Upright: The Evolutionary Key to Becoming Human
What distinguishes humans from their closest evolutionary ancestors? Brain size? Language? Complex social structures? Anthropologist Stanford, who is co-director of USC's Jane Goodall Primate Research Center, answers directly in this evenhanded account, which is part history of science and part scientific detective story. Drawing on the research of evolutionary biologists, anthropologists and paleontologists, Stanford argues that upright posture is what made us human, since it led to the development of a larger brain size and, by freeing our lungs, to the ability to use speech. According to Stanford, upright posture offered various benefits. For one, it aided the gathering of food through the development of the rotating shoulder cuff, which allowed mobility in holding and grasping sources of food. Other anatomical developments related to bipedalism include strong upper leg and gluteal muscles and a broader and shorter pelvis that would support the thighs and upper back. Upright posture also gave bipeds the ability to see far ahead in their hunts, allowing for better views of prey and self-protection from predators. Finally, this posture led to the development of tools that could be used in the hunt and the kill. Stanford contends that bipeds developed these physical traits and began to walk upright over a long period of time, from about 1.8 million years ago to 300,000 years ago. This thesis will likely generate disagreement among evolutionary biologists who believe that bigger brain size led humans to stand upright, but his sober and well-documented study merits close attention by anyone interested in human origins. Illus.Copyright 2003 Reed Business Information, Inc.