The original Americans came from Siberia in a single wave no more than
23,000 years ago, at the height of the last Ice Age, a new study has
They may have stayed in the north for thousands of years before
spreading in two distinct populations throughout North and South
America, according to a new genomic analysis.
This Ice Age migration over a land bridge between Siberia and
Alaska is distinct from the arrival of the Inuit and Eskimo, who were
latecomers, spreading throughout the Arctic beginning about 5,500 years
ago, the researchers said.
The analysis, using the most comprehensive genetic data set
from Native Americans to date, was conducted using three different
The data consisted 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
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,
but as we get more ancient genomes sequenced, we will be able to put
more precise dates on the times of migration," said co-author Yun Song,
associate professor at the University of California, Berkeley.
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 archaeological
record - the Clovis culture," said Rasmus Nielsen, a UC Berkeley
"We can date this split so precisely in part because we
previously have analysed the 12,600-year-old remains of a boy associated
with the Clovis culture," Nielsen said.
Researchers found that both populations of Native Americans
have a small admixture of genes from East Asians and
Australo-Melanesians, including Papuans, Solomon Islanders and Southeast
Asian hunter gatherers.
"It's a surprising finding and it implies that New World
populations were not completely isolated from the Old World after their
initial migration," said Eske Willerslev from the Natural History
Museum, University of Copenhagen, who headed the study.
"We cannot say exactly how and when this gene flow happened,
but one possibility is that it came through the Aleutian Islanders
living off the coast of Alaska," Willerslev added.
The study appears in the journal Science.