Doctoral Dissertation Research: The evolution of early hominin locomotor anatomy

Washington University, Saint Louis MO

Investigators

Abstract

Bipedalism is the ability to habitually stand and walk upright on two legs and is one of the defining features of humans. Consequently, our understanding of human evolution depends on reconstructing how and why bipedalism evolved. This doctoral dissertation research project uses information about the “family tree” of extinct human species to reconstruct how, when, and why skeletal features that are critical for bipedalism evolved. This reconstruction allows the project investigators to test key hypotheses about human origins, including those concerning the role that environmental factors may have played in shaping our evolutionary history. This study investigates how ecological conditions have influenced human evolution, a line of inquiry that is particularly important in the context of global climate change. This project also supports the research of an early career female scientist from an historically underrepresented group in STEM and contributes to the diversity of scholarship in Biological Anthropology. This research tests two hypotheses relating patterns of character evolution to the ecological, temporal, and geographical contexts in which skeletal traits related to hominin bipedalism evolved. The first hypothesis addresses the patterns and processes by which bipedalism originated and subsequently evolved, as well as the selective history that may have shaped its evolution. The second hypothesis concerns whether the evolution of derived locomotor traits is temporally correlated with paleoenvironmental change and whether incorporating available paleoenvironmental data improves evolutionary models. Patterns of character evolution are analyzed using maximum parsimony and Bayesian inference. Random and non-random evolutionary models are tested to examine which model is the most appropriate for explaining the evolution of hominin locomotor anatomy. The project helps answer several fundamental questions in paleoanthropology: How does phylogeny inform our understanding of the evolution of postcranial traits that function mechanically during bipedalism? What does the pattern of evolution for these traits tell us about how, why, and when bipedalism evolved during human evolution? What are the evolutionary forces driving the evolution of these characters? What are the magnitude and direction of changes in morphological characters that enhance bipedalism? How might changes in bipedal features relate to changes in the environment? Answers to these questions substantially inform our understanding of the evolution of one of the first and most fundamental hominin adaptations. 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.