THE NEW FABLE OF THE BEES: MULTILEVEL SELECTION, ADAPTIVE SOCIETIES, AND THE CONCEPT OF SELF INTEREST

Darwin’s theory of natural selection, which explains how individual organisms can become exquisitely adapted to their environments, does not explain the evolution of adaptive societies with equal ease. To understand the nature of the problem, imagine a mutant individual who behaves in a way that increases the survival of everyone in her society, including herself, to an equal degree. Such a “no-cost public good” might not appear very feasible (and will soon be amended), but is useful for illustrative purposes. By increasing the fitness of everyone, the mutant trait will not increase in frequency within the society (other than by drift, which can equally cause a decrease in frequency). This example illustrates the elementary fact that natural selection is based on relative fitness. It’s not enough for a mutant trait to increase its own survival and reproduction; it must do so more than alternative traits in the population. The relative nature of fitness makes the evolutionary forces within a population insensitive to the welfare of the population as a whole.