ABSTRACT
Aerobic activities are those which can be sustained entirely by oxygen-based metabolism. The rate of oxygen consumption during an activity, called VO2, is often used as a measure of energy for aerobic activities. Activity costs tend to increase with body size, and so to account for differences in body size, energy expenditure during an activity is often expressed as metabolic equivalents, the ratio of activity energy expenditure to basal metabolic rate. Comparative biology offers a valuable methodological approach to examine evolutionary physiology in living taxa. By comparing performance or morphology in humans and our closest living relatives, the great apes can better understand how, and potentially when, major changes in evolutionary physiology occurred. Reconstructions of locomotion and behavior in the earliest hominins generally suggest that, although they walked bipedally, in many respects they more closely resemble nonhuman great apes in activity patterns and behavior.
