Understanding hind limb weight support in chimpanzees with implications for the evolution of primate locomotion
Article first published online: 10 NOV 2008
Copyright © 2008 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 138, Issue 4, pages 395–402, April 2009
How to Cite
Raichlen, D. A., Pontzer, H., Shapiro, L. J. and Sockol, M. D. (2009), Understanding hind limb weight support in chimpanzees with implications for the evolution of primate locomotion. Am. J. Phys. Anthropol., 138: 395–402. doi: 10.1002/ajpa.20952
- Issue published online: 11 MAR 2009
- Article first published online: 10 NOV 2008
- Manuscript Accepted: 8 SEP 2008
- Manuscript Received: 10 JUN 2008
- L.S.B. Leakey Foundation
- NSF. Grant Number: BCS-0424092
- primate origins;
Most quadrupedal mammals support a larger amount of body weight on their forelimbs compared with their hind limbs during locomotion, whereas most primates support more of their body weight on their hind limbs. Increased hind limb weight support is generally interpreted as an adaptation that reduces stress on primates' highly mobile forelimb joints. Thus, increased hind limb weight support was likely vital for the evolution of primate arboreality. Despite its evolutionary importance, the mechanism used by primates to achieve this important kinetic pattern remains unclear. Here, we examine weight support patterns in a sample of chimpanzees (Pan troglodytes) to test the hypothesis that limb position, combined with whole body center of mass position (COM), explains increased hind limb weight support in this taxon. Chimpanzees have a COM midway between their shoulders and hips and walk with a relatively protracted hind limb and a relatively vertical forelimb, averaged over a step. Thus, the limb kinematics of chimpanzees brings their feet closer to the COM than their hands, generating greater hind limb weight support. Comparative data suggest that these same factors likely explain weight support patterns for a broader sample of primates. It remains unclear whether primates use these limb kinematics to increase hind limb weight support, or whether they are byproducts of other gait characteristics. The latter hypothesis raises the intriguing possibility that primate weight support patterns actually evolved as byproducts of other traits, or spandrels, rather than as adaptations to increase forelimb mobility. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc.