The peopling of America: Craniofacial shape variation on a continental scale and its interpretation from an interdisciplinary view

Abstract

Twenty-two years ago, Greenberg, Turner and Zegura (Curr. Anthropol. 27,477-495, 1986) suggested a multidisciplinary model for the human settlement of the New World. Since their synthesis, several studies based mainly on partial evidence such as skull morphology and molecular genetics have presented competing, apparently mutually exclusive, settlement hypotheses. These contradictory views are represented by the genetic-based Single Wave or Out of Beringia models and the cranial morphology-based Two Components/Stocks model. Here, we present a geometric morphometric analysis of 576 late Pleistocene/early Holocene and modern skulls suggesting that the classical Paleoamerican and Mongoloid craniofacial patterns should be viewed as extremes of a continuous morphological variation. Our results also suggest that recent contact among Asian and American circumarctic populations took place during the Holocene. These results along with data from other fields are synthesized in a model for the settlement of the New World that considers, in an integrative and parsimonious way, evidence coming from genetics and physical anthropology. This model takes into account a founder population occupying Beringia during the last glaciation characterized by high craniofacial diversity, founder mtDNA and Y-chromosome lineages and some private autosomal alleles. After a Beringian population expansion, which could have occurred concomitant with their entry into America, more recent circumarctic gene flow would have enabled the dispersion of northeast Asian-derived characters and some particular genetic lineages from East Asia to America and vice versa.

MORPHOMETRIC AND mtDNA ANALYSES OF ARCHAIC SKELETAL REMAINS FROM SOUTHWESTERN SOUTH AMERICA

“…As early as 9,000 BP, the four founding haplogroups were present and no haplogroups different to the Amerindian ones have been described. These results support the one-way migration hypothesis which recently has been also positively contrasted using complete sequences of mtDNA (Fagundes et al 2008;Perego et al 2009;Tamm et al 2007), and even craniometric distance data (González-José et al 2008) It is noteworthy that, to our knowledge, haplogroup A had not been found in the Americas in Paleoindian or Early Archaic skeletal remains. Until now the oldest member of this haplotype in the New World dated to 4,504 ± 105 years BP (Kaestle and Smith 2001).…”

Probing deeper into first American studies

“…The earlier form is the Paleoamerican, which is believed to show more similarity to that of the first modern humans still present today in living Africans and Australo-Melanisians (47,50,52); the later form is Mongoloid. Rather than representing different source populations, these 2 types may instead be extreme forms along a morphological continuum of variation (49). This dual pattern contrasts with the genetic evidence that suggests homogeneity in terms of haplogroups from east Asia (28,33,44).…”

“…Some researchers believe it is indicative of climatic adaptations more than genetic signals (55). Others point to gene drift and adaptations to local evolution after the first people arrived and then spread out over the Americas (49). Whatever the reason may be, the combined data reveal significant variation in early crania morphology, probably suggesting separate migrations into the Americas from different source areas and/or the first immigrants were already heterogeneous at the time of entry.…”

“…Initially, these studies observed variation in skull form and suggested that early Americans had ancestral links with ancient populations known from Asia and that the variation can be accommodated in a single biological population, the Mongoloids (47), a conclusion also made by early genetic studies. However, crania analyses also show an increasingly wide range of characteristics, leading some researchers to believe that 2 early populations had different times of entry into the Americas and diverse biological and genetic origins (47)(48)(49)(50)(51), not only including northeast Asia but south Asia and possibly Europe, Africa, and AustraliaMelanesia. The earlier form is the Paleoamerican, which is believed to show more similarity to that of the first modern humans still present today in living Africans and Australo-Melanisians (47,50,52); the later form is Mongoloid.…”

Estudios De Los Dermatoglifos en Fueguinos

“…Sea como fuere, la síntesis del conocimiento actual establecería un modelo en que el poblamiento precolombino del confín austral de América estaría directamente relacionado con la expansión de los grupos que poblando ambas vertientes de la cordillera andina ocuparían el territorio fueguino dando lugar a una morfología diferenciada en el contexto americano pero explicable dentro del parentesco con los grupos andinos y patagónicos como se infiere de los resultados de los análisis de la diversidad craneal (González-José et al 2004) y molecular (Lipschutz et al 1946;Matson et al 1967;Llop, 1996;Moraga et al 2000) en el marco de una hipótesis del poblamiento americano que contemplaría los extremos de diversidad en una continuidad morfológica ya presente en el poblamiento inicial de Beringia (González-José et al 2008).…”