Wednesday, November 20, 2013
The genome of a young boy buried at Mal’ta near Lake Baikal in eastern Siberia some 24,000 years ago has turned out to hold two surprises for anthropologists
The first is that the boy’s DNA matches that of Western Europeans, showing that during the last Ice Age people from Europe had reached farther east across Eurasia than previously supposed. Though none of the Mal’ta boy’s skin or hair survives, his genes suggest that he would have had brown hair, brown eyes and freckled skin. The second surprise is that his DNA also matches a large proportion — about 25% — of the DNA of living Native Americans. The first people to arrive in the Americas have long been assumed to have descended from Siberian populations related to East Asians. It now seems that they may be a mixture between the Western Europeans who had reached Siberia and an East Asian population. The other surprise from the Mal’ta boy’s genome was that it matched to both Europeans and Native Americans but not to East Asians. The scientists' interpretation was that the ancestors of Native Americans had already separated from the East Asian population when they interbred with the people of the Mal’ta culture, and that this admixed population then crossed over the Beringian land bridge that then lay between Siberia and Alaska to become a founding population of Native Americans. The scientists estimate that 14% to 38% of Native American ancestry may originate through gene flow from this ancient population. A European contribution to Native American ancestry could explain two longstanding puzzles about the people’s origins. One is that many ancient Native American skulls, including that of the well-known Kennewick man, look very different from those of the present day population. Another is that one of the five mitochondrial DNA lineages found in Native Americans, the lineage known as X, also occurs in Europeans.