Doctoral Dissertation: A Comparative Analysis of Femur Morphology in Australopithecus afarensis: Implications for the Evolution of Bipedal Locomotion

Arizona State University, Scottsdale AZ

Investigators

Abstract

This project focuses on the proximal femur of the early hominin species Australopithecus afarensis from the Pliocene of eastern Africa (ca. 3.6-3.0 Ma). During the last decade, several new fossil specimens of the proximal femur have been recovered at Hadar, Ethiopia, home of the well-known "Lucy" skeleton. The combined A. afarensis proximal femur sample now numbers 15 primarily adult specimens, some of which will be described for the first time in this study. It is unusual to be able to draw on such a large fossil sample of a single anatomical element to quantify size and shape variation in a fossil species. Several significant questions about early hominins and their locomotor strategies will be investigated using this relatively large fossil sample. The degree of size and shape variation in the A. afarensis proximal femur will be assessed to determine whether it is comparable to that of other hominoids, as it should be if the fossils comprising A. afarensis represent a single species practicing a single mode of locomotion (bipedal walking). The shape of the A. afarensis proximal femur will be compared to that of recent humans, apes and other early hominins in order to identify shared features among groups with shared locomotor strategies, such as bipeds and quadrupeds. Finally, features of the femur that have been argued to be adaptations to bipedal locomotion will be explored in a novel way. A phylogenetic method will be used to examine the pattern of change in femoral features from a hypothetical common (non-bipedal) ancestor to bipedal descendants. The combined analyses will contribute to a better understanding of the proximal femur of A. afarensis, and of the variation in features of the proximal femur as they relate to the evolution of bipedal walking. This research will add important new data to the picture of early hominin evolution and adaptation in Africa. Beyond its intellectual interest, research highlighting the importance of Ethiopian fossils for the study of human evolution contributes to international awareness of the importance of Ethiopia to field and laboratory research, and helps to create local research and training opportunities. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a student to establish a strong independent research career.