Understanding how musculoskeletal trait evolution facilitated the development of walking capabilities in our hominin ancestors is a major goal in human evolutionary biology. Among a myriad of now extinct hominins, the emergence of Australopithecus (A.) afarensis about 3.9 million years ago is argued to represent a major adaptive shift in bipedal walking capabilities as compared with the last common ancestor of modern humans and chimpanzees. Yet, as a species, A. afarensis exhibits a suite of skeletal traits in the pelvis and lower limb that differentiate it from both living human and chimpanzee species. How this unique combination of traits interacts to determine locomotor function has been an area of longstanding interest and disagreement. Traditional methods based on static analysis of isolated traits are unable to account for the integrated function of the musculoskeletal system in locomotion. Thus, we have adopted an approach based on computer models of the musculoskeletal system that parameterize these traits, and dynamic simulations of bipedal gait that account for integrative function and task demands. This presentation will focus on a decades-long effort to integrate these modeling and simulation approaches with empirical studies in the most relevant extant species, to better understand how the changes we observe in the fossil record would have affected locomotor performance during hominin evolution.