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

Locomotor diversity and midfoot mobility in gorillas


1Department of Anthropology, New York University, 2Human Origins Program, Department of Anthropology, National Museum of Natural History, Smithsonian Institution

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The recent discovery and description of Australopithecus sediba from South Africa and the Burtele partial foot from Ethiopia has renewed interest in the evolution of the foot in Plio-Pleistocene hominins, as their morphology suggests that early bipeds may have been more diverse in their locomotor repertoires than previously thought. Interpreting the fossil record depends on an accurate understanding of the relationship between bony morphology and locomotor function. Among extant hominids, gorillas are diverse behaviorally, ecologically, and in their locomotor habits, offering an opportunity to understand postcranial morphological diversity in closely related living taxa. Although all gorillas are primarily terrestrial knuckle walkers, western gorillas are characterized by a greater degree of arboreality than eastern gorillas. Here we use laser scans and a three-dimensional methodology to test the hypothesis that western gorillas have more mobile calcaneocuboid and cuboid metatarsal joints than eastern gorillas, increasing mobility in the midfoot and facilitating arboreal locomotion. Our comparative analyses of the calcanei and cuboids of 51 eastern and 29 western gorillas confirmed our functional predictions. Western gorillas have cuboids that exhibit statistically significantly more concave fourth metatarsal facets and larger calcaneal processes, and calcanei with correspondingly deeper cuboid facets than eastern gorillas. These results have implications for understanding hominid pedal evolution and the ways in which natural selection alters bony anatomy in response to ecological, behavioral, and locomotor demands.

This research was supported by a Wenner-Gren Foundation post-PhD grant to M.W.T (Grant No. 7822).

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