Postural Feeding Hypothesis for the origin of bipedalism.

This page contributed by: Kevin Hunt
Maintained by: Dewi Morgan
Principal advocates: Jolly, Rose, Tuttle and Hunt
Created: Sep 25 '95.
Early fossil humans have many chimpanzee-like features, not all of them well explained. Understanding chimpanzees, and through them proto-humans, therefore requires explaining chimpanzee anatomy, diet and social system first. Chimpanzee anatomy is best explained as a natural engineering solution to this suspensory behavior and vertical climbing. Chimps have a peculiar cone-shaped torso that I suggested serves to distribute stress more evenly across the entire torso during arm-hanging, preventing structural failure at high-stress "hot-spots." The australopithecine torso is chimp-like; early ominids were suspensory.

Hunt's chimpanzee feeding observations showed that chimps were bipedal when they ate small fruits from short trees, as the small-object feeding hypothesis suggested (Jolly & Plog, 1985). Surprisingly, however, chimpanzees were bipedal both in the trees and on the ground when eating these types of fruits (Hunt, 1994). When reaching up from the ground, small fruits encourage bipedalism because it takes two hands to fill the mouth. In trees, chimps stood bipedally to feed among the smallest branches, maintaining their balance by using a forelimb in a semisuspensory manner. The presence of chimp-like shoulders, torsos and hands in australopithecines, and a mechanically inefficient locomotor bipedalism suggests that bipedalism evolved, not for walking, but for postural harvesting, often in the trees with the body stabilized by arm-hanging.

Refs:

The Evolution of Human Bipedality: Ecology and functional Morphology (In Depth)
Kevin D. Hunt; Journal of Human Evolution ('94) 23 pp 183-202
My misc refs page.
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