Objective: This project investigates trabecular bone structural variation in the proximal humerusand femur of hunter-gatherer, mixed-strategy agricultural, medieval, and human groups toaddress three questions: (a) What is the extent of trabecular bone structural variation in thehumerus and femur between populations with different inferred activity levels? (b) How doesvariation in the proximal humerus relate to variation in the proximal femur? (c) Are trabecular bone microstructural variables sexually dimorphic?
Methods: The proximal humerus and femur of 73 adults from five human groups with distinctsubsistence strategies were scanned using a micro-computed tomography system. Centralizedvolumes of interest within the humeral and femoral heads were extracted and analyzed to quantify bone volume fraction, trabecular thickness, trabecular separation, connectivity density,degree of anisotropy, and bone surface density.
Results: In the humerus and femur, groups with the highest inferred activity levels have higher bone volume fraction and trabecular thickness, and lower bone surface density than those with lower inferred activity levels. However, the humeral pattern does not exactly mirror that of the femur, which demonstrates a steeper gradient of difference between subsistence groups. Nosignificant differences were identified in trabecular separation. No consistent patterns of sexual dimorphism were present in the humerus or femur.
Conclusions: Reduced skeletal robusticity of proximal humeral and femoral trabecular bone corresponds with reduced activity level inferred from subsistence strategy. However, human trabecularbone structural variation is complex and future work should explore how other factors (diet, cli-mate, genetics, disease load, etc.), in addition to activity, influence bone structural variation.