Hip extensor mechanics and the evolution of walking and climbing capabilities in humans, apes, and fossil hominins.
Abstract
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.
Type
Journal articleSubject
HipPelvis
Animals
Hominidae
Humans
Hylobatidae
Anthropometry
Gait
Range of Motion, Articular
Walking
Anatomy, Comparative
Posture
Fossils
Adult
Male
Biological Evolution
Biomechanical Phenomena
Hamstring Muscles
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https://hdl.handle.net/10161/19411Published Version (Please cite this version)
10.1073/pnas.1715120115Publication Info
Kozma, Elaine E; Webb, Nicole M; Harcourt-Smith, William EH; Raichlen, David A; D'Août,
Kristiaan; Brown, Mary H; ... Pontzer, Herman (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.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
Elaine Kozma
Associate In Research
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 a
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