Detecting natural selection in modern human skulls

MARTÍNEZ-ABADÍAS N, ESPARZA M, SJØVOLD T, GONZÁLEZ-JOSÉ R, SANTOS M, HERNÁNDEZ M, KLINGENBERG CP

Columbus, OH, USA

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

American Association of Physical Anthropology

In human evolution, selection is implicitly assumed to be one of the main forces driving evolutionary change and adaptation, but direct evidence of this is rarely available, especially for morphological traits such as skull shape. The main goal of this study is to assess how life-history and fitness measures relate to skull morphological variation, which is the most direct evidence of natural selection. To do this, we use a unique large collection of modern human skulls with genealogical associated data from Hallstatt (Austria). We combine morphological and demographical data and apply multivariate quantitative genetic methods to estimate selection on a three dimensional reconstruction of the skull morphology. Then, we compare the obtained selected pattern with the secular changes observed in this population over a period of almost 200 years. Our results show that selection significantly acted on the evolutionary changes observed in the skull morphology of the Hallstatt’s population during the 18th and the 19th centuries. Indeed, we detect relatively strong directional selection on skull shape and weak stabilizing selection on skull size. However, we find that the expected responses to these selection regimes do not correspond to the actual evolutionary patterns of skull morphology. Therefore, these results emphasize the major role of selective forces both in skull size and shape, but suggests that microevolutionary factors other than natural selection are also contributing to the evolution of the skull in the Hallstatt’s population and obscuring the effects of natural selection.