Different approaches to integration in human skulls: insights from quantitative genetics and studies of artificial deformation

GONZÁLEZ-JOSÉ R, MARTÍNEZ-ABADÍAS, N

Columbus, OH, USA

Congreso; Annual Meeting of the American Association of Physical Anthropology; 2008

American Association of Physical Anthropology

Artificially deformed skulls can be viewed as a “natural experiment” in which particular, recurrent, and localized strains are applied to the skull during early postnatal periods. These plastic changes result in an adult phenotype which strongly departs from the population’s average variability. Here we apply a double approach to investigate the effects of artificial deformation on the inherent patterns of morphological integration in the human skull. Differences in patterns of integration among the neurocranium, basicranium, and face were estimated after the analysis of two different databases. One of them consists of six Amerindian populations including deformed and non-deformed skulls, and presenting three ubiquitous deformatory types: anular, plano-lambdic, and fronto-occipital. The second database consists of a non-deformed series of skulls with genealogical associated data, which enables the estimation of the G matrix of additive genetic variance-covariance among traits. Simulations of response to selection were used to estimate the output of a putative selective event towards classic deformatory types. The “expected” patterns of integration and their putative disruptions were then compared with the “observed” covariances in the Amerindian groups, estimated after a Partial Least Squares analysis. In general terms, the observed integration patterns resemble the expected ones. This suggests that the genetic background implicit in G and the plastic response to strains experienced during post-natal periods follow similar developmental pathways. Finally, both analyses indicate that deformation practices affecting the basicranium results in a stronger disruption of the neurocranium-basal complex observed among other types, supporting previous assertions about the integrative role of the cranial base.