Our ancestors crossed over a now-submerged land bridge between Siberia and Alaska at the height of the last ice age.
Genomic analysis showed that these original Americans hung out in the north for perhaps thousands of years before spreading in two distinct populations throughout North and South America.
The northern and southern Native American populations apparently 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.
This Ice Age migration is distinct from the arrival of the Inuit and Eskimo, who spread throughout the Arctic beginning about 5,500 years ago.
The findings were to be reported in the July 24 issue of Science.
Due to the large amounts of water trapped on land as ice, sea levels at the height of the last ice age stood some 350 to 400 feet lower than today. Since the Bering Strait is only about 18 stories deep, it remained above water. This provided a land bridge over which our ancestors were able to walk.
Thanks to Marcus Muraca for this link