Friday, December 19, 2008

Homo floresiensis: More Evidence for Speciation in East Asia

According to a story out of Biology News Net, Kieran McNulty and Karen Baab of SUNY Stony Brook have demystified some of the fog surrounding the "hobbit" species (I hate that term) that was discovered in the Indonesian island of Flores.

Comparing the simulation to the original Flores skull discovered in 2003, McNulty and Baab were able to demonstrate conclusively that the original "hobbit" skull fits the expectations for a small fossil hominin species and not a modern human. Their study was published online this month in the Journal of Human Evolution.

The cranial structure of the fossilized skull, says the study, clearly places it in humanity's genus Homo, even though it would be smaller in both body and brain size than any other member. The results of the study suggest that the theorized "hobbit" species may have undergone a process of size reduction after branching off from Homo erectus (one of modern day humanity's distant ancestors) or even something more primitive.

Here is the conclusion from the Journal of Human Evolution article that is currently in press:

The numerous primitive features of the mandible (Brown, in this issue) and postcranial skeleton (Brown et al., 2004; Morwood et al., 2005; Argue et al., 2006; Larson et al., 2007; Tocheri et al., 2007; Jungers et al., 2008), combined with the shape of the cranium, suggest that the ancestor of H. floresiensis was more primitive than the majority of Asian H. erectus specimens, perhaps resembling the oldest Sangiran dome fossils (Kaifu et al., 2005). Here, the overall shape of the LB1 cranial vault was most similar to the East Turkana hominins and D2280 from Dmanisi (see also Brown et al., 2004; Argue et al., 2006). These results concur with the hypothesis that the Liang Bua fossils may have descended from a hominin population more primitive than Asian H. erectus that underwent a process of size reduction.

Any way you shake it, the evidence is adding up that this does indeed represent a species of hominin/hominid that is separate from what else is going on in Wallacea at this point in time and further supports this "bush" notion of hominid evolution. As modern humans, we have grown accustomed to the idea of being the only species of Homo running around. As far as fauna are concerned, that is the exception to the rule. I think we also cling to this unilineal notion of human evolution in East Asia that is turning out to be unwarranted. There was, evidently, a bit of experimentation going on. What is stunning is the sheer primitiveness of the H. floresiensis fossils.

Baab, K and McNulty, K (2009) Size, shape, and assymetry in fossil hominis: The status of the LB1 cranium based on 3D morphometric analyses. Journal of Human Evolution. (in press)

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