| Although it is known that early human body proportions varied dramatically during the Pleistocene, it is not well understood whether or how these changes in body shape influenced the later stages of the evolution of human bipedalism. Changes in gait mechanics related to variation in body proportions could have implications for interpretations of early human fossil morphology and behavior.; Three major questions were addressed in this research: (I) Is variation in lower limb length related to variation in gait temporal variables that might influence locomotor efficiency? (II) Are variation in lower limb length and crural index related to variation in the mechanics of the swing phase of walking in ways that might influence locomotor efficiency? (III) Are long tibiae related to increases in A-P bending moments on the lower limb during the stance phase of walking?; To answer these questions, I used high-speed video, force plates, and motion analysis software to analyze the gait of 27 modern human subjects. Lower limb length, tibia length, and crural index were tested for association with a number of kinetic and kinematic variables.; I found that individuals with longer limbs have longer strides, lower stride frequencies, and smaller limb angular excursion angles, possibly reducing the energetic cost of locomotion. However, my results suggest that cost of locomotion may be increased somewhat in individuals with long limbs, and/or low crural indices, because they do not appear to compensate in any way for the greater moment of inertia of their swinging limbs. Finally, people with longer tibiae incur greater bending moments on the lower limb during the first half of stance phase. During the second half of stance, they moderate bending moments through a complex of compensatory mechanisms.; If these patterns apply to fossil members of the genus Homo , groups with short limbs and low crural indices (e.g. the Neandertals) may have had less efficient locomotion, potentially affecting subsistence strategies. Hominins with long tibiae (e.g. H. ergaster) may have experienced higher bending moments along the limb during walking, possibly resulting in greater structural reinforcement of the lower limb joints and diaphyses. |
