Biomechanical hypotheses have been developed to suggest that both body size and body proportions should cause predictable changes in the locomotion of quadrupedal animals. These suggestions have been used to reconstruct locomotor modes of fossil primates. However, these hypotheses have not been adequately tested experimentally. Using a high-speed 3D motion analysis system in conjuction with a force platform, this study will quantify the locomotor patterns and mechanics of a closely related group of Old World monkeys that habitually move quadrupedally on the ground (vervets, patas monkeys, baboons, pig-tailed macaques). The primary goal is to measure the effects of both body size and body proportions on locomotor performance variables. Three different types of comparisons will be made: intraspecific comparisons between males and females of each species since they differ in body size but have similar body proportions; narrow interspecific comparisons between individuals that have similar body mass, but differ in body proportions; and broad interspecific comparisons across the entire sample. These data will be useful for evaluating the mechanical hypotheses that relate body size and body proportions to locomotion. In addition, experimentally established relationships between locomotor behavior and morphology will increase the level of confidence that is placed in the functional interpretations of the locomotor morphology of fossil primates.
