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


Skeletal correlates of climbing behavior in the ankles of rainforest hunter-gatherers

THOMAS S. KRAFT1, VIVEK V. VENKATARAMAN1, JEREMY M. DESILVA2 and NATHANIEL J. DOMINY1,3.

1Biology, Dartmouth College, 2Anthropology, Boston University, 3Anthropology, Dartmouth College

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Paleoanthropologists use associations between behaviors and their skeletal correlates in modern humans to infer behavior in the fossil record. Rainforest foragers, many of whom express the pygmy phenotype, have diverse locomotor repertoires that include significant amounts of dense forest-walking, vertical climbing, and digging. While theoretical considerations and empirical data suggest that navigation through dense understorey, in addition to vertical climbing behavior, would favor small stature, skeletal correlates of behavior in modern rainforest hunter-gatherers remain largely unstudied, despite the relevance of these populations for reconstructing the activity patterns of hominins.

Great apes bear several features in the ankle that are associated with vertical climbing. To test whether habitually climbing humans express similar features, we compared five skeletal traits of the distal tibia between great apes, non-climbing humans, and climbing humans (African pygmies and Southeast Asian negritos): 1) Size-standardized anterior width, 2) depth of the tibial articular surface, 3) tibial angle, 4) thickness of the medial malleolus, and 5) metaphyseal shape. Our results indicate few differences between climbing and non-climbing humans. Although the precise activity patterns of the individuals we studied cannot be known, our results suggest that climbing behavior is not reflected in the aspects of ankle morphology studied here. In addition, it is not clear whether these traits in the ankle are controlled by genetic or ontogenetically-plastic processes, and frequent climbing in humans may be also be facilitated by other mechanisms. Regardless, skeletal correlates of climbing in modern hunter-gatherers could inform functional interpretations of fossil hominins.

T.S.K. and V.V.V. are supported by National Science Foundation Graduate Research Fellowships. We acknowledge the support of a Friedman Family Fellowship at Dartmouth College.

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