Siberian boy's ancient DNA holds surprises
By New York Times News Service
Nov. 28, 2013 at 10 p.m.
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. Although none of the Mal'ta boy's skin or hair survive, his genes suggest he would have had brown hair, brown eyes and freckled skin.
The second surprise is that his DNA also matches a large proportion - some 25 percent - 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 Mal'ta boy was aged 3 to 4 and was buried under a stone slab wearing an ivory diadem, a bead necklace and a bird-shaped pendant. Elsewhere at the same site some 30 Venus figurines were found of the kind produced by the Upper Paleolithic cultures of Europe. The remains were excavated by Russian archaeologists over a 20-year period ending in 1958 and stored in museums in St. Petersburg, Russia.
There they lay for some 50 years until they were examined by a team led by Dr. Eske Willerslev of the University of Copenhagen. Willerslev, an expert in analyzing ancient DNA, was seeking to understand the peopling of the Americas by searching for possible source populations in Siberia. He extracted DNA from bone taken from the child's upper arm, hoping to find ancestry in the East Asian peoples from whom Native Americans are known to be descended.
"The study was put on low speed for about a year because I thought it was all contamination," Willerslev said.
His team proceeded anyway to analyze the nuclear genome, which contains the major part of human inheritance. They were amazed when the nuclear genome also turned out to have partly European ancestry. Examining the genome from a second Siberian grave site, that of an adult who died some 17,000 years ago, they found the same markers of European origin. Together, the two genomes indicate that descendants of the modern humans who entered Europe had spread much farther east across Eurasia than had previously been assumed and occupied Siberia during an extremely cold period starting 20,000 years ago that is known as the Last Glacial Maximum.
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. Willerslev's 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.