Columbus and the natives: a family reunion

From Nature: 

DNA was taken from the boy's arm bone

The 24,000-year-old remains of a young boy from the Siberian village of Mal’ta have added a new root to the family tree of indigenous Americans. While some of the New World's native ancestry clearly traces back to east Asia, the Mal’ta boy’s genome — the oldest known of any modern human — shows that up to one-third of that ancestry can be traced back to Europe.

The results show that people related to western Eurasians had spread further east than anyone had suspected, and lived in Siberia during the coldest parts of the last Ice Age.

“At some point in the past, a branch of east Asians and a branch of western Eurasians met each other and had sex a lot,” says palaeogeneticist Eske Willerslev at the University of Copenhagen, who led the sequencing of the boy’s genome. This mixing, he says, created Native Americans — in the sense of the populations of both North and South America that predated — as we know them. His team's results are published today in Nature¹.  ...

This new origin story helps to resolve several peculiarities in New World archaeology. For example, ancient skulls found in both North and South America have features that do not resemble those of East Asians. They also carry the mitochondrial haplogroup X, which is related to western Eurasian lineages but not to east Asian ones.

On the basis of these features, some scientists have suggested that Native Americans descended from Europeans who sailed west across the Atlantic. However, says Willerslev, “you don’t need a hypothesis that extreme”. These features make sense when you consider that Native Americans have some western Eurasian roots.

“There remains some debate about whether there was a single expansion of human groups into the Americas or more than one,” says Theodore Schurr, an anthropologist from the University of Pennsylvania in Philadelphia. “The data from this paper support a single-migration scenario,” he says, but still allows for several sequential ones from the same intermingled Siberian gene pool.