A Comparative Ontogenetic Study of Biomechanical Adaptations in the Long Bones of South African Khoisan and Sadlermiut Inuit

This research examines and compares the biomechanical adaptations of juveniles from two different climate-adapted populations: Khoisan foragers from South Africa and Sadlermiut Inuit from Nunavut, Canada. Cortical bone measurements were recorded at three diaphyseal locations on the Sadlermiut and Khoisan humeri, tibiae and femora using biplanar radiographs. Biomechanical strength properties were calculated using the Eccentric Ellipse Method (EEM). EEM calculations were interpreted with consideration to the known behavioural patterns of the two groups. Humeral AP and torsional bending strength were greater in the Sadlermiut compared to the Khoisan – most likely caused by kayak paddling among the Sadlermiut. Few differences were found between the Khoisan and Sadlermiut tibiae and femora. The Khoisan and Sadlermiut may not have been participating in lower body activities with sufficient, or sufficiently different, intensity to produce unique osteogenic responses. The juveniles demonstrated an increase in humeral strength at around age 12 which was concluded to be attributable to the onset of adult activities. However, the strength increases seen in the juvenile tibiae and femora occurred at expected ages for normal growth and could not be fully attributed to the adoption of adult activities.