The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Testing evolutionary mechanisms for patterns of craniofacial morphology: distinguishing between neutral forces and selective forces of evolution

NORIKO SEGUCHI, RYAN W. SCHMIDT and ASHLEY MCKEOWN.

Department of Anthropology, The University of Montana, Missoula

Friday 4:00-4:15, Parlors Add to calendar

Recent studies have investigated the degree to which cranial morphology reflects population history under control of stochastic microevolutionary processes or conversely, is related to adaptive changes reflected in diverse environmental conditions. Most studies suggest that changes in cranial morphology preserve a strong population history signal and a weaker adaptive or dietary signal. In contrast, some studies have indicated that size-related craniometrics such as cranial form or nasal aperture shape are influenced by selective forces, primarily climatic in nature. Therefore there is still some debate about the use of craniofacial morphology as a legitimate tool to recover recent human evolutionary and population history.

Here, we aim to provide a framework for distinguishing between neutral forces and selective forces of evolution as a guide to improve our use of craniofacial traits for reconstructing population history. Twenty-four craniofacial measurements and 15 craniofacial indices from Africa and Europe were used to test whether the observed morphological patterns are due to natural selection and shaped by differences in climate, or to neutral processes and/or gene flow. Data were subjected to non-parametric correlation tests, the Relethford-Blangero method, and spatial analysis, including a test of the 'isolation-by-distance' model using Mantel matrix correlation.

Our results indicate the configuration of face and skull modules appears to be neutral. However, weak correlations exist between morphology and climatic variables, specifically nasal and facial height. These correlations indicate some adaptive value to climate, whether from diversifying selection or cultural buffering. These facial dimensions may be useful for investigating various selective pressures.

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