Doctoral Dissertation Improvement Grant: The Locomotor Ontogeny of Pan

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The goal of this project is to document how chimpanzee locomotion and anatomy develop from infancy through adulthood. Specifically, the extent to which changes in locomotor behavior over time influence changes in skeletal anatomy will be investigated. Infant chimpanzees are typically carried by their mothers when traveling and principally move using their upper limbs. In contrast, juvenile chimpanzees move entirely by themselves, relying more on quadrupedal locomotion. Quadrupedal knuckle walking increases as individuals age. These behavioral transitions are predicted to result in correlated changes in anatomy, with an initial increase in lower limb bone strength and shape as chimpanzees mature from infancy to juvenility. A second change, in knuckle morphology, related to the stress of knuckle-walking, is expected to occur as individuals age and spend more time moving quadrupedally. This project will integrate observations of chimpanzees in the wild with measurements of bones in museums and analysis conducted in the laboratory. Fieldwork will be conducted in Kibale National Park, Uganda, to document the locomotor behavior of chimpanzees of different ages. Chimpanzees will also be filmed to analyze individual variation in performance within and between locomotor modes. Chimpanzee skeletons from museums will be analyzed using morphological measures, micro CT scanning, and digital photography. Chimpanzees are our closest living relatives and their behavior likely includes elements shared with our ancestors. A systematic study of how chimpanzee movement affects the shape of bones may enable us to identify morphological features induced by behaviors such as knuckle-walking, bipedalism, and suspension. These features can then be used to reconstruct locomotor behavior in fossil apes and humans and provide a better understanding of how humans evolved into bipedal creatures. Results promise to shed light on problems relevant to several fields of study, including functional morphology, bone growth and development, and human evolution.