The Behavioral Ecology of Locomotion

Abstract

One of the cornerstones of modern evolutionary biology is the insight that an individual that is more tailored to his environment should have a higher survival and reproductive potential than his less adapted neighbors. Behavioral ecology attempts to explain behaviors as adaptive, or not, only in particular ecological contexts. And life history theory highlights that the developmental stage of an individual is an integral part of the environment and that development is an inherently sequential process. But how do these seminal ideas help us understand the evolution of hominid bipedality?

Bipedality can be thought of as a suite of possible styles, with different forms optimizing diverse traits. The locomotor form of an individual can be optimized for many characteristics, including 1) efficient use of energetic, thermal, temporal and water budgets; 2) range; 3) velocity or acceleration; 4) endurance, fatigue and injury protection; and 5) burden carrying. All could be important in different ecological circumstances and, indeed, many may act in concert with others, but which ones? when? how? and how can we tell from the fossil record?

While female australopithecines appear to have excelled at slow speeds and short distances, the locomotor form of Homo seems to be oriented toward relatively long distance travel and endurance walking and running. Understanding these aspects of the locomotor regime does not, however, inform about the other elements of the behavioral repertoire, nor does it elucidate why the transition took place and what the functional implications of it are.

The task of understanding bipedality as a fundamental adaptation of Hominidae can only be a truly fruitful endeavor if we keep in mind that males and females may have different ecological perspectives; children, adolescents, and adults may interact with the environment in different ways; and the environment is a complex set of interacting, dynamic factors.