The relationship between femur shape and terrestrial mobility patterns

Abstract

Femoral diaphyseal cross-sectional shape is commonly used to interpret levels of terrestrial logistic mobility (TLM; daily distance covered on land by individuals or groups) in human archaeological populations. However, variation in femoral diaphyseal shape can be influenced by factors other than TLM, such as other lower limb habitual activities, differences in body physique (especially body breadth), age of onset of activities, terrain type, and other environmental and cultural factors. Therefore, similarly shaped femora can occur in populations with different levels of TLM depending on whether the shape differences are due to changes in anteroposterior or mediolateral bending strength. In this chapter, I discuss factors that influence femoral diaphyseal shape and robusticity by comparing diaphyseal shape between individuals with normal mobility and limited or impaired ambulatory ability, examining temporal trends in Native American and modern US populations, and examining ontogenetic factors and non-ambulatory activities on femoral diaphyseal cross-sectional shape. I also discuss and summarize why using multiple biomechanical properties and several bones can provide a clearer picture of the pattern of activity obtained from long bone morphology. I argue that basic femoral diaphyseal shape ratios can be used to estimate levels of TLM when all variables are carefully considered, and that the use of multiple bones and indicators provides a more robust understanding of the mechanical loads that cause similarities and differences in long bone morphology than shape alone.