Genome pins down arrival and spread of first Americans


The Bering land bridge allowed migration of the first Americans.
SCIENCE PHOTO LIBRARY/SPL CREATIVE

The original Americans came from Siberia over a land bridge in a single wave no more than 23,000 years ago, at the height of the last Ice Age, according to a new genomic analysis.

This population spent thousands of years in the north before spreading in two distinct populations throughout North and South America, the study to be published in the journal Science says.

The Inuit and Eskimo were comparative latecomers, spreading throughout the Arctic from around 5,500 years ago.

The findings by University of California Berkeley researchers are the result of an analysis of the most comprehensive genetic data set from Native Americans to date.

The data consist of the sequenced genomes of 31 living Native Americans, Siberians and people from around the Pacific Ocean, and the genomes of 23 ancient individuals from North and South America, spanning a time between 200 and 6,000 years ago.

"There is some uncertainty in the dates of the migration and the divergence between the norther and southern Amerindian populations," said Yun Song, a UC Berkeley associate professor and lead researcher on the study. "But as we get more ancient genomes sequenced, we will be able to put more precise dates on the times of migration."

The international team concluded that the northern and southern Native American populations diverged between 11,500 and 14,500 years ago, with the northern branch leading to the present day Athabascans and Amerindians broadly distributed throughout North America. The southern branch peopled Central and South America, as well as part of northern North America.

"The diversification of modern Native Americans appears to have started around 13,000 years ago when the first unique Native American culture appears in the archeological record: the Clovis culture," said another author, Rasmus Nielsen.

"We can date this split so precisely in part because we previously have analyzed the 12,600-year-old remains of a boy associated with the Clovis culture."

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