Evaluating microevolutionary models for the early settlement of the New World: The importance of recurrent gene flow with Asia

Abstract

Different scenarios attempting to describe the initial phases of the human dispersal from Asia into the New World have been proposed during the last two decades. However, some aspects concerning the population affinities among early and modern Asians and Native Americans remain controversial. Specifically, contradictory views based mainly on partial evidence such as skull morphology or molecular genetics have led to hypotheses such as the "Two Waves/Components" and "Single Wave" or "Out of Beringia" model, respectively. Alternatively, an integrative scenario considering both morphological and molecular variation has been proposed and named as the "Recurrent Gene Flow" hypothesis. This scenario considers a single origin for all the Native Americans, and local, within-continent evolution plus the persistence of contact among Circum-Arctic groups. Here we analyze 2D geometric morphometric data to evaluate the associations between observed craniometric distance matrix and different geographic design matrices reflecting distinct scenarios for the peopling of the New World using basic and partial Mantel tests. Additionally, we calculated the rate of morphological differentiation between Early and Late American samples under the different settlement scenarios and compared our findings to the predicted morphological differentiation under neutral conditions. Also, we incorporated in our analyses some variants of the classical Single Wave and Two Waves models as well as the Recurrent Gene Flow model. Our results suggest a better explanatory performance of the Recurrent Gene Flow model, and provide additional insights concerning affinities among Asian and Native American Circum-Arctic groups.

Global Geometric Morphometric Analyses of the Human Pelvis Reveal Substantial Neutral Population History Effects, Even across Sexes

“…Such studies have highlighted that human cranial variation can largely be thought of as a proxy for neutral genetic variation in terms of understanding past population history [1], [15], leading to insights into factors such as the divergence of Neanderthals and modern humans [95], [96], the dispersal of modern humans [10], [30], [97], the demographic signature of the Neolithic expansion [98], [99], and the settlement of the Americas (e.g., [100]–[102]). Our study indicates that shape data for the human pelvis might provide an important adjunct to, or substitute for, cranial data in anthropological questions of this type.…”

A mixed model for the relationship between climate and human cranial form

“…Numerous subsequent studies have applied and expanded upon these methods (Harvati and Weaver, 2006b;Hubbe et al, 2009;von Cramon-Taubadel, 2009;Betti et al, 2010;de Azevedo et al, 2011;Noback et al, 2011;von CramonTaubadel, 2011;Evteev et al, 2014). The results vary.…”

The cranial morphology of the Botocudo Indians, Brazil

“…Therefore, in spite of the ongoing debate concerning the reasons behind the origin of the New World's morphological variability Powell, 2005;Sardi et al, 2005;Gonz alez-Jos e et al, 2008;Hubbe et al, 2010Hubbe et al, , 2011de Azevedo et al, 2011), there is general consensus that the Early Americans exhibited a cranial pattern not represented today among most Native Americans (Jantz and Owsley, 2001;Gonz alezJos e et al, 2005;Neves et al, 2007b;Hubbe et al, 2011). On the other hand, it is still debated for how long this Paleoamerican morphology remained in the continent.…”