The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)


Chimpanzee bipedal gait mechanics and early hominin gait evolution

BRIGITTE DEMES1, NATHAN E. THOMPSON1, MATTHEW C. O'NEILL1 and BRIAN R. UMBERGER2.

1Department of Anatomical Sciences, Stony Brook University, 2Department of Kinesiology, University of Massachusetts

March 26, 2015 2:15, Grand Ballroom C Add to calendar

Striding bipedal walking with the center of mass (CoM) vaulting over the stance foot is a hallmark feature of humans. Here we present data on the CoM mechanics of the facultative bipedal gait of our closest living relative, the chimpanzee, in order to shed light on the gait mechanics of the last common ancestor and early hominins. CoM oscillations were documented for 81 bipedal walking strides of three chimpanzees. Full-stride ground reaction forces were recorded as well as kinematic data to synchronize force to gait events and to determine speed. Despite being a bent-hip, bent-knee gait, chimpanzee walking employs pendulum mechanics with vertical oscillations of the CoM that are similar in pattern and relative magnitude to those of humans. Maximum height is achieved during single support, minimum height during double support. The mediolateral oscillations of the CoM are more pronounced than in human walking. Despite the pendular nature of chimpanzee bipedalism, energy recoveries from exchanges of kinetic and potential energies are low and highly variable. This variability is probably related to the poor phasic coordination of energy fluctuations. The pronounced side sway is not passive, but constitutes 10% of the total work of lifting and accelerating the center of mass. CoM oscillations of bipedally walking chimpanzees are distinctly different from those of ‘chimpanzee-like’ bent-hip, bent-knee gait of humans with a flat CoM trajectory, thereby limiting insights to be gained from such a gait for hominin evolution. The last common ancestor was probably capable of supporting and accelerating an oscillating CoM.

Supported by NSF BCS 0935321 and NSF BCS 0935327.