Ontogeny of Postcranial Robusticity among Holocene Hunter-gatherers of Southernmost Africa

• Main Author: Harrington, Lesley
• Other Authors: Pfeiffer, Susan
• Language: en_ca
• Published: 2010
• Subjects: growth; hunter-gatherer; biomechanics; southern Africa; childhood; physical activity; bone mass; ontogeny; 0327
• Online Access: http://hdl.handle.net/1807/24766

Ontogenetic patterns in postcranial robusticity are analysed in the skeletons of eighty-two juvenile Later Stone Age hunter-gatherers with estimated ages at death ranging from infancy to late adolescence. Robusticity is quantified from cross-sectional geometric properties of diaphyses at sixteen sites throughout the skeleton, using radiography and casting methods. Skeletal growth profiles for strength measures are analysed with locally-weighted regression and additional curve fitting to evaluate developmental trajectories. Ethnographic accounts of infancy and childhood in modern Ju/'hoansi (Khoesan) communities provide a culturally-relevant interpretive framework for evaluating skeletal correlates of behaviour. This research demonstrates that bone strength properties can be functionally linked to behaviour among juveniles toward the reconstruction of patterns of physical activity among prehistoric children. Postcranial strength measures vary predictably with age such that developmental patterns and timing in appositional growth can be assessed reliably. The onset of walking among Later Stone Age juveniles is evident by two years of age from proportional lower to upper limb strength measures. The lower limb continues to adapt to increasing loading demands especially in response to torsional forces, and bending in the medio-lateral plane; biomechanical shape measures illustrate the gradual development of the femoral pilaster. Individual humeral strength is symmetrical with respect to the orientation maximal bending forces experienced throughout development, but the magnitude of the functional adaptive response is greater, on average, in the right limb with more than 70% of the sample over the age of six displaying right-side dominance. Humeral asymmetry and side dominance does not emerge until late childhood, and the majority of arm strength is accrued during adolescence, relative to the sex-combined mean values for Later Stone Age adults. Evidence for sexual dimorphism in upper limb properties is evident by late adolescence whereas sex-based patterns of mobility reflected in lower limb strength have yet to emerge. These results illustrate the developmental patterns that underlie postcranial markers of subsistence activities in Later Stone Age hunter-gatherers.