Doctoral Dissertation Improvement: Locomotor Function and the Evolution of the Primate Pelvis

Arizona State University, Scottsdale AZ

Investigators

Abstract

Locomotion is crucial to understanding extant and extinct primate biology because it is a fundamental component of daily activities such as foraging, travel, and predator avoidance. Locomotion is usually inferred in fossil taxa from associations between skeletal form (for example, limb and torso morphology) and locomotion in extant primates. The bony pelvis is a particularly important part of locomotor anatomy because it links the hindlimb locomotor system with the trunk, serves as anchorage for the primary propulsive musculature, and distributes forces that arise during locomotion. It is therefore expected to be influenced by the differing mechanical requirements of alternate locomotor behaviors. However, our understanding of comparative primate pelvic shape and its relationship to locomotor mechanics is limited. The goal of this project is to determine the functional relationship between three-dimensional pelvic skeletal morphology and locomotor behavior in extant primates. A series of adaptive hypotheses will be tested within a broad, comparative sample of 42 primate species using three-dimensional morphometric data collected on pelvic bones located in museum collections. Comparisons among taxa belonging to different locomotor groups will be undertaken to determine the pelvic skeletal correlates of locomotor behavior while controlling for the potentially confounding effects of differences in phylogeny and body size. Because little is known about how the pelvis functions to resist stress during locomotion, biomechanical hypotheses of pelvic stress resistance will be tested using experimental strain data collected on a small sample of primate cadavers. Peak strains associated with loading regimes will be compared to those predicted to determine how the pelvis responds to loading. The resulting data will form the basis of a general biomechanical model of pelvic stress resistance that will inform hypotheses of adaptation. Together, these two approaches will contribute to a better understanding of the interaction between form and function in the primate pelvis, which is crucial for accurate inference of fossil hominin locomotion. Understanding living primate variation is crucial to interpretation of our own evolutionary history. This study will provide new insights into primate anatomy by answering an over-arching biological question regarding how pelvis shape and function vary among primates in relation to their locomotion. Results of this research will be applicable to reconstructions of locomotion in fossil primates, including our human ancestors, and will further our understanding of human evolution.