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


Hormonal contributions to sex differences in baboon skeletal robusticity

LYNN E. COPES1, HEATHER DROUGHT2, TARPIT PATEL3 and ROBIN BERNSTEIN2.

1Department of Surgery, Yale University School of Medicine, 2Department of Anthropology, George Washington University, 3Department of Orthopaedics, Washington University

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Slender bones (narrow relative to length) are generally assumed to be weaker than robust bones (wide relative to length). However, slender bones compensate for the natural variation in bone shape by adjusting bone quality traits such as tissue mineral density (TMD) to support the loads incurred during daily activities (achieve mechanical functionality) – a consideration of great import given the ubiquitous use of skeletal shape in the fossil record to predict activity patterns and population affinity. Using microCT scans of bones from adult captive baboons (Papio anubis), we tested the hypothesis that the correlation between bone shape and quality would be higher in weight-bearing relative to non-weight bearing bones (N=35). We also investigated patterns of hormones involved in osteogenesis as potential mediators of these relationships. Osteocalcin, adiponectin, and osteoprotogerin concentrations were assayed in serial blood samples collected from a group of juvenile baboons (N=25) and were expected to reveal sex-specific differences around the time of sexual maturation.

The expected inverse relationship between TMD and slenderness existed in the humerus and tibia but not in the femur, ulna, radius, or clavicle. Females invariably exhibited the lower values of shape variables and higher quality measures in these elements. Our analyses revealed significant sex differences in absolute hormone concentration and patterns with age, with notable associations with puberty. These results indicate that the relationship between bone shape and tissue quality are site- and sex-specific and that hormones play a vital role in the development of this subtle interplay.

Funding provided by a grant from the Wenner-Gren Foundation to LC.

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