Biomechanical beam analysis of long bones from a late 18th century slave cemetery in Cape Town, South Africa

This study aims to quantify the physical demands of a sample of late 18th century skeletons from an unmarked burial site on Cobern Street, Cape Town, South Africa. Historical studies suggest that these individuals were either slaves or "free black" people of low socioeconomic standing. Cortical cross-sectional areas of paired humeri and tibiae from the Cobern Street collection (N = 29), a modern cadaver collection (N = 31), and a hunter-gatherer collection (N = 30) were compared by means of biomechanical beam analysis on computerized tomography scans. Results showed that the Cobern Street sample, both males and females, were closer to the modern group in total tibial cortical area and in the second moments and polar moments of cortical area, than to the hunter-gatherer group. It is assumed that these results can be explained by differences in lower limb activity. Tibial strength properties showed the hunter-gatherer peoples to be highly mobile and active walkers in comparison to the Cobern Street and modern samples. The males from the Cobern Street sample showed significantly higher values for humeral strength properties than either the hunter-gatherer or modern individuals, attesting to their status as manual laborers. The humeral cross-sectional strength properties for females were very similar between the Cobern Street and modern groups but again significantly different from the hunter-gatherer sample. The domestic chores performed by females of the recent cadaver sample may be very similar to those performed by the Cobern Street sample.