From Nature:
The first people to colonize the Americas were a band of just 70 hardy explorers and their families, a genetic study suggests. Analysis of Native Americans’ genes shows that their ancestors represented just a tiny fraction of the Asian population at the time. This intrepid group is thought to have made the arduous journey across a long-lost land bridge between Siberia and Alaska about 14,000 years ago. The research suggests that this entire group might have numbered just 200 people, since experts generally expect populations to be about three times the size of the group that ultimately pass on their genes.
“The number of founders might be a surprise to some, although we knew that there was a bottleneck of some magnitude,” says Jody Hey of Rutgers, the State University of New Jersey, who carried out the study. The fact that the most plausible way on to the American continent involved a trek through the frozen north probably meant that few attempted the journey.
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