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Web edition: January 21, 2013
Print edition: February 9, 2013; Vol.183 #3 (p. 18)
A 40,000-year-old human skeleton previously excavated in China has yielded genetic clues to Stone Age evolution.
Ancient DNA from cell nuclei and maternally inherited mitochondria indicates that this individual belonged to a population that eventually gave rise to many present-day Asians and Native Americans, says a team led by Qiaomei Fu and Svante Pääbo, evolutionary geneticists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
The partial skeleton, unearthed in Tianyuan Cave near Beijing in 2003, carries roughly the same small proportions of Neandertal and Denisovan genes as living Asians do (SN: 8/25/12, p. 22), the scientists report online January 21 in the Proceedings of the National Academy of Sciences.
Stone Age people and their close evolutionary relatives interbred infrequently, the researchers suspect. DNA analyses of additional human fossils from Asia and Europe are needed to illuminate how often cross-species flings occurred tens of thousands of years ago.
Citations
Q. Fu et al. DNA analysis of an early modern human from Tianyuan Cave, China. Proceedings of the National Academy of Sciences. Published online Jan. 21, 2013. doi:10.1073/pnas.1221359110.
Suggested Reading
B. Bower. Tangled Roots. Science News. Vol. 182, Aug. 25, 2012, p. 22. Available online: [Go to]
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The strong expression of the Neandertal and Denisovan genes indicates an interbreeding affecting many individuals within the interacting groups so as to affect group genetics enough at the time that the effects would not simply be submerged in the norm of the larger group. At the times this occurred, the interbreeding would not have been "minimal". Subsequent instances of interbreeding may have been less widespread among the groups, perhaps involving occasional individuals, and thus would be more prone for the effects to die out.
The above would apply unless the genes transferred provided a major survival benefit, in which case a smaller number of individuals need have input the new genes. This is also a sample of the surviving groups. The hazards of life during the time would also have wiped out groups that were simply unlucky rather than having genetics unsuitable to the general environment, so some interbreeding may have occurred among groups who then died out before they interbred with the surviving groups.
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