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Erik Trinkhaus, Glenn Conroy, Charles Hildebolt, Herman Pontzer, Christopher Ruff, Richard Smith
Date of Award
Restricted Access Dissertation
Doctor of Philosophy (PhD)
The goal of this research was to explore the developmental acquisition of postcranial strength throughout ontogeny in both recent and Late Pleistocene populations. By combining both developmental and biomechanical perspectives, a better understanding of immature behavior, changing loading regimes during growth, and the ultimate origins of adult patterns of postcranial robusticity was attained. Cross- sectional geometry of the mid-shaft humerus, femur, and tibia was first analyzed in a large and diverse sample of Holocene remains under the age of eighteen (n=626). Patterns of postcranial strength in a sample of Late Pleistocene Neandertals (n=21) and early modern humans (n=82) were then evaluated against this developmental baseline. Four specific research questions were addressed: (1) How do strength proportions between postcranial elements vary during growth? (2) How does humeral asymmetry develop during growth? (3) What is the pattern of tibial and femoral shape change during growth? And (4) How do populations vary in size standardized cross-sectional properties during growth, and when during development do populational differences arise?
The results of the above analyses highlight the affects of mechanical on the growing skeleton, but also emphasize the influence of other intrinsic and extrinsic factors. Through the analysis of strength proportions during growth, it is possible to detect changes in the biomechanical environment related to the developmental adaptation of bipedalism, and draw tentative conclusions about this transition in different populations. Humeral asymmetry develops slowly over the course of growth, only approaching adult levels in adolescence. Patterns of humeral asymmetry in immature individuals may be related to early practice and experimentation with subsistence technologies used by adults. Femoral and tibial shape changes over the course of growth, with early patterns of cross-sectional strength reflecting the biomechanical demands of immature human gait. Lastly, the populational differences in standardized cross-sectional properties that typify adult populations appear very early in development. These differences are related to a combination of factors including activity pattern, genetic propensities, and nutritional status.
Cowgill, Libby W., "The Ontogeny of Recent and Late Pleistocene Human Postcranial Robusticity" (2008). Retrospective Theses and Dissertations. 15.