Trabecular Bone Structural Variation of the Human Distal Tibia, Talus, and Calcaneus.

Based on the principles of bone functional adaptation, bone structure has been interpreted as reflective, at least in part, of the mechanical loading environment experienced by an individual during their lifetime. However, the extent to which reduced skeletal robusticity in modern humans over the last 10,000 years is the result of reduced activity and increasing reliance on agricultural subsistence strategies, rather than genetic or environmental factors known to influence skeletal phenotype, is not well understood. The objective of this study is to investigate how bone structure varies between human groups with distinct subsistence strategies, and thus different levels of physical activity and mechanical loading. Here we compare trabecular bone structure in the distal tibia, talus, and calcaneus of three archaeological groups from central and southern Illinois with varying levels of mobility from relatively low mobility mixed strategy agriculturalists to relatively high mobility hunter-gatherers. High-resolution CT image data of the distal tibia, talus, and calcaneus was used to quantify trabecular bone microarchitecture variables including bone volume fraction and degree of anisotropy. Bone structural variables are compared between subsistence groups using registered point clouds and Bayesian multilevel modeling to test whether bone structure differs between groups with different inferred mobility and activity levels, but similar population history and environmental context. Results indicate that variation in trabecular bone structure for the distal tibia, talus, and calcaneus support the hypothesis that more highly mobile subsistence groups have greater trabecular robusticity. Investigating the relationship between bone structure variation and differences in activity and mobility is important for understanding the role of behavioral, ecological, and biological factors in determining human skeletal phenotype.