Gene Expression

How were the Americas peopled?

Until recently archeologists held to a model called Clovis First which posited that the Amerindians were descended from Siberian hunters who swept down from Beringia 13,000 years ago and spread rapidly north to south. Findings such as Monte Verde have thrown a cloud over the cleanliness of this hypothesis and there doesn’t seem to be any claimant to the throne at this point.

Geneticists have been weighing in on this topic now and then. Roughly, one line of results seems to suggest that the Amerindians have been resident on the New World for far longer than 10,000 years. Another finding has been that the ancestors of the indigenous people went through a massive population bottleneck and subsequent demographic expansion. It doesn’t seem like geneticists have yielded results with enough precision to decide the matter, but here is another forthcoming study, New Ideas About Human Migration From Asia To Americas:

“These archaeological dates suggested two likely scenarios,” the authors wrote: Either the ancestors of Native Americans peopled Beringia before the Last Glacial Maximum, but remained locally isolated – likely because of ecological barriers – until entering the Americas 15,000 years before the present (the Beringian incubation model, BIM); or the ancestors of Native Americans did not reach Beringia until just before 15,000 years before the present, and then moved continuously on into the Americas, being recently derived from a larger parent Asian population (direct colonization model, DCM).

“Our data supports the second hypothesis: The ancestors of Native Americans peopled Beringia before the Last Glacial Maximum, but remained locally isolated until entering the Americas at 15,000 years before the present.”

Actually, this isn’t that new of an idea. Others have posited that Beringia was the scene of a great deal of in situ evolution. Nevertheless, the idea seems plausible, and I’m especially pleased to see data for back migration. The Inuit peoples after all span the Old and the New Worlds. No reason they need be pioneers.


  1. #1 Suvrat Kher
    October 29, 2007

    Interesting results. A minor quibble. As it appears in your post it is really the first hypothesis that seems to be supported by the new MtDNA data. You did not include this para from the Science daily release:

    “Thus, for this study the team set out to test the two hypotheses: one, that Native Americans’ ancestors moved directly from Northeast Asia to the Americas; the other, that Native American ancestors were isolated from other Northeast Asian populations for a significant period of time before moving rapidly into the Americas all the way down to Tierra del Fuego.”

    Here it becomes the second hypothesis.

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