First Americans Arrived From Siberia

Nov. 27, 2007 -- A new genetic study bolsters claims that Native Americans are descended from one migrant group that crossed a lost land link from modern Siberia to Alaska -- not waves of arrivals from Asia, as rival theories say.

The new study by the University of Michigan, published late Monday, examined genes of indigenous people from North to South America and from two Siberian groups, the university said in a report introducing the research.

Analysis found one unique genetic variant widespread across both the northern and southern American continents -- suggesting that all Native Americans were descended from a single group, not various ones as the rival theory holds.

This variant "has not been found in genetic studies of people elsewhere in the world except eastern Siberia," the report said.

"If there were a large number of migrations, and most of the source groups didn't have the variant, then we would not see the widespread presence of the mutation in the Americas," Noah Rosenberg, a geneticist who worked on the study, was quoted as saying.

Anthropologists and archeologists have long argued over whether Native Americans are descended from migrants who crossed by land to the northwest 12,000 years ago, or waves of arrivals by sea and land from elsewhere in Asia and Polynesia beginning up to 30,000 years ago.

The land link has long since disappeared, giving way to the Bering Strait -- a narrow sliver of sea separating the far northwestern U.S. state from far eastern Russia.

The study also found that genetic diversity increased the further away people were from the Bering Strait -- as would be expected if the migration were "relatively recent," the report said, citing the authors of the study.

It is published in the specialist journal PLoS Genetics.