inferior and lateral orbital margins is similar to YV0999 but the perimeter of its orbital margins projects resembling the rim of eye glasses. This condition not seen in L. hudienensis or the African apes. The shape of the orbits in chimpanzees and gorillas does not differ greatly from YV0999 but their lower and lateral margins are relatively blunt.

(8) Zygomaticofacial foramen. One, positioned between the zygomaticofrontal suture and the zygomaticomaxillary suture. Narrow, long and slit-like in shape. The zygomaticofacial foramen in orangutans is situated in the same location and is also long, narrow and slit-like, but there are often more than one and they are slightly longer. Sivapithecus GSP15000 preserves the foramen on the left side, it is also relatively long, narrow and slit-like. The zygomaticofacial foramen of gorillas and YV0999 are relatively close seems to be somewhat more narrow. Chimpanzees have relatively small, rounded foramina.

(9) Infraorbital foramen, One, positioned just below the junction of the zygomaticomaxillary suture with the lower margin of the orbit. This is similar to the position in chimpanzees and gorillas. It is also similar to the position in humans. It is shifted more to the center in orangutans.

(10) Zygomatic arch. The zygomatic arch originates between the DP4 and M1, the location of the starting point is very low, the lower margin is very thin. In orangutans the root of the zygomatic arch begins at the level of M2 but the lower margin of its root is very thin. In chimpanzees and gorillas the origin is positioned at the level of M1 and the root is positioned low but has a thick lower margin. In PDYA2 adult maxilla lateral aspect retains the base of the zygomatic arch, Its leading edge positioned at M1, indicating that in adult individuals the base of the zygomatic arch is more forwardly placed and the upper jaw protrusion is less.

(11) Nasal piriform aperture and nasal bones. The piriform aperture is long, narrow and oval, The anterior nasal gutter is weakly expressed. Nasal bones are relatively broad. The nasal aperture of the orangutan is close to that of YV0999 but the nasal bones are narrow. The nasal aperture of African apes is relatively broad and the nasal bones are broad. The anterior nasal gutter is weakly expressed in both orangutans and gorillas. Chimpanzees do not have a structure like the anterior nasal gutter. Both Australopithecus and humans have broad nasal bones

(12) Nasal alveolar clivus. This area has been damaged beyond recognition. From what remains it trends towards being stepped, thus differing from the orangutan.

(13) The hard palate and dental arcade. The palate is relatively deep, two incisive foramina, Dental arcade narrow, anterior portion of the arcade is arched, Both sides extend evenly posterolaterrally. The greater palatine foramen is narrow and deep. It is positioned near the alveolar margin. In both the young and adult orangutan there is only one, very small and narrow slit-like incisive foramen. The tooth rows project laterally and then turn inwards, Gorillas and chimpanzees both have two incisive foramina located close to the alveolar margin similar to YV0999. The greater palatine foramen in orangutans and chimpanzees is located closer to the median plane.

(14) Canine fossa. Maxillary samples from the Yuanmou Basin show a relatively weak canine fossa. Thee canine fossa is very well expressed in orangutans but lacking in chimpanzees. During research it was observed that In gorillas some young specimens have it and others don’t. Its lost in adults.

(15) Facial index. Based on the values shown in the table African great apes have relatively narrow faces while orangutans have relatively broad faces. The Yuanmou specimen is relatively close to the Asian ape.

(16) Face in toto. Tthe degree of prognathism in the YV0999 snout is very weak. The facial planum beneath the orbits is close to the vertical, only slightly slanted backwards. In the Orangutan the jaw projects to a significant extent; in side view the eyes are sunken inward. In the African Great Apes and Australopithecus prognathism is weak, the infraorbital plane is vertical similar to YV0999.

In short, the juvenile skull of L. hudienensis in its weak supraorbital ridge, lack of supraorbital concavity, form of the lateral orbital and orbital area, very thin base of the zygomatic arch, pear-shaped nasal aperture shape and facial index is relatively similar to like aged orangutans and differs from like aged chimpanzees and gorillas. The breadth of the interorbital distance and nasal bones and relatively high position of the lacrimal fossa, etc. is relatively similar to chimpanzees and gorillas of similar age. In addition the short width of its hard palate and the arched anterior of the dental arcade is clearly different from orangutans of similar age. The single infraorbital foramen and the position of the infraorbital foramen is very similar to juvenile Austarlopithecus.

In summary, the pongine like traits of YV0999 relate primarily to the morphology of the orbits and the supraorbital region, and the shape of the nasal aperture. In all other respects, including traits that are usually considered diagnostic of hominines such as 1) interorbital distance, 2) number and placement of facial foramina, 3) shape and configuration of the hard palate and maxilla, 4) size and morphology of the post-canine teeth (to be discussed later), etc. the Yuanmou juvenile sorts with the African Great apes and early and later hominans. So at 8 mya do we have the third chimpanzee, the second orangutan or the "first" hominan?

Literature Cited:

GAO Feng et al. 2006. An infant skull of Lufengpithecus from Yuanmou, Yunnan province, China. In: Yang, D., Yang, S. (Eds.), Collected Works for the 40th Anniversary of Yuanmou Man Discovery and International Conference on Paleoanthropological Studies. Yunnan Science and Technology Press, Kunming, pp. 40–63. 251.

Harrison T, JI X, SU D. 2002. On the systematic status of the Late Neogene hominoids from Yunnan Province, China. Journal of Human Evolution, 43:207~227

HE Zhiqiang. 1997. Yuanmou Hominoid Fauna (in Chinese), Kunming: Yunnan Science Press.

Ho, C. K. (1990). A new Pliocene hominoid skull from Yuanmou southwest China. Hum. Evol. 5:309–318.

QI Guoqin and DONG Wei (eds.) 2004. State Key Project of the 9th Five Year Plan — Origin of Early Human and Environmental Background Series monograph II: Lufengpithecus hudienensis Site. Science Press, Beijing, China.

QI Guoqin et al. 2006. Taxonomy, age and environment status of the Yuanmou hominoids Chinese Science Bulletin 51(6):704—712.

XU Qinghua and LU Qingwu. 2008. State Key Project of the 9th Five Year Plan — Origin of Early Human and Environmental Background Series monograph III: Lufengpithecus lufengensis - An Early Member of Hominidae. Science Press, Beijing.

ZHANG, Xingyong. et al. 1988. A preliminary study of the fossil skull of Ramapithecus unearthed at Hudie Hill of Yuanmou County. Sixiang Zhanxian 5:55–61.

Unraveling the Genetics of High Altitude Adaptations in Tibetans

2010-07-22T19:59:00.000-07:00

In an unusual confluence of events three studies on the genetics of high-altitude adaptations among Tibetans have recently been published. They all target alleles associated with genes in the hypoxia-inducible factor (HIF) oxygen signaling pathway that have been subject to strong and recent positive selection in Tibetan highlanders. One gene in particular EPAS1 maintains low hemoglobin levels in the face of low oxygen concentrations at high altitude. During acclimatization to high altitudes individuals from lower altitudes increase their production of red blood cells and hemoglobin to compensate for the lower atmospheric pressure which inhibits the absorption of oxygen into the blood stream. This however has a number of deleterious effects associated with high altitude sickness.

In a collaborative effort that included scientists from the China, Europe and the U.S., Yi et al. (2010) identified more than 30 genes with alleles that have become more prevalent in Tibetans than Han Chinese. More than half of these are related to how the body uses oxygen. One allele seen in 90% of the Tibetans studied was seen in only 10% of Chinese, indicating that it underwent extremely severe positive selection in the 3,000 years since the Tibetan and Han Chinese populations split. It is found near EPAS1 and codes for a protein involved in sensing oxygen levels and perhaps balancing aerobic and anaerobic metabolism. The mutation may be in a transcription factor that regulates the activity of EPAS1.

Other strongly selected variants were near the genes for the fetal and adult versions of the globin genes, which produce the structural proteins of hemoglobin. Two other genes showing a dramatic shift in frequency have been linked to anemia, while several other genes have been linked to diseases, including schizophrenia and epilepsy, possibly caused by low oxygen levels in the womb. The full story can be found at Science Daily.

In another study Simonson et al. (2010) identified 10 unique oxygen-processing genes associated with HIF that help Tibetans live at higher altitudes. The Tibetans have genetic adaptations to prevent polycythemia (a process in which the body produces too many red blood cells in response to oxygen deprivation), as well as other health abnormalities such as swelling of the lungs and brain (edema) and hypertension of the lung vessels leading to eventual respiratory failure. Even at elevations of 14,000 feet above sea level or higher, where the atmosphere contains much less oxygen than at sea level, most Tibetans do not overproduce red blood cells and do not develop lung or brain complications. The full story can be found at Science Daily.

The third paper is by Beall et al. (2010). This study by scientists from China, England, Ireland, and the United States pinpoints a genetic variant of the EPAS1 gene linked to low hemoglobin in the blood -- that helps explain how Tibetans cope with low-oxygen conditions. The study sheds light on how Tibetans, who have lived at extreme elevation for more than 10,000 years, have evolved to differ from their low-altitude ancestors The full story can be found at Science Daily.

Storz offers a technical review of all three articles in the same issue of Science that carries the Yi et al. (2010) and Simonson et al. (2010) articles. Unfortunately the full review is not available to non-subscribers to the journal.

All these studies are looking at the same set of genetic factors from slightly different perspectives. They attest to the fact that we have entered into a new phase of teasing apart the genetic mechanisms behind human adaptation. China in collaboration with other nations is playing a leading role in these investigations

Literature Cited:

Beall, C., G. Cavalleri, et al. (2010) Natural selection on EPAS1 (HIF2%u03B1) associated with low hemoglobin concentration in Tibetan highlanders. Proceedings of the National Academy of Sciences 107, 11459-11464.

Simonson, T. et al. (2010) Genetic Evidence for High-Altitude Adaptation in Tibet. Science, 329, 72–75.

Storz, J.F. (2010) Genes for High Altitudes Science 329 (5987), 40-41.

Yi, X. et al. (2010) Sequencing of 50 Human Exomes Reveals Adaptation to High Altitude. Science 329, 75 - 78.

Animal Connection: New Hypothesis for Human Evolution and Human Nature

2010-07-22T07:55:00.000-07:00

- What Does China Tell Us?

Pat Shipman has a new book in press (see above title) and an academic article coming out in Current Anthropology which elaborates on the role animal species have played in the evolutionary transformation of man-apes into ape-men and eventually fully human beings, replete with the ability to communicate using symbolic representations (aka art). Central to her hypothesis is the idea that the “interdependency of ancestral humans with other animal species -- "the animal connection" -- played a crucial and beneficial role in human evolution over the last 2.6 million years” (see write-up in Science Daily). Basically Shipman argues that as humans assumed the role of a top predator they began to study the behavior of their competitors (and I assume their prey) in order to learn how to hunt. They thus began to identify and empathize with other species. Symbolic representations, domestication and language were the ultimate end results.

Her thesis makes some interesting observations and I’m sure there is an element of truth in it. But is it the whole truth and nothing but the truth? I doubt it. I haven’t yet read the book or article (they’re both in press) so I don’t know how she develops her ideas, but in regards to symbolic representations of animals this occurs at the tail-end of the human Odyssey. It certainly took a long time to materialize. The same for domestication and perhaps language as well. They all seem to be manifestations of modern human behavior that distinguishes us from our archaic forebears. The earliest scratch marks on ochre forming geometric designs date to ~ 70,000 from the Middle Stone Age site of Blombos Cave in South Africa, while animal representations occurred much later in time during the upper Paleolithic in Europe. Domestication occurred primarily during the Neolithic.

Perhaps the earliest intentional marks on a material object however are recorded in China. The abstract of an article published in the Chinese Science Bulletin in 2004 (Gao Xin et al.), regarding excavations at Xinglongdong in the Three Gorges Region of South China, states:

Rich paleoanthropological materials were unearthed in primary context from the Xinglongdong Cave in Fengjie County, Chongqing, South China, including a human tooth, numerous mammalian fossils, some stone artifacts and a Stegodon tusk exhibiting intentional engravings. Based on biostratigraphic data and uranium series dating, the cave was utilized as a human shelter about 120000 to 150000 years ago. It is the first time that an archaic Homo sapiens fossil has been unearthed from the Three Gorges Region. Engravings on the Stegodon tusk appear in groups, making up simple and abstract images. It is the earliest known engravings created by human beings; it exhibits great potential for the study of the origin of art and the development of ancient cultures in south China and bears important implications for the origin of modern humans in East Asia.

The relevant section of the article reads as follows:

Two elephant (Stegodon orientalis) tusks, belonging to 2 individuals, were unearthed from the bottom of the second layer inside the cave. These two tusks were apparently intentionally placed parallel to one another (Fig. 5), which initially drew the attention of the second author. After cleaning, engraved lines became apparent on the surface of one tusk. The tusk is measured 184 cm long with the tip partially broken. Engravings appear on the tip of the tusk, concentrated in an area of 50 cm². These engravings in clude straight (vertical and oblique) and curved lines, and are simple but deep and bold, appearing in groups. Here we describe two such groups of incisions: Group 1 consists of six engraved lines and can be further divided into three parts, arranged vertically. The distal sector includes three fine, short, oblique lines (12 mm, 26 mm, and 16 mm long, respectively). These lines stretch toward the tip of the tusk, with two engravings initiating from the groove of the third. The middle part consists of a short, shallow, horizontal line (7 mm long and 1.4 mm wide) and a long, deep, vertical line (37 mm long and 1.5 mm wide). These two lines intersect forming a roughly cross-shaped figure. The proximal segment includes only one oblique line (41.5 mm in length), starting near the tail of its vertical counterpart. Under a microscope, these engraved lines exhibit “V” shape in cross section. Compositionally, this group somewhat resembles a leafless branch (Fig. 6(a)). Group 2 consists of four lines. The first one is straight and relatively long (110 mm long and 1.21.5 mm wide), running parallel to the long axis of the tusk. The other three lines are curved and relatively short (20 30 mm) and wide, clearly stretching from the mid-section of the first, yielding a crest-shaped composition (Fig. 6(b)). The tasks and engravings have been examined from many aspects, taphonomically, morphologically, mechanically, and artistically. The two tusks of different individuals appear parallel to each other in the deep end of the cave, about 50 m away from the entrance; no remains of other body parts were found in close association with them, which indicate that the tusks were neither the remain of in situ natural death of the elephants nor the result of other elephants’ movement of the dead companion, an elephant behavior that has been observed occasionally. The possibility of other animal drawing these huge and meat-less teeth to the deep side of the cave can also be eliminated. The nature of the deposit indicates that flowing water was not a factor in the formation of the archaeological record. Therefore, it is reasonable to believe that the presence of the tusks was the result of human transportation and arrangement. The lines on the tusk described above are distinct from marks or traces found on animal bones and teeth produced by natural agents such as weathering, root etching, abrasion, trampling, animal gnawing, and scratching[ 7], and they can be easily differentiated from rubbing traces created when the animal was alive, which normally appear in groups of oblique, short, thin, shallow and parallel lines (Fig. 7). The fact that such engravings appear on elephant tusk eliminates the possibility that they are tool marks resulting from butchering or skinning of game. The means by which the lines were created and the way they were composed indicate that they are not the careless or accidental products of human beings either. The above observations and analyses assure us that the lines on the tusk are human intentional creations. They exhibit some unique characters: (1) They are deep and bold and exhibit clear starting points, unlike natural rubbing traces or damage marks; (2) they vary in length, depth, starting points, and stretching directions; (3) they are generally V-shaped in cross-section, typical of sharp stone tool marks, different from animal tooth marks that are normally U-shaped in cross-section; (4) the curvilinear lines with different curvatures cannot be explained by any natural formation; (5) correlations and connections can be found among these lines; and (6) they are arranged in groups and form regular patterns (Fig. 6(c)). Therefore, these images were apparently intentionally engraved to imitate natural phenomena or attempt to express some abstract thought, the significance of which we cannot yet fully comprehend. Questions might arise on the workability of the elephant tusk by ancient hominids using stone tools. Actually Stegodon tusks are not very hard materials. Unlike young Stegodon individuals whose tusks were covered by a thin layer of enamel, adult Stegodon’s tasks remained only dentine, enamel was usually wore off. Simple experimentations were carried out by the team using limestone tools similar to those found in the Xinglongdong cave to engrave on a piece of modern elephant tusk, and similar lines were created. The presence of some flint chunks and debris from the cave can be taken as a clue that more suitable engraving tools might exist at the site.

This Chinese evidence and the engravings in South Africa suggest that the earliest attempts to convey information symbolically did not entail naturalistic representations of animals, but abstract representations that are currently hard to interpret.In their discussion of the site the authors state the following:

The elephant tusk with human engravings unearthed from the cave is a significant discovery. A series of analysis conducted on this finding, including the taphonomic context and the appearance, directions, curvatures, morphology and composition of the lines, convincingly points to the fact that these lines on the tusk are distinct from marks or traces found on animal bones and teeth produced by various natural agents; they are the result of human engravings, and they were apparently intentionally engraved to imitate natural phenomena or attempt to express some abstract thought. Therefore, the tusk yields the earliest archaeological evidence that could be related to primeval artistic creativity by human beings ever found so far.

Human artistic expression is undoubtedly rooted in the Paleolithic. The fragmentary data collected so far prevent us from reconstructing a precise history of its development in that remote period. However, newly unveiled archaeological evidence enables us to make a rough sketch of how such a process might have played out. Human and other animal figures and cave paintings discovered in Africa and Europe, some of which can be dated to 30-40 ka, have been generally accepted as unquestionable early human art works[10]. The discovery of red ochre pieces with geometric engravings from the Blombos Cave in South Africa might have traced the history of human artistic activity back to 77 ka. Ivory engravings of 120,000 - 150,000 years old reported in this paper provide new clues on the origin of human artistic creations. Based on archaeological evidences, we believe that even though the general tendency of pictorial art during the past 30,000 years is from realism to abstract, it might have experienced an opposite developmental trend in the embryonic stage: the earliest work might have initiated from single, simple and rough engraved lines, poorly controlled, highly abstract in character and difficult for us to interpret. Ivory engravings reported in this article are such examples. A further advance may have involved multiple, finer, more complex and better-controlled lines, possibly yielding geometric or other recognizable compositions, which are still subject to varying interpretations. Ochre engravings from the Blombos cave may be taken as a representative of this stage. As artistic expression matured carved, sculpted, or painted figures or representations of anthropomorphic, zoomorphic or other subjects, with early interpretable morphologies and sometimes meanings, were developed. Engraved animal figures and female anthropomorphs discovered at Mal’ta and other Upper Paleolithic sites in south-central Siberia and the parietal art associated with Magdalenian horizons from Spain and southern France [11] are prime examples of this stage.

Artistic creativity is one of the unique attributes of modern human cognition and behavior. Therefore, one research topic closely related to the origin of art is the origin of modern humans. For years, two hypotheses in this regard, namely “Out of Africa” vs. Multi-regional continuity”, stand in sharp opposition to each other; both are seeking archaeological backing. Ochre engravings from the Blombos cave were quickly assigned as the supporting evidence for the former theory upon their discovery. Are the materials described in this paper supportive of the latter? We can at least conclude that the human ancestors who occupied Xinglongdong Cave on the eastern periphery of the Qinghai-Tibet Plateau some 120-150 ka already possessed consciousness and behavior patterns that might be described as “modern”. They not only made and used stone tools, but also attempted to use engravings and possibly other means to express complex ideas that are as yet incomprehensible to modern-day humans. Therefore, this discovery not only provides invaluable information for the study of the origin of art and the development of ancient cultures in the Three Gorges Region of south China, but also bears important implications for the origin of modern humans in East Asia.

Once again we're finding that simple scenarios based on an incomplete and inadequate archeological and fossil record tend to skew our understanding of the human past. This is not to denigrate what others have found and the interpretations that have been previously made. But we should keep an open mind to new evidence and their implications once discoveries in hitherto poorly sampled regions of the world come to light. There is only one human story to be told but we as yet can barely see its outline nonetheless its details.

More on the Proximal Femur of Lufengpithecus.

2010-07-19T06:25:00.000-07:00

Recent articles by Holliday et al. (2010) and Harmom (2009) comparing the morphology of the proximal femur in extant African hominids (Gorilla, Pan and Homo) and early hominans are aimed at distinguishing them from one another, allowing for at least “genus level” identification of fossil specimens. Both studies use multivariate statistical analysis to identify character states that discriminate various early hominans, such as Australopithecus, Paranthropus and early Homo, from the extant African apes. This is a very important consideration as more and more proximal femora crop up in the fossil record.

For instance, Holliday et al. (see a useful review by Afarensis) state that, relatively speaking, the following features separate hominan from non-human hominid femora:

Large femoral heads
Long femoral necks
Less cranially projecting greater trochanters, and
Less posteriorly-positioned lesser trochanters

Holliday et al. attribute these differences to adaptations for bipedalism. They state that, “Importantly, most of the features that distinguish Homo (or for that matter, all hominins) from the African apes are related to bipedalism.” These are enumerated and analyzed as follows:

The long femoral neck increases the moment arm for the gluteal abductors (tensor fasciae latae, gluteus medius, and gluteus minimus).
The small size (i.e., reduced height) of the greater trochanter is argued to reflect a reduction in size of the gluteus medius and gluteus minimus muscles.
The reduction in height of the greater trochanter relative to the position of the superior margin of the head is an ontogenetic consequence of the developing bicondylar angle
A ‘‘lower’’ greater trochanter tends to reduce bending on the (longer) hominin femoral neck (provided the iliac origin of the gluteal abductors were lowered, as well) – but the exact functional significance of this trait (if any) remains equivocal).

Based on the above criteria any hominid (s.l.) possessing a relatively large femoral head, long femoral neck, less projecting greater trochanter and less posteriorly positioned lesser trochanter should be considered an erectly bipedal hominan. Moreover, relative to recent humans, all the early hominans are characterized by long and antero-posteriorly thin necks, shorter greater trochanters, a more lateral position of the lesser trochanter, and medio-lateral expansion of the proximal shaft.

In addition, Harmon (2009) states that, “there is a general consensus that Australopithecus and Paranthropus femora are longer-necked than those of modern humans, and that these early hominins have smaller femoral heads and antero-posteriorly flattened necks as well. The suite of features that characterize australopith femora make them unique among hominoids, and “bipedal femora as a group differ from non-bipeds in having an inferiorly positioned greater trochanter and a NSA(neck/shaft angle) value that does not overlap with those of orangutans.”

How does the Lufengpithecus femur (PA 1276) stand up (npi) in comparison to other hominids? Xu and Lu (2008) unequivocally state that, the length of the neck in PA 1276 is the same as in KNM-ER 738, i.e. “the neck is long, the distance from the intertrochanteric crest to the lip of the head being about 46 mm." The size of the head is also nearly identical (33.4 mm x 33.4 in PA 1276 vs. 32.8 mm x 33.6 mm in KNM-ER 738). Visual inspection also confirms the other two criteria mentioned by Holliday et al. as indicative of bipedalism in early hominans. Thus as Xu and Lu state, "the head, neck and shaft of the Lufengpithecus femur possess the characteristics and the robustness seen in the late Australopithecus femur KNM-ER 738. And the fovae capitis of both femora have an eccentric placement in the articular surface of (the) head. In sum, we can infer that the two kinds of femora possess equivalent loading function.” They go on to state that "In Lufengpithecus, Australopitehcus and early Homo the values of the sagittal diameters of the femoral necks fall in the upper parts of the vertical diameters of the femoral necks. In relation to the values mentioned above , the diameters of the area of transition between femoral heads and necks are also increased. These kinds of constructional characteristics were attributed to the adaptation to bipedal walking. The loading of weight at the femoral necks is heavier than in the quadruped, because their trunks were oriented vertically. In order to increase the loaded stress of the femoral neck, the neck has necessarily become larger."

So, based on the criteria recently established to identify hominan proximal femora in the fossil record, Lufenpithecus fits the bill.

Literature cited:

Holliday, Hutchinson, Morrow, and Livesay (2010) Geometric Morphometric analysis of hominid proximal femora: Taxonomic and phylogenetic considerations. Homo – Journal of Comparative Human Biology 61:3-15.

Harmon, E.H. (2009) The shape of the early hominin femur. Am. J. Phys. Anthropol. 139:154–171.

Xu Qinghua and Lu Qingwu (2008) Lufengpithecus lufengensis - An Early Member of Hominidae. Science Press, Beijing.

The Baoshan Mandible

2010-07-17T01:29:00.000-07:00

For all you Lufengpithecus freaks out there in cyberspace I happened upon this photo of the Baoshan Lufengpithecus mandible while surfing the Chinese web. It’s the only photo of this poorly documented specimen that I’ve come across.

The one Chinese language academic reference I have regarding the Baoshan mandible is: “Geng, D. (1994). The position of the Baoshan hominoid fossil in the study of human origins. Yunnan Soc. Sci. 1994(1), 78–83.” The article details the domestic and overseas reporting of the find, the circumstances surrounding its discovery and the geographical location of the site. It also offers a brief description of the specimen and discusses its evolutionary significance. The most comprehensive English language summary of the site is given by Terry Harrison, Ji Xueping and Denise Su, in their article “On the systematic status of the late Neogene hominoids from Yunnan Province, China, Journal of Human Evolution Volume 43, Issue 2, August 2002, Pages 207-227.” They offer a description of the site location and its biogeochronological placement based on the information given in Geng’s article, but they don’t have any discussion of the specimen itself other than what it consists of. I’ll take the liberty of quoting the material from their article that relates to Baoshan:

Yangyi, Baoshan

The hominoid locality of Yangyi in Baoshan Prefecture is located 350 km west of Kunming. The locality is situated on the eastern slopes of the Gaoligongshan mountains, between the Nu River and the Lancang River, and is the most westerly hominoid locality in Yunnan Province (Figure 1). In 1992, Xu Qinghua of IVPP discovered a left mandible fragment with C–M3 of a female hominoid in the uppermost lignite layer of the Qingshuigou coal mine at Yangyi. The specimen has not yet been formally described, but several news articles and reviews have made reference to the discovery (Xu, 1992; Geng, 1994; Zhang, 1994). The age of the Yangyi deposits has not been reliably established. Based on the associated proboscideans, the Yangyi fauna is suggested to be younger than the Lufeng and Xiaohe faunas (Yunbo, 1975; Jiang et al., 1983; Zong et al., 1996). It corresponds well with other Pliocene faunas from China, including that from the Shagou Formation, Yuanmou Basin [which has an estimated age of _3–4 Ma, based on paleomagnetic correlations (Jiang et al., 1989; Urabe et al., 2001)] and the Yushean aged fauna from northern China (correlated with the Ruscinian and Villanyian in Europe, MN 14–16, 5·2–2·6 Ma) (Qiu & Qiu, 1995). If an estimated age of 3–5 Ma is confirmed, the fossil primate from Yangyi will be, with the exception of Gigantopithecus, the youngest known representative of an extinct hominoid genus from Eurasia (Figure 3).

Figure 1. Map showing the location of fossil sites (solid squares) in Yunnan Province (adapted from Ho, 1988; Meng, 1997).

Figure 3. Chronology of late Neogene and Quaternary hominoids from key localities in China and the rest of Eurasia. The abbreviations in [ ] following locality names refer to hominoid taxa known from those sites: D, Dryopithecus; Gi, Gigantopithecus; Gr, Graecopithecus (= Ouranopithecus); L, Lufengpithecus; O, Oreopithecus; S, Sivapithecus. Sources: Andrews et al. (1996); Pan (1994); Flynn et al. (1995); Qiu & Qiu (1995); Pickford & Liu (2001); Ni & Qiu (2002).

Geng’s article goes further in discussing some of the background to the Baoshan hominoid discovery and a brief description of the specimen and its significance. A brief summary translation follows.

Baoshan Fossil Ape - Baoshan history: in ancient times the western region of Yunnan Province was regarded as "a boundless uninhabited wilderness." In the 1980s and 90s archaeological discoveries confirmed that primitive Paleolithic and Neolithic humans lived and bred there and carried out a broad range of activities. Ape fossils found in the Yangyi region of western Yunnan caused quite a stir both internationally and domestically.

Yangyi is located 30 km southeast of Baoshan City, Yunnan Province, in a 2 sq. km sub-basin on the south side of Baoshan Dam. On January 9, 1992, ape fossils were unearthed from a coal seam at the Qingshuigou Mine north of Yangyi Dam, in Baoshan City,Yunnan Province. Fossils included the left mandible and a single premolar of an ape and some fossil herbivores, primates and other mammalian specimens. The jaw preserves intact six teeth, the canine, two premolars, and three molars. It is very rare that the jaw and teeth are so well preserved, unlike ape fossils excavated in the past both domestic and foreign that are mostly flattened, twisted, fractured or even completely broken. This lower jaw is very complete and provides a reliable basis for study. One of the most important traits in the transition from ape to human is the shape of the mandibular first lower premolar. In apes it is triangular and fan shaped with a single sharp tip. In humans it has two cusps that are nearly equal in size. The Baoshan 1^st lower premolar is changing from a single cusped fan-shaped tip to a bicuspid tooth with one large and one small tip but not to the point in which the cusps are equivalent in size as in humans. The Yangyi specimen is similar in size, shape and other aspects to the 8 million year old ape fossils from Lufeng in Yunnan. The Yangyi samples are similar to those from Lufeng, but the second and third molar crown width has become shorter and the third molar in particular has become shorter in width. This is more evolved than in Lufeng and closer to the condition seen in the 4 my old australopithecines. The morphological features and stratigraphic position of the fossils unearthed show that their age is between 8-4 million years ago. This is a period in the evolution from ape to human both in China and abroad that is lacking in fossils. Over the last 10 years there has been a concerted effort both at home and abroad to fill in this gqap. The Baoshan. Yangyi ape fossils help fill in this gap and show that Yunnan was an important area in the transition from ape to human.

The Baoshan site is the fourth Lufengpithecus site known in Yunnan. The four sites include in chronological order (based on the most recent dates): Kaiyuan (~11 mya), Yuanmou (~ 8 mya), Lufeng (6-7 mya), and Baoshan (~ 3-4 mya). There are definite differences and similarities between specimens from these sites.

Addendum:

As the Yangyi, Baoshan mandible may be (conservatively) comparable in age to Ardipithecus ramidus I thought it would be interesting to compare the two. What follows is a side-by-side comparison of the Baoshan lower mandibular tooth row (C-M3) to the same sequence from Aramis.

The Baoshan Lufengpithecus is to the left, Aramis Ardipithecus to the right (not to scale). I'll let readers draw their own conclusions. But, let me just say this. If the Baoshan mandible had been found in East Africa from comparatively dated deposits would it be considered anomalous or a good example of any early hominin (to use the current jargon)?

Could There Have Been Non-Hominan “Hominids”?

2010-07-16T13:07:00.000-07:00

To begin with let me clarify that by “hominid” I mean a hominoid primate that has the appearance of being a possible human ancestor and by hominan I mean a member of the subtribe Hominina that includes direct human ancestors and collateral relatives descended from the Last Common Ancestor (LCA) we share with the chimpanzee.
The last few essays that I’ve posted have dealt with Lufengpithecus and other indeterminate hominoid remains from China. These include a number of dentognathic specimens that have been compared to fossil orangutans, a non-orang large bodied ape (possibly allied to Lufengpithecus), or early species of Homo cum Meganthropus.

The recent descriptions and analyses of L. lufengensis and L. hudienensis by Chinese colleagues show that this late Miocene hominoid was distinct from living and fossil orangs and orang relatives such as Sivapithecus. Lufengpithecus had a suite of craniofacial and dentognathic features long associated with African apes and humans. It also possessed basicranial and femoral traits that have been used to infer bipedalism in a number of late Miocene apes such as Sahelanthropus and Orrorin purported by their respective discoverers to be early hominans.

The questions then arises, was Lufengpithecus a bona fide hominan or something else, and if something else what? Given its age (6.1-6.9 mya) and morphological features, L. lufengensis, if found in Africa would most likely be accepted into the ranks of human ancestry. Its geographical location and affinities to L. hudienensis (~ 8 mya) from the Yuanmou basin and L. keiyuanensis (~ 11 mya) from Kaiyuan complicate the issue as this lineage of Asian apes can be traced back in time towards the middle Miocene, long before the genetic evidence suggests that the LCA of chimpanzees and humans lived.

I have a solution to the riddle of these Asian “mystery apes” and their affinities to the extant hominoids including humans, but first let’s look at some previous solutions that have been proffered. Jeff Schwartz and his colleagues have a unique solution to the above quandary. They propose that the orangutan (Pongo) not the chimpanzee (Pan) is our closest living relative. This throws everything for a loop and the “hominid”-like features of Lufengpithecus then fall nicely into place. An early ancestor of humans should have a surfeit of derived orang-like traits mixed in with pre-orang-like retentions and ipso facto - presto problem solved.

Another solution is that Lufengpithecus is a relic of the pre-orang divergence great apes. It would thus retain a suite of primitive features some of which are retained in the African hominines and other in the Asian pongines. If that is the case then the features that Lufengpithecus shares with the African apes and humans are symplesiomorphies (shared primitive features) and the features it shares with the Asian orangutan are likewise a different set of symplesiomorphies. Lufengpithecus should then have none of the shared derived features of either the African ape/human clade or the Asian ape clade. This would make the basicranial and femoral traits for bipedalism that it shares with Sahelanthropus, Orrorin and Ardipithecus symplesiomorphies of the Great Ape/human clade. That has been my preferred solution to a problem that no one else probably even recognizes.

But I’ve been thinking of late (this has been my downfall) that maybe Lufengpithecus is an early pongine, and its hominine-like traits are primitive retentions from the hominid (sensu lato) LCA. The bipedal adaptations its shares with African hominines could well be parallelisms. Thus “hominid”-like features may have evolved independently in various lineages of both African hominines and Asian pongines. The present day apes are highly derived and adapted to a closed canopy tropical forest environment and their adaptations for suspensory locomotion in the trees and knuckle walking/fist walking on the ground are likewise parallelisms.

So here is where the title of this essay comes into play. The early “hominid” grade of evolution may have been entered by two or more separate hominoid lineages. Lufengpithecus may have been a “hominid grade” pongine. The implications are rather staggering. There may well have been bipedal pongines. They may have begun to use very simple, barely diagnosable stone tools. There may have been an adaptive radiation of pongine “hominids” thus explaining some of the indeterminate hominid-like remains (Longupo, Jianshi, Meganthropus, etc.) found in China and Java. Of course Gigantopithecus fits nicely into this scenario as an Asian analogue of robust australopiths.

The above scenario, which elaborates on my previous post resurrected from i5 years ago, is in keeping with recent trends in interpreting the hominoid fossil record. Rampant parallelisms, a bushy phylogenetic tree with a proliferation of hominoid, hominid, hominine, hominin and hominan lineages. Why not a proliferation of Asian pongine lineages evolving in ways parallel to the African hominines? Then when Homo erectus entered East Asia it would have encountered other “hominid grade” hominoids. Sort of an early version of the “Out of Africa” replacement hypothesis but a couple of million years earlier.

An Old Essay That Is Still Relevant

2010-07-14T20:35:00.000-07:00

Way back in 1995 I posted the following article on the web. It was a precursor to the paper I co-authored with Tracey Crummett and Milford Wolpoff on "Longgupo: Early Homo colonizer or late Pliocene Lufengpithecus survivor in south China?" It goes on to comment on other controversial hominoid remains from South China and Java. Given the recent retraction by Russ Ciochon that the Longgupo mandibular specimen is an early Chinese hominid and his conversion to accepting it as an East Asian "mystery ape" I thought it was appropriate to re-post my initial observations on the subject. Over the last 15 years more material of the sort mentioned in the following essay have been brought to light. In a future post I will review these new finds and put them in their proper context. The first part of the following re-post includes a section on Longgupo which is substantially the same as the published article.

Implications of New Fossil Material Attributed to Plio-Pleistocene Asian Hominidae

Introduction

The recent description of fossil material attributed to an early form of Homo from Longgupo cave in Sichuan, China (Huang et al. 1995) raises new questions about the role Asia played in the evolution of the modern Hominoidea. On the one hand it refocuses attention on the fossil record of Asian Mio-Pliocene hominoids such as Sivapithecus, Ramapithecus and Lufengpithecus and the role they played, if any, in human phylogenesis. On the other hand it reopens questions about early hominid dispersal patterns and the evolutionary emergence of particular hominid taxa.

Longgupo, Wushan, Sichuan

The Longgupo remains, which consist of a fragmentary mandible and an isolated incisor, are dated between 1.8-2.0 MYA and regarded by their Chinese discoverers and American colleagues as too primitive to be considered H. erectus (Huang et al. 1995). Wood and Turner (1995) concur, suggesting they most likely represent an early form of Homo, such as H. habilis, or perhaps H. ergaster. If accepted as a full-fledged hominid, the small size and primitive morphology of the preserved mandibular dentition (P4 and M1) would probably warrant erecting an entirely new species for the specimen.

Based on the Longgupo material some have argued that a dispersal of early Homo into Asia prior to the advent of more advanced forms in Africa supports the claim that Asian H. erectus, was a side-branch on the human evolutionary tree, uninvolved in the African origins of later humans (Culotto 1995). A number of Chinese researchers, however, have an entirely different perspective. They have long argued that dentally progressive hominoids, such as Lufengpithecus known from the Miocene and early Pliocene of Yunnan province in southwestern China, are direct human ancestors and that this area of southern Asia, not eastern or southern Africa, was the true cradle of humankind. Early Pliocene hominoids from the Yuanmou basin of Yunnan, for instance, have been described as having small distolingually elongated P4's, and low crowned molars, lacking in cingula, with broad talonids and squarish outlines (Lu 1991), all features similar to those seen in the Longgupo specimen. Chinese advocates of an Asian origin for the Hominidae (humans and their direct ancestors) emphasize these hominid-like dental features of Late Tertiary southern Chinese apes.

Some Chinese paleontologists dismiss the African australopithecines as specialized off-shoots of the human family tree not directly involved in the origins of the genus Homo, much as some in the West dismiss H. erectus as not being directly involved in the later descent of modern humans. Remains such as those recovered at Longgupo, which bear a striking resemblance to the Yunnanese ape Lufengpithecus mentioned above, are seen as the "missing link" between these southern Chinese apes and later Chinese hominids. If the Longgupo specimens are accepted as representing a true hominid then it follows that the hypothesis of a southern Chinese origin for the Hominidae merits serious consideration. Many in the West, will categorically reject such a notion as absolutely unwarranted and contrary to all known facts. Chinese paleoanthropologists, however, find the proposition that Asian H. erectus was an evolutionary dead-end unrelated to modern Asians just as untenable as many Western scientists find claims for human descent from Chinese apes.

It can also be argued, however, that the Longgupo specimens are not true hominids after all, that Lufengpithecus and its descendants were not human ancestors and that Longgupo represents a heretofore unknown continuation of the Lufengpithecus ape lineage into the Plio-Pleistocene of southern China.

The Significance of Lufengpithecus in Human Evolutionary Studies in China

What sort of ape was Lufengpithecus? When first discovered in the late 1970s and early 1980s two morphs were recognized, a relatively gracile form initially attributed to Ramapithecus lufengensis, and a larger more robust form attributed to Sivapithecus yunnanensis. At the time the discoveries were made Ramapithecus was still regarded by many paleanthropologists as the earliest and most primitive hominid, based primarily on dental features thought to be derived in the human direction. Sivapithecus was considered to be an early pongid only indirectly related to the smaller hominid. It wasn't long, however, before these two fossil taxa were re-evaluated based on new fossil discoveries in the Siwaliks of Pakistan and molecular evidence which indicated that Ramapithecus occurred too early in the fossil record to be a direct human ancestor. The similarities between the two forms were quickly recognized and most researchers eventually came around to viewing Ramapithecus merely as the female of Sivapithecus. Further research showed that the Chinese specimens were distinct from those recovered in the Siwaliks and in 1987 the genus and species Lufengpithecus lufengensis was erected to accommodate them. Prior to this reassessment, however, Chinese researchers were convinced that Ramapithecus lufengensis was a direct human ancestor and some still are today. In this regard Wu and Oxnard published a series of papers in the early 1980s that focused on the hominid- like features of the smaller Lufeng morph.

With the demise of Ramapithecus, the Lufeng material was quickly reevaluated. More recently Lufengpithecus has been characterized as a highly sexually dimorphic large-bodied hominoid with uncertain affinities to other living and extinct great apes (Wu and Wang 1987, Kelley and Etler 1989, Kelley and Xu 1991, Wood and Xu 1991). It must still be recognized, however, that the smaller Lufeng morph, now regarded as the female of Lufengpithecus lufengensis, does have certain dental traits that closely approximate those of early hominids (Wu and Oxford 1983a, 1983b). These include relatively low-crowned canines; incipiently bicuspid lower P3s with tall protoconids and low-lying metaconids; a foreshortened, lozenge-shaped lower P4 with protoconid and metaconid of approximately equal size; and low-crowned, thickly enameled molars. There are other features of the female Lufengpithecus dentition, however, that can be characterized as typical for Late Miocene apes with thickly enameled teeth. The long axis of lower P3 is oriented from the mesiobuccal to the distolingual; lower P4 is double rooted with a slender mesially positioned slit-like anterior fovea, an elevated trigonid and a depressed, elongate talonid that is skewed slightly distolingually; and lower M1 has cusps arrayed round the periphery of a broad talonid basin, with salient buccal protoconid and hypoconid that wear quickly, producing enamel windows, an endoconid that projects slightly distolingually and a small buccally displaced hypoconulid separated from the large endoconid by a short longitudinal groove.

In comparison to the above, the Longgupo mandible, which contains a well-worn P4 and M1, has virtually identical morphological features. The lower P4 is primitively double-rooted and shaped and configured like that from Lufeng with an elevated trigonid basin and a depressed and elongated talonid. Moreover, the mesial face of the P4 has an interproximal facet for the P3 that is displaced markedly lingually. This shows that the P3 crown was sectorial, with its long axis oriented from the mesiobuccal to the distolingual, the normal orientation for the P3 in apes with teeth of this size and the condition noted above in female Lufengpithecus. The lower M1 at Longgupo is a non-descript hominoid molar that does not differ from the description of the female Lufengpithecus M1 given above in any meaningful way. In all of the above features which relate to the preserved dentition at Longgupo the two forms are virtually identical.

Dimensionally the Longgupo dentition is also nearly identical to female Lufengpithecus. The dimensions of the Lufeng female lower P4 are: average MD length 7.89 mm, sd=0.65, n=35; average BL breadth 9.08 mm, sd=0.52, n=34. The dimensions of the Longgupo specimen are: MD length 7.4 mm, BL breadth 9.1 mm; well within the 95% confidence limits of the Lufengpithecus female range of variation. The dimensions of lower M1 of the female Lufengpithecus are: average MD length 10.57 mm, sd= 0.48, n=35; average BL breadth 9.08 mm, sd=0.37, n=35. The dimensions of the Longgupo lower M1 are MD length 11.1 mm, BL breadth 10.1 mm, again well within the 95% confidence limits of the size range of female Lufengpithecus. Moreover, female Lufengpithecus M1s are relatively longer than broad with a L/B ratio of 1.10, the L/B ratio of the Longgupo lower M1 is identical. Early hominid M1s vary in this regard but tend to be shorter and broader, either close to square in occlussal outline or broader than wide. Based on the above comparisons it can be seen that dimensionally as well as morphologically the dentitions of female Lufengpithecus and the Longgupo mandibular specimen are nearly indistinguishable. In comparing the Longgupo P4 to those known from Lufeng Huang and Fang (1991) made only one observation, that the buccal face of the Longgupo specimen is more rounded than that seen in Lufengpithecus, which is more convexly triangular. The Lufeng site, however, is 5 My older than Longgupo, and it is rather remarkable that there has been so little change in the preserved dental morphology. Similar hominoid material from Yuanmou, also in Yunnan, dated to the Early-Middle Pliocene, approximately intermediate in age between Lufeng and Longgupo, has moreover been described as somewhat more progressive than Lufeng (Lu 1991), meaning apparently that it has an even greater resemblance to the dentition of early hominids. Hence the rounding of the buccal face of lower P4 in the Longgupo specimen relative to that seen in female Lufengpithecus can be attributed to progressive evolutionary change during the 5 My that separate them.

Given the above comparisons there is no discernible reason why Longgupo cannot be seen as a descendent of Lufengpithecus that survived into the Late Pliocene and early Pleistocene of southern China. The most obvious affinities of the specimen lies therefore with Lufengpithecus and not early Homo. The Longgupo jaw is not that of the earliest Chinese hominid, it is, rather, that of a late occurring Chinese fossil ape.

Other Purported Plio-Pleistocene Hominids from China

Another claim for a Plio-Pleistocene hominid in China rests with two incisors known since the 1960s from another locality in Yuanmou, Yunnan (Hu 1973). Dated to 1.7 MYA by paleomagnetism (Qian 1985), the Yuanmou incisors are very large and distinctly H. erectus-like in their enamel patterning and over-all construction, quite at variance to the small gracile incisor recovered at Longgupo. Persistent questions about the original provenance of the Yuanmou specimens and their relative scantiness mitigate against over reliance on them as proof positive of early Pleistocene hominids in south China. Nevertheless, the Yuanmou specimens can be argued to represent a hominid close to the base of the H. erectus lineage in China.

There are other specimens from China, collected from both traditional Chinese apothecaries (i.e. "Hemanthrpopus") and early Pleistocene cave deposits, that have in the past been favorably compared to African australopithecines due to their large size and derived cuspal morphology (von Koenigswald 1957, Gao Jian [Xu et al.] 1975, Franzen 1985). The dating of these remains is problematical but most likely falls within the early Pleistocene. Assessment of the true affinities of these specimens has been controversial, with some investigators suggesting that they can be accommodated within the known variation of H. erectus (Zhang 1984), while others have suggested possible links to the still poorly understood fossil orang-utan of the southern Chinese and insular southeast Asian Pleistocene (Gu et al. 1988) or the enigmatic Southeast Asian Meganthropus.

One sample of four lower molars from Jianshi, Hubei (Gao Jian [pseudonym for Xu et al.] 1975) has generated considerable interest (Pope 1977, Franzen 1985) because of their large size, archaic appearance, inferred antiquity and association with Gigantopithecus. The original investigators (Gao Jian 1975) suggested australopithecine affinities for the assemblage. More recent comment (Zhang 1984), however, discounts this likelihood and suggests that the material can be accommodated within the hypodigm of Asian H. erectus. Of the four molars one, PA 507, a right lower M1, was collected from an apothecary shop in Badong county, Hubei and lacks proveniance. The other three (PA 502-504) were found in situ at Longgudong (E 110o 04', N 30o 38'), a horizontal karst cave, in association with Gigantopithecus teeth and a typical southern Chinese Stegodon-Ailuropoda faunal assemblage. A few relatively archaic elements are represented in the fauna (i.e. Tetralophodon serridentoides, Gomphotheriidae, Machairodontidae) and a number of the taxa are intermediate in size between samples from sites attributed to the early Pleistocene (Gigantopithecus Cave at Liucheng) and middle Pleistocene (Yanjinggou) respectively. Based on the analysis by Zhang (1982) of the evolutionary increase in tooth size within Chinese Gigantopithecus, it can be inferred that the relatively large size of the Gigantopithecus teeth at Longgudong indicates at least an early middle Pleistocene, if not a late early Pleistocene age for the material. Neither age is contravened by other elements within the faunal assemblage.

Of the four molars, PA 502 and 503 from Longgudong are most likely antimeres given their metric and morphological similarities. They were originally designated as left and right lower M2 by Xu et al. but if so they are rather anomalous. A more likely designation would be lower M3. PA 504, also from Longgudong, is considered to be a right lower M2. PA 507, collected at Badong, is thought to be a right lower M1. All four molars are distinguished by their large size. They have lengths and breadths that are near or well beyond the upper limits for these dimensions in the Zhoukoudian Locality 1 sample. Another peculiarity of these molars, particularly PA 504 and PA 507, is their low length-breadth index (BL width/MD length x 100) indicating the long and narrow contour of the teeth. The values of this index for PA 504 (88.9) and PA 507 (84.7) are substantially less then the lowest recorded values at Zhoukoudian (89.4 for lower M1 sp. #34, 89.7 for lower M2 sp. # 43). While the absolute dimensions of the Jianshi molars fall beyond the upper range of most samples of early Homo and their length-breadth indices are also uncommonly low for hominids in general, all the above dimensions and index values fall well within the range of variation of fossil orangs as described by Hooijer (1952).

Morphological features of the Jianshi molars that have been used to suggest affinities to H. erectus or gracile australopithecines such as presence of a protoconidal cingulum, development of lingual and distal accessory cusps, disposition and relative proportions of the major cusps, etc. are features also seen in fossil orang- utans. In addition Hooijer (1952) makes note of the fact that in nearly all cases the greatest breadth of lower M1 in his sample of fossil orangs falls across the talonid, while in lower M2 it generally falls across the trigonid. This same pattern can be seen in the Jianshi molars. Hooijer also comments that in his sample of fossil orang molars there is a great amount of variation in the type and extent of crenulation of the occlusal surface with some specimens being of the "coarsely wrinkled type". The crenulation of the Jianshi molars is relatively weak but the development of accessory ridges and grooves observable in the specimens could well fall within Hooijer's latter category. The possibility that some or all of the Jianshi teeth may actually represent a Pleistocene form of Pongo must therefore be given due consideration (see also Gu et al. 1988). In this respect Xu et al. make note of the fact that in the IVPP collection of fossil orang teeth from cave deposits in southern China (Pei 1935, Kalke 1972, Gu et al. 1987, Zhou 1988) there is at least one specimen rather like the Jianshi molars (Gao Jian 1975).

Von Koenigswald also procured a large collection of southern Chinese Pleistocene orang teeth from Chinese drugstores (von Koenigswald 1957). Of the more than 1500 specimens so obtained a number were noticed to differ from the others "in having less wrinkles and a double cusp on the middle of the upper molar" (von Koenigswald 1981). These were given the designation Hemanthropus peii (von Koenigswald 1957) and were regarded by him to show affinities to both Meganthropus as known in Java and Australopithecus as known in south Africa. Their large size clearly distinguished them from H. erectus. Von Koenigswald (1981) notes, moreover, that his fossil orang teeth are "much bigger than those of the modern form, some of them even surpassing the large teeth of the gorilla" (see also Pei 1935). Given Hooijer's observations about the large degree of morphological variation in the collection of fossil orang teeth he studied and the large size of the southern Chinese orangs noted by both von Koenigswald and Pei it seems reasonable to suggest that Hemanthropus can also be accommodated within Pongo.

Also to be considered in the above calculus is the possibility, mentioned above, that large-bodied hominoids other than Pongo and Gigantopithecus may be found in early Quaternary deposits of southern China. As previously discussed, hominoids from the late Miocene site of Lufeng and from early-middle Pliocene sites in the Yuanmou basin, both located in the southern Chinese province of Yunnan, represent a distinct lineage of southern Chinese ape named Lufengpithecus. The affinities of Lufengpithecus are still unclear but most investigators while noting similarities to Pongo have also noted many differences. Lufengpithecus is characterized by extreme sexual dimorphism and thick enameled molars that preserve a late Miocene ape morphology. Some of the large-sized fossil hominoid molars from southern China that lack derived features of modern orangs could possibly be attributable to large males of this genus that persisted into the early Pleistocene.1 Given Hooijer's observations about morphological variability in Pleistocene orang teeth from Java, von Koenigswald's remarks on the large size of orang teeth from southern China and the possibility of the persistence of forms such as Lufengpithecus into the early Pleistocene of southern China, it seems reasonable that the specimens under consideration can best be accommodated under the rubric of Pleistocene "large-bodied hominoid" rather than some form of Asian australopithecine or a widely size varying form of Asian H. erectus.

On the other hand, if all the above specimens are recognized as valid hominids we are left with the possibility of considerable taxonomic diversity amongst hominids from the early Pleistocene of East Asia, with perhaps three distinct lineages represented, i.e. a small-bodied form of early Homo (Longgupo), a large-bodied form which shows phenetic similarities to Australopithecus (Jianshi, "Hemanthropus") and another form that is consistent with attribution to H. erectus (Yuanmou).

Implications of the Re-dating Of Indonesian Hominids

Turning to the situation in Indonesia, the re-dating of strata that have produced hominid remains at Sangiran and Modjokerto to 1.6-1.8 MYA (Swisher et al. 1994), opens up an entirely new Pandora's box of diversity. Some of the specimens dated to the earliest Pleistocene have long been recognized as well-evolved forms of H. erectus. The Indonesian paleoanthropologist Prof. T. Jacob (1981) has in the past allied one of them, Sangiran 17 (Pithecanthropus VIII), with H. erectus soloensis, long thought to be a late occurring archaic human that persisted into the upper Pleistocene (approximately 100-200 KYA) of Java, while some have seen similarities between the Modjokerto juvenile cranium (H. modjokertensis) and H. habilis (Tobias and von Koeningswald 1964, Cronin et al. 1981). Other sites, from what could be equally old stratigraphic horizons, have yielded remains of hyper-robust individuals attributed by some to an australopithecine-like taxon, Meganthropus (Robinson 1953, Franzen 1985, Tyler 1995). In Java, as in China, we have specimens from the same time and place possibly representing three very different grades or clades of hominid.

If All the Above Claims Are Accepted, What Are the Implications for Our Understanding of Human Evolution?

If, for the sake of argument, we accept all of the above evidence as representing valid Plio-Pleistocene Asian hominids, and there seems to be a much greater willingness to do so now than in the recent past, what do we get? Apparently at least three and possibly four distinct hominid lineages in Asia at or near the Plio-Pleistocene boundary: a small, gracile form of early Homo in China; a form, H. modjokertensis, in Java, thought by many until the early 1980s to be conspecific with H. habilis (Cronin et al 1981); a larger, fully evolved form of H. erectus in China and Java; and larger still, a form attributed to a kind of robust australopithecine, both in China and island Southeast Asia. Hominid diversity of this magnitude would be highly reminiscent of that encountered in East Africa at approximately the same time, where Australopithecus boise, H. habilis, H. rudolfensis and H. ergaster are said to occur more or less sympatrically and synchronically (Wood 1992).

What, if accepted, does this apparent diversity say about hominid dispersal patterns? It would seem, for one, that it would not have take much in the way of cultural accouterments for hominids to have made their way from Africa to the far reaches of east Asia and Sundaland. It could be argued, of course, that other higher primates have had little difficulty in dispersing throughout Africa, Europe and Asia, where their remains are found in deposits that date from the early Miocene to the middle Pliocene, so why should early hominids have been any different? Given the success of their progeny, it could be argued that they were very hardy creatures, perfectly capable of meeting whatever environmental challenges they may have encountered on their trek to the Far East. Moreover, it could be argued that various early hominid lineages dispersed soon after their first appearance, suggesting that some later lineages may have diverged in Asia rather than Africa. Thus the possibility has been raised that H. erectus actually evolved in Asia from a species of early Homo, perhaps returning to Africa fully formed and ready to smite its more primitive brethren, the australopithecines. Another line of reasoning, well-liked by proponents of the "Out of Africa" hypothesis, is that H. erectus evolved in Asia and stayed there, part of an evolutionary side-show that had no bearing on the origins of later H. sapiens (Culotta 1995). The prospect of multiple hominid species spread far and wide during the early Quaternary also fits in well with the perspective that sees hominids as no less prone to rapid and frequent speciation than any other mammalian group (Tattersall 1986, Foley 1991).

If we accept the above scenario, the early Quaternary landscape of the orient would have been replete with a dazzling array of hominoids. In addition to the purported hominid-types mentioned above, Plio-Pleistocene Asia was also inhabited by a variety of pongids (sensu stricto), including the immense ape Gigantopithecus, the gorilla-sized fossil orang-utan, and perhaps descendants of the chimpanzee-sized Mio-Pliocene southern Chinese ape Lufengpithecus. Add to this the whole panoply of gibbons known throughout the Pleistocene of southern China and southeast Asia and you get quite an interesting and diverse menagerie. Then again, if we accept the argument that hominids were able to disperse so quickly after their first appearance on the evolutionary scene we may have to cast our nets much further afield when looking for potential human ancestors than previously assumed.

A More Realistic Appraisal

The above embroidery is, however, contingent on the correct dating, identification and interpretation of the specimens considered. And herein lies the rub. As discussed above many of the specimens under consideration are very fragmentary and/or very poorly preserved and subject to varying and at times contradictory interpretations. The dating of other specimens is still subject to doubt. It will therefore be difficult to accept the intriguing picture of hominid diversity painted above, or the prospects for early human ancestry in Asia, until far more substantial discoveries are forthcoming.

Literature Cited

1. Cronin, J.E., Boaz, N.T., Stringer, C.B. and Rak, Y. 1981. Tempo and mode in hominid evolution. Nature 292:113-122.
2. Culotta, E. 1995. Asian hominids grow older. Science 270:1116-1117.
3. Etler, D. A., Crummett, T. L. and Wolpoff, M. N. 1995. Earliest Chinese hominid mandible may be an ape. Submitted.
4. Foley, R. 1991. How many species of hominid should there be? J. Hum. Evol. 20:413-27.
5. Franzen, J. L. 1985. Asian australopithecines? In, Hominid Evolution: Past, Present and Future. Ed. E. Delson, pp. 253-263. New York: Alan R. Liss.
6. Gao Jian (Xu, C., Wang, L. and Han, K.). 1975. Australopithecine teeth associated with Gigantopithecus. Vert. PalAsiat. 13:81-87.
7. Gu, Y., Huang, W., Song, F., Guo, X. & Chen, D. 1988. Two fossil orang-utan teeth from Xiashan Cave with a discussion on some relative problems. In: Guangdong Provincial Museum and the Museum of Qujiang County (ed.), Treatises in Commemoration of the 30th Anniversary of the Discovery of Maba Human Cranium, 65-66. Beijing.
8. Hu, C. Z. 1973. Ape-man teeth from Yuanmou, Yunnan. Act. Geol. Sin. 1:65-71.
9. Huang, W., Ciochon, R., Gu, Y., Larick, R., Fang, Q., Schwarcz, H., Yonge, C., de Vos, J. and Rink, W., et al. 1995. Early Homo and associated artifacts from Asia. Nature 378:275-78.
10. Jacob, T. 1981. Solo Man and Peking Man. In, Homo erectus: Papers in Honor of Davidson Black. Eds., B. A. Signon and J. S. Cybulski. pp. 87-103. Toronto: University of Toronto press.
11. Lu, Q.W. 1991. Book review: Other Origins. The Search for the Great Ape in Human Prehistory. Internat. J. Primatol. 12:537-538.
12. von Koenigswald, G. H. R. 1957. Remarks on Gigantopithecus and other hominoid remains from southern China. Proc. Kon. Nederl. Akad. Wet. (B) 60: 153.
13. Qian, F. 1985. On the age of "Yuanmou Man"-a discussion with Liu Tung- sheng et al. Act. Anthropol. Sin. 4:324-31.
14. Robinson, J.T. 1953. Meganthropus, australopithecines and hominids. Amer. J. Phys. Anthropol. 11:1-38.
15. Swisher, C. C., Curtis, G. H., Jacob, T., Getty, A.G., Suprijo, A. and Widiasmoro. 1994. Age of the earliest known hominids in Java, Indonesia. Science 263:1118-21.
16. Tattersall, I. 1986. Species recognition in human paleontology. J. Hum. Evol. 15:165-175.
17. Tobias, P.V. and von Koeningswald, G. 1964. A comparison between the Olduvai hominines and those of Java, and some implications for hominid phylogeny. Nature 204:515-18.
18. Tyler, D. E. 1995. The current picture of hominid evolution in Java. Act. Anthropol. Sin. 14:313-323.
19. Wood, B. 1992. Origin and evoultion of the genus Homo. Nature 355:783-90.
20. Wood, B. and Turner, A. 1995. Out of Africa and into Asia. Nature 378:239-240.
21. Zhang, Y.Y. 1984. The "Australopithecus" of west Hubei and some early Pleistocene hominids of Indonesia. Act. Anthropol. Sin. 3: 85-92.

An Early Entry of Modern Humans into East Asia?

2010-07-13T21:39:00.001-07:00

Until recently a lack of diagnostic human fossils in China between 30-120,000 ya created a significant lacuna in the record of human evolution in East Asia. The time span in question is crucial as it is during this period that genetic evidence suggests modern humans dispersed out of Africa to eventually populate the rest of the world. The question thus arises - how do the earlier erectine and archaic pre-modern human fossils from China relate to modern human populations there and elsewhere in East Asia?

Traditionally a strong case has been made that there is morphological continuity between earlier human populations and their modern counterparts in China. Thus, the model of “regional continuity” between archaic and modern humans in East Asia is a paradigm that has been widely accepted by those who specialize in Asian paleoanthropology. Until recently genetic evidence tended to contradict this hypothesis. For example, extensive study of Y-chromosome haplotypes in a sample of nearly 100,000 Chinese shows 100% possession of African derived mutations that emerged prior to the African diaspora of modern humans beginning approximately 75-60,000 ya, while extensive MtDNA research in China likewise shows a recent diversification of maternal lineages, precluding any significant contribution of archaic pre-modern paternal Y-chromosome or maternal MtDNA lineages to the modern Chinese gene pool. The MtDNA and Y-chromosome genetic loci, however, are not subject to recombination. Therefore, if any interbreeding between resident archaic Asians and dispersing moderns occurred ancient maternal MtDNA lineages and paternal Y-chromosome lineages could have been lost by pervasive lineage extinction. On the other hand, the possibility of hybridization between archaics and moderns could have led to the introgression of positively selected nuclear genes, which could have become imbedded in the modern human genome by selective sweeps

This possibility has been supported by a number of studies including the analysis of the worldwide distribution of single nucleotide polymorphisms (SNPs) and genetic microsatellites that indicate periodic hybridization and genetic admixture between local archaics and transient moderns in both the eastern Mediterranean and East Asia consistent with a late Pleistocene “Out of Africa” dispersal event and subsequent migration of moderns further east. Based on projected mutation rates and the relevant fossil record, it has been projected that episodes of interbreeding occurred approximately 60,000 years ago in the eastern Mediterranean and about 45,000 years ago in eastern Asia. These dates are consistent with the initial spread of H. sapiens out of Africa and later entry into East Asia.

Interbreeding between closely related species in hybrid zones is commonplace within the higher primates and can be inferred by genetic and population studies, blurring the distinctions between otherwise well defined groups. Other difficulties in defining species result from genetic drift and the resulting populational partitioning seen in wide-ranging species. Recent studies have revealed evidence of such deep population structure for both early modern humans in Africa and Neanderthals in Eurasia complicating the interpretation of extant genetic diversity. Deep population structure is often accompanied with incomplete lineage sorting, complicating the determination of extant species clades. Moreover, the dispersal of modern humans has been complex and may include episodic instances of back migrations and secondary dispersals into adjacent regions. Some deeply rooted haplotype trees for various genetic loci show a distinctive Asian pattern of distribution, suggesting either introgression from extra-African archaic hominan lineages or prior lineage sorting within the dispersing African population with retrogressive extinction of the sampled lineage in their continent of origin. These autosomal lineages have coalescence dates ranging from 1.8 mya to 160 kya indicating that archaic hominan populations in Asia may have undergone multiple periods of genetic drift (differentiation) and gene flow (consolidation), leading to a greater degree of genetic diversity with more deeply rooted genetic lineages than seen in globally distributed modern humans of today. The fact that haplogroup D of the microcephalin gene likely originated in Asia from a lineage separated from modern humans 1.1 mya and introgressed into humans by 37 kya, is consistent with the MtDNA data from the Denisova hominan and lends credibility to the possibility that the Denisova hominan is the result of admixture between modern humans and an East Asian population of archaics that samples the ancient population structure of East Asia.

There are, in addition, counter-indications in the fossil record that suggest an early extra-African dispersal of modern humans into East Asia. For instance, there is unequivocal fossil evidence of modern humans at Skhul and Qafzah in Israel dated to approximately 100,000 ya, tens of thousands of years prior to the genetic dispersal of the ancestor of all living moderns out of Africa, estimated to have occurred between 60-75,000 ya. Consistent with an early dispersal of AMHS out of Africa prior to the ancestors of living populations are a series of modern looking isolated teeth dated in excess of 100,000 years from a number of southern Chinese sites such as Xinglongdong in the Three Gorges Region; Mulanshan, Ganqiandong, Lunadong and Mohuidong in Guangxi; Huanglongdong in Yunxi, Hubei; Lianhuadong in Zhenjiang, Jiangsu; Zhangkoudong in Yiliang and Xiannrendong in Xuchou, Yunnan, the recently excavated partial cranium from Xuchang, Henan in central China dated to between 80-100 kya and the edentulous mandible from Mulanshan dated to 110,000 ya. This recently published East Asian evidence supports an early date for an initial dispersal of AMHS out of Africa around 120,000 ya. This would be an event independent of the later dispersal that gave rise to the spread of modern people in China represented by the human remains from Tianyuan, Hebei dated to ca. 34,000 ya.

While these finds of early modern humans in China are fragmentary they hold out the distinct possibility that there was an early extra-African movement of modern humans out of Africa prior to the dispersal event that gave rise to all living non-African populations. Perhaps this earlier dispersal occurred amongst populations that were still behaviorally pre-modern. If early moderns with a middle Paleolithic culture entered Asia as long ago as 120,000 ya, it raises the possibility that they interbred with the archaics they encountered. This is in full accord with recent comparisons of the nuclear genomes of Neanderthals and modern Eurasians which documents the admixture of archaic genes into the modern human genome in the Near East and East Asia. Behaviorally modern people who arrived somewhat later may have then interbred and ultimately replaced these hybrid populations.

Below is a photo of the recently published; edentulous mandible from Mulanshan, Guangxi dated to 110,000 ya (Jin, C. et al. 2009 The Homo sapiens cave hominin site of Mulan Mountain, Jiangzhou District, Chongzuo, Guangxi with emphasis on its age. Chinese Sci Bull. 54: 3848-3856.)

One, Two, Three, Many Bipeds…Bipedalism is Nothing Special

2010-07-10T22:28:00.000-07:00

Mark my words, a paradigm shift is in the making. Let me be the first to announce it. One hundred years from now (if we survive as a species and continue to advance in our scientific knowledge of the past) paleoanthropologists will take it as a given that hominids (in the traditional sense of the term) were one of a multitude of bipedal ape lineages that emerged in the late Miocene and early Pliocene, 5-8 mya. Parallelisms are rampant in primate evolution. Many now think that the defining upper body features of extant hominoids (including gibbons, orangutans, gorillas, chimpanzees and humans) for suspensory below branch locomotion evolved in parallel. More recently, the knuckle walking terrestrial locomotor pattern of chimpanzees and gorillas has been put forth as an example of parallel evolution. Why should bipedalism be any different? If it has been as successful an adaptation as the fossil record suggests (almost all hominoid fossils found in Africa over the last 6-7 million years have been or are thought to have been bipeds) why shouldn’t bipedalism have evolved independently in several different late Miocene ape lineages? My recent posts regarding Lufengpithecus support this hypothesis. Lufengpithecus, a late Miocene ape from Yunnan in southern China, seems to possess the very same basicranial and femoral adaptations for bipedalism that have been used to assign the likes of Sahelanthropus, Orrorin and Ardipithecus to the Hominidae (s.s.). This raises an interesting conundrum. Either Lufengpithecus is an early Asian hominid (s.s.) or bipedalism was an important constituent part of the locomotor repertoire of more than one late Miocene ape lineage. Given the fact that the non-hominid Oreopithecus also had features consistent with bipedalism it is becoming ever more apparent that there may have been multiple bipedal lineages during the late Miocene and early Pliocene. Perhaps Sahelanthropus, Orrorin and Ardipithecus represent other pre-hominid bipedal lineages as well. Or, as I’ve previously suggested, perhaps adaptations for bipedalism occurred in the LCA of the Great Ape clade (including humans), the African ape clade (including humans), or the chimpanzee/human clade. No matter which of these musings proves true (if any) the possibility that there were one, two, three or many bipedal hominoid lineages during the late Miocene and early Pliocene should be taken seriously.

A Chinese Ape in Our Ancestry? Part 4

2010-07-09T14:53:00.000-07:00

The overall phenetic similarity between the post-canine dentition of Lufengpithecus lufengensis and Ardipithecus ramidus is striking. This is particularly true given the fact that the two are separated by approximately two million years in time and thousands of miles in space. This is not the place to give a detailed morphometric analysis. It will suffice to illustrate the similarities with a few side to side visual comparisons. As is said a picture is worth a thousand words.

Lower post-canine dentition Upper post-canine dentition

Ardipithecus ramidus (left), L. lufengensis (right) Ardipithecus ramidus (left), L. hudienensis (right)

Of course we're dealing with rather nondescript typical Late Miocene thick-enameled hominoid teeth so the similarities are not all that startling. Nevertheless, they are real and pervasive. No wonder that when first described female specimens of Lufengpithecus were mistaken for early hominids (s.s.). The female canines are likewise very similar to homologues in Ardipithecus although the male canines are much larger, indicating a high degree of sexual dimorphism, at odds with what's seen in early hominids (s.s.). It seems to me that the only derived, defining character of hominids (s.s.) that stands the test of time is a significant decrease in the amount of canine sexual dimorphism from what is seen in other Late Miocene apes including Lufengpithecus. As this most likely denotes a profound change in species specific sexual reproductive strategies and socionomic relationships within the primate troop, a reduction in canine sexual dimorphism may be taken as the defining characteristic of hominids (s.s.).

To sum up, recent studies of Lufengpithecus show that it is most likely not a member of the orang clade, or if it is it must be nearly identical to the LCA of the modern great apes and humans. It is much too late in the fossil record to be that ancestor but it could be a relic species that epitomizes it. On the other hand, Lufengpithecus could be an early pre-hominid, phenetically close to the LCA of chimps and humans. Or, as many Chinese paleoanthropologists think Lufengpithecus was a bona fide hominid (s.s.). The latter supposition will be scoffed at by many in the West as just another example of Chinese hubris or wishful thinking. But why not? If Sahelanthropus at 7 mya is accepted as a hominid (s.s.) then the Hominidae must have diverged around the same time that Lufengpithecus hudienensis appears in the fossil record (~ 8 mya). For Lufengpithecus and Sahelanthropus to both be hominids would necessitate a quick dispersal of hominids from their center of origin immediately upon their origination. This is not so far-fetched as earlier and later cross continental hominoid dispersals are known in the fossil record. Where the poorly known Lufengpithecus keiyuanensiss dated to ~ 12 mya fits into all of this is currently unresolved. It is far too early to be a hominid (s.s.) so it may warrant a separate genus. No matter how its phylogenetic relationships are eventually resolved Lufengpithecus demonstrates that the basicranial and femoral traits previously thought to be diagnostic of the Hominidae (s.s.) may not be so. Either Lufengpithecus was a hominid (s.s.) or it demonstrates that the LCA of chimpanzees and humans, the African apes and humans, the modern great apes and humans, or some collateral branches thereof, shared in traits which have been thought to be diagnostic of erect bipedalism. With the recently published description of the Ardipithecus ramidus skeleton, combined with the greater clarity of the species defining traits of Lufengpithecus lufengensis, it now seems clear that bipedalsim may no longer be diagnostic of the Hominidae (s.s.). As with brain size, tool making, culture and any number of other defining traits that were once thought to make us "human" rather than "ape," bipedalism may fall by the wayside and no longer hold sway. The first direct humans ancestors had ape-sized brains, tool-making is commonly seen in the great apes and communal hunting and meat sharing occurs in chimpanzees. Cultural transmission is not unique to humans and now bipedalism may turn out to have been a trait that developed in our pre-hominid (s.s.) ancestors. What then makes us "human?" It may very well have been the development of social moieties that reduced direct male on male competition and regulated access to sexual reproduction.

A Chinese Ape in Our Ancestry? Part 3

2010-07-08T22:16:00.000-07:00

Lufengpithecus has generally been considered a primitive member of the Orangutan clade. The latest dating of the Lufeng site places it between 6.9~6.2 mya, or in the latest stage of the Late Miocene, well within the time span of the Last Common Ancestor (LCA) we share with the chimpanzee. But Lufeng is in South China, a region that had orangutans as recently as a few thousand years ago, and not East Africa, so its been assumed that Lufengpithecus is simply an ancestral orang of sorts. But how orang-like was it? Another hominoid from the Late Miocene of Lufeng, Laccopithecus is gibbon-like in many aspects of its craniofacial anatomy but has been identified as a pliopithecid, based on its dentition, by a number of specialists in hylobatid phylogeny. Pliopithecids are primarily European in distribution, so it would not be anomalous if Lufengpithecus turned out to be an intrusive element in the southeast Asian biozone in which its been found.

If we look at some basic features of the Lufeng cranium we can see that it has a number of plesiomorphic hominoid traits that are also retained in extant pongines. These include arched supraorbital costae rather than a horizontal supraorbital torus, a salient frontal trigone in males and a triangular lower face with anterior teeth (canines and incisors) oriented in a manner similar to those seen in the protohominoid Afropithecus (16-18 mya), which retains a whole suite of primitive catarrhine features. It can be argued, therefore, that the orang-like features seen in Lufengpithecus are primitive retentions that don't necessarily indicate an ancestor-descendant relationship between them.

Afropithecus (left), Lufengpithecus (center), Pongo (right)

On the other hand, Lufengpithecus has a number of traits usually considered characteristic of the African ape/human clade.These include retangularly shaped orbits, a broad interorbital distance, an African sub-nasal morphology with a relatively broad nasoalveolar clivus and double-barreled incisive foramina (rather than the narrow nasoalveolar clivus and slit-like incive foramen seen in orangutans), frontal sinuses, lachrymal fossae, infra-orbital foramina, enamel prism 3B pattern, and a long formation period of incisors, etc. Some of these traits are illustrated below:

A case can be made, as the Chinese editors Xu Qinghua and Lu Qingwu do, that the total morphological package of Lufengpithecus is more like that of an African ape than an Asian ape. Moreover, based on the same criteria used by many paleoanthropologists to identify both Sahelanthropus and Orrorin as a hominid (s.s.), it can be argued that so is Lufengpithecus. This is the position taken by Xu and Lu. My thinking is slightly different. I think that the successive LCA's of the modern great apes, the African apes (including humans), and chimpanzees and humans, all had incipient adaptations for bipedalism that have been recognized as hominid (s.s.) autapomorphies when they are actually hominoid synapomorphies. Its interesting to factor Oreopithecus into this equation since it lived around the same time, in a similar environment and had adaptations consistent with some form of bipedalism, again suggesting that many traits considered to be derived in hominids (s.s.) are actually what should be expected in a variety of Late Miocene hominoids, including the LCA.

Next we'll look at the teeth and jaws of L. lufengensis

A Chinese Ape in Our Ancestry? Part 2

2010-07-08T21:03:00.000-07:00

In an earlier post I reported on the basicranium of Lufengpithecus lufengensis as described in a 2008 monograph. The basicranium illustrated comes from the crushed male cranium of specimen PA 644. There are also complete but crushed basicrania of a juvenile specimen PA 844 (left) and a female specimen PA 677 (right). These can be seen in the following plates, but they haven’t been configured in a fashion to make their traits readily discernible and they haven’t been described in detail, so its very difficult to confirm the placement of the foramen magnum as in PA 644. Nonetheless, there is more than enough morphology present to eventually allow for a computer assisted reconstruction of both specimens.

There is, however, another specimen that comes into play that has not received the attention that is warranted. It is a well-preserved male left proximal femur (PA 1276) that is configured in the 2008 monograph. On first glance it looks remarkably similar to the proximal femur of Orrorin which has been put forth as conclusive evidence for bipedalism and hominid (s.s) status in that taxon. Below is a comparison of the L. lufengensis proximal femur (left) and Orrorin's (right).

Without going into too great detail I will quote from the conclusion reached in the English summary of the 2008 monograph, "the complex contour of the femoral head and neck of the Lufengpithecus femur is similar to those of Australopithecus and early Homo, and differs distinctly from the mushroom shape seen in modern apes." Furthermore, "The position of the fovea capitis of the Lufengpithecus femur is markedly different from that of modern apes." and "In the Lufengpithecus femur...the degree of development of the fovea capitis and its location are similar to those of early and late Australopithecus." In addition, "the degree of development of the intertrochantic crest of the Lufengpithecus femur nears that of the late Australopithecus femur KNM-ER 738." The monograph has much more to say about this femoral specimen, but I hope this cursory introduction leaves the reader with the impression that the Orrorin femur is not nearly as hominid-like as previously stated or, on the other hand, the L. lufengensis femur is equally hominid-like. Coupled with the evidence from the basicranium presented in my previous post Lufengpithecus is looking more and more interesting as a potential protohominid (s.s.). Below are line drawings comparing the Lufengpithecus femur to a number of ape and hominid (s.s.) femora.

Next I'll review a suite of craniofacial traits that show Lufengpithecus to be more African ape-like than Asian ape-like.

Videos on Chinese Paleoanthropology

2010-07-07T22:13:00.000-07:00

CCTV – the acronym for Central China TV - has produced a number of documentaries dealing with paleoanthropological discoveries in China. Their international service has produced English language programs but most are in Chinese only. Links to Chinese paleoanthropological videos are listed after the break.

Homo erectus from Yiyuan, Shandong is hardly known outside of China. Yiyuan is one of half a dozen Homo erectus sites discovered in China since the famous discoveries at the "Peking Man" site of Zhoukoudian:
http://english.cctv.com/program/newfrontiers/20100311/102314.shtml
http://english.cctv.com/program/newfrontiers/20100312/102187.shtml
http://english.cctv.com/program/newfrontiers/20100315/102228.shtml

New excavations and research results at Zhoukoudian:
http://english.cctv.com/program/cultureexpress/20091022/101696.shtml

Two Chinese language documentaries on the history of Peking Man and the Zhoukoudian site, with lots of archival film footage:
http://v.ku6.com/show/iN86YKESx2mVQLMS.html
http://v.ku6.com/show/Ummqe7ln4pdeYEQ4.html
http://v.ku6.com/show/1sOQCEjSXqCktrvU.html

http://www.cabrillo.edu/~detler/Zhoukoudian Part 1.flv
http://www.cabrillo.edu/~detler/Zhoukoudian Part 2.flv

A Chinese language documentary on the H. erectus crania from Yunxian, Hubei, including clips of yours truly discussing their significance:
http://www.cabrillo.edu/~detler/Yunxian video Part 1.flv
http://www.cabrillo.edu/~detler/Yunxian video Part 2a.flv
http://www.cabrillo.edu/~detler/Yunxian video Part 2b.flv
http://www.cabrillo.edu/~detler/Yunxian video Part 2c.flv
http://www.cabrillo.edu/~detler/Yunxian video Part 2d.flv

A news report on the reconstruction of the second Yunxian cranium by a joint Franco-Sino team lead by Li Tianyuan and the DeLumley's:
http://www.cabrillo.edu/~detler/yunxian_whtv.wmv

Early Paleolithic archaeology in the Nihewan Basin, Hebei:
http://bugu.cntv.cn/life/humanities/tianxiadaguan/classpage/video/20091120/100627.shtml
http://v.ku6.com/show/r8BqLUSWqWIcZxtt.html

A beautifully produced Chinese language documentary on the history of paleoanthropological research in China with a focus on the Wushan hominoid from Longgupo, Sichuan:
http://tv.sohu.com/20100126/n269828171.shtml
http://tv.sohu.com/20100126/n269828121.shtml

Two Chinese language documentaries on the Homo erectus site of Yuanmou, Yunnan. Second with Prof. Zhou Guoxing:
http://www.tudou.com/programs/view/6QlKBc2GPwU
http://v.youku.com/v_show/id_XMTM0OTgyMDk2.html

Crazy plan to build monumental "Human Ancestor Worship Altar" in Yunnan commemorating East Asian human ancestry: http://www.tudou.com/programs/view/GNupH0Aqi6c

A Chinese language documentary on the Homo erectus site of Lantian, Shaanxi:
http://v.youku.com/v_show/id_XMTU5ODEzMzY=.html
http://v.youku.com/v_show/id_XMTU5ODIyODA=.html

A Chinese language documentary on the Homo erectus site of Hexian, Anhui:
http://v.youku.com/v_show/id_co00XMTY3MTM1NDg=.html
http://v.youku.com/v_show/id_XMTY3MTM2MjA=.html

A Chinese language documentary on the Nanjing Homo erectus site at Tangshan:
http://video.sina.com.cn/v/b/26577520-1665804467.html

A Chinese language documentary on the archaic cranium and partial human skeleton from Jinniushan in Liaoning:
http://www.cabrillo.edu/~detler/Jinniushan 1.mp4
http://www.cabrillo.edu/~detler/Jinniushan 2.mp4
http://www.cabrillo.edu/~detler/Jinniushan 3.mp4

A Chinese Ape in Our Ancestry?

2010-07-05T18:10:00.000-07:00

As paleoanthropologists home in on the Last Common Ancestor (LCA) of apes and humans, it seems that many have been barking up the wrong tree. Rather than being rather chimp-like, it's turning out that the LCA was perhaps more hominid-like (in the old sense of the word) than previously thought. This has been highlighted by the recently published account of the Ardipithecus ramidus partial skeleton, which at 4.4 mya is considered by many paleoanthropologists to be one of our earliest direct ancestors.

A. ramidus retains a suite of primitive upper body traits and a mix of lower body traits indicative of an incomplete adaptation to bipedalism. According to Tim White et al. Ardi does not show any signs of a knuckle-walking morphology, casting doubt on the long held supposition that its recent ancestor, the LCA of chimps and humans, was a knuckle-walker. White’s team suggests that knuckle-walking evolved in parallel between gorillas and chimpanzees. Based on the results of the Ardipithecus research it can now be hypothesized that the chimp/human LCA was an incipient biped or at least had pre-adaptations that were later exapted for bipedalism. As Oreopithecus bambolii (a Late Miocene ape from Italy with a pelvis and lower limbs that suggest adaptations for bipedality) demonstrates, traits generally associated with bipedalism are found in at least one non-hominid Late Miocene ape lineage. Taking these considerations into account it may well be the case that the hominid-like traits of Ardipithecus, Sahelanthropus and Orrorin (all thought by many to be early pre-Australopithecine human ancestors) are actually what we should expect in the LCA.

Another Late Miocene ape that may shed light on the nature of the LCA is found not in Africa but in Asia. I'm speaking of the "enigmatic" ape Lufengpithecus from Yunnan in southern China. Specimens of Lufengpithecus have been known since the 1970s and were first attributed to Ramapithecus lufengensis and Sivapithecus yunnanensis. At that time ramapithecines were still thought to be basal hominids while sivapithecines were seen as ancestral pongids. This hypothesis was challenged in 1979 with the discovery of GSP 15000, the partial skull of a sivapithecine from the Siwaliks Hills of Pakistan, remarkably orang-like in morphological features. A thorough revaluation of ramapithecine and sivapithecine specimens in the early 1980s led to the realization that Ramapithecus fossils were female sivapithecines and that the sivapithecines included a number of genera broadly ancestral to the modern great apes, including humans. Sivapithecus itself is generally thought to be an early relative of extant orangutans.

Genetic research, combined with an enhanced record of hominid evolution, reinforced the idea that the African apes and humans shared a unique common ancestor to the exclusion of the Asian orangutan and that Chimpanzees and humans were sister lineages. The temporal and geographical placement, ecological setting and physical adaptations of the LCA of chimpanzees and humans have thus become the “holy grail” of paleoanthropology. The time and place of this LCA is equivocal. The time is thought to be between 5-7 mya although some would suggest a more recent age (~ 4 mya) and others an earlier one (~8 mya). The place is generally thought to be the horn of Africa although some would extend the region to include adjacent areas of North and East Africa and perhaps southeastern Europe. The ecological setting and physical nature of the Chimpanzee/human LCA is more controversial. Until the analysis of Ardipithecus was recently published it was generally assumed that the LCA was more chimpanzee-like than not. The partial skeleton of Ardipithecus however shows that the LCA retained a suite of primitive locomotor characters not seen in either of its descendants, holding out the possibility that it was actually more bipedal that previously thought. Hence some 5-7 million year old fossils with seeming adaptations to bipedalism such as Sahelanthropus, Orrorin and Ardipithecus itself may in fact be morphologically representative of the LCA. In my estimation this is indeed the case and the LCA is already known but unrecognized. The Last Common Ancestor is thus in reality the Lost Common Ancestor.

Well, let’s get back to Lufengpithecus. When first described the female Lufengpithecus remains were attributed to Ramapithecus lufengensis and were thought to be ancestral hominids (aka hominins of current usage). This was warranted given the very australopithecine-like appearance of its dentition. Of course we now know that the hominid-like dental traits of R. lufengpithecus, i.e. the relatively short canines, incipiently bicuspid lower premolars, and thick enameled, bunodont molars, are character states commonly seen in late Miocene female apes. The male Lufengpithecus remains were much more pongine-like with tusk like canines, semi-sectorial lower P3s and large, thick-enameled, crenulated molars. Back in 1989 Jay Kelly and I demonstrated that the two sets of teeth were statistically uni-modal and hence represented females and males of a single highly dimorphic species. Nonetheless, the Lufengpithecus teeth, like the dentitions of many late Miocene apes, are characterized by thick molar enamel and have striking similarities to australopithecine homologues.

Two recent monographs, one edited by Xu Qinghua and Lu Qingwu (2008), describing the major discoveries of Lufengpithecus lufengensis in the late 1970s and early 1980s from the Lufeng site in Yunnan, and the other edited by Qi Guoqin and Dong Wei (2004), reviewing hominoid material collected in the Yuanmou basin, go a long way towards clarifying the temporal relationships of the two sites and the morphological characteristics of their fossil hominoids. Lufeng is shown to be 6.2-6.9 million years old and the sites in the Yuanmou basin between 7.2 and 8.2 mya. The Lufeng material is assigned to L. lufengensis and the Yuanmou material to L. hudienensis. I will focus on the 2008 monograph dealing with L. lufengensis as it is much more comprehensive in describing the hominoid fossils collected.

PA 644, the holotype of the L. lufengensis, consists of a nearly complete splanchnocranium (minus the lower jaw) the anterior portion of the neurocranium (frontal bone delimited by the frontal trigone), and a substantial portion of the basicranium.

The specimen, attributed to an adult male, shows an interesting amalgam of features. It has an airorhynchous face, relatively thick supraorbital costae and a salient frontal trigone, all characteristic of extinct and extant Asian pongines (these traits are also seen in the early Miocene protohominoid Afropithecus), combined with rectangular orbital contours, a large incisive canal and the broad interorbital distance seen in African hominines (the latter trait also seen in Afropithecus). It can be argued that most of these traits are plesiomorphic character states to be expected in the ancestral morphotype of the modern great ape/human clade. The concave mid-facial contour is perhaps the single character that is derived in the direction of modern pongines, although this trait may be a pre-pongine derived trait of modern hominoids relative to their protohominoid ancestors. Thus, craniofacially Lufengpithecus, in preserving a suite of ancestral hominoid character states that have been subsequently partitioned between the pongines and hominines, seems to be morphologically close to the LCA of the modern great apes and humans. The specimen under discussion however is far too late in the fossil record to be that common ancestor. It may however represent a relic of the earlier lineage that included it.

Besides the craniofacial features preserved in PA 644 a largely intact but crushed basicranium is also present. It seems to be nearly as well preserved as the recently described basicrania of Ardipithecus ramidus and Sahelanthropus (see illustrations below: left Ardipithecus ramidus, center Sahelanthropus tchadensis, right Lufengpithecus lufengensis).

Until the publication of the Lufengpithecus lufengensis monograph in 2008 there had been no description of the cranial base of the PA 644 cranium. This is unfortunate because much has been made of the basicranial morphology of both Ardipithecus and Sahelanthropus. According to Brunet et al. in Sahelanthropus, “The basicranium has small occipital condyles associated with an apparently large foramen magnum. Despite damage, the foramen magnum seems to be longer than wide, and not like the rounded shape typical of Pan. As in A. ramidus, the basion is intersected by the bicarotid chord; the basion is posterior in large apes and anterior in some of the later hominids.” These basicranial traits are taken to be strong indicators of bipedalism in both Sahelanthropus and Ardipithecus. According to White et al. in Ardipithecus ramidus “The occipidal condyle is small, measuring 16 x 17.5 mm. The anterior border of the foramen magnum (basion) is intersected by a bicarotid chord connecting the centres of right and left carotid foramina, and the endocranial opening of the hypoglossal canal is placed more anteriorly relative to the internal auditory meatus than in great apes. This condition, as in other fossil hominid taxa, reflects a shortened basioccipital component of the cranial base relative to modern African ape crania.” These basicranial traits are taken to represent derived characters shared among all hominids indicative of bipedality (see this review of James Ahern's paper: "Foramen Magnum Position Variation in Pan troglodytes, Plio-Pleistocene Hominids, and Recent Homo sapiens: Implications for Recognizing the Earliest Hominids," by Afarensis).The appearance of the PA 644 male Lufengpithecus cranial base is consistent with these descriptions. The conclusion that must be drawn is that either Lufengpithecus was as well-adapted to bipedalism as both Sahelanthropus and Ardipithecus or the features seen in all three are not indicative of obligatory bipedalism but of facultative bipedalism and that these traits are to be expected in the LCA of the great ape and human lineages.

More to come.

Its time to sink the genus Australopithecus

2010-06-22T18:29:00.000-07:00

With the recent description of the partial skeletons of Ardipithecus ramidus from Aramis and Australopithecus afarensis from Woranso-Mille, both in Ethiopia, a clear distinction can be made between pre-human and fully human adaptations to bipedality. When we include Au. anamensis in the equation, which is assumed by most to be a slightly older and more "primitive" version of Au. afarensis, the separation between Ardipithecus and Australopithecus is reduced to 200 ky, a mere blip on the paleoanthropological radar screen. The morphological distance is, however, far greater in both cranial capacity (less than 400 cc in Ardipithecus vs. more than 400 cc in Australopithecus) and overall locomotor pattern. To go from Ardipithecus to Australopithecus in such a short span of time seems hard to imagine (see previous post). On the other end of the temporal spectrum the recent description of Australopithecus sediba, dated to 1.9 mya from the Republic of South Africa, highlights the difficulty in separating late occurring australpiths from early members of the genus Homo. It thus seems, on the one hand, that adaptationally Australopithecus is much more similar to Homo than it is to Ardipithecus, while on the other hand, it is becoming more and more difficult to separate late occurring Australopithecus from early Homo. The rationale for maintaining the genus Australopithecus appears to be evaporating. It makes more sense to sink Australopithecus into the genus Homo while retaining it as a subgenus to distinguish it from later occurring, increasingly more human-like fossil hominins. For the sake of convenience, and other considerations, I think the genus Homo can be divided into four subgenera H. (Australopithecus), H. (Paranthropus), H. (Pithecanthropus), and H. (Homo). For example, “Lucy” would belong to H. (Australopithecus) afarensis, South African robusts to H. (Paranthropus) robustus, “Java Man” to H.(Pithecanthropus) erectus and “Heidelberg Man” to H. (Homo) heidelbergensis. Each one of these subgenera represents a clearly definable morphotype identifiable by a set of synapomorphies indicating a shared common ancestry as a "species clade" composed of distinct "paleo-demes" as discussed by Howell (1999). Colloquially we can refer to these constructs as australopiths, paranthropes, pithecanthropes, and archaics (i.e. pre-modern humans) vis-à-vis modern humans.

To quote the venerable resource Wikipedia, “in zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic and specific name … However, it is not mandatory, or even customary, when giving the name of a species, to include the subgeneric name.” Thus “Lucy” would commonly be referred to as H. afarensis, etc., etc. This is in partial conformity to the geneticist Morris Goodman’s suggestion that the African Great Apes be sunk into the genus Homo because of their overall genetic similarity to H. sapiens and J. T. Robinson’s suggestion that Au. africanus be revised to H. africanus. Goodman’s view, while biologically correct, seems to be a bit too radical for most people’s taste, while Robinson’s suggestion now appears to have been prescient. In the light of these precedents the sinking of Australopithecus into Homo, as a subgenus, seems eminently reasonable.

Ardipithecus fades into the past

2010-06-21T22:23:00.000-07:00

The long awaited publication of the partial hominin skeleton from Woranso-Mille, Ethiopia (shown on the left) should send shock waves through paleoanthropology. Yohannes Haile-Selassie et al. describe the specimen, which is dated by radiometric and paleomag techniques to 3.58 mya, in the on-line edition of PNAS now available. Older than “Lucy” by nearly 400 ky and slightly younger than the Laetoli footprints, the specimen includes key skeletal elements that clarify the anatomical adaptations for bipedality in early australopith hominins. According to the authors they are surprisingly modern, supporting contributing author Owen Lovejoy’s long-standing argument that A. afarensis had a modern striding gait and had lost functional adaptations for arboreality. At nearly 3.6 mya the Woranso-Mille hominin is less than one million years removed from Ardipithecus ramidus (~4.4 mya), but shows a near modern upper and lower limb morphology. Ar. ramidus on the contrary shows an extremely primitive post-cranial anatomy that is in many ways more Proconsul-like than modern ape-like, with well-developed arboreal adaptations. It would require a very quick evolutionary makeover to account for the necessary transformation of Ar. ramidus into Au. afarensis as described in the paper. Before this publication the degree of bipedalism that the partial skeleton illustrates was thought to be restricted to the genus Homo. If we reject the ancestor/descendant relationship between Ar. ramidus and Au. afarensis, where does that leave Ardipithecus as a hominin? It is most likely that Ar. ramidus represents a relic species, phenetically little removed from the last common ancestor of the African apes and humans. This conclusion thus leaves unanswered the question, from whence came Australopithecus?

International Symposium on Paleoanthropology in Commemoration of the 20th Anniversary of the Discovery of the Skulls of Yunxian Man

2010-06-21T17:40:00.000-07:00

I attended an international conference celebrating the 20th anniversary of the discovery of “Yunxian Man” held in China from June 14-17. “Yunxian Man” is known from two complete crania (skulls without the lower jaw) found and excavated between June 1989 and June 1990 in the central Chinese province of Hubei. It was announced at the conference, held in Yunxian City, that the skulls have been re-dated to nearly 1.0 million years ago by Chinese scientists.

At the Conference I compared the new age attributed to “Yunxian Man” with the 1.0 million year old date given to a previously unknown human mitochondrial DNA (MtDNA) lineage announced earlier this year by German scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig. The team, led by Johannes Krause and Svante Pääbo, sequenced ancient mitochondrial DNA from a finger bone of a hominin found in Denisova Cave in southern Siberia. While the specimen comes from a population that lived about 30,000 to 48,000 years ago in the Altai Mountains in Central Asia a detailed analysis of the Denisova mitochondrial genome shows that it shared a common ancestor with modern humans and Neanderthals about 1.0 million years ago. Other recent research at the same Institute provides evidence that modern and archaic humans (including Neanderthals) had interbred on first contact.

Prof. Li Tianyuan, the principal investigator of “Yunxian Man,” and I gave papers at the Chinese symposium detailing how the Yunxian skulls exhibit a mix of features seen in both Homo erectus and H. heidelbergenis. H. heidelbergenis is thought by many scientists to be the common ancestor of both Neanderthal Man and modern humans. I proposed that given its age and physical features “Yunxian Man” is an ideal candidate for the 1.0 million year old common ancestor of H. heidelbergenis and the Denisova hominin. This would place the origins of H. heidelbergenis in Asia rather than Africa as previously thought.

Dr. Wu Xinzhi, the dean of Chinese paleoanthropologists, who chaired the meeting, gave a paper in which he presented evidence of Neanderthal-like traits in later human fossils from China, suggesting that Neanderthals, known to have lived near Denisova Cave, spread south into China interbreeding with indigenous Chinese hominins. This supports the idea that human evolution has been characterized by a complex web of interactions between multiple incipient human lineages that hybridized with one another on first contact, spurring the evolutionary events that led to the emergence of modern H. sapiens and other hominin species.

In keeping with these new developments I proposed a “Multiple Dispersal” model for human evolution more in keeping with recent genetic evidence than the earlier Multi-regional or Out of Africa Replacement models. In the Multiple Dispersal model humans evolved into distinct species after leaving Africa nearly 2.0 million years ago. Some of these species subsequently spread into adjacent regions hybridizing with the hominins they encountered. The westward dispersal of Yunxian Man’s descendents eventually gave rise to archaic humans in Europe (H. heidelergensis) and Africa (H. rhodesiensis), which then evolved respectively into the Eurasian Neanderthals (H. neanderthalensis) and the African ancestors of modern H. sapiens. New genetic evidence suggests that modern humans then spread out of Africa 60,000 years ago meeting up and hybridizing with Neanderthals in the Near East and the archaic descendents of H. yunxianensis in East Asia.

Other papers presented at the conference discussed evidence for an early appearance of modern H. sapiens in China. Dr. Shen Guanjun, who has re-dated many Chinese hominin sites using advanced radiometric techniques, said that a number of Chinese sites yielding modern human teeth were older than 100,000 years in age, tens of thousands of years before they are supposed to be there according to the Out of Africa theory of modern human origins. In a following paper Dr. Liu Wu showed how these teeth had typical East Asian features still seen in today’s Asian populations. I proposed that this evidence supported the likelihood of an early dispersal of modern humans out of Africa which hybridized with local archaic Chinese. A second wave of moderns coming out of Africa reached China around 45,000 years ago They then mixed with the earlier hybridized Asians giving rise to the Asian populations of today. Similar patterns most likely also occurred in Europe and elsewhere, lending further support to a Multiple Dispersal model for human evolution.

A Multiple Dispersal Hypothesis for Interpreting the Pattern of Hominan Evolution in China

2010-06-11T20:22:00.000-07:00

The Yunxian hominans are represented by two complete crania discovered in 1989 in Yun County (Yunxian), Hubei Province. Although crushed and distorted to varying degrees they are the most complete early middle Pleistocene hominan crania known. They preserve intact the face, cranial vault and cranial base and as such are extremely important materials for assessing the amount of variation in local paleodemes, and regional populations of Pleistocene hominans. They also serve as an invaluable resource for evaluating the amount and character of polytypic variation in archaic hominans. A conference celebrating the 20th anniversary of the discovery of the Yunxian crania will be held in China in early June. I'll be presenting a paper at the conference proposing a multiple dispersal hypothesis for interpreting hominan evolution in China and elsewhere.

This idea was broached in our initial article on the Yunxian hominans that appeared in Nature. In it we concluded,

"The new evidence of fossil hominid variability in east Asia afforded by the Yunxian crania indicates that Middle Pleistocene hominids were highly polytypic and regionally differentiated, perhaps even at the demic level. But the differential distribution of character states associated with H. sapiens in regionally disparate Middle Pleistocene human populations suggests that the events leading to the emergence of modern humans were not restricted to one region of the world alone. In addition, the mix of characters in the Yunxian crania demonstrates that the taxon H. erectus is founded on a set of ancestral hominid traits and regional polymorphisms. It hence has no meaning in a cladistic framework. In light of these considerations we feel that it is best to view all Middle Pleistocene hominids in a broad perspective as an essential part of one evolving lineage in direct ancestry to modern humans."

We still adhere to the basic conclusions reached above which infers that all middle Pleistocene hominans should be recognized as belonging to a single species. In the ensuing years, however, it has become accepted by many that there were multiple hominan lineages throughout the Pleistocene that should be recognized at the species level. Modern evolutionary biology does not require complete cross-species genetic isolation for separate species to be recognized in a closely related species clade. Gene flow via hybrid zones and genetic introgressions between closely related species is well established. Coupled with persuasive evidence for the recent out of Africa hypothesis for modern human origins a number of Pleistocene species of the genus Homo are now recognized. These are generally restricted to hominan lineages in western Eurasia and Africa, representing the ancestors of Neanderthals in Europe and modern humans in Africa. Hence H. ergaster is proposed as a basal, ancestral taxon that gave rise to H. antecessor in the West and H. erectus in the East. H. antecessor in turn gives rise to H. heidelbergensis/H. neanderthalensis in Europe and H. rhodesiensis/H. sapiens in Africa. If the same methodology is applied to the Asian fossil record a whole different set of taxa can be proposed. If this cladistic scheme is accepted the Yunxian hominans seem to play a pivotal role bridging the gap between East and West. Given their early age and geographical placement it is hypothesized that they serve as a good source for later western archaics that eventually gave rise to European Neanderthals and African moderns. The abstract for our paper appears below:

A Multiple Dispersal Hypothesis for Interpreting the Pattern of Hominan Evolution in China

Dennis A. Etler, LI Tianyuan

Abstract: China has historically been a proving ground for alternative hypotheses of hominan evolution. During the mid 20th century its human fossil record was touted as persuasive evidence for a model of genetic continuity across grade transitions, culminating in the emergence of modern humans in regional contexts. More recently, the same record has been posited as evidence for the replacement of regionally dispersed archaic humans by African derived anatomically modern Homo sapiens. There is, however, yet another perspective. It proposes that the evolution of the genus Homo, since the late early Pleistocene approximately 2.0 mya, was characterized by multiple pulses of human dispersal out of Africa, and subsequent reticular evolution of emergent hominan lineages. This latter proposal relies on evidence from the sequencing of modern and ancient MtDNA, the Y-chromosome and the autosomal genome, combined with research into the population genetics and biogeography of a variety of extant primate species, and a recalibration of the human fossil record based on new dates for key specimens. It is hypothesized that these extra-African dispersals, associated with genetic bottlenecks and drift, as well as vicariance events and gene flow between various regional hominan paleo-demes, via hybrid zones, genetic introgressions and selective sweeps; can account for the transitions seen in the hominan fossil record of China and elsewhere. In this scenario an extra-African dispersal is responsible for the initial late early Pleistocene (ca. 2.0 mya) peopling of Eurasia by the transitional “habiline grade” species H. georgicus (part of a species clade including the Dmanisi remains from the Republic of Georgia and, perhaps such far-flung Sundaland paleo-demes as H. palaeojavanicus, H. modjokertensis, and the much later relic species H. floresiensis from the Indonesian island of Flores). Members of this species clade may also be responsible for early middle Pleistocene lithic assemblages in the Nihewan basin of northern China and the as yet poorly documented early middle Pleistocene hominan presence in southern China. This is followed by the early middle Pleistocene (ca. 1.65 mya) Eurasian dispersal of H. ergaster and the subsequent transcontinental radiation of an “erectine grade” species clade, including H. leakeyi in Africa, H. antecessor in Europe, H. erectus in Java, and H. lantianensis in China. At approximately 1.0 mya it is hypothesized that H. lantianensis gave rise to H. pekinensis in northern China and H. yunxianensis in southern China. The back migration of H. yunxianensis to western Eurasia, approximately 600,000 ya, is hypothesized to have led to the vicariance of the archaic species clades H. heidelbergensis/neanderthalensis in Europe and H. rhodesiensis/helmei/sapiens in Africa, replacing H. antecessor and H. leakeyi, respectively. The emergence of archaic (pre-modern) humans, H. mapaensis in South Asia and southern China, and H. daliensis in northern China at approximately 400,000 ya is hypothesized to be the result of in situ rectilinear evolution and gene flow from modernizing archaic populations further west. This is followed by a proposed African dispersal of H. sapiens idultu (AMHs) into the Levant, South Asia and East Asia, commencing approximately 120,000 ya, with the subsequent hybridization with, or replacement of, archaic hominans by anatomically modern but behaviorally pre-modern humans in India and China. Finally the dispersal of behaviorally modern H. sapiens sapiens (BMHs) out of Africa, beginning approximately 60,000 ya, led to the emergence of fully modern Chinese hominans by approximately 35,000 ya. These sequential dispersals, vicariances, and subsequent transitions, cum replacements in the fossil record, can account for the refashioning of the human genome in east Asia along increasingly modern lines, culminating in a demographic shift towards parameters consistent with a recent “out of Africa” hypothesis, while accommodating a certain degree of genetic admixture and morphological continuity throughout the history of the human presence in East Asia.

I'm baaaaaaaaaaack!!!!!!!!!!!!!!!!!

2010-06-11T17:30:00.000-07:00

For all you loyal followers (1), I'm back. I can't rightly recall why I suspended operations in 2006. Probably just felt it was too big a burden with too little a return. But I've since realized that I actually may have a slight presence on the web so maybe the effort is worth while after all. Since then I've had a few narrow escapes with the grim reaper, heart surgery, an automobile accident, kidney failure and a ruptured gall bladder, but I ingratiated myself to the hospital staff and they gave me a reprieve. Better to thank your doctors than thank "god". Anyway, now that I'm back on track and about to leave for China for an "International Conference on The Yunxian Hominids," celebrating the 20th anniversary of their discovery in 1989, I feel that it's an appropriate time to rev things back up.

A lot has gone on in China over the last four years. I'll try to update this site so it can serve as a repository for posts dealing with new developments (and a review of older developments) in the paleoanthropology and paleontology of China and East Asia.

A Silly Creationist Article

2006-09-28T19:50:00.000-07:00

Some of you may be familiar with a website called Playfuls.com. For whatever reason its a prominantly listed byline on Goolge News. The recent announcement of Selam, the 3.3 mya australopithecine child from Dikika, elicited news stories from all major and minor news services as well as many popular scientific magazines such as Scientific American and National Geographic, but the lead story listed by Google News regarding Selam was from the Science and Technology page at Playfuls.com. It therefore, was the first report regarding this important paleoanthropological story seen by literally millions of on-line viewers. And, much to the discredit of Google News, what a doozie of misinfomation and sham anti-scientific, creationist gibberish it was!

Below is a verbatim copy of the account with my appended comments in bold type.

Every television, every Internet radio or news site (including Google News) has been stuffed with fresh details from about 3 million years ago concerning a…skeleton. Which should have been our eldest ancestor.

The specimen, dated to approximately 3.3 mya, is not considered by any knowledgeable commentator to be “our eldest ancestor.” The author should take an elementary Anthropology class at any college or university in which he will find out that there are far older fossils within our direct ancestry.

The bones discovered in Ethiopia are now thought to be the oldest ever discovered, with an estimated age of 3.3 million years. That is 150,000 years before Lucy in Dikika area, North Eastern Ethiopia, Dr. Zeresenay Alemseged of the Max Plank Institute in Leipzig, Germany, said.

No. They are not the oldest ever discovered. Fossils attributed to Australopithecus afarensis from Laetoli in Kenya are dated to approximately 3.7 mya while fossils attributed to Au. anamensis in Kenya are dated to 4.2 mya. Older material attributed to Ardipithecus from Ethiopia is dated between 4.4-5.8 mya.

If you didn’t know this by now, Lucy (her bones to be more exact) was considered until the recent dig from her “natal” country the oldest of OUR ancestors. The scientific community that has been studying the relics from which allegedly we were born says they have now found an older ancestor, which apparently died at the age of three.

Again, wrong. Lucy is no longer considered the “oldest of OUR ancestors” and has not been so considered for over twenty years.

The skeleton was included in the primitive human ancestor category Australopithecus afarensis and Zeresenay Alemseged of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, an Ethiopian paleoanthropologist who led the team that discovered it, said about it that: "This is something you find once in a lifetime."

True. Finding a fossil specimen of this sort is exceedingly rare and a “once in a lifetime” discovery for whomever does so.

Apparently, this relic offers clues about how the line between ape and human got blurred in the past. From the waist down, the skeleton looks like a human's. But her upper body had many apelike features: a small brain, a nose flat like a chimpanzee's and a face long and projecting. Her finger bones were curved and almost as long as a chimp's.

Basically correct. Australopithecines do show a mix of ancestral “ape-like” and derived “human-like” features. That’s why they are considered so important and why they serve as unequivocal evidence for the fact of human evolution.

The discovery was praised by Lucy’s discoverer, Donald Johanson, director of the Institute of Human Origins at Arizona State University. “Clearly, we have a species in transition" and the species "sits at a critical point of human evolution."

A well stated comment by Dr. Johanson.

The first piece of the child was found on December 10, 2000 in Dikika area. Recovering the partial skeleton, however, required intensive searching and sifting over four successive field seasons from 2000-2004, said the leader of the team of paleoanthropologists.

No comment. Simple reiteration of what’s been reported.

Some parts of the skeleton are missing-the pelvis, the lowest part of the back and parts of the limbs-but what is preserved is remarkably complete. The brain case, the lower jaw with most of its teeth, both collar bones, many vertebrae and ribs, the fingers, both kneecaps and the delicate bone that holds open the throat, called the hyoid, are all present.

Should also mention the well-preserved scapulas (shoulder blades).

"One must travel forward in time more than 3 million years, to a Neanderthal infant from Dederiyeh, Syria, to find a comparably complete infant skeleton," anthropologist Bernard Wood of George Washington University wrote in an editorial for Nature.

True.

"We don't often get the opportunity to see a 3 to 4 million-year-old hominid in the course of growing up," Wood said in an interview. "This fossil is a bright beam of light on the problem of human growth and development and how it evolved."

True.

The fossil has been named "Selam", which means peace in Ethiopia's official Amharic language.

"The scientific significance of the finding is multifold, contributing substantially to our understanding of the morphology, body plan, behavior, movement and development patterns of our early ancestors," Dr. Zeresenay said.

"Reconstruction of an entire body of a three-year-old Australopithecus afarensis child would take place after full cleaning and preparation of the fossil," he added.

At least the above passages are all standard reportage that needs no comment in this context. But now comes the "craziness."

But, allow me to express some scientific doubts concerning not only the remains of the so-called human ancestors, but also about the entire evolutionary theory involved in explaining how human kind appeared.

This is where things get totally confused. First off the doubts about to be expressed are anything but scientific, as they are not based on objective evidence but the subjective belief system of the commentator.

First, I do agree that evolution is a certain and palpable fact in every domain of life, as we know it. It has rules that are beyond doubt and can even be seen in action during our life cycle.

OK, so far, a certain concession to a reality based world, but don't hold your breadth.

But these rules are just so primitive to explain the complexity of the human being, as known by the same scientific community. Paleoanthropologists think that at one moment in time, apes separated from their humanoid counterparts and evolved differently.

Aha, human exceptionalism incarnate! But let us not digress. It must first be rebutted that the so-called “rules” of evolution are anything but primitive. Evolutionary processes involve many complex interactions within the genome and between communities of organisms and the ever changing environmental conditions they encounter. Evolutionary biologists are the first to admit that we have much to learn regarding how evolution takes place and that it is not a simple process. All living things on earth have evolved “complexity” of one sort or another and many species of vastly different sorts have adaptations as complex or more complex than those of us humans. We have unique features that distinguish us, but so do all forms of life, a topic that could be elaborated upon ad infinitum.

Moreover, the commentator has a fundamental misunderstanding of what Paleoanthropologists “think”. We do not think that “apes” and “their humanoid counterparts” separated from one another at a specific “moment in time,” that’s just plain silly, as if there was some line drawn in the sand seperating one from the other. The ancestors of our closest living relative among the apes, the chimpanzee, and our ancestors began to gradually diverge from one another about 6 mya. It can be assumed that the divergence between the two lineages was at first virtually imperceptible. It may have taken hundreds of thousands of years before the two lineages became distinct from one another at the species level. Speciation does not occur “overnight” as the commentator presupposes. Now comes the old creationist saw "if humans evolved from apes why are there still apes?"

But this raises some serious questions, among which many of you might find familiar interrogations: why apes evolved so little during the same period in which “humanoid apes” allegedly evolved so dramatically? What triggered such separation (was it the environment, the social interaction of those “special apes” or a conglomerate of factors) and are we ever going to find the famous “missing link” that united the two species?

Firstly, the fossil record shows that living apes have evolved quite a bit from their Miocene ancestors. Human ancestors until about 2 mya were in fact very “ape-like” in most features other than the way they moved around on two legs. Our dramatic evolution towards the modern human condition began millions of years after our lineage split from the last common ancestor we shared with chimps. The old saw of “why are there still apes if we evolved from them?” shows a profound ignorance of how evolution takes place. Some lineages retain many ancestral features, while other lineages evolve new features as they adapt to different conditions. Fish appeared before the land dwelling vertebrates which evolved from them, so why are there any fish left in the world? This is a specious argument, i.e. for the unschooled it has the ring of truth or plausibility but for anyone remotely familiar with modern biology it is totally fallacious. What triggered the divergence of chimp and human ancestors from our shared last common ancestor is a subject of continuing research and debate but that is what science is all about. As for the “missing link” between apes and humans, modern biologists and anthropologists understand that there was no such thing. There was a last common ancestor of chimps and humans that was a unique species unto itself. There were transitional forms between this last common ancestor and the sequence of fossil species leading to modern humans. The idea of a “missing link” between apes and humans is an old discredited idea that few if any serious scientists still hold. The phrase should be discarded. In fact, if you still want to use the term, the human fossil record is actually full of “missing links” between more ancestral and more derived human species.

But what about the “missing link”? Was it a single individual that has “given birth” to a whole new species, whose genome would modify repeatedly in such short time and eventually become us? According to the verified laws of genetics, modifications in a species’ genome take place rather randomly and in order for these modifications to “live” a multitude of favorable factors have to occur to make that species adopt on a large scale the new features (we are talking about a certain “inertia” of a species, which protects it from potentially aberrant “evolutions”).

Again, a complete misunderstanding of evolutionary biology. What the commentator is suggesting is the long discredited “hopeful monster” hypothesis that has not had any adherents for more than half a century. No one suggests that a new species is “born” overnight. That’s just a thinly veiled modified form of creationism. The whole notion is contrary to modern evolutionary thinking. The rest of the comments are directed against this straw man.

One key feature for a genetic modification to resist is to be adaptative. The famous missing link should have found its way better into the world and this should have been the reason for its thriving and evolution. But this also means two things: the interaction with the “former-species” should have been abruptly and bilaterally suppressed, and the ape species must have been way inferior to the apes we know today.

This is a very confused passage. As stated above, there was no “missing link”. There was no sustained interaction between chimp and human ancestors after they began diverging from one another. In fact it was the lack of interaction between the two incipient species that led to their divergence from one another, as they adapted to differing sets of conditions. Speciation is a result of the imposition of barriers between populations that were once united by gene flow. It can be assumed that some geographical barrier may have led to the initial divergence of the chimp and human lineages. The rest of the comments in this paragraph show a profoundly naïve misunderstanding of how species originate and diverge from one another.

Arguments: an interaction between our primitive ancestors and the apes from which they supposedly evolved would have lead to some sort of annihilation between the “new” and the “old” The individuals would wither sexually interact (and since we are discussing about a small minority of humanoid individuals their new features would again fall into oblivion when confronted with the majority’s) or the new “smarter” minority would begin hunting down their ape-relatives for food.

This paragraph is complete gibberish and does not deserve comment.

I have no intention of exhausting the questions or arguments against or in favor of evolutionism in this article. But I have to warn you that evidence points towards where we want them to point. If we want to believe that our grand-grand-grand…father was a monkey, we will search for a proof to sustain our belief. But if we believe in God we already have the proof in front of us, even before we begin our search

Now, the true agenda of all creationists comes to the fore. What he is saying is that no matter what the physical evidence for evolution, including human evolution, may be, I’ll just believe whatever the hell I feel like believing. If I believe in creationism then no amount of argumentation can ever deflect me from that belief.

I honestly dislike considering myself a relative of some funny chimp, although I heard about the performances Sultan had in Kohler’s experiments. And I don’t find a reliable source of explanations for the complexity that surrounds me a partial skeleton which dates back million years ago.

Rampant prejudice and know-nothingism here.

I do have a soul and I do believe in God. I know that he created the Universe and that he created the humans. I dispatch Good from Evil because I am a moral human being, and I also know that I am far from perfection. I have come to know that on course of my evolution, but I don’t compare my evolution to an animal’s.

If only ID creationists were so honest. These articles of faith cannot be argued with, but they have nothing to do with the scientific evidence for human evolution.

The God in which I believe created me as the ultimate purpose of His entire creation and he also gave me the power to protrude His secrets with the wisdom He has endowed me with. He didn’t give that to a monkey. Moreover, he made the monkey and all other animals obey me as their master.

What kind of silly god would waste his time on the likes of us? If we have dominion over all life on earth, we’re doing a damn poor job of it as we’ve nearly driven “the monkey” and many other species to extinction in much of the world.

And no, He did not sacrifice His Son for an ape, nor is His Son a relative to a chimpanzee.

Sorry, I cannot take any of this claptrap seriously.

This is my scientific belief. I call it scientific because I have far better proof of the existence of God than I have for the existence of the famous “missing link” between me and the animal world.

This is not a scientific belief. Your proof of the existence of God is purely subjective. If you do not consider yourself part of the animal kingdom please forego all the medical advances achieved over the last century based on experiments done on animal models of human physiology. In other words, go back to the Middle Ages and live your life accordingly.

Who doesn’t believe me should go to Israel on the day the Resurrection of Jesus is celebrated by the Orthodox Church. He would then witness there how candles in the Holy Tomb kindle without “logical” explanation and their fire, along with the candles’ fire, burns without hurting those who keep their palms above. And how the Patriarch’s beard remains intact although he first enters in contact with the fire of Resurrection.

Irrelevant nonsense.

I DO believe in God but I don’t believe in Australopithecus afarensis.

‘Nuff said. I TOO DO NOT believe in Australopithecus afarensis, I accept the existence of Au. afarensis as a scientific fact, neither do I believe in God nor do I accept “his” existence as a fact, as there is no comparable evidence in support thereof.

Why even bother responding to this idiocy? I actually feel embarassed doing so. But when silliness of this sort gets widely disseminated on the web through a prominent link on the likes of Google News there needs to be some response. So be it.

Update on Forthcoming Posts

2006-08-31T10:42:00.000-07:00

I've been preoccupied with the start of the new semester and other distractions, but plan on a number of new posts in the immediate future. Right now I'm working on an extensive post dealing with the historical geology of China and east Asia in general. There is surprisingly little available on-line relating to this important topic, which is necessary background for understanding the natural history and evolutionary biology of China. Nevertheless, I've been able to compile a fairly comprehensive overview relating to this subject matter.

I'll also be posting on recent articles concerning the relationship of Neanderthals to modern humans based on both archeological and genetic data, and further research regarding the status of the Flores hominid.

More on the Pre-Cambrian Fossils of China

2006-08-13T19:13:00.000-07:00

In my previous post I introduced readers to the pre-Cambrian fossil record of China. The Doushantuo Formation has garnered most attention, but there are other notable Ediacaran sequences in South China. These were the subject of a recent conference entitled: The Cryogenian and Ediacaran of South China: Ice Ages, Animal Embryos, Acritarchs, and Algae, held from June 6-16, 2006 in Beijing. Pre-Congress excursions visited major Neoproterozoic sites throughout South China. The following excerpts from the Congress program gives a feel for these exciting discoveries:

The Neoproterozoic is emerging as one of the focuses in the study of Earth system history. Recent progress in the study of Cryogenian and Ediacaran successions of South China has significantly expanded our knowledge about Neoproterozoic Earth system history. For example, the discovery of animal embryo and macroalgal fossils in the Doushantuo Formation and unusually preserved Ediacara fossils in the Dengying Formation provides key paleontological evidence for the evolution of multicellular eukaryotes. Recently acquired high-resolution radiometric ages from Cryogenian-Ediacaran successions of South China place critical constraints on the pace of early multicellular evolution. In addition, the occurrence of multiple Cryogenian glacial deposits and diverse Ediacaran acritarchs will help to clarify the global picture of Neoproterozoic climate change and biostratigraphic correlation.

Pre-Cambrian acanthomorph (spiney bodied) acritarch from Wang'an Doushantuo

The pre-Congress excursions included Doushantuo phosphatized animal embryos and algae at Weng’an, Doushantuo acritarchs and macroalgae in the Yangtze Gorges area, and Dengying Ediacara fossils in the Yangtze Gorges area. As the program states:

The Ediacaran Doushantuo Formation represents ~80 million years of geologic history immediately following the Marinoan glaciation. The Doushantuo Formation at Weng’an begins with a ~8-m-thick cap dolostone, followed by two phosphorite intervals that are separated by what appears to be an exposure surface. The upper phosphorite interval contains cellularly preserved multicellular algae, many of which can be interpreted as florideophyte red algae, perhaps related to coralline reds. Additionally, the upper phosphorite also yields several forms of acanthomorphic (spiney bodied, ed.) acritarchs, some of which also occur in the Doushantuo Formation in the Yangtze Gorges area. But what makes the Doushantuo Formation an internationally known stratigraphic unit are the exquisitely preserved animal embryos and other possible micrometazoans.

Branched tubular fossils preserved in Doushantuo phosphorites.
Image credit: Virginia Tech

The overlying Dengying Formation consists of thick-bedded peritidal dolostones and finely laminated subtidal limestones. Laminated limestones of the middle Dengying Formation contains vendotaenids (sheathed bacteria?, ed.), horizontal trace fossils, and three-dimensionally preserved Ediacara fossils. The tubular fossil Sinotubulites also occurs in the middle and upper Dengying Formation. The Dengying Formation is overlain by earliest Cambrian phosphorite, chert, and carbonate that contain small shelly fossils and Michrystridium-like acritarchs.

The participants will also have an opportunity to look at acritarchs and macroalgal fossils of the Doushantuo Formation, as well as tubular fossils, trace fossils, vendotaenids, and Ediacara fossils in the Dengying Formation.

Dengying vendobionts

Macroscopic fossils from the Dengying Formation were recently described by Xiao et al.:

Ediacara fossils are among the oldest known macroscopic andcomplex life forms. Their bodyplan, ecology, and phylogeneticaffinities have been controversial. On the basis of taphonomicobservations, Seilacher [Seilacher, A. (1989) Lethaia 22, 229–239]proposed that the core elements of the Ediacara biota, the vendobionts,were constructed with serially or fractally arranged quiltsor tube-like units. However, anatomy of quilt walls has beenrarely reported, because most Ediacara fossils are preservedas casts and molds in siliciclastic rocks with inadequate morphologicalresolution. Here, we report an Ediacara form, uniquely preservedin situ and in three dimensions with its organic walls castby early diagenetic calcite, from bituminous limestone of the551- to 542-mega-annum Dengying Formation of South China. Despitediagenetic tampering, serial sections show that the Dengyingform consists of biserially arranged, tube-like quilts, eachwith two vertical side walls, a floor, a roof, and an open distalend. Three-dimensional morphological complexity of the Dengyingform excludes a microbial interpretation but is broadly consistentwith vendobionts. Unlike classic frondose vendobionts sensuSeilacher, however, the Dengying form probably lacked a smoothmargin and had distally open quilts. It probably lived procumbentlyat or near the water–sediment interface and shows evidencefor substrate utilization. Despite its uncertain phylogeny,ontogeny, and functional biology, the Dengying form adds toEdiacaran biodiversity, places key constraints on the ecologyand extinction of Ediacara organisms, and points to the needto explore an alternative taphonomic window for Ediacara biology.

Early Cambrian vendobiont Stromatoveris

The vendobionts referred to above are frond-like life forms that were a major constituent of global Ediacaran biotas and appear to be among earth's earliest animals. Their relationship to Cambrian taxa has long been controversial, but the recent description of well preserved early Cambrian specimens from China, reviewed at Pharyngula, point to the possibility that they represent basal Ctenophores (comb jellies). If this analysis is upheld, it would be one of the first confirmations of an extant animal phylum having pre-Cambrian roots.

Phosphatized Pre-Cambrian Embryos of China

2006-08-13T10:36:00.000-07:00

China is justifiably reknowned for remarkably preserved Cambrian fossils from the Chengjiang Lagerstätte that have been discussed here previously. Perhaps of equal significance are microscopic fossils recovered from the earlier pre-Cambrian Doushantuo Lagerstätte in Guizhou province to the northwest.

The Doushantuo Formation is dated between 590-565 mya. This is a period after the worldwide glaciation of "Snowball Earth" fame and before the onset of the Cambrian. It is known biochronologically as the Ediacaran and is characterized by enigmatic fossils that show only tentative links to later Cambrian phyla. Other Ediacaran fossils are idiosyncratic and perhaps did not survive in later biotas.

This post will summarize recent research on microscopic embryos from the Doushantuo Formation that preserve remarkable morphologic detail, both externally and internally. PZ Myers at Pharyngula has a number of posts regarding this material and I will defer to his expertise in discussing these finds. His first post simply introduces these microfossils and the fact that they actually are what they are said be be, unbelievably well-preserved microscopic fossil embryos from 570 mya! Research up to that point was merely able to describe the external structure of the embryos, including their stage of division, and other phenetic differences between them, suggesting that they represented a variety of life forms. What the adult organisms were like is still in large measure unknown, although some were, and still are, thought to be early bilaterian animals. This link gives a synopsis of the diversity of animaforms tentatively identified with the Doushantou phospherites.

The second post at Pharyngula discusses recent work that helps elucidate exactly under what circumstances embryos of these sorts can be preserved. The research also explains why there seems to be differential survival of these organisms at certain prefered stages of development. The third post discusses the developmental biology of these early embryos and how it reflects a type of asymmetry seen in relatively sophisticated metazoan animals.

The final post is of greatest significance as it reports on recently published descriptions of the internal structure of similarly preserved embryos from the Lower Cambrian Kuanchuanpu Formation, in Shaanxi Province, China. The researchers used an advanced imaging technique called synchrotron-radiation X-ray tomographic microscopy (SRXTM) that allows for the unprecedented non-invasive analysis of the previously indeterminate submicrometre internal structure of phosphatized embryos.

The scalidophoran Markuelia from the Cambrian of China and Siberia.

The recent study is concerned with early Cambrian fossil embryos assigned to the genus Markuelia, which turns out to be a stem Scalidophoran, a group of vermiform animals including the priapulid "penis worms". Although the article in the latest issue of Nature does not report on similar phosphatized specimens from the Ediacaran Doushantuo Formation referred to above, it does state that:

... together with evidence from comparative taphonomy, the case is now very strong for rejecting claims of anthozoan planula larvae, hydrozoan and bilaterian gastrulae, as well as minute adult bilaterians from the Ediacaran Doushantuo phosphorites.

This is an important statement as it was thought by many that certain specimens from Doushantuo assigned to a new genus and species Vernanimalcula guizhouena, were in fact the earliest bilaterian in the fossil record. The results of this latest study apparently place these earlier claims in doubt.

Vernanimalcula guizhouena , purported to be the earliest bilaterian fossil may need to be re-evaluated based on research results using synchrotron-radiation X-ray tomographic microscopy (SRXTM)

It will definately be interesting when this new technique is applied to the Doushantuo embryos.

Update on Chinese Paleontology

2006-08-13T07:47:00.000-07:00

In keeping with this blog's focus on Chinese paleontology here's a link to a brief review of a Cretaceous lamprey from The Lancelet. Once again the Chinese fossil record provides new insights into the course of evolution across the phylogenetic spectrum. The task of chronicling the prehistory and natural history of China is an immense challenge. Over the last few decades paleontological research in China has burgeoned and has added crucial knowledge about the evolutionary history of diverse lineages. Access to this vast array of resources has also expanded exponentially as Chinese and foreign paleontologists have entered into mutually beneficial collaborations. There has, however, not been a thorough going popular review of Chinese prehistory since the publication of J. Gunnar Andersson's classic work on the natural history of China, Children of the Yellow Earth, in 1934.

As I continue to document the fossil record of China on the web with original contributions and links to other blogs, I will periodically publish indices of posts pertaining to particular aspects of Chinese paleontology arranged in chronological order. This will ultimately serve as a scafolding for a comprehensive overview of Chinese natural history.

Chronological index of posts dealing the non-primate fossil record of China:

Early Cambrian Echinoderms of China

Early Chinese Fish-like Vertebrates and Pre-vertebrates

The Chinese Evidence for the Evolutionary Origin of Fish

Origins of Lobe-finned Fish

Panda's on the Mend

Upcoming posts will deal with pre-Cambrian phosphatized embryos, Mesozoic mammals, fossil birds, and Angiosperm origins.

A Species Odyssey: A New Form of Scientific Creationism

2006-08-08T23:47:00.000-07:00

Happened to see a two part series on the Science Channel recently called "A Species Odyssey." It attempts to portray the course of human evolution from the earliest purported "hominids" such as "Toumai" and "Orrorin" through to the demise of the Neanderthals and the emergence of modern humans. It is done in a dramatic, narrative style using state of the art animatronics to depict proto-human ancestors and various extinct mammals, and actors with fanciful make-up to simulate how more human-like ancestors may have appeared.

Although the series tries to present the saga of human evolution from a science-based perspective, the science behind it is, unfortunately, all wrong. I was astonished by the license the producers took with the known fossil record.

The opening scenes focus on a troop of proto-hominids, called alternatively either monkeys or apes, who are faced with an increasingly desiccated east African environment, leading to the retreat of their forested refugia and the spread of more foreboding savannah grasslands. In response, individual apes meet the challenge by standing upright and taking the first bipedal steps. This is presented in an episodic fashion leaving the impression that evolution proceeds by quantum leaps and willful intent. In point of fact, the so-called "savannah hypothesis" of bipedalism has been abandoned by nearly all researchers over the last twenty years. It is now widely accepted that bipedalism emerged in the forests not out on the savannah. The shift to an open grasslands adaptation occurred millions of years later with the advent of the genus Homo.

In this same sequence the first "hominid" is depicted as some sort of "hopeful monster," born to a pair of retrograde apes, sort of like the baby Jesus born to redeem a bestial past. This sequence sets the almost Biblical tone of the next two hours and is as false a notion as any creationist screed concerning human origins that I've ever encountered. In these videos natural selection and evolutionary adaptations just simply happen sui generis. Confront an ill-adapted vulnerable hominid with an environmental challenge, give it the will to survive and presto the new physical or behavioral trait appears, deus ex machina, almost instantaneously. This series and many other popular accounts of human evolution and evolution in general seem to have an inherent tendency to see evolution in volitional and teleological terms. The bad science that this projects and the naive and corrupted version of evolution thus presented become grist for the mill of ID creationists who can use these mischaracterizations of evolutionary theory to validate their own preconceptions and misrepresentations of what evolutionary biology is all about.

This really becomes an unintended form of scientific creationism cast in a secular mold. There is a mythic, almost otherworldly aura surrounding the emergence of various human adaptations throughout the videos. These are none other than scriptural-like recountings of key human innovations, more or less akin to culture hero creation stories found in nearly all human societies. It may make for good or bad theater but not science, and to my mind does a grave disservice to developing a true understanding of the evolutionary process.

In addition to this fundamental misconception of how evolution actually takes place, the series is replete with plain and simple factual errors. One glaring mistake is to unequivocally state that two species of australopithecine, Austalopithecus afarensis and Australopithecus anamensis co-existed and were competitors. This is simply not true, "anamensis" preceded "afarensis" in the fossil record and most anthropologists see it as the latter's direct ancestor. The purported behavioral differences between these two species shown in the video are without any foundation and totally made up out of whole cloth.

I could go on and on about all the factual errors and mistakes made in this production. Not only do they give a distorted picture of human evolution, but they also play into the hands of critics of human evolutionary research as they perpetuate false claims and notions that become straw men for creationists to attack.

One major theme throughout the series is the idea that there were primal conflicts between different species of prehuman. These species however are portrayed more or less as rival gangs along the lines of Canaanites versus Isrealites. There is no understanding of the biological species concept and the various species of hominid are shown interbreeding at will.

An encounter between Neanderthals and a modern human female

The reverential and naive narrative comes across as almost religious in tone, as if the producers were consciously trying to create a new secular version of Genesis. Moreover, the depiction of human ancestors also leaves me cold. Although some of the graphics are well done, the way early humans are shown moving about their environs is very stilted and unrealistic.

In sum, much of this series is totally fabricated and only vaguely reflective of what we really know about human evolution. In my opinion it does much more harm than good. A dramatic series of this sort could be done in a truly scientific manner that is consistent with what we really know, rather than in the bowdlerized fashion given here.

More on Euarchontans

2006-08-06T15:33:00.000-07:00

A recent post here at Sinanthropus discusses the relationship of primates to other mammals within a supraordinal clade called Euarchontaglires and their possible Asian origins. Euarchontaglires consists of two closely related groups: Euarchonta, including the mammalian orders Primates, Dermoptera (flying lemurs or colugos) and Scandentia (tree shrews), and Glires, including Rodentia and Lagomorpha (rabbits, hares and pikas). Until recently bats (Chiroptera) were usually included with the primates, flying lemurs and tree shrews in a group called Archonta. With the realization that bats are not closely related to other archontans the core archontans have been reformulated as euarchontans (i.e. true archontans).

Relationships within the supraordinal mammalian clade Euarchontaglires

Darren Naish over at Tetrapod Zoology has a post on the controversy surrounding the suggestion that "flying foxes" or fruit bats are distinct from other bats (microchiropterans) and are actually close relatives of primates and other euarchontans. These megachiropterans or megabats are an interesting group that for a brief period in the late 1980s were thought by some to be so-called "flying primates." As Darren shows this view is no longer favored. Megabats are widely distributed throughout the equatorial latitudes of Southeast Asia, Australasia and Africa, as one would expect given their volent adaptation. While not apparently closely related to euarchontans it is interesting that megabats share the same biogeographic zone as the "flying lemur" and the tree shrew, along with the prosimian tarsier in insular southeast Asia, as well as a suite of neurological features with primates, a neat example of evolutionary convergence if there ever was one.

Rethinking the Role of Pliopithecids in Hominoid Evolution

2006-08-05T19:39:00.000-07:00

The pliopithecids are some of the most enigmatic fossil primates, long thought to be gibbon ancestors. They boast, however, a series of primitive dental, cranial and post-cranial features that have led many to doubt their earlier assumed hominoid affinities and ancestral gibbon status. Some go so far as to suggest that they predate the emergence of the catarrhine crown group and are a continuation of an ancestral anthropoid clade that evolved convergently with modern catarrhines.

Epipliopithecus vindobonensis

On the other hand, relatively complete cranial remains attributed to pliopithecids in both Europe (Epipliopithecus vindobonensis) and China (Laccopithecus robustus) bear an uncanny resemblance to modern gibbons. Can it be that pliopithecids have been given a bad rap? I will argue in this post that regardless of their primitive morphological features the place of pliopithecids in hominoid phylogeny should be reconsidered based primarily on biogeographic and biochronologic grounds.

Modern gibbon

For instance, molecular studies indicate that the last common ancestor (LCA) of living hominoids, including the lesser and greater apes may have existed as recently as 15 mya. This date is consistent with a 6 million year old molecular age for the chimpanzee/human LCA and a 12 million year old molecular age for the LCA of the Asian orangutan and the African apes and humans. These dates are in accord with the fossil record which has protohominid ancestors of the australopitecines such as Sahelanthropus and Orrorin appearing 6-7 mya, orangutan-like Asian apes such as Sivapithecus emerging ~ 12 mya, and gorilla-like European ancestors of African apes such as Ouranopithecus appearing slightly later (see my previous posts on homind origins here and here). It can, therefore, be legitimately argued that ancestral gibbons should occur in the fossil record around 15 mya.

From Stauffer et al. 2001

As argued previously there is what might be called a phylogenetic node of approximately 1 to 2 million years duration that can be hypothesized to surround any given primate LCA. That is to say, it should be virtually impossible to distinguish the immediate predecessor and the immediate successors of an LCA from the LCA itself, particularly when dealing with a fragmentary fossil record dominated by extremely liable dental remains. Factor into this picture the potential for homoplasy amongst primates (i.e the frequency of parallelisms and convergences between primate lineages) and we get an extremely complex evolutionary matrix.

It can be argued, for instance, that the last common ancestor of the living hominoids may have retained a suite of primitive features lost in parallel by its living descendants. It can also be argued that many traits thought to be shared derived features of living hominoid taxa, such as a suspensory locomotor adaptation, likewise evolved in parallel. As regards extant hylobatids (i.e. the living gibbons and siamangs) it can be further argued that some of their uniquely derived features, such as their adaptation for extreme brachiation abilities and lack of body-size and canine-size sexual dimorphism evolved relatively recently and should not characterize stem hylobatids (that is hylobatid ancestors occurring prior to the LCA of living gibbons and siamangs which arguably lived relatively recently within the last 3-4 million years).

With all these caveats in mind how then can the hominoid LCA be recognized in the fossil record? First off, it should have all the primitive features retained by the living hylobatids vis-à-vis the great apes and humans, such as a fenestrated palate. Secondly, its retention of other primitive features, lost in all living hominoids, should not preclude it from being the LCA or close to it. Thirdly, the appearance of features seen in some hominoids but lost or transformed in hylobatids should also be expected (i.e. ancestral gibbons may not have been suspensory brachiators and they were most assuredly highly sexually dimorphic). Finally, and perhaps most importantly, recognition of secular temporal trends leading from a primitive ancestor to more and more derived descendants showing an increasing accretion of gibbon-like features through time, can serve to link highly derived extant hylobatids with primitive ancestors in the fossil record.

Let’s illustrate a possible interpretation of pliopithecids as hominoid cum hylobatid ancestors in light of the above considerations. Firstly, most researchers discount pliopithecids as hominoid ancestors because they possess a suite of pre-catarrhine-like features seen in both prosimian and platyrrhine primates, but lacking in living and extinct old world monkeys and apes. Pliopithecids are also distinguished by possession of uniquely derived features not seen in other anthropoids, in particular the so-call pliopithecine triangle on the occlusal surface of their lower molars. Finally, those features that they share with modern gibbons are said to be either primitive retentions or homoplasies of little or no phylogenetic significance. These are all powerful arguments against the hominoid affinities of pliopithecids.

But let’s look at these data through the prism of secular evolutionary trends amongst pliopithecids and hylobatids. The earliest and most primitive pliopithecids are now known from Asia. In particular, the primate fossil taxa Dionysopithecus and Platodontopithecus from the early Miocene site of Sihong in Jiangsu, China discussed in my last post, are now widely regarded as the base of the pliopithecid adaptive radiation. Slightly later, the classic pliopithecids of Europe make their first appearance. The apparent Asian origin of pliopithecids is in keeping with the previously discussed possibility that the primates themselves had Asian origins and the evidence for the Asian origins of the anthropoids per se, to be discussed in a future post.

This is where biogeographic and biochronologic considerations come into play. Both gibbons and orangutans are found exclusively in Asia. Molecular data place the LCA of living hominoids between 15-17 mya. It seems logical then that the hominoid LCA should be found in Asia between 15-17 mya and, lo and behold, there are candidates in the guise of Dionysopithecus and Platodontopithecus. But isn’t it a stretch to argue that these scrappy specimens are close to the hominoid LCA when Africa is replete with abundant protocatarrhines and protohominoids from the earliest Miocene, preceding the Sihong material by millions of years? According to the argument presented here, the African finds may merely be fortuitous and could represent either an ultimate source for the Asian LCA of the hominoids or collateral protocatarrhines that dispersed earlier from Asia to Africa and eventually went extinct without issue.

Let’s follow this line of argumentation a bit further. It is now generally agreed upon that the early pliopithecids, with a wealth of primitive features, are followed by more derived pliopithecids from the middle and late Miocene, placed in a subfamily called the Crouzeliinae. Most of the features distinguishing crouzeliines from pliopithecines (the earlier subfamily of pliopithecids) relate to minute dental features and will not be discussed herein. Crouzeliines, however, tend to shown a decrease in some typical pliopithecid features such as degree of expression of the pliopithecine triangle and an increase in post-cranial features relating to a suspensory locomotor adaptation, such as increased curvature of the phalanges.

The most recent member of the Crouzeliinae is Laccopithecus robustus from the late Miocene (~ 7 mya) Chinese site of Lufeng in the southern province of Yunnan.

Laccopithecus robustus

Laccopithecus is one of the best represented plioipithecids. As David Begun, an authority on European pliopithecids states:

Laccopithecus robustus is known from a rich sample of about 90 specimens, including a partial cranium with a well-preserved face and palate, as well as a number of more fragmentary jaws, associated dentitions, isolated teeth and a proximal phalanx (Pan, 1998) ... Laccopithecus robustus is a medium-sized primitive catarrhine ... Females are close in molar size to siamangs, whereas males are somewhat larger ... There are no pliopithecine triangles on any of the lower molars and the buccal cingula are minimally developed ... Two damaged mandibular symphyses suggest that the anterior part of the mandible was robust with well-developed transverse tori while the posterior portion appears to have been relatively gracile in transverse dimensions ... The male upper canine is very large and strongly bilaterally compressed. All three upper anterior teeth in fact closely resemble their homologues in hylobatids, though this is not the case for the lower incisors, which are lower-crowned and broader in hylobatids. Another important distinction from hylobatids is the presence of sexual dimorphism in canine morphology, as in nearly all other anthropoids ... The cranium of L. robustus is badly damaged, as is the case for most specimens from Lufeng. The palate is narrow anteriorly, as in Epipliopithecus and it appears to have been fenestrated. As in Epipliopithecus, Anapithecus and Hylobates, the nasal aperture is tall but small and narrow overall, with a narrow base and an apex that reaches above the lower level of the orbits ... Finally, the single proximal phalanx of Laccopithecus is long and curved, with strong muscle markings suggestive of suspensory positional behavior (Meldrum & Pan, 1988).

The above is an abridged description highlighting certain secular trends relating features characteristic of primitive pliopithecids to features reminiscent of later hylobatids. What we see is the retention of primitive features (fenestrated palate) only seen in hylobatids amongst living hominoids, the loss of a derived feature associated with earlier pliopithecids (the pliopithecine triangle), the presence of a primitive character (canine and size sexual dimorphism) retained in the great apes but lost in extant hylobatids, and the enhancement of adaptations for suspensory movement in the trees.

Although still rather sketchy, an argument can be framed that the pliopithecids are the Asian root of the hominoid radiation and their Asian members represent a processional lineage leading from a Dionysopithecus/Platodontopithecus-like ancestor through the more advanced crouzeliine Laccopithecus to the modern gibbons and siamang of southeast Asia. Laccopithecus, which is in the right place and at the right time, thus becomes a crucial link between the pliopithecids and later hylobatids.

Of Rock Rats and Drunken Apes

2006-08-05T09:45:00.000-07:00

The Laotian Rock Rat (Laonastes aenigmamus) was first described scientifically in April 2005 and identified as a member of an entirely new family of mammals.

Reconstruction of Laonestes

It gained international attention again on March 10, 2006 when scientists published a paper in Science magazine re-identifying the animal as a member of the Diatomyidae, a family of rodents that had been previously thought extinct. Laonastes is thus a “relic species” or "living fossil" whose last known relatives lived 11 million years ago.

As Mary Dawson and Chris Beard, paleontologists at the Carnegie Museum of Natural History, stated:

Diatomyids are rodents that lived during the middle Tertiary (34 - 11 million years ago) in southern Asia, central China, and Japan. They were rodents of medium size and highly characteristic molar teeth and jaw structure. Three known fossil genera- Fallomus, Diatomys, and Willmus- are recognized in the Diatomyidae. Some fossils are known from isolated teeth and jaw fragments. Others such as Diatomys are better known and more widely distributed.

According to Wikipedia:

The family has a nearly continuous fossil range from Early Oligocene fossils of Fallomus from the Lower Chitarwata Formation (32.5 Ma; Bugti Member, Bugti Hills; Flynn et al., 1986) in Balochistan, Pakistan to Middle/Late Miocene fossils (11 Ma) of Diatomys in east and southeast Asia.

Laonastes is in fact so similar to Diatomys that details of the morphology of the former were predicted by reference to the latter. Accordingly, when Chinese paleontologist Li Chuankui, who originally described the genus, recently discovered a new species of Diatomys it showed a remarkable degree of similarity in its skull, tooth and jaw structures to the living Laonastes.

Given the fact that Laonastes and Diatomys are so similar in morphology, a study of the living environment of the Laotian Rock Rat may help us better understand the paleoevironment of other diatomyids. In addition, by better understanding their paleoenvironment, the biogeographic distribution of diatomyids in the fossil record can help us better understand the dispersal patterns of other associated sympatric species.

The type species of the Diatomyidae, Diatomys shantungensis, was first described in 1974 by Prof Li Chuankui from the well known early Miocene site of Shanwang in Shandong province, China. Shanwang is of special interest because of the prolific nature of its fauna and flora and the unprecedented state of preservation of its fossils, found in a very fine-grained diatomitic lacustrine depositional environment. The site has thus become the type site for the Chinese early Miocene. As we shall see, this is of particular interest to students of primate evolution.

Remarkable state of preservation of Diatomys shantungensis from diatomitic deposits at Shandong, China

Sihong, in Jiangsu province, is another important fossil bearing site. First found in the 1950s it was initially thought to contain an early Pleistocene fauna. Reevaluation of the original specimens and additional discoveries led to recognition that the site was contemporary with Shanwang and represented a similar paleoecology. In this regard it is interesting to note that Diatomys shantungensis is known from both sites.

Though relatively unheralded, Sihong is an extremely important site from a paleoprimatological perspective. Geochronologically both Shanwang and Sihong are now recognized to be of early Miocene provenience, ~ 17 mya. Given the abundance of fossil mammals recovered at Shanwang it was always a dream of Chinese paleontologists that fossil primates, in particular fossl hominoids, might eventually be found there. Alas, to this date no primate material has been forthcoming from Shanwang. The more southerly, contemporaneous Sihong site has, however, more than fulfilled the hopes of not only Chinese paleontologists, but paleontologists worldwide, with the recovery of a significant primate fauna, including what are arguably early protohominoids similar to the proconsuline protoapes of East Africa and/or the proto-gibbon-like pliopithecids of Miocene Europe.

Lower molars of Platodontopithecus from the early Miocene site of Sihong, Jiangsu, China (from Harrison and Gu, 1999)

The placement of protoapes in East Asia at the same time they appear in East Africa is a challenge to commonly held beliefs about the exclusivity of Africa as the homeland for the catarrhine and hominoid adaptive radiations and speaks to the fact that the biogeographic distribution of primate groups in the late Paleogene and early Neogene is much more complicated than previously thought.

It is in this manner that the discovery of the Laotian Rock Rat gains added significance. As a relic of the early Miocene Shangwangian biochronologic age, Laonestes opens up a window on this long gone epoch, when early ape-like creatures may have spread throughout south, east and southeast Asia. What relationship these early protoapes (represented until now mostly by isolated teeth and some scrappy jaw fragments) have to the later appearance of true modern apes in the same region during the Middle and Late Miocene (7-12 mya) is a topic that has garnered little attention. Only with the recovery of more diagnostic elements of the cranial and post-cranial skeletons of these early apes will their relationships to other primates become better understood.

Shangwangian-like faunas are, however, found spread throughout south, east and southeast Asia during the early Miocene, so we can tentatively assume that the protoapes of Sihong had a similar distribution (for that matter, one primate taxon from Sihong, Dionysopithecus, named after the Greek god of wine, has been found in Pakistan).

The Diatomyidae, the family to which the Laotian Rock Rat has been assigned is described by Qiu and Li as follows:

DIATOMYIDAE: Diatomys shantungensis, collected from Shanwang and Sihong, is the only Chinese species of this family. Diatomys was first considered indeterminate to family and questionably referred to Geomyoidea (Li, 1974). Some students transferred it to the family Pedetidae (McKenna and Bell, 1997). We follow P. Mein and L. Ginsburg (1997) in their definition of a new family for this genus plus probably Fallomus. Diatomys is also known from Thailand, Pakistan, and Japan (Kato and Otsuka, 1995), and appears to be a kind of wet/warm-adapted animal distributed in a tropical or subtropical area.

This suggests that the environment in which modern Laonestes is found is a biological refugia and good analog to what the environments of Shanwang and Sihong may have been like 17 million years ago when protoapes roamed the forests of East Asia.

Recent Discoveries of Interest

2006-08-01T23:38:00.000-07:00

One reason for "Sinanthropus" is to serve as a clearing house for info on Chinese paleontology. With that goal in mind I am using this post to highlight three recent discoveries regarding quite different aspects of the Chinese fossil record. These include the recent description of Mesomyzon mengae, a new early Cretaceous lamprey; the discovery and analysis of Gansus, the earliest known amphibious bird; and the capture of the Laotian Rock Rat (Laonastes aenigmamus). Before discussing these finds in future posts, I'd like to direct a word of thanks to Michael J. Ryan for the above links to his Palaeoblog. My next post will discuss the discovery of the Laotian Rock Rat and how it relates to hominoid evolution in Asia during the early and middle Miocene.

Check-out This Blog's Sister Site

2006-07-30T19:48:00.000-07:00

I've just recently updated the sister site to this blog, "The Fossil Evidence for Human Evolution in China." (N.B. the prior url for the site - www.chineseprehistory.org - was hijacked by a commercial outfit much to my chagrin). I've added a link to "Sinathropus" and a video file of a Chinese newscast reporting on the reconstruction of the Yunxian 2 cranium of Homo erectus that my colleague Prof. Li Tianyuan and I described back in the early 1990s. The site has a catalogue of Chinese hominid discoveries and many other resources relating to Chinese paleoanthropology, including pdfs of articles I've written on the subject, so check-it out if you haven't already.

Hopping Across Laurasia

2006-07-29T09:54:00.000-07:00

My previous post introduced readers to the fascinating research of Smith et al. regarding the dispersal of the earliest known euprimate genus Teilhardina from its apparent birthplace in China across the northern hemisphere to North America. Smith et al's. research is based on a high resolution assessment of the sedimentary environments in which the fossils were found. New investigative techniques allowed them to determine whether the fossil-bearing deposits were laid down before, during or after a climatic maximum that occured near the Paleocene/Eocene transition ~ 55 mya. A sequence based on carbon isotope ratios showed that Teilhardina asiatica was earliest, followed by T. belgica and T. americana . The spread of Teilhardina out of Asia into first Europe and then North America, across what was the more or less contiguous supercontinent of Laurasia, happened at a time when global warming is hypothesized to have spread a continuous canopy of evergreen forest across the northern latitudes. Many other mammalian genera are documented to have followed a similar eastward dispersal route.

Studies of this sort are what makes paleontology such an exciting field and shows it to be an experimental science in which hypotheses are generated by preliminary analysis of data collected in the field and then tested by falsifiable experimentation in the lab. There is one "true" story of the evolution and spread of life on earth which we are constantly unraveling with new and ever more analytic techniques.

Below is a figure from Smith et al's PNAS article that illustrates the research they conducted:

Paleogeographic map showing hypothetical migration routes of Teilhardina during the earliest Eocene. (A–C) Timing of migration is obtained by correlations of the ¹³C excursion in North America (A), Europe (B), and Asia (C). T. brandti and other modern mammals first occur in the Lower Double Red (1,512 m) of Polecat Bench, Wyoming, which is situated above the minimum value of the ¹³C excursion (spike at 1,507 m). The Lower Double (L.D-) Red has an estimated age of 19–25 Kyr above the P/E boundary, based on soil carbonate nodules (SNC) and dispersed (disp.) organic carbon (DOC) (14, 20, 21). U.D-, Upper Double; Purp., purple; Fm, formation. (D) We hypothesize that Teilhardina dispersed through continuous forest from southern Asia to Europe and from nothern Europe to North America during the first 25 Kyr of the PETM.

New Evidence for the Asian Origins of Primates

2006-07-28T19:09:00.000-07:00

A recent study by University of Michigan paleontologists Thierry Smith, Ken Rose and Philip Gingerich in the Procedings of the National Academy of Sciences has given unprecedented temporal resolution to the biogeographic first appearence of early Eocene primates. The research centers on the primate genus Teilhardina, recognized as one of the first true primates to appear in the fossil record. It was first discovered in Belgium in 1927 and originally described as belonging to the fossil genus and species Omomys belgicus by famed theologian and paleontologist Teilhard de Chardin. In 1940 Gaylord Simpson attributed the material to a new genus and species given the honorific nomen Teilhardina belgica. In 1970 a similar species, Teilhardina americana was described from early Eocene deposits in Wyoming. Then in 2004 an Asian form, Teilhardina asiatica, was discovered from the earliest Eocene (~55 mya) of the Hengyang Basin, China.

The skull of Teilhardina asiatica sp. nov. (IVPP V12357). a, Dorsal view of the skull. b, Reconstruction of the skull based on IVPP V12357, with grey shadow indicating the missing parts. Scale bar, 5 mm.

The earliest true primates (i.e. euprimates) have been sorted into two seperate groups; the omomyids and adapids. The omomyids have long been thought to be ancestral to later haplorhine primates (tarsiers and anthropoids), while adapids have been seen as broadly ancestral to later strepsirhine primates (the living lemurs and lorises). As the most primitive known omomyid, Teilhardina appears to be close to the last common ancestor of these two early groups of euprimates.

Teilhardia seems to fit in near the base of the primate family tree close to numeral 2 on the figure above

What Smith et al. have succeded in doing is sequencing the first appearence of the three regional species of Teilhardina. This has been determined by studying the carbon isotope ratios of deposits that have yielded the fossils in their respective regions. According to a UM press release:

To achieve such precision, they used a carbon isotope curve recently documented on all three continents. Carbon in the atmosphere, earth and living organisms differs in the proportion of carbon-12 and carbon-13 present. A flood of carbon- 12 is associated with the onset of an event known as the Paleocene-Eocene thermal maximum (PETM), one of the most rapid and extreme global warming events recorded in geologic history. It was during the PETM that modern primates first appeared 55 million years ago. Teilhardina in Asia precedes the maximum flood of carbon-12, Teilhardina in Europe coincides with it, and Teilhardina in North America appears just after the maximum.

The most likely scenario has Teilhardina, and hence the omomyids in general, originating in Asia and quickly dispersing first to Europe and then across northern Laurasia to North America. The earliest adapid primate, Cantius, is currently known only in Europe and North America from slightly younger deposits than Teilhardina. The presense of adapids in Asia is problematical and still largely unresolved. Nevertheless, the current study confirms that the earliest true primate in the fossil record is from China, pointing to a possible Asian origin for the euprimate radiation.

Is there other evidence pointing to an Asian origin for primates? In a word, yes. Recent molecular studies indicate that modern placental mammals can be divided into four major clades: Afrotheria, Laurasiatheria, Xenarthra and Euarchontaglires. These groups seem to have biogeographic significance. Afrotheres include living orders of mammal that are primarily indigenous to Africa, such as elephants, manatees, hyraxes, aardvarks and some small insectivorous forms. Xenarthrans are the sloths, giant anteaters and armadillos indigenous to South America. Laurasiatheres include virtually all other placental mammals (various ungulates, cetaceans, bats, carnivorans, insectivores, etc.) and seem to have had an origin in the northern hemisphere Laurasian supercontinent spanning North America Europe and Asia. Euarchontaglires is the most interesting of these supraordinal mammalian clades from an anthropocentric perspective. It includes primates as well as the closely related tree shrews (Scandentia) and flying lemurs (Dermoptera) in the subgroup Archonta, and rodents and rabbits in the subgroup Glires. The extant archontans, other than primates, i.e. the tree shrews and flying lemur are found exclusively in continental and insular southeast Asia. Rodents and Lagomorphs (rabbits, hares and pikas) are global in distribution, but some of the earliest rodents are known from the Chinese Paleocene, as are the anagalid ancestors of lagomorphs. The biogeography of extant and extinct members of the euarchantaglires clade thus suggests East Asian and/or southeast Asian origins. Another indicator of East Asian origins for the primates, in particular, is the presense of the earliest anthropoid-like primates, the eosimiids, from the middle Eocene of China.

As things now stand a persuasive argument, based on biogeographic, molecular and fossil evidence, can be made for the Asian origins of euprimates, as well as other euarchontaglires, during the late Paleocene.

Early Pleistocene Asian Hominid Redux

2006-07-23T00:15:00.000-07:00

The recent surge of interest in possible Asian origins for the genus Homo prompts me to republish a piece I wrote a decade ago regarding what was then known of the earliest Asian hominins. Back then it was widely accepted by proponents of the “Out of Africa” hypothesis that Homo erectus was an evolutionary side branch of the human family tree, restricted to Asia, that eventually went extinct without issue.

Popular "Out of Africa" phylogeny that isolates Homo erectus as a uniquely Asian species

Our lineage was universally accepted to have evolved in Africa from descendents of H. ergaster, which was considered to be the last common ancestor of all later hominins, including both H. erectus and H. sapiens. In this scenario H. ergaster diverged into an Afroeuropean lineage, which subsequently split into European Neanderthals and the African ancestors of modern H. sapiens, and an Asian lineage, comprising H .erectus and its localized descendents in East and Southeast Asia. The hunt was thus on for early antecedents of an exclusively Asian H.erectus.

With the discovery of relatively complete hominin cranial remains circa one million years BP in Ethiopia and Europe that are nearly indistinguishable from penecontemporaneous classic H. erectus from China and Java, the idea of an exclusively Asian H. erectus distinct from an ancestral East African H. ergaster has, however, begun to recede. The acceptance of H. ergaster as a distinct hominin taxon is no longer as widely accepted as previously and H. erectus is now generally recognized as the pandemic early Pleistocene ancestor of all later hominins, including modern humans.

Widely accepted hominin phylogeny in which H. erectus is seen as the common ancestor of all later humans with a late survival in Asia as a relic species

As discussed in previous posts the discovery of the Dmanisi hominins dated to ~1.7 mya in the Republic of Georgia, has prompted some to suggest that the genus Homo had an extra-African origin. Is there really any substantial evidence for this hypothesis besides that presented and discounted in my previous posts on the Dmanisi remains? Not much new has emerged in the fossil record of China or Java relating to the presence of Plio-Pleistocene hominins (aka hominids) since I wrote the article mentioned at the top of this post although D. Tyler et al have recently described fragmentary and heavily distorted fossil remains attributed to “Meganthropus.” I will comment of that material in due course. Meanwhile, please proceed to my article on Plio-Pleistocene Asiatic hominids presented here.

Lessons from Supposed Anglo-Saxon Apartheid

2006-07-21T16:57:00.001-07:00

An interesting study by Dr Mark Thomas et al., of the University College, London, Department of Biology et alia, suggests that, “The native Britons were genetically and culturally absorbed by the Anglo-Saxons over a period of as little as a few hundred years." A UCL press release on the research can be found here.

The study, which appears in the recent edition of the Proceedings of the Royal Society B: Biological Sciences, attempts to reconcile historic and archeological evidence for a limited incursion of Anglo-Saxons during their invasion and occupation of Britain, with genetic evidence showing the wholesale replacement of indigenous Celtic Y-chromosomes with those derived from a continental German substrate. As the article's abstract states:

The role of migration in the Anglo-Saxon transition in England remains controversial. Archaeological and historical evidence is inconclusive, but current estimates of the contribution of migrants to the English population range from less than 10000 to as many as 200000. In contrast, recent studies based on Y-chromosome variation posit a considerably higher contribution to the modern English gene pool (50–100%). Historical evidence suggests that following the Anglo-Saxon transition, people of indigenous ethnicity were at an economic and legal disadvantage compared to those having Anglo-Saxon ethnicity. It is likely that such a disadvantage would lead to differential reproductive success. We examine the effect of differential reproductive success, coupled with limited intermarriage between distinct ethnic groups, on the spread of genetic variants. Computer simulations indicate that a social structure limiting intermarriage between indigenous Britons and an initially small Anglo-Saxon immigrant population provide a plausible explanation of the high degree of Continental male-line ancestry in England.

While interesting in and of itself, the study highlights that rapid genetic replacement can occur when two populations come into sustained contact, with hard to document demographic factors leading to fundamental shifts in the genetic composition of descendent populations.

This has a direct bearing on the controversy surrounding the role of Neanderthals in the descent of modern Europeans. My previous post hails the announcement that a concerted attempt has been initiated to completely decode the Neanderthal genome. This will eventually allow scientists to determine with certainty the contribution, if any, that Neanderthals made to modern European populations.

No matter what the ultimate outcome of these future studies may be, the issue of genetic replacement must take into account demographic factors such as those discussed in the research described above. There is no question that modern humans replaced the more archaic Neanderthal population of Europe in a relatively short span of time (~ 8000 year). The dynamics of this replacement are still debated and should be the focus of future research (see here, abstract A28 for example). Less emphasis should be placed on subjective questions of whether or not Neanderthals were a separate species of humankind.

Imminent Sequencing of the Neanderthal Genome

2006-07-21T01:39:00.000-07:00

In approximately two years time what will be perhaps the seminal event of the 21st century will take place. The complete Neanderthal nuclear genome will be sequenced in a collaborative effort by the Max Planck Institute for Evolutionary Anthropoloy in Leipzig, Germany, and 454 Life Sciences Corporation, in Branford, Connecticut. Prof Svante Pääbo, Director of the Institute's Department of Evolutionary Anthropology, and Dr. Michael Egholm, Vice-President of Molecular Biology for 454 Life Sciences will jointly direct the project, made possible by financing from the Max Planck Society. 454 Life Sciences' newly developed sequencing technology has made it possible to extract and sequence nuclear DNA from fossil bone, a hopeless task using traditional techniques.

The significance of sequencing the nuclear genome of Neanderthals cannot be overestimated. Not only will it definitively demonstrate the nature of their relationship to modern humans, it will also define what it is that makes us distinct from our immediate pre-modern ancestors. Combined with the sequencing of the Chimpanzee genome we will be in the position to understand, to an unprecedented degree, the genetic transformation from ape to human. The implications for medical research are also stupendous, as we will be able to hone in on significant genetic sequences unique to modern people and compare them to both pre-modern human and pre-human sequences. As the techniques employed become more sophisticated the prospects for unraveling other aspects of our evolutionary past will increase exponentially. We will eventually be able to infer the nuclear genome of the chimpanzee/human last common ancestor and the genomes of ancestors throughout the course of human evolution. What an exciting prospect! Read more details about the project and view a webcast press conference about it from this Max Planck Institute press release and learn more about the techniques involved from this press kit by 454 Life Sciences.

Problems with “Out of Savannahstan”

2006-07-12T12:41:00.000-07:00

A recent story in the popular science magazine “New Scientist” by Marek Kohn (Made in Savannahstan, NS July 1-7, 2006, pp 34-39) reviews a provocative article by Robin Dennell of the University of Sheffield, UK, and Wil Roebroeks of Leiden University, the Netherlands that appeared in the British journal “Nature” last December.

Dennell and Roebroeks hypothesize that hominins from the remakable Late Pliocene (~1.7 mya) Dmanisi site in the Republic of Georgia are the descendents of a yet unknown group of proto-humans that had previously dispersed into a belt of savannah extending from northern Africa across into southern Asia. It is this stock that adapted to the rigors of a grasslands environment and gave rise to Homo erectus, which then, much like the prodigal son, returned to Africa to smite its primitive cousins, the australopithecines (including early members of the genus Homo such as H. habilis and H. rudolfensis which they believe were advanced australopitecines.)

A linchpin of this scenario is the placement of australopithecines in Chad, far to the west of their previously known range of distribution, 3 to 3.5 mya, suggesting that australopithecines were capable of wide-ranging dispersals. This, in combination with early dates (> 1.5 mya) for Indonesian H. erectus from Sangiran and Mojokerto led the authors to speculate that there was an early dispersal of australopithecines out of Africa into Asia, where they were subjected to intensive selection resulting in the evolution of H. erectus. The sudden appearance of H. erectus in East Africa commencing ~ 1.8 mya, replacing species of so-called “early Homo,” was the result of their subsequent redeployment back into Africa.

There are a number of problems with the underlying premises of this “Out of Asia” hypothesis for the origins of Homo erectus. First, the presence of australopithecines in Chad is not unexpected given the recent discovery of 7 million year old Sahelanthropus in the same country. While I do not accept the hominin (aka hominid) status of Sahelanthropus, I do recognize it as a likely candidate for “Last Common Ancestor” of the African apes and humans (see previous post). As I see it, descendents of Sahelanthropus that stayed in northern Africa and dispersed east into Ethiopia and throughout the Rift Valley evolved into later australopithecines, while separate descendent lineages of Sahelanthropus that dispersed southward into equatorial Africa evolved into Gorillas and Chimps. In this scenario the presence of australopithecines in north central Africa at the time in question (3-3.5 mya) is to be expected, as it’s part of their ancestral homeland.

The small brain size, archaic facial morphology and Oldowan like tools of the Dmanisi hominins are also no surprise if one is familiar with fossil hominins from East Asia. I have previously favorably compared the Lantian skullcap from Gongwangling in China (dated at ~ 1.2 mya) with early H. erectus from East Africa. The Gongwangling calotte is estimated to have had a small cranial capacity (~ 780 cc) and a less derived facial morphology than later Chinese or Indonesian H. erectus. The hypothesis that there was a dispersal of an early grade of H. erectus out of Africa commencing ~ 1.8 mya is thus consistent with all available evidence and does not, at this time, require any premature modification. The quest for australopithecine fossils in Asia has been Quixotic at best and until there is some physical evidence for their presence outside of Africa hypotheses such as those of Dennel and Roebroeks will find only limited and I would suggest, ill-informed support (the presence of a "habiline" hominin at the Longgupo site in Sichuan, China dated to ~ 1.9 - 2.0 mya as proof of an early dispersal of pre-erectus hominins into Asia has been critiqued and is no longer generally accepted).

The article by Kohn makes reference to some preconceptions concerning the dispersal of H. erectus out of Africa perpetuated by commentators such as Ian Tattersall. One such idea is that humans expanded their range into Asia, or vice versa, due to a “typically insatiable human wanderlust.” This is just plain silly. Species, whether human or not, do not consciously decide to strike out on transcontinental treks, they expand into adjacent territory that they are equipped to exploit, both physically and behaviorally. Humans, incidentally, were not the first hominoids to disperse throughout the Old World. Did late Miocene apes, which ranged from Spain to China, have an “insatiable wanderlust?” No, they had the behavioral and physical adaptations that enabled them to exploit contiguous environments spread across the southern tier of Eurasia. This is, obviously, how all-major dispersals take place and humans are no different from other species in this regard.

If, as I have suggested in previous posts, the australopithecines are the lineal descendents of late Miocene European apes that were displaced southwards into northern Africa at the end of the Miocene because of climatic and environmental deterioration in their native clines, it would appear that the southern tier of Eurasia was inhospitable to large-bodied hominoids for a considerable span of time. Northern and northeastern Africa, which retained the open woodlands environment that suited these hominoids, was the cauldron in which the australopithecines evolved. As this environment slowly dried out and was replaced by expanding grasslands, robust australopithecines and the ancestors of the genus Homo diverged. The adaptations forged by early Homo for life on the savannah allowed for range expansion as soon as they emerged, hence the rapid dispersal of early Homo, commencing around 1.9 mya into the Middle East and the Caucus region and rapid subsequent eastward expansions into east and southeast Asia. This scenario is in keeping with the broad outline of human evolution generally accepted by most contemporary anthropologists and does not need any major revision based on presently available evidence.

As Templeton has documented using genetic data, there were apparently multiple dispersals out of Africa beginning ~ 1.9 mya. This was coupled with a considerable amount of back migration and multidirectional genetic admixing throughout the latter phases of human evolution. What the Dmanisi remains demonstrate is that between 1.7 and 1.9 mya there was what appears to have been a rapid transition from a “habiline to an “erectine” grade of hominin evolution. It is not surprising to find specimens during this period that show different mixes of primitive and derived features. What we’re witnessing may be the human lineage in the throes of evolutionary change as new genetic combinations are sorted out and eventually become channelized into the morphotype of classic Homo erectus, a pattern that once established remained virtually unchanged for nearly one million years.

Part of this transition was the development of new stone tool fabrication techniques, eventually leading to the emergence of a full-fledged Acheulean tradition by ~ 1.65 mya in East Afria. Earlier Oldowan-like traditions now appear to have spread into Eurasia prior to the spread of more sophisticated hand-axe traditions. But the idea that early Homo needed Acheulean tools and large brain size to expand their range out of Africa was never a viable hypothesis. For decades it was noted that Chinese and Indonesian H. erectus lacked major components of the Acheulean tradition and the so-called Movius line was established to separate the early Paleolithic into eastern and western traditions. The stone tool industries of Asian H. erectus were referred to as part of a chopper/chopping tool complex of a basically Oldowan nature. Early H. erectus in Asia is also noted for relatively small cranial capacities (i.e. the previously mentioned Lantian skullcap.). It’s been known for decades that hand-axes and large brains were not prerequisites for human expansion into the Far East.

In sum, australopithecines were not adapted to the savannah environments that were spreading across the southern tier of Eurasia at the end of the Miocene. It was the spread of these grasslands that spelled doom for the Eurasian hominoid antecedents of the African australopithecines. Africa seems to have been the incubator for the australopithecine adaptation to the woodland/grassland ecotone, a stable adaptation that remained little changed for nearly 2 million years (~ 4.5 – 2.5 mya). This environment does not seem to have prevailed in more northerly latitudes. As grasslands began sreading in Africa at ~ 2.5 mya generalized australopithecines seem to have split into robust lineages and those evolving towards the genus Homo. As of today genetic, archeological and paleontological evidence all points to an initial dispersal of Homo out of Africa at ~ 1.9 mya. Once this range expansion was achieved there seems to have been episodic genetic exchange between widely dispersed demes of an emerging H. erectus, the longest lasting hominin species and direct ancestor of all later humans.

Comments on the Flores hominid

2006-07-09T15:40:00.000-07:00

Gary Richards, an old friend and colleague from my days at the Laboratory for Human Evolutionary Studies (now the Human Evolution Research Center) at the University of California, Berkeley has a recent article in the Journal of Evolutionary Biology (DOI link) challenging the validity of Homo floresiensis. He argues that changes in developmental pathways of an isolated population of modern humans could have produced the idiosyncratic features seen in the Flores remains. Both John Hawks and Carl Zimmer offer useful reviews of Gary’s contribution, which can be found here and here.

I’ve always been skeptical of the view that the Flores hominid was an insular dwarf derived from an antecedent population of Indonesian H. erectus. The association of “H. floresiensis” with a modern human tool-kit and the presence of short-statured peoples throughout the region led me to suspect that if insular dwarfing was the cause for the features seen in the Flores remains, the process was acting on a population of modern humans rather than a relic population of H. erectus.

Gary’s article clearly shows that populational dwarfism among extant humans varies as to etiology and that the stature of LB1 does not fall too far below the lower limit of the range of variation seen in modern humans. Many of the seemingly “primitive traits” seen in the Flores remains may be due to allometric scaling effects or the result of alterations in developmental pathways brought on by changes in the expression of human growth hormones and associated factors. In addition, mutational effects leading to extreme size reduction, combined with inbreeding may have led to an increase in the incidence of microcephaly within individual demes of Flores hominids. This would help account for the unlikely recovery of an individual with such an extremely small cranial capacity as the LB1 specimen.

The article argues that more wide-ranging comparisons must be made between the Flores sample and localized human populations to better understand how “Homo floresiensis” fits into the panoply of human evolution and endemic adaptation. Gary concludes that:

When one applies the concept of maximum parsimony (Sober, 1988) to the totality of evidence available on the Flores remains, one finds significant support for the remains being a variant of H. sapiens and little support for a species-level distinction. Given this position, I suggest that the LB1–LB9 individuals represent the remains of a H. sapiens group which became dwarfed in an island environment via changes in the GH–IGF-I axis (Human Growth Hormone-Insulin-like Growth Factor I Axis). Acquisition of a dwarfing condition may either have occurred prior to or after the group arrived on the island. If it can be demonstrated that the totality of the recovered remains sample the same population, it appears that a mutation in the MCPH gene family or a secondary modification of the GH–IGF-I axis arose in the later part of their occupation of the island and was transmitted within a local group. Whereas I consider the ‘primitive’ features identified in the LB1–LB9 individuals to be consistent with the scenario presented above, only a detailed analysis will be able to clarify the value of these features for phylogeny reconstruction.

This seems to me to be an extremely well balanced analysis and one that addresses the major contradictions generated by the Flores remains.

Folkloric accounts by local residents of Floresian “hobbits” suggests that there was ongoing contact between the dwarfed population and settled villagers, leading to interbreeding and resultant genetic exchange between the two populations, again mitigating against “Homo floresiensis” being a distinct human species. No matter how one cuts it, however, the recovery of the Liang Bua remains expands the range of modern human variation to the brink of an incipient speciation event and helps document an extremely interesting episode in recent human evolution.

More on the "Lost Common Ancestor"

2006-07-08T20:59:00.000-07:00

Happened upon John Hawks website cum blog, which has a recent post regarding Sahelanthropus. Hawks has had a long standing collaboration with Milford Wolpoff, and he, Wolpoff, Brigitte Senut, Martin Pickford and James Ahern have published a critique of Toumai as an ancestral hominid. Interestingly enough, Senut and Pickford have made claims about the hominid status of Orrorin tugenensis, a 6 million year old hominoid from the Turgen Hills of Kenya, similar to those made by Brunet et al. about Sahelanthropus. Orrorin, discovered in 2000 and nicknamed "millenium man," consists of a proximal femur and other fragmentary skeletal and dentognathic remains, that have been described as "the first human" by Pickford and Senut. As the search for the "first human" is a very competitive business, it is not surprising that Pickford and Senut concur with Wolpoff et al's analysis of Sahelanthropus as an ape, although they differ in their interpretation as to its overall affinities. Pickford and Senut's insistance that Orrorin was a bipedal hominid with a modern human gait, has also been challenged, so there is a certain irony in their collaboration with Wolpoff et al. in deconstructing Sahelanthropus.

Although there is a general willingness to accept Orrorin as a biped and hence an early hominid, the nature of its bipedalism has been called into question, with White et al. suggesting that the anatomy of the femur was more primitive than seen in australopithecines. Of course bipedalism in late Miocene hominoids has been argued for some unequivocally non-hominid apes such as the 8 million year old remains of Oreopoithecus from Tuscan lignites in Italy, so bipedalism in and of itself should not necessarily serve as the sole criterion for being human. As I argued in my last post, faculative bipedalism may have been part of the morphotype of the African ape/human LCA and not indicative of true homind status. It is interesting that no one seems to be arguing for this interpretation. It's either argued that a six million year old divergence date for the human/chimp split is too recent or that the fossils in question do not possess the features they are said to possess and are not really hominids after all. This is exemplified by a quote of Vince Sarich's from an article in Science by Ann Gibbons:

The first molecular study back in 1967 dated the split between
humans and apes to 5 million years ago, and Vince Sarich of the University
of California, Berkeley, co-author of the study, still stands by
that date. “I still bet that either the morphology or dates or both will
be found wanting for these ‘6-million-year-old hominids,’ ” he says.

The idea that the LCA of African apes and humans may have had preadatations for bipedalism that are expressed morphologically as early signs of a bipedal adaptation, does not seem to have been entertained by anyone besides yours truely. I agree with White et als. contention that Sahelanthropus, Orrorin and Ardipithecus represent the same taxon, but differ as to their interpretation that it is a hominid. As I said in my last post all three should be recognized as representative of the "lost" common ancestor of chimps and humans, a view consistent with their chronometric age and the consensus 5-6 million year old divergence date for the LCA established by genomic analysis. Again let me reiterate, because it seems to be a point no one is willing to concede, based on current evidence, the most parsimonious position regarding the phylogenetics of Sahelanthropus, Orrorin, and early forms of Ardipithecus is that they are indistinguishable from the human/chimp LCA and that this LCA possessed more hominid-like features vis a vis its locomotor and dietary adaptations than anyone has been willing to acknowledge.

Thoughts on the "Lost Common Ancestor"

2006-07-06T11:11:00.000-07:00

Just saw the Science Channel documentary, “Pre-human: Riddle of the Skull.” It’s the first attempt to popularize the discovery and explain the significance of the Sahelanthropus cranium. For those of you who need a reminder, a remarkably well-preserved, but distorted cranium of a hominoid dubbed Sahelanthropus tchadensis was discovered in 2001 in the North African country of Chad by a French paleontological team led by M. Brunet. The video reviewed the evidence, based on faunal studies, that Toumai, as the specimen has been nicknamed, is between 6 and 7 million years old. In the video Brunet, and various colleagues, argue that Toumai, is a full-fledged human ancestor, a hominid in the classic sense of the term, and as such the oldest and most primitive member of the “human family.” There are, however, some real problems with this assessment.

First, let’s look at some of the evidence they put forth regarding the “hominid” (or hominin if you prefer) status of Toumai. This includes aspects of cranial anatomy elucidated by a virtual reconstruction conducted by a team including D. E. Lieberman and D. Pilbeam, who were prominently interviewed in the video. The reconstruction demonstrates that the nuchal plane of the occiput, i.e. the surface of the skull base where the neck muscles attach, is more horizontally oriented than in the great apes and within the range of variation of austrlopithecines such as “Lucy,” suggesting that Toumai was well-adapted to bipedalism. This combined with a relatively vertical face and reduced canines with apical wear (i.e. wear at the tip of the canine crown) are said to clearly place Sahelanthropus within the hominid camp. In contrast to these human-like features the mostly complete cranium has a very small brain (between 320 and 380 cc) comparable in size to that of chimpanzees and on the lower end of the australopithecine range. It also has massive brow ridges, suggesting that it may be a male, as well as two rooted pre-molars, likewise a primitive ape-like trait. All things considered. Brunet, et al. forcefully argue in the video that Toumai was a habitual biped, belonging to a species that was beginning to adapt to a new hominid lifestyle.

Virtual reconstruction of the TM 266 cranium (Frankfurt Horizontal plane orientation, orthographic projection). a, Frontal view. b, Right lateral view. c, Superior view. d, Inferior view. Scale bar, 5 cm.

Although Brunet et al. consider Toumai to be on the human side of the chimp-human split, they concede that Sahelanthropus was very close to their last common ancestor (LCA). This is where the problems begin. A recent article in Nature by David Reich, a geneticist at Harvard Medical School in Boston, and colleagues, places the chimp-human split at no more than 6.3 million years ago — nearly a million years later than the fossils of Sahelanthropus suggest. The authors also claim that early hominids interbred with their chimp cousins yielding a hybridized human genome with a mosaic of DNA with varying degrees of similarity to the chimp genome. While the latter claim is the most controversial, I find the implications of the former claim more provocative.

Actually a date of ~ 6 million years or younger for the LCA has been reported on repeatedly, based on multiple genetic analyses going all the way back to Vince Sarich’s pioneering immunological work in the late 60s. Sarich’s late divergence hypothesis sounded the death knell for Ramapithecus as an exclusive human ancestor precisely because the youngest “ramapithecine” fossils were too old and would have lived prior to the LCA. Sarich’s initial divergence date was calculated around 4 mya. More recently an overwhelming body of genetic evidence places the divergence date at no more than 6 million years. The sole holdouts for an early divergence date for the human/chimp split are Arnason et al., who posit a date of ~ 10.5 - 13 mya., based on MtDNA datasets that do not take into account mutation rate increases in primates and utilize non-primate calibration points. The implications of an early divergence for the chimp/human LCA are stated by Arnason et al. as follows:

The revised estimates of primate divergence times suggest a new hypothesis for primate evolution and dispersal: that the divergence between strepsirhines (lorises, lemurs) and anthropoids was contemporary with the break-up of Southern continents about 90 MYBP, with strepsirhines becoming isolated on Madagascar and later dispersing to Africa (and Asia) and anthropoids evolving in South America and subsequently colonizing Africa (and Asia), or possibly North America.

Those who accept an early date for the chimp/human divergence based on genetic evidence should accordingly adopt the above scenario as well. I doubt, however, that proponents of an early date for the human/chimp divergence will actively promote hypotheses of primate evolution in accord with what Arnason et al. propose, as they are totally inconsistent with mainstream thinking. Accepting early divergence dates for the chimp/human LCA thus amounts to cherry-picking a convenient date to support an interpretation of Sahelanthropus and other similar fossils as bona fide hominids (sensu stricto).

What then are the implications of accepting the genetic evidence for a late divergence of the chimp and human lineages? Well, to paraphrase Vince Sarich when he debunked the hominid status of Ramapithecus, “I don’t care what it looks like, if it’s more than 4 million years old it’s not a hominid.” Following the same logic, accepting the modern genetic evidence for a 6 million year old divergence date for the chimp/human LCA implies that Sahelanthropus, Orrorin, and early forms of Ardipithecus are not in the direct line of human ancestry. What then do they represent? Given the time range within which these fossils are found, the obvious conclusion is that they are representative of the LCA or a species very close to it! For all intents and purposes I propose that African hominoids from ~ 5.5 – 7.5 mya that show a mix of African ape and human features should be considered part and parcel of the population from which the human/chimp LCA was derived. To reiterate, Sahelanthropus, Orrorin and Ardipithecus kadabba should be considered to be the long sought after last common ancestor of the African Apes and humans. The hominid-like features of these fossils must, therefore, be the common inheritance of all African hominoids, including the chimpanzee and gorilla, as well as ourselves. This, of course necessitates that not only have humans evolved away from the LCA, but so have chimps and gorillas. But that should come as no surprise, since that is what evolution is all about. Just as the LCA was not a human, neither was it a chimp nor a gorilla. In other words, the African ape/human LCA apparently possessed many more human-like features in its locomotor adaptation, dentition and masticatory apparatus than most researchers currently accept.

One may legitimately ask, from whence did this human-like LCA come? The answer is also revelatory, as the logical candidate is not African but European. The best candidate for immediate ancestor of the African ape/human LCA is none other than the late Miocene Grecian hominoid Ouranopithecus macedoniensis, which has long been promoted as a true hominid (sensu stricto) by L. De Bonis and G. Koufos. Others have noted strong similarities between Ouranopithecus and both gorillas and chimps. Ouranopithecus is noted for its thick molar enamel, high degree of sexual dimorphism, with females having particularly human-like canines, and large gorilla like faces and extremely prominent brow ridges. The one nearly complete face of Ouranopithecus is thought to be a male, but it has relatively small canines no larger than a modern female gorilla's. It has a very well developed brow ridge, but again, it is not any larger than that of a modern female gorilla's, suggesting that modern African apes are hypertrophied relative to their Miocene ancestors.

Ouranopithecus male Gorilla female

Note the similarities between the male Ouranopithecus and female gorilla.

•

Ouranopithecus is dated between 8 – 10 mya in Greece, at a time when the environment was very similar to what is later seen in the area of North Africa where Sahelanthropus was discovered. The extinction of hominoids in Europe during the late Miocene may have been coincident with their dispersal into North Africa as climatic zones shifted south.
Ouranopithecus, and its descendent Sahelanthropus, can be thought of as adapted to a mosaic environment of woodlands interspersed with grasslands, requiring a locomotor pattern emphasizing incipient bipedalism and heavy chewing associated with sclerophyllic (drought resistant) vegetation. In this way the African ape/human LCA would have had a suite of preadaptations (now referred to as exaptations) that became enhanced amongst the later australopithecines as climatic deterioration continued apace during the terminal Miocene/early Pliocene transition in north and northeast Africa. The ancestors of gorillas and chimpanzees continued to disperse further south, encountering more tropical environments, leading to a loss of the hominid-like features inherited from their late Miocene European and North African ancestors.

Late Miocene Vegetation Zones

Accepting these ideas will require a major paradigm shift away from viewing human evolution as a result of a tropically adapted African ape acquiring hominid features as it expanded into or became isolated within increasingly harsh environments associated with late Miocene/early Pliocene climatic change. Human evolution is better seen as a continuation of trends established within European hominoid populations during the Miocene, which then were transferred south into northern Africa. North Africa then becomes a staging ground for the expansion of some populations of LCAs eastward into Ethiopia and then down the East Africa Rift Valley into South Africa, where they evolved into australopithecines and later human ancestors, and others populations which dispersed directly southward into equatorial Africa, producing the modern gorilla and chimpanzee.

Another consideration, brought to light by Reich et al., is that as populations of the LCA began to disperse, there would have been a considerable period of time when their descendents would not have diverged to the extent that they were genetically isolated from one another and hybridization could have potentially occured. This is illustrated in the chart below.

Ape relationships are shown as grey lines for the chimpanzee (Pan troglodytes), bonobo (P. paniscus), gorilla and orangutan (Pongo pygmaeus). The approximate times of divergence are derived from commonly accepted genetic data. The phylogenetic relationships among hominids (grey shaded area) are uncertain. The solid red bars denote the time span of the fossil species and/or the uncertainty of fossil ages. The last common ancestor of chimpanzees and humans (LCA) should fall within the temporal radius defined by the yellow circle. Early members of the chimpanzee and human lineages could hybridize and would be very difficult to distinguish from one another. A synchronous taxonomic classification would place initial members of the chimpanzee and human clades in the same genus, if not the same species of hominoid. Note that the estimated age of Sahelanthropus tchadensis predates molecular estimates of the time of the chimpanzee–human divergence. This species and other purported early hominids (hominins in more current parlance) are coincident in time with the LCA. Their human-like features should be inferred to be part of the LCA morphotype. The yellow circle represents the temporal radius within which the speciation of the chimp and human lineages began. Limited gene flow between parapatric populations of the LCA would persist after the initial divergence event, which may have been initiated by chromosomal rearrangements.

The fact is that early members of the human and chimpanzees lineages would have been nearly identical to one another for a considerable span of time. Their point of divergence can only really be discerned in hindsight. If Sahelanthropus is considered to be a hominid (hominin) it would imply that those adaptations that distinguish it from the coeval chimpanzee ancestor evolved in an extremely rapid fashion. The video thus portrays Toumai as very much a "hopeful monster" and human evolution as a dramatic departure from what had preceded it. I think it is much more realistic to view the first members of the human clade to be nearly indistinguishable from the LCA. In fact, it can be persuasively argued that the australopithecines, in preserving and enhancing many of the dietary and perhaps locomotor adaptations of late Miocene apes such as Ouranopithecus, were much more like the LCA than either the extant chimp or gorilla. In this manner, human evolution remains within the mainstream of hominoid evolution and is not some aberrant evolutionarily contingent phenomenon.

Early Cambrian Echinoderms of China

2006-07-01T12:40:00.000-07:00

As previous posts have shown the Lower Cambrian Chengjiang fauna of Yunnan, China has yielded a vast array of primordial animal fossils. I’ve focused on chordates and their allies as they are intrinsically interesting to us, their descendents. One of the more interesting non-chordates is an early echinoderm dubbed Vetulocystis catenat. PZ Myers over at Pharyngula has this post from 2004:

This week's Nature includes a wonderful description of an exotic group of deuterostomes from the lower Cambrian, 520 million years ago. Deuterostomes are animals characterized by their embryology: when they gastrulate, the site of closure of the migrating tissues, the blastopore, becomes the anus of the animal. This is in contrast to the protostomes, in which the blastopore becomes the mouth. We chordates are deuterostomes, as are echinoderms, some marine worms called hemichordates, and the urochordates, or sea squirts.

Shu et al. have identified some animals called vetulocystids, and they are most closely related to modern echinoderms. Echinoderm evolution is confusing and complicated, largely because the modern forms are so highly derived and distinct from the ancestral forms, and because the echinoderm lineage has been spectacularly diverse morphologically. The authors jump from some somewhat speculative interpretations of the fossil anatomy (the specimens, as you can see below, are peculiar and the structures difficult to identify) to an idea that clarifies the organization of the deuterostome lineage.

Other Early Chinese Fish-like Vertebrates and Pre-Vertebrates

2006-07-01T09:20:00.000-07:00

As we go further back in time we encounter ever more ancestral organisms. In China precursors to the fish-like forms discussed in previous posts are found in the early Cambrian Chengjiang deposits from the southern province of Yunnan. A number of important early chordates and their allies have been described from these deposits. The vertebrates, which include mammals, birds, reptiles, amphibians and fish, have their origins within this assemblage. Clear fossils of primitive jawless fish (agnathans) have long been known from the Lower Ordovician Period (~475 million years ago), with more questionable examples from the earlier Cambrian Period (510-545 million years ago). Some of the newly described fossils from Chengjiang have been clearly identified as agnathans, a discovery that pushes back the fossil record of the vertebrates about 50 million years.

The specimens from Chengjiang include (descriptions from Vertebrate section of Palaeos and other sources):

Haikouella - originally thought to be a stem vertebrate, is now regarded as a Vetulicolian or other stem deuterostome. The Deuterostomes (meaning "secondary mouth") are a major animal taxon that includes the echinoderms (e.g., crinoids, starfish, sea urchins) and the chordates (e.g., sea squirts, lancelets, and vertebrates). The deuterostomes belong to a larger group within the Animalia called the Bilateria, owing to their bilateral symmetry along a median axis: note that some deuterostomes (i.e. echinoderms) are bilateral as embryos, later maturing to have radial symmetry. Shu & Conway Morris (2003) have made a point of "emphatically contest[ing] the vertebrate affinities of Haikouella, emphasizing the absence of eyes, notochord, myomeres, or brain.

Examples of Haikouella and a reconstruction of H. jianshanensis. (A, B, and E to J) H. jianshanensis; (C and D) H. lanceolata. All are lateral views, except for (I) and (J). In (A)and (B), the dorsal posterior segments are faintly visible [specimen (226)]. The complete specimen with well-preserved dorsal segments (totaling 10) is shown in (C). A drawing of the anterior of (C) is shown in (D). The anterior with an expanded median zone [specimen (010)] is shown in (E) and (F), and the anterior with a closed median zone [specimen (358)] is shown in (G) and (H). An oblique view [specimen (238)] is given in (I) and (J). (K) A reconstruction of H. jianshanensis. Abbreviations are as follows: sal segments; Du, dorsal unit; Eg, ?epipharyngeal structure; Emz, expanded median zone; Es, esophagus; Exg, external gills; G1 to G6, gill arch 1 to 6; L.Cmz, left closed median zone; L.Du, left dorsal unit; L.g1 to L.g6, left gill arch 1 to left gill arch 6; Ls, left skirt; M, mouth; R.Cmz, right closed median zone; R.Du, right dorsal unit; R.g1 to R.g6, right gill arch 1 to right gill arch 6; Rs, right skirt; S, skirt; Sb, bar of skirt; Sbsb, space between skirt and body; Sg, ?spiral gut; Tmmz, thin membrane covering median zone; Vbv, ventral blood vessels; Vnc, ?ventral nerve cord; and Vu, ventral unit. Scale intervals are in millimeters.

Haikouella and related forms are classified as Yunnanozoans. They branched off the chordate or hemichordate lines very early on and are probably not far removed from the last common ancestor of deuterostomes as the diagram below suggests.

Haikouella must have been an important part of the Chengjiang biota as more than 1400 specimens were studied for the analysis of their characteristics as detailed in the Science article below.

Shu D, Conway Morris S, Zhang ZF, Liu JN, Han J, Chen L, Zhang XL, Yasui K, Li Y (2003) A New Species of Yunnanozoan with Implications for Deuterostome Evolution. Science 299(5611):1380-1384

Yunnanozoon lividum - from the Early Cambrian (about 530 million years ago) of Ma'anshan, Chengjiang, Yunnan, People's Republic of China has been described as the oldest known example of a hemichordate, but see above. The phylum (or 'supergroup') Hemichordata is closely associated with the phylum Chordata, which includes the vertebrates along with other groups such as cephalochordates and urochordates. As with Haikouella, the identification of Yunnanozoon is very significant for understanding the early evolution of chordates and their allies.

Yunnanozoon lividum

Haikouichthys - originally described by Shu et al. (1999) as one of two possible vertebrates on the basis of unique specimens from Chengjiang. The other taxon, Myllokunmingia, remains unique. It has been suggested that Myllokunmingia is the same as Haikouichthys, Hou et al. (2002). The issue of Myllokunmingia's exact characteristics and affinities became somewhat less urgent after five hundred new specimens of Haikouichthys were found near Haikou. Portions of the anatomy were then redescribed on the basis of this massive body of new data by an all-star cast of Chinese and Western early vertebrate specialists, Shu et al. (2002). They at first pronounced Haikouichthys to be not merely a chordate but a lamprey-like jawless fish, with gill bars supporting its gills. Myllokunmingia is said to have pouch-like structures associated with its gills, which also makes it a jawless fish. On the other hand a cladogram by Shu et al. (2003) identifies Haikouichthys as a basal chordate, or possibly a basal craniate, but not a vertebrate. Nevertheless, Haikouichthys has a number of characteristics thought to be derived features shared with true vertebrate. These discoveries emphasize the complexity of early vertebrate origins, but they do not change prevailing ideas about the evolution of fishes from earlier chordates. They do, however, change the timing of these transitions. It's now clear that the origin of vertebrate fishes is very early in the Cambrian. By the same token, the subsequent evolution of the fishes proceded at a much slower pace. It took about 30 m.y. before the cartilaginous structure of the earliest jawless fishes began to change into bone.

For more on early Chinese vertebrates such as Haikouichthys and Myllokunmingia see this article by R. Monastersky from Science News Online.

Cathaymyrus diadexus – also from the Early Cambrian at Ma'anshan, Chengjiang, Yunnan, People's Republic of China, is the oldest known example of a cephalochordate. The form of Cathaymyrus resembles Pikaia from the Middle Cambrian Burgess Shale of Canada, but this animal is about 10 million years older. Some paleontologists have suggested that the vertebrates, evolved from cephalochordates like Cathaymyrus.

Cathaymyrus diadexus

Xidazoon stephanus - from the Early Cambrian at Haikou, Kunming, Yunnan, People's Republic of China is more problematic as its relationship to the known animal groups is ambiguous. The anterior of this animal resembles an agnathan fish known as a pipiscid, but the segmented tail-like posterior is more like that of an invertebrate, such as an arthropod. Because of its enigmatic nature, Xidazoon has at present been assigned to the pseudo-phylum "Problematica". Nevertheless, this animal has great importance in the study of the evolution of the primitive deuterostomes and protostomes.

Xidazoon stephanus
Reconstruction is supervised by Prof. Shu Degan.

More on the Origins of Lobe-finned (Sarcopterygian) Fish in China

2006-06-30T19:12:00.000-07:00

Prior to the discovery and description of Meemannia eos discussed in my last post a number of ancestral boney-fish (osteichthreys) had been found in southern China during the late 1990s. Below is a reprint of an overview of these discoveries by Nature editor Henry Gee and relevant graphics from the Chinese Academy of Sciences website.

Gone Fishing

Published online: 01 March 2001; | doi:10.1038/news010308-2
Henry Gee

Our fishy ancestors shed some ancient excess baggage.

How vertebrates evolved from splashing about in ancient seas and lakes to strolling along the beach on a Sunday afternoon is a question of abiding interest to biologists, and takes an odd turn in a study of fossil fishes published this week¹.

The research, by Per Erik Ahlberg of the Natural History Museum in London and colleagues, describes the discovery of a primitive and ancient fossil lobe-finned fish, and sheds light on a bizarre early episode in the evolutionary history of modern vertebrates.

Being land animals, our view of what's important in life is somewhat skewed. The fact is that the vast majority of vertebrates (animals with backbones) are those that we don't see very often -- fishes. Humans and most of the land animals we're familiar with (dogs, cats, horses and so on) can be seen as fishes that have become specialized for living out of water. To do this, their fins have become elaborated into legs.

Land vertebrates belong to a group of fishes called the lobe-finned fishes, or sarcopterygians. Sarcopterygians were once widespread, especially during the Devonian Period (408-362 million years ago), the so-called 'age of fishes'. But now only the land vertebrates, lungfishes and coelacanth survive.

Biologists have been particularly interested in studying the sarcopterygians because they are our aquatic forebears. How did they diverge from actinopterygians, the ray-finned bony fishes? And how are bony fishes as a whole related to other vertebrates such as sharks and exotic, extinct fishes such as placoderms and acanthodians?

The work by Ahlberg's team has caused quite a bit of surprise.

The researchers describe a very primitive sarcopterygian called Achoania from 400-million-year-old rocks in Yunnan in southern China. Remarkably, there is evidence that the eyes of this fish were held in place by stalks of tough connective tissue. This finding was something of a surprise because eyestalks are unknown in sarcopterygians, or indeed any bony fish alive today. But they are typical of sharks, which went down a separate branch on the tree of life millions of years before.

Ahlberg's team also find evidence for eyestalks in a previously known fossil sarcopterygian called Psarolepis This fish, which comes from rocks in Yunnan of similar age to those that yielded Achoania was once thought to have been an unremarkable sarcopterygian, if a rather primitive one. But further work²showed that Psarolepis had many features, such as prominent spines associated with its fins, that are very un-sarcopterygian, and more associated with acanthodians, placoderms and early sharks. What's more, work on a still-unnamed braincase of a primitive actinopterygian from Australia showed that it, too, may have had eyestalks³.

Three lessons can be learnt from the discoveries. First, that the ancestors of bony fishes in general, and sarcopterygians in particular, spent some time shedding primitive features characteristic of fishes in general before diversifying into a range of forms -- one of which gave rise to the land vertebrates. Second, that many features thought to have been specializations of archaic creatures such as acanthodians and placoderms had a more general distribution among vertebrates.

Finally, the work suggests that the Yunnan region of southern China was the birthplace of sarcopterygians, and therefore of the tetrapods, which include land vertebrates like ourselves. Some 400 million years ago, Yunnan and adjacent parts of Vietnam formed an isolated continent, a 'Garden of Eden' that saw the initial stages of sarcopterygian evolution.
References

Zhu,M., Yu, X. & Ahlberg, P. E.A primitive sarcopterygian fish with an eyestalk Nature 410,81 - 842001. | Article | PubMed | ChemPort |
Zhu,M., Yu, X. & Janvier, P. A primitive fossil fish sheds light on the origin of bony fishes. Nature 397,607 - 6101999. | Article | ChemPort |
Basden,A. M.,Young, G. C.,Coates, M. I.& Ritchie, A. The most primitive osteichthyan braincase? Nature 403,185 - 1882000. | Article | PubMed | ChemPort |

The Chinese Evidence for the Evolutionary Origins of Fish

2006-06-30T00:14:00.000-07:00

In this post we’ll discuss the origins of the modern class of boney fish, which as we will see is directly relevant to our own ancestry. First off I’ll present a basic review of fish systematics. There are three extant classes of aquatic vertebrates generally referred to as “fish.” These include the jawless lampreys and hagfish (class Agnatha), the cartilaginous sharks and rays (class Chondrichthyes) and the aforementioned boney fish (class Osteichthyes). The boney fish are further divided into the familiar ray-finned fish (subclass Actinopterygii) and the lesser known lobe-finned coelacanth and lungfish (subclass Sarcopterygii). The actinopterygians are dominated by the teleosts, which include all living boney fish other than sturgeon, gars and their allies. The fossil record of fish is replete with many extinct groups belonging to all the above taxa as well as many other higher order taxa that have since gone extinct (such as placoderms, and acanthodians).

One of the major issues in the evolution of boney fish is the relationship between the ray-finned actinopterygians and the lobe-finned sarcopterygians. When and where did their divergence take place and what were the morphologic characteristics of the common ancestor of these two major groups of fish? This divergence event has a direct bearing on our own evolution as well. Systematically Osteichthyes is a paraphyletic taxon in that it does not contain all the descendants of the common ancestor referred to above. This is due to the fact that the lobe-finned sarcopterygians are the evolutionary source for the terrestrial tetrapods, the four-limbed vertebrates that include amphibians, reptiles and mammals, hence our very origins are tied to the evolutionary split between ray-finned and lobe-finned fish. In this regard the recent announcement by Chinese scientists of a fossil species that had aspects of both extant suborders of boney fish discussed above, which lived more than 405 million years ago in southern China, sheds new light on the origin of the very evolutionary lineage that eventually gave rise to modern human beings.

Zhu Min and his team of researchers at the Institute of Vertebrate Paleontology and Paleoanthropoly, Chinese Academy of Sciences (CAS), originally found the fossils of the ancient fish in 2001 and 2002 at Qujing in Southwest China's Yunnan Province. In the following three years, Zhu and his colleagues discovered more remains that confirmed that this ancient species provides a link between the ray-finned and lobe-finned fish that followed. Zhu and his fellow researchers called it Meemannia eos which translates as “Miman’s Dawn Fish," in honor of the famed Chinese paleontologist Md. Zhang Miman, an academic at the Chinese Academy of Sciences. Its discovery is an exciting step forward for research into the evolution and diversification of ancient fish and other vertebrates.

Martin Brazeau, over at The Lancelet, discusses this transition based on the recently described Chinese fossil Meemannia eos, and rather than reiterate his comments I present them in full below:

“I guess one can't really talk about an evolution transition having 'ends', since one might even consider the origin of vertebrates as a whole to be part of the origin of tetrapods story. However, we focus a lot on the transformation from sarcopterygian (lobe-finned) fishes to the earliest tetrapods like Acanthostega and Ichthyostega. Lest we forget the origin of the sarcopterygians themselves. This is a murky and poorly understood part of vertebrate evolution where the fossils are limited to what we affectionately call "thumbnail skulls". These are usually braincases and associated snouts that aren't much bigger than, well, your thumbnail (and kind of shaped like them too).

“In recent years, we have seen the publication of a number of really peculiar thumbnail skulls from China, nearly all of which belong to some kind of sarcopterygian. One of the defining features of the sarcopterygian skull is a joint that runs right through the braincase. The only living sarcopt to retain such a feature is the modern coelacanth. However, once upon a time in the Devonian, most sarcopterygians were built this way. We know these skulls are sarcopterygian because of this division of the skull and braincase, as well as the histology of the dermal bone. Sarcopterygians are unique in having had a system of pores and canals running through an enamel-like layer on the outside. This tissue matrix is called cosmine. One will often hear of "cosmine-covered osteolepiforms" or "cosmine covered sarcopterygians", to distinguish these forms from taxa that later lose cosmine (for instance, the loss of cosmine is a character that Tiktaalik shares with tetrapods).

“But apart from these defining features of sarcopterygians, the thumbnail skulls from China also have a strange mélange of characters from all kinds of other fish groups: actinopterygian (ray-finned) fishes, sharks, placoderms, and acanthodians. For instance, it was recently noted that several of these taxa had the bony facet for the attachment of an eyestalk -- a cartilage rod found in some modern sharks that supports the eyeball. Similar facets have been seen in fossil shark braincases and later in ray-finned fish braincases. Psarolepis, for instance, was shown to have a cheek very similar to that of an actinopterygian and it even had a spine on a shoulder girdle that was associated with the skull. The actual identity of some of these parts, however, may be disputed because we still haven't got whole skeletons of these fishes.

“Today (5-04-06) in Nature a new piece is added to this puzzle: Meemannia eos. This new taxon is peculiar as far as sarcopts go. It has something sort of like cosmine, but somewhat more rudimentary. However, another interesting aspect is the absence of an intracranial joint, like the one described above.

This 405-Myr-old fish shows a mixture of basal actinopterygian and sarcopterygian features. a, b, Dorsal view of skull roof (a, holotype, V14536.1; b, V14536.2). e, f, Ventral view of posterior portion of the skull roof with incompletely preserved oto-occipital structures (e, V14536.4; f, illustrative drawing). c, d, g, h, Reconstruction of skull roof (c) compared with two actinopterygians, Dialipina (d) and Cheirolepis (g), and one sarcopterygian, Powichthys (h). Abbreviations: am.a, am.e, anterior and external ampullae; cav.cr, cranial cavity; cav.so, supraotic cavity; Dsp, dermosphenotic; It, intertemporal; lc, otic portion of the main lateral line canal; lcc, lateral cranial canal; P, parietal; pdf, posterior dorsal fontanelle; pl.m, pl.p, middle and posterior pit-lines; Pp, postparietal; re.u, utricular recess; sac, sacculus; sca, anterior semicircular canal; soc, supraorbital canal; St, supratemporal; T, tabular; IX, exit of the ninth cranial nerve. Open arrow in c, g and h indicates the position of the orbit. Scale bar, 5 mm (a, b, e, f). From Zhu et al. 2006.
“Immediately, one is faced with two options: was the joint lost or was it simply primtive? The answer appears to be the latter, and that Meemannia is the most primitive sarcopterygian known to date. The skull roofing bones of Meemannia are curiously similar to those of primitive ray-finned fishes. In fact, the authors note, the snout appears to have been loosely attached to the rest of the skull, a feature also seen in placoderms. The weight of the evidence appears to support the conclusion that Meemannia is a rather 'primitive' animal.

The figure is based on two most parsimonious trees that differ in the positions of Ligulalepis. Bremer support values are shown at nodes. Tree length 222, consistency index 0.6216, homoplasy index 0.3784, retention index 0.7807, rescaled consistency index 0.4853. See Supplementary Information for details. Insets compare the histological features of Meemannia (b) with those found in actinopterygians (Andreolepis, a) and crown-group sarcopterygians (Porolepis, c). From Zhu et al. 2006
“Furthermore, I mentioned that it had cosmine or something very much like it. The authors note that what we see in Meemannia the cosmine structure is unique among sarcopterygians and offers some clues about its natural history. In previous decades, the pore-canals have been suggested to represent a system something like the ampullae of Lorenzini in sharks. This is a network of electrosensory organs that sharks have spread over their faces, and the networks of the ampullae are quite similar to that seen in cosmine. Of course, cosmine-covered sarcopterygians are all extinct and we have no way of knowing what the function of the cosmine canals and pores were for. However, the new fossil suggests a rather different function: growth. Unlike the cosmine of other sarcopterygians, but somewhat like the enamel tissue of actinopterygians, the cosmine of Meemannia grew by the addition and expansion of layers. This suggests that Meemannia's cosmine growth is more primitive. Furthermore, this unique mode of growth suggests that he pore-canals may be a vascular system that supprted this, and may not necessarily have been for sensory purposes. However, I don't see these options as neccessarily exclusive, so I'm not sure if we can really rule out a sensory function just yet.

“Meemannia is another addition to the story of the early evolution of bony vertebrates. It's another clue about how this event proceeded and how the two major lineages of bony vertebrates emerged. We still need a lot more clues and a lot more work to figure out the details, but the fossils from China are (once again) helping to disperse the fog.”

Also worth a mention here is that Meemannia eos is named after the renowned vertebrate palaeontologist Chang Mee-mann for her enormous contribution to vertebrate palaeontology, especially in China. Her influence on palaeoichthyology has been enormous and she is easily one of the most respected contributers to the field of early vertebrate and early fish evolution.

Zhu, M. et al. 2006. A primitive fish provides key characters bearing on deep osteichthyan phylogeny. Nature 441: 77-80. <link>

See also:

Basden, A.M. et al. 2000. The most primitive osteichthyan braincase? Nature 403: 185-188. <link>

Zhu, M. et al. 1999. A primitive fossil fish sheds light on the origin of bony fishes. Nature 397: 607–610. <link>

Zhu, M. et al. 2001. A primitive sarcopterygian fish with an eyestalk. Nature 410: 81–84. <link>

Pandas on the Mend?

2006-06-21T18:52:00.000-07:00

The giant panda is one of the world’s most endangered and elusive species. It is found only in a restricted mountainous region in China with an unusual dietary dependence on bamboos found only in these mountains. This elusive nature has shielded important knowledge needed to save it from extinction, until now. (Image courtesy of Cardiff University)

Despite recently expressed concerns for the survival of the Giant Panda due to persistent problems associated with habitat destruction (see Nature Reserves Aren't Protecting Pandas, Study Shows; April 6, 2001) and attempts to increase Giant Panda numbers by artificial means (see Researcher Says Panda Cloning "Worth The Risk", July 7, 1999), it may have a brighter future than previously thought. The following account documents the results of a recent survey of giant panda numbers taken by a joint Sino-Canadian scientific team.

“Scientists at Cardiff University, using a novel method to estimate population, have found that there may be many more giant pandas remaining in the wild than previously thought. Understanding population trends for giant pandas has been a major task for conservation authorities in China for the past thirty years, during which time three national surveys were carried out. The first two revealed alarming evidence of decline in the numbers of giant pandas. However, the most recent survey, carried out in 2002, showed the first evidence of a recovery, thanks largely to protection measures taken by the Chinese government including a network of natural reserves and strictly enforced bans on poaching and deforestation.
"However, given the variable accuracy of traditional ecological population recording methods, scientists from Cardiff's School of Biosciences working with a team in China used a novel approach to accurately estimate population size. The results are published in the international journal Current Biology.

"The team led by Professor Michael Bruford, Cardiff School of Biosciences and Professor Fuwen Wei, Institute of Zoology, the Chinese Academy of Sciences used recently developed 'non-invasive' methods for counting wild animal populations to re-examine panda population estimates. This method profiles DNA from panda faeces to provide a more accurate population profile.

"Professor Bruford said: 'Our results found that previous surveys underestimated the population by more than 50%. These finding indicate that the species has a much better chance of long-term viability, although we must not become complacent, since the population size is still perilously low.'
"The scientists anticipate that these results are likely to be replicated in other key reserves indicating that there may now be many more giant pandas remaining in the wild than previously thoight."

This is of course very encouraging news, particularly for those of us who have a passing knowledge of Chinese prehistory. The giant panda is a conservationist icon and its study in the wild by George Schaller and Chinese colleagues (The Giant Pandas of Wolong) in the early 1980s was a clarion call for renewed efforts to save endangered species worldworld. The giant panda was a major faunal element throughout China south of the Qinling Mts. during the Pleistocene and ranged as far north as the "Peking Man" site during climatic optimums. It survives today as a relic of times gone-by, much as if the giant sloth or glyptodon had survived until today in the American southwest.

The giant panda is now known to be a true bear and not a member of the racoon family as long thought. Its relationship to the smaller red panda, which is regarded today by most systematists as closely tied into the basal radiation of mustelids and procyonids amongst the arctoid canrivorans, is thus paraphyletic. The term "panda" is, like the term "monkey" amongst Primates, purely gradistic in nature and doesn't represent a phylogentic clade. Both species , moreover, seemingly represent early, specialized offshoots of the respective clades to which they belong.

Welcome to Sinanthropus

2006-06-21T14:28:00.000-07:00

Sinanthropus - The genus name originally given to "Peking Man" by Davidson Black, is the title of this blog. It will focus on breaking news regarding the prehistory of China and adjacent regions of Asia. Over the past two decades China has become a major player in the unfolding story of organismic evolution here on planet Earth. From the very origins of life on earth, through the emergence of multicellularity, and the major phyla of plant and animal life, the fossil record being uncovered in China is unparalelled. Virtually every major form of life on earth seems to have its earliest representatives well-represented in the annals of Chinese prehistory, from Precambrian embryos, to the earliest chordates, primeval fish and amphibians, from feathered dinosaurs to early mammals and the first flowering plants, China has become center stage in the unfolding drama of the evolution of life on earth. My specialty has been the study of human evolution in east Asia and I will post extensively on that and related topics, as well as the whole gamut of studies relating to the natural history of China. My first posts will deal with recent finds. I will add posts on previous discoveries and their implications on a continuing basis.