Assorted developments in palaeoanthropology

The notion that Neanderthals were dim and brutish compared with us continues to be undermined, but although their brain capacity was as large and in some cases distinctly larger than that of fully modern humans, its shape was significantly different; longer towards the rear than our more rounded brain. Studies of a Neanderthal baby and three children reveal that just after birth the Neanderthal brain was virtually identical to that of fully modern babies, i.e. elongate, but remains so in childhood through to maturity, whereas modern children’s brains develop towards the roundness of adults. Consequently, there must have been differences in the parts of the brain from which aspects of behaviour stem: Neanderthals almost certainly behaved differently from us both in childhood and as adults (Harvati, K. et al. 2010. Evolution of middle-late Pleistocene human cranio-facial form: a 3-D approach. Journal of Human Evolution, v. 59, p. 445-464. See also: Gibbons, A. 2010. Neandertal brain growth shows a head start for moderns. Science, v. 330, p. 900-901).

The now widely accepted hypothesis that modern humans did not begin to leave Africa to colonise Eurasia until about 60 ka may be under threat from reports of what seem to be fully modern human remains in China dated to ~105 ka (Liu, W. et al. 2010. Human remains from Zhirendong, South China, and modern human emergence in East Asia. Proceedings of the National Academy of the US, v. 107, p. 19201-19206). The dating appears to be sound, being based on the uranium-series (230Th) method applied to flowstone that rests on top of the sedimentary layer containing the remains in Zhirendong cave. The precipitated calcite layer completely sealed in the fossils as soon as it began to form about 105 ka ago, indicating that they are older still. Whether or not the remains are of fully modern humans is uncertain. Had they been found in Europe there would be little doubt about their affinities, the only other contemporary hominins being the Neanderthals. The problem in South China is that it was inhabited by H. erectus and the finds may be from ‘late’ members of that archaic species which arrived more than a million years earlier than fully modern humans. Judging by the DNA evidence for three interfertile hominin genetic groups cohabiting Eurasia, there is a host of possibilities for the Zhirendong fossils. One line of evidence that does not rule out that they are fully modern is the occurrence of stone tools more advanced than used by Asian H. erectus beneath the 74 ka Toba volcanic ash in India. It seems inevitable that these remains will be tried for DNA sequencing

See also: Dennell, R. 2010. Early Homo sapiens in China. Nature, v. 468, 512-513

It is well accepted that as with all forms of life the twists and turns in hominin evolution was surely tuned by changes in their environments. But that is not just linked to the immediate milieu of individuals: environments change on all scales up to that of the entire planet and reflect physical as well as biological processes. The largest scales are generally assumed to be the province of climate change, yet animals also occupy a landscape subject to geophysical forces such as tectonics and erosion. Geoffrey Bailey and Geoffrey King of the University of York, UK and the Institute de Physique du Globe in Paris, France have championed the view that water supplies and topography, for example, are just as influential over hominin evolution as interspecies competition and changing vegetation patterns for almost two decades. They have now put their ideas to rigorous tests (Bailey, G.N.& King, G.C., 2010 (in press) Dynamic landscapes and human dispersal patterns: Tectonics, coastlines, and the reconstruction of human habitats. Quaternary Science Reviews doi:10.1016/j.quascirev.2010.06.019). This fascinating and well illustrated paper correlates known hominin sites in Africa with variations in topography and its roughness, derived from global elevation data from the Shuttle Radar Topography Mission (SRTM), active seismicity, Neogene uplift and volcanicity.

Perspective view of the Afar depression and en...

Afar Depression: a cradle of human evolution

They concentrate on the rich palaeoanthropological pickings of the Afar Depression and the Sterkfontein area of South Africa, applying their ideas and findings to the eastern coast of the Red Sea at the recently discovered Palaeolithic site of Harat Al Birk south of Jeddah, and the Red Sea islands that would have been connected to either side of the Red Sea during the last glacial maximum because of a 130 m lower sea level. This application is vital for directing searches for new site that relate to the pathways out of Africa for early modern humans. Though a largely empirical study, it forms a link between human evolution and geological and landscape change that is not yet widely grasped and linked to climate studies.

See also: Marshall, M. 2010. Evolution by shake, rattle and roll. New Scientist, v. 208 (13 November 2010), p. 8-9.

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