Doctoral Dissertation Research: Trabecular and cortical skeletal correlates to locomotor ontogeny in hominoids

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

The growth and development of the human skeleton is affected by the way it is used across the life course. In order to understand how human skeletal development evolved, it is useful to study skeletal development in other closely related primates. The goal of this doctoral dissertation project is to investigate how changes in locomotion across the chimpanzee life course are reflected in the skeleton. Chimpanzees change from moving mostly in the trees when they are young to moving more on the ground as they age, providing an opportunity to examine how chimpanzee trabecular (spongy) and cortical (compact) bone are modified as locomotion changes across the life course. The research will contribute to our understanding of bone biology, specifically the sensitivity of the skeleton to changes in movement throughout life, which can be used to better reconstruct the locomotion of extinct fossil apes and humans, particularly the evolution of terrestriality. This research will be used in K-12 science outreach and exhibited at natural history museums. CT scans and 3D prints of Pan troglodytes and fossil hominoids (apes) will also be part of an international exhibit focused on ape evolution and conservation. All CT scans generated from this project will be shared with the museums where the data were collected, furthering scientific access and inquiry. Bones are a crucial source of data from the fossil record because they undergo modification in response to the mechanical loads placed upon them during movement (e.g. walking, running, climbing). However, most studies to date focus on either trabecular or cortical bone and not the two together in one study. Chimpanzees modify how they move through their life, shifting from more arboreal to more terrestrial substrates from infancy to adulthood. Thus, if the skeleton is responding to these changes, the investigators hypothesize that these transitions will be detectable in trabecular and cortical bone. This study will also address whether both bone types respond to locomotor changes during development, and will apply these findings to other species, extant and fossil, to help in recovering patterns of movement and substrate usage. These questions will be addressed using microCT scans of trabecular bone in the fore- and hindlimb as well as pQCT scans of cortical bone in the shaft of the femur, tibia, humerus, and radius. The prediction is that trabecular and cortical bone at each life history stage will reflect the locomotor behaviors used at that time. By further studying the relationship between ontogenetic changes in behavior and cortical and trabecular bone structure, novel anatomical proxies sensitive to loading patterns may be identified and used to reconstruct the locomotor repertoires of fossil apes and humans. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.