The effects of terrain on long bone robusticity and cross-sectional shape in lower limb bones of bovids, Neandertals, and Upper Paleolithic modern humans

Abstract

Theoretically, flexed joint postures on sloped surfaces should increase anteroposterior (AP) bending stresses in both human tibiae and bovid metacarpals; however, irregular terrain should also introduce increases in mediolateral (ML) bending stresses in distal limb bones via increased variation in the orientation of ground reaction forces on the feet and nonlinear locomotion. To investigate the effects of terrain type on lower leg bone cross-sectional geometry, this study uses Neandertal and Upper Paleolithic samples plus a large comparative sample of flat terrain (85 species), mountainous (19 species), and mixed terrain (5 species) bovids to see to what extent terrain affects relative AP to ML strength in lower leg bones. Section moduli at the midshaft were compared between groups occupying contrasting terrains. Results suggest that although locomotion on mountainous terrain routinely introduces elevated AP and ML bending stresses to distal limb segments, perhaps with greater relative increases in the ML direction, the signal for locomotion in non-flat terrain in the cross-sectional properties of the human tibia is an increase in overall bending strength and a slight increase in AP relative to ML bending strength due to lateral buttressing by the fibula.