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It has been difficult to determine when this unique trait emerged, but they could have been on their feet before over 3 million-year-old Laetoli footprints were made (Reader and Andrew 413). The prints though did not bear semblance to that of modern, they were indeed those of a bipedal primate. Bipedalism Features They are the impressions of feet that lacked a distinctive human rounded ball, ors welling, at the base of the great toe, that had no well-defined arch, and that retained ever so slightly divergent great toes.

Transformation from a quadrupedal knuckle walking to bipedalism involves various anatomical changes; development of longer legs angling of femur inwards, the feet develop an arch, the bigger toe is elongated, the pelvis is lowered, and it broadens. Additionally, the spinal cord of the hominid develops in such a manner that the vertebral bends frontward to sustain bipedalism traits. The Postural Feeding Hypothesis There are several competing hypotheses that have been put forward by anthropologists to explain the origin of bipedalism in hominids using non-human primates as referential models for our common ancestors.

The postural feeding hypothesis (McGrew et al 282) explains bipedalism from an ecological view and explains the shared feeding behaviours exhibited by the chimpanzee and australopithecines are sufficiently common in other apes to influence anatomy. The hominids fed on relatively short trees and this gave them certain selection characters and instead adopting an upright posture and this lead to bipedalism. The other great apes for example chimpanzees do not have a straight gait and human straight gait is much more efficient than their bipedalism and quadrapedalism Hunt came up with the hypothesis after spending close to seven hundred hours observing chimpanzees in the wilderness in central Tanzania (Lewin 115).

From his observation of these great apes in the wild, he found out that their feeding habits bordered on postural and this lead to bipedalism. The hypothesis suggests that early hominids would reach out for fruits by dangling with the front limbs, and bipedalism was applied by grasping for an overhead branch. He found out that 80% of bipedalism was observed during chimpanzee feeding with arm hanging to stabilize the posture, this become the corner stone of the hypothesis. The australopithecines have shown adaptations of the torso form to arm hanging which infers that the apes adapted to arboreal bipedal fruit collection.

A major basis of this hypothesis is the argument that the existence of bipedalism during certain aspects of life in extant apes provides evidence of the selective pressures that led to hominid bipedalism. According to this model, the early origin of bipedalism later evolved gradually into a habitual way of movement and this steadily led to bipedalism by the early man. Heat Hypothesis by Wheeler Peter Wheelers heat hypothesis proposes a thermoregulatory selective adaptation of bipedal hominids to increased heat loss, increased cooling, condensed heat gain and condensed water necessities (McGrew et al 282).

By adopting the bipedal posture, hominids were exposed to cooler air since the speed of wind is faster further away from the ground. Additionally, the