First Americans Arrived in Three Waves From Siberia
A detailed genetic analysis has settled the question of how and when the first Americans arrived in the continent. Scientists have found that Native American populations from Canada to the southern tip of Chile arrived in at least three waves. Most are descended entirely from a single group of migrants that crossed over through Beringia, a land bridge between Asia and America that existed during the ice ages, more than 15,000 years ago. Once in the Americas, people expanded southward, sticking to the coast with populations splitting off along the way. “There are at least three deep lineages in Native American populations,” said David Reich, professor of genetics at Harvard Medical School.