Doctoral Dissertation Research: Functional Morphology and Macroevolution of the Mammalian Cervical Vertebral Column

Bipedal locomotion is a hallmark trait of the human evolutionary lineage, representing a major transition away from the apes and other primates. This pivotal shift can be investigated through studies of the neck, as the human neck is adapted to balance and stabilize the head during bipedal movements. This doctoral research project will test how the shape of the bones of the neck relate to locomotion and posture in a diverse sample of mammals. The findings will be used to interpret fossilized neck bones from extinct human relatives to learn about their early forms of bipedalism, as well as potentially informing clinical research. This project will also support the sharing of three-dimensional scan data through digital repositories and the training and mentorship of student researchers, including those from groups underrepresented in scientific fields. Cervical vertebrae in the hominin fossil record can provide insight into the interplay between the head, neck and trunk during key locomotor and postural transitions. Currently, however, functional interpretations of these fossils are limited to broad categories such as "human-like" neck mobility or "ape-like" neck posture. The goal of this dissertation is to improve hominin neck reconstructions by experimentally testing how cervical vertebral shape relates to neck function, locomotor mode, and trunk posture. This goal will be addressed in three objectives: 1) quantify the relationship between vertebral shape and neck mobility using bending mechanics experiments, 2) develop neck posture models in living species using virtual reconstruction methods, and 3) evaluate patterns of vertebral shape change across diverse mammalian groups using phylogenetic comparative methods. The objectives will be tested in a broad sample of primates, rodents, and marsupials. These groups contain species with independently-evolved forms of bipedal locomotion and upright trunk posture, allowing for independent verification of form-function relationships. This project will provide the foundational data necessary to quantitatively interpret functional information from cervical vertebral fossils, furthering our understanding of the nature and biomechanical demands of bipedalism in early hominins. 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.