STEPS · STEPS: Biomechanical simulations of hominin locomotion across complex terrains

Human bipedalism is a rare and distinct form of locomotion, unlike that of any other animal. Despite its uniqueness, its evolutionary origins and ecological significance remain elusive. By walking on two legs, early hominins not only freed their hands to hold, manufacture, and use stone tools, but also gained the ability to interact with the environment in new ways, driving innovations in social structure, diet, and survival strategies. This ultimately led to the success of Homo, our genus, which expanded into diverse habitats, including those beyond Africa, while other hominins were more limited in their geographic distribution. Understanding how and why bipedalism became Homo’s primary adaptive strategy is key to explaining our species' evolutionary success in occupying diverse habitats. STEPS focuses on movement across complex, realistic landscapes similar to those likely traversed by hominins, which exerted selective pressures on their skeletons, driving anatomical and functional changes for efficient locomotion. It will investigate how hominins navigated such terrains bipedally despite their anatomical differences that likely affected their efficiency in doing so. Musculoskeletal models of seven hominin species spanning the last four million years will be constructed and their movement across complex terrains simulated. The predictive simulations will be guided by an empirical framework of human movements across experimentally-constructed substrates. STEPS will determine whether the Homo body plan offered greater efficiency compared to other hominins. Only by tackling such a project can scientists understand why the Homo genus was so successful at occupying diverse habitats, whilst other groups (australopiths) were not. STEPS will thus enhance our understanding of how anatomical features influenced locomotor strategy and dispersals, focusing on the role of the foot-ground interface as a driving force that shaped human evolution.