But why did bipedalism prove more successful than quadrupedalism? The answer lies in behavioral ecology. Large sized groups gain an advantage over smaller sized groups because they are usually able to outcompete their adversaries by sheer numbers. Also, there is a greater probability of there being more adaptively fit individuals than in small groups. The increased intra-group competition make large groups more versatile in inter-group competition. Should ever a fight arise, the most likely victor would have been the bipedal hominids.

There were other advantages, as our hominid ancestors soon discovered. For instance, an upright stance decreased body surface directly exposed to solar radiation, while exposing more to the cooling winds above the savanna grasses. The result is more foraging time, the decreased likelihood of brain overheating, and the ability to support larger group sizes. (Wheeler, 1984). Secondly, this made the creature seem more impressive, which helped in scaring off predators. Thirdly, the increased height meant a better vantage point, so they could spy food sources and detect predators from longer distances. Furthermore, upright feeding positions were much more energy-conservative, considering that the average piece of food was a meager berry the width of your pencil eraser and not very nutritious. (Hunt). Lastly and probably most importantly, the adoption of bipedalism freed the hands, which cleared the road for better provisioning and tool-making. Lovejoy also believes this to have heralded forth the general practice of monogamy [pair bonding] as opposed to polygamy [multiple mates to an individual]. (Lovejoy, 1981).

Understanding the purpose and necessary mechanisms of bipedalism may be useful in many practical fields, in the engineering of seatbelts, air bags, or artificial limbs. It will also shed new light on the evolution of our earliest hominid ancestors, especially the muddled identity of Ardipithecus ramidus [early, primitive hominid from 4.4 to 4.0 million years ago] and Australopithecus anamensis [another early hominid from 3.7 to 4.1 million years ago, and their relation to the later australopithecines.

The Isabell and Young Alternative Responses Hypothesis is one of the most beautiful and eloquent of all the theories that attempt to explain the purpose bipedalism. It accounts not only for why we are who we are, but the similarities and differences between chimp and human behavioral patterns.

   

Copyright ©2001-2003, Allegra H., all rights reserved. Please contact me via e-mail if you wish to reproduce this material.