Biological anthropologists have long maintained a keen interest in the adaptations that allowed primates to successfully invade the arboreal habitat, where stability is paramount. Decades of research have identified anatomical features, such as grasping hands and feet, and behavioral mechanisms, such as the use of distinctive walking styles, which arguably facilitate stability on branches. Nevertheless, we still have an incomplete understanding of the mechanisms by which primates actually keep balance when moving about in the trees. The proposed research will remedy this gap by carrying out a series of experiments to understand balance performance in both New and Old World monkeys. In so doing, we will gain deeper insight into several fundamental issues of primate, and human, evolution -- such as the functional importance of grasping hands and feet and the possible consequences of tail loss among the apes. Basic data on the balance capabilities of common laboratory primates may also be of use to researchers studying primate stability in more clinical settings, perhaps shedding light on human balance disorders. Moreover, the collaborations engendered by this research will broaden educational experiences of STEM students at the host institution and neighboring colleges and universities, helping to build a collaborative network of research and training throughout the region.
Investigators will address three specific research aims. First, to determine the relationship between morphological variation and the capacity for grasping force production, functionally-informed hand and foot musculoskeletal anatomy will be combined with experimental data on maximum grip strength. Second, to generate quantitative measures of stability, researchers will collect detailed biomechanical data from monkeys moving over simulated arboreal substrates. Finally, a series of force sensors mounted on compression springs will be used to gauge balance performance on mobile branches, providing a measure of arboreal balance control in a more naturalistic setting. This fundamental biomechanical research will 1) allow testing of long-held assumptions about the nature of primate locomotor adaptation, 2) inform reconstructions of grasping ability and locomotor performance in the primate fossil record, and 3) introduce a novel set of research methodologies to the discipline of biological anthropology.