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


The relationship between cortical bone thickness and curvature in metatarsals of Homo and Pan and implications for hominin foot morphology

JULIET MCCLYMONT1, TEA JASHASHVILI2, KRISTIAN J. CARLSON2,3 and BERNHARD ZIPFEL1,2.

1Bernhard Price Institute, University of the Witwatersrand, 2Institute for Human Evolution, University of the Witwatersrand, 3Department of Anthropology, Indiana University

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Hominoids practice a diverse array of locomotor behavior, from obligate terrestrial bipedalism to arboreal suspensory behavior, which is reflected in the variable morphology found in their foot bones. That hominin foot bones reflect locomotor behavior is also clear, but the forms of locomotor behaviors to be inferred are less clear. Pressure plate studies indicate that the center of pressure tends to move medially in the human foot during the last half of stance phase of bipedal gaits, while it tends to remain relatively more lateral in the chimpanzee foot during the last half of stance phase. Here we compare metatarsals of Homo sapiens [n=25] and two species of Pan (Pan paniscus [n=16] Pan troglodytes schweinfurthii [n=23] in order to explore Homo and Pan metatarsal morphology and foot function. Specifically, we address whether cortical thickness is associated with diaphyseal curvature in metatarsals. We also track these associations across metatarsals of the foot in order to determine whether species exhibit medial versus lateral trends suggested by plantar pressure studies.

We evaluate thickness of cortical bone along metatarsal diaphyses (I-V) using linear dimensions at medial, lateral, plantar and dorsal regions of interest (ROIs), which are coordinated with morphometric thickness maps of diaphyses. The relationship between diaphyseal curvature and cortical thickness at plantar and dorsal ROIs differs. These relationships are evaluated within the sample for single metatarsals as well as across metatarsals within a foot. Implications of these relationships for hominin foot form and function are discussed.

We would like to thank the Department of Science and Technology, National Research Foundation, the University of the Witwatersrand and the Claude Leon Foundation, South Africa for the funding that facilitated the analysis of this research.

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