Two distinct groups from Asia settled in the New World and not one single migration as suggested by previous genetic studies, experts said Monday after comparing the skulls of early Americans.
Paleoanthropologists from Brazil, Chile and Germany compared the skulls of several dozen Paleoamericans, dating back to the early days of migration 11,000 years ago, with the more recent remains of more than 300 Amerindians.
"We found that the differences between Early and Late Native American groups match the predictions of a two-migration scenario far better than they do those of any other hypothesis," they said.
"In other words, these differences are so large that it is highly improbable that the earliest inhabitants of the New World were the direct ancestors of recent Native American populations."
Their landmark research found differences in the cranial morphology that could only be explained by the fact that the last common ancestor of the Early and Late Native American groups came from outside the continent.
The experts agreed the differences were best explained by a scenario in which a first wave of settlers came across the Bering Strait from Northeast Asia followed by a second group from East Asia much later via the same route.
"We conclude that the morphological diversity documented through time in the New World is best accounted for by a model postulating two waves of human expansion into the continent originating in East Asia and entering through Beringia," they said.
"This disparity between our results and those of most genetic studies points to a large gap in our understanding of the peopling of the New World."
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PloS ONE paper: www.plosone.org/article/info:doi/10.1371/journal.pone.0011105