Phenotypic Evolution of Human Craniofacial Morphology After Admixture: A Geometric Morphometrics Approach.

MARTÍNEZ ABADÍAS, NEUS; GONZÁLEZ-JOSÉ, ROLANDO; GONZÁLEZ MARTÍN, ANTONIO; DER MOLEN, SILVINA VAN; ARTURO TALAVERA,; PATRICIA HERNÁNDEZ,; MIQUEL HERNÁNDEZ,

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY

Año: 2006 vol. 129 p. 387 - 398

0002-9483

An evolutionary, diachronic approach to the phenotypic craniofacial outcome arisen on a human population after high levels of admixture and gene flow was derived by means of geometric morphometrics. Admixture has long been studied after molecular data. Nevertheless, few efforts have been made to explain the morphological outcome on human craniofacial samples. The Spanish-Amerindian contact can be considered as a good scenario for such an analysis. Here we present a comparative analysis of craniofacial shape changes observed between two putative ancestor groups, Spanish and pre-contact Aztecs, and two diachronic admixed groups, corresponding to early and late colonial periods from Mexico Central Valley. Quantitative shape comparisons upon Amerindian, Spanish, and admixed groups were used to test the expectations of quantitative genetics for admixture events. In its simplest form, this prediction states that an admixed group will present phenotypic values falling between those of both parental groups. Results show that, in general terms, although the human skull is a complex, integrated structure, the craniofacial morphological outcome observed fits the theoretical expectations of quantitative genetics. Thus, it is predictive of the population structure and history. In fact, results obtained after the craniofacial analysis are in accordance with previous molecular and historical interpretations, which evidence that admixture is a main microevolutionary agent influencing modern Mexican gene pool. However, expectations are not straightforward when moderate shape changes are considered. Deviations detected at localized structures, such as the upper and the lower face, highlight the evolution of a craniofacial pattern exclusively inherent of the admixed groups, indicating that quantitative characters might respond to admixture in a complicated, non-directional way.