The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Does the primate zygomatic arch respond to food material properties?


Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University

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The morphology of the primate craniofacial complex is thought to be influenced by the material properties of food. This relationship is often used to explain facial morphology in fossil taxa, yet a comparative analysis linking the two is lacking. Species that process more mechanically demanding foods (i.e., hard and/or tough diets) are expected to have more robust morphologies to combat higher magnitude forces. This hypothesis was tested using the dimensions of the zygomatic arch, a bony structure important in jaw adduction. Primate taxa that consume more mechanically resistant foods were predicted to possess more robust zygomatic arches than those with less resistant diets. Arch robusticity was represented as cross-sectional area (CSA) and measured from microCT scans on anthropoid and strepsirhine skulls (n= 163). Taxa were grouped into two mechanical dietary types (hard/tough and soft/brittle) based on their broad dietary categories (e.g., frugivore, folivore). Phylogenetic generalized least squares regression was used to evaluate the relationship between CSA and a size surrogate (palate breadth) for both diet types while also considering the effect of shared ancestry. The results for strepsirrhines were not significant. Among anthropoids, the two diet types scale in the same manner with size, indicating no significant difference between diet types. Results indicate that observable arch differences among primates are not due to the physical properties of food alone. Implications for interpreting fossil morphology as well as limitations of using dietary category as a proxy for food material properties are discussed.

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