The timing of the dispersal of our species from Africa is a continuing and lively topic of debate. Evidence that modern humans existed in China more than 100,000 years ago is both equivocal and thought-provoking.
A report by Liu et al., just published in Proceedings of the National Academy of Sciences1, describes modern-human remains from south China that are dated to more than 100,000 years ago. Most researchers would agree that Homo sapiens originated in East Africa between about 190,000 and 160,000 years ago2; that members of the species briefly entered the Levant some 100,000–60,000 years ago3 (when they were displaced by Neanderthals); but that they did not disperse across southern Asia and to Australia until 50,000–60,000 years ago4,5. The new Chinese find implies that they could have left Africa up to 50,000 years earlier — how likely is this?
First, the discovery itself. The remains come from Zhirendong ('Homo sapiens cave'), which is a small cave in Guizhou Province. It was first filled with sediments, the bottom parts of which were eroded by water and replaced by younger deposits, leaving the older sediments as a remnant hanging from the cave roof. The younger sediments are capped by several flowstones — calcite deposits produced inside caves by the action of water — that occur immediately below this remnant and have been dated by the uranium-series (230Th) method to between about 28,000 and 108,000 years ago. The flowstones are in stratigraphic order, with the oldest at the bottom. Because they are continuous across the floor of the cave, they also prevented younger material from being introduced into the underlying deposits.
The human fossils were found below the oldest flowstone, and so they are about 100,000–113,000 years old, and possibly older. The associated faunal remains (of 21 large mammal species and 34 small ones) include some species now extinct in the region, such as the orang-utan (Pongo) and giant tapir (Megatapirus). Overall, 25% of the large mammals are extinct, and a late Middle Pleistocene age of the fauna is therefore consistent with the stratigraphic dating. The age and context of the human remains therefore seem sound.
Those remains consist of the front part of a mandible (lower jaw) and two molar teeth. The latter are small, and would be considered as modern in a Late Pleistocene west Eurasian (post-Neanderthal) sample, but there are insufficient east Asian specimens to show that they are unequivocally modern. Here, the mandible is the key piece of evidence. As described by Liu et al.1, this possesses characteristics seen in both early modern humans and late archaic ones; in China, these are referred to as either 'archaic Homo sapiens' or 'late Homo erectus'. Modern aspects of the mandible include a feature called the anterior symphysis; archaic aspects are the lingual symphysis, and the mandible's overall robustness compared with the gracile (lighter) build of younger, modern-human ones.
The authors1 interpret these characteristics as indicating that modern humans arrived in south China more than 100,000 years ago, and then interbred with the indigenous population. As they point out, this is incompatible with a scenario whereby an immigrant African population of modern humans totally replaced the local population, with no interbreeding.
Is it likely that modern humans entered China as early as 100,000 years ago? Most researchers would disagree: the earliest unequivocal evidence for modern humans from southeast Asia is a cranium from Niah Cave, Borneo, dated to around 40,000 years ago6, and the colonization of Australia by H. sapiens probably occurred no earlier than 50,000–60,000 years ago4,5. Various estimates based on genetic analyses of modern populations suggest that H. sapiens first entered south Asia some 50,000–60,000 years ago7.
However, an earlier exit is not impossible. We need to remember that there is no skeletal evidence for the Homo lineage between Borneo and East Africa over the time span 40,000–100,000 years ago, and so it is a major assumption that modern humans were absent from southern Asia at this time. On palaeoclimatic grounds (as well as proximity to East Africa), it seems unlikely that modern humans entered the Levant in the last interglacial, some 125,000–110,000 years ago, but not the Arabian Peninsula. Once in eastern Arabia, there would have been few barriers to their dispersal eastwards into India.
Recent evidence8 from India indicates that, before 74,000 years ago (the age of the Toba eruption in Sumatra, Indonesia, ash from which forms a major marker horizon across India), stone-core-flaking techniques were similar to those from East Africa, and this implies that modern humans may already have been in India then. Some genetic analyses also suggest that modern humans were in south Asia before the Toba eruption9. Modern humans may therefore have entered southeast Asia earlier than currently thought.
All this is speculation until the requisite fossil evidence is found. However, one note of caution is necessary about the Zhirendong remains. Although there are several Chinese mandible specimens from the early part of the Middle Pleistocene, particularly from the Zhoukoudian locality, there are none from the later Middle Pleistocene. Because of this gap, we do not know how gracile the mandibles of H. erectus became in China between 300,000 and 150,000 years ago.
Does the Zhirendong specimen indicate an early immigrant population of H. sapiens that became more robust by interbreeding with the local population; or (more parsimoniously) does it simply indicate a late H. erectus population that became more gracile over time (Fig. 1)? If Liu et al.1 are correct, we would expect to discover specimens of H. sapiens from south Asia and Arabia that are at least as old as the Zhirendong fossil. But if that fossil represents a late and increasingly gracile example of H. erectus, we would not.
Clearly, more fossils are needed. Meanwhile, this discovery allows tests of the hypothesis that our species left Africa much earlier than currently thought.
Liu, W. et al. Proc. Natl Acad. Sci. USA 107, 19201–19206 (2010).
White, T. D. et al. Nature 423, 742–747 (2003).
Shea, J. J. Quat. Sci. Rev. 27, 2253–2270 (2008).
Klein, R. G. Evol. Anthropol. 17, 267–281 (2008).
Mellars, P. Science 313, 796–800 (2006).
Barker, G. W. W. et al. J. Hum. Evol. 52, 243–261 (2007).
Macaulay, V. et al. Science 308, 1034–1036 (2005).
Petraglia, M. et al. Science 317, 114–116 (2007).
Cabrera, V. M., Abu-Amero, K. K., Larruga, J. M. & González, A. M. in The Evolution of Human Populations in Arabia (eds Petraglia, M. D. & Rose, J. I.) 79–87 (Springer, 2009).
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