Functional Explanations in Sociobiology

In this essay I defend functional explanations in sociobiology against the charge that they are exercises in speculative story-telling. I distinguish proximate and ultimate biological functions, and discuss their role in functional explanations. I characterize functional explanations as a kind of "consequence explanation", and argue that sociobiologists need to justify a "functional fact" in addition to a "consequence law". Two methods used to supply evidence for functional hypotheses, the technique of optimality analyses and the comparative method, are discussed and illustrated with examples. I argue that adequate evidence for hypothesis about the function of a trait can be provided by the method of comparison, but not by optimality analyses. The comparative method contains an inductive phase that provides independent warrant for, and so serves to establish the high probability of, functional hypotheses. Independent warrant cannot be provided by optimality analyses alone: the model-building approach itself mandates the sacrifice of the truth of a hypothesis to its predictive power. I conclude that while the sociobiologist may wish to employ the optimality analysis as a heuristic strategy, reliable functional explanations are better sought through the use of the comparative method.