Biomechanical analysis of vertical climbing in the spider monkey and the Japanese macaque

Climbing is one of the most important components of primate locomotor modes . We previously reported that the kinesiological characteristics of vertica l climbing by the spider monkey and Japanese macaque are clearly different, based on their kinetics and kinematics. In this study, a more detailed ana lysis using inverse dynamics was conducted to estimate the biomechanical ch aracteristics of vertical climbing in the spider monkey and Japanese macaqu e. One of the main findings was the difference in forelimb use by the two s pecies. The results of a joint moment analysis and estimates; of muscular f orce indicate that the spider monkey uses its forelimbs to keep the body cl ose to the substrate, rather than to generate propulsion. The forelimb of t he Japanese macaque, on the other hand, likely contributes more to propulsi on. This supports the idea that "forelimb-hindlimb differentiation" is prom oted in the spider monkey. The estimated muscular force also suggests that the spider monkey type of climbing could develop the hindlimb extensor musc les, which are important in bipedal posture and walking. As a result, we co nclude that the spieler monkey type of climbing could be functionally pread aptive for human bipedalism. This type of climbing would develop the hip an d knee extensor muscles, and result in more extended lower limb joints, a m ore erect trunk posture, and more functionally differentiated fore- and hin dlimbs, all of which are important characteristics of human bipedalism. (C) 2000 Wiley-Liss, Inc.