Hip extensor mechanics and the evolution of walking and climbing capabilities in humans, apes, and fossil hominins.


The evolutionary emergence of humans' remarkably economical walking gait remains a focus of research and debate, but experimentally validated approaches linking locomotor capability to postcranial anatomy are limited. In this study, we integrated 3D morphometrics of hominoid pelvic shape with experimental measurements of hip kinematics and kinetics during walking and climbing, hamstring activity, and passive range of hip extension in humans, apes, and other primates to assess arboreal-terrestrial trade-offs in ischium morphology among living taxa. We show that hamstring-powered hip extension during habitual walking and climbing in living apes and humans is strongly predicted, and likely constrained, by the relative length and orientation of the ischium. Ape pelves permit greater extensor moments at the hip, enhancing climbing capability, but limit their range of hip extension, resulting in a crouched gait. Human pelves reduce hip extensor moments but permit a greater degree of hip extension, which greatly improves walking economy (i.e., distance traveled/energy consumed). Applying these results to fossil pelves suggests that early hominins differed from both humans and extant apes in having an economical walking gait without sacrificing climbing capability. Ardipithecus was capable of nearly human-like hip extension during bipedal walking, but retained the capacity for powerful, ape-like hip extension during vertical climbing. Hip extension capability was essentially human-like in Australopithecus afarensis and Australopithecus africanus, suggesting an economical walking gait but reduced mechanical advantage for powered hip extension during climbing.





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Publication Info

Kozma, Elaine E, Nicole M Webb, William EH Harcourt-Smith, David A Raichlen, Kristiaan D'Août, Mary H Brown, Emma M Finestone, Stephen R Ross, et al. (2018). Hip extensor mechanics and the evolution of walking and climbing capabilities in humans, apes, and fossil hominins. Proceedings of the National Academy of Sciences of the United States of America, 115(16). pp. 4134–4139. 10.1073/pnas.1715120115 Retrieved from https://hdl.handle.net/10161/19411.

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Herman Pontzer

Professor of Evolutionary Anthropology

How did the human body evolve, and how does our species' deep past shape our health and physiology today? Through lab and field research, I investigate the physiology of humans and apes to understand how ecology, lifestyle, diet, and evolutionary history affect metabolism and health. I'm also interested in how ecology and evolution influence musculoskeletal design and physical activity. Field projects focus on small-scale societies, including hunter-gatherers and subsistence farmers, in Africa and South America. Lab research focuses on energetics and metabolism, including respirometry and doubly labeled water methods.

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