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


Biomechanical implications on the onset of walking

LIBBY W. COWGILL and ROB'YN JOHNSTON.

Anthropology, University of Missouri, Columbia

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In 2003, Ruff detected a developmental shift in the ratio of femoral to humeral strength in a longitudinal sample of children from the Denver Growth Study, which was associated with the adaptation of bipedal locomotion. However, it is unclear if this transition can be detected using archaeological, cross-sectional data, which is likely to contain additional error relative to longitudinal studies. This analysis is the first to explore whether the developmental onset of walking can be identified in the long bones of a large, temporally diverse sample of immature individuals.

Ratios of femoral, tibial, and humeral strength from seven samples of individuals under the age of eighteen (n=436) were explored using the cross-sectional polar second moment of area. The patterns detected in the analysis of recent modern humans were compared to a very small sample of Late Pleistocene Neandertals and modern humans. Despite great variation, clear changes in these ratios were identified around the age of the onset of walking. In addition, these ratios differ by sample, although the differences detected appear to be closely related to differences in crural index among samples. In addition, Neandertals displayed significant differences in their long bone ratios around the onset of walking. However, the extremely small fossil sample available in the relevant age group makes these differences difficult to interpret. Further research in this area may provide additional information about the onset of walking in the past and in additional fossil groups.

Support provided by the Leakey Foundation, Wenner-Gren Foundation, and NSF BCS-0549925.

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