Testing Evolutionary and Dispersion Scenarios for the Settlement of the New World

Instituto de Investigaciones Arqueológicas y Museo, Universidad Católica del Norte, San Pedro de Atacama, Chile.
PLoS ONE (Impact Factor: 3.23). 06/2010; 5(6):e11105. DOI: 10.1371/journal.pone.0011105
Source: PubMed


Discussion surrounding the settlement of the New World has recently gained momentum with advances in molecular biology, archaeology and bioanthropology. Recent evidence from these diverse fields is found to support different colonization scenarios. The currently available genetic evidence suggests a "single migration" model, in which both early and later Native American groups derive from one expansion event into the continent. In contrast, the pronounced anatomical differences between early and late Native American populations have led others to propose more complex scenarios, involving separate colonization events of the New World and a distinct origin for these groups.
USING LARGE SAMPLES OF EARLY AMERICAN CRANIA, WE: 1) calculated the rate of morphological differentiation between Early and Late American samples under three different time divergence assumptions, and compared our findings to the predicted morphological differentiation under neutral conditions in each case; and 2) further tested three dispersal scenarios for the colonization of the New World by comparing the morphological distances among early and late Amerindians, East Asians, Australo-Melanesians and early modern humans from Asia to geographical distances associated with each dispersion model. Results indicate that the assumption of a last shared common ancestor outside the continent better explains the observed morphological differences between early and late American groups. This result is corroborated by our finding that a model comprising two Asian waves of migration coming through Bering into the Americas fits the cranial anatomical evidence best, especially when the effects of diversifying selection to climate are taken into account.
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.

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    • "Although both craniometric and archaeological evidence is very important to understand human peopling and diversification in the Americas, new research needs to consider additional lines of evidence (e.g., ancient DNA) in combination. Despite the difficulty of recovering ancient DNA (Kemp et al. 2007, Raff et al. 2011), future results derived from molecular and morphological data collected from the same populations (Hubbe et al. 2010) should be contrasted directly to elucidate if the genetic structure of American populations was already established with the founding groups. In the last decade, interesting results are emerging that delineate an even more complex scenario, overcoming the previous dichotomization of the one/two migratory waves (de Azevedo et al. 2011) or even the fact that not all molecular studies favor a one-migration model (Perego et al. 2009). "

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