Ecological variation in Later Stone Age southern African biomechanical properties

Behavioural ecology suggests that human populations modify their behaviour, including subsistence strategy, technology, and mobility, in response to ecological variation. This paper examines if cross-sectional geometric properties (CSGPs) indicative of habitual physical behaviours, including manual activities and terrestrial mobility, vary among southern African Later Stone Age (LSA) Mediterranean Cape coast (n = 85), semiarid central interior (n = 53), and hyperarid Namib Desert (n = 17) individuals. Results will be contextualised using the dietary breadth model, which accounts for the search and handling costs associated with acquiring and processing resources. CSGPs were assessed for humeri, femora, and tibiae using periosteal moulds and 3D laser surface scans at the humerus middistal (35%) location as well as the femur and tibia midshaft (50%) locations. Humerus strength indicators were higher among central interior and Namib Desert females. This may have occurred due to decreased resource quality and quantities in these semiarid and arid ecologies. Females in particular may have enhanced resource-processing efforts to maximise nutritional intake in sparse ecologies. Lower limb biomechanical properties indicative of strength were highest among Cape coast individuals, but it is not clear if search efforts were higher in this region, or if other factors like complex terrain imposed a biomechanical cost for individuals living in this region. Overall, local ecologies interact with subsistence strategies to impact upper limb habitual activities among LSA southern African groups.