Conclusion: What Next?

Abstract

This chapter begins by showing why one standard way of describing the functions debate—as a debate between the selected effects theory, fitness-contribution theory, and causal role theory—is misguided. I then summarize three main conclusions. First, I argue that, to the extent that function statements are causal explanations, there are no current, viable alternatives to the selected effects theory. Second, I argue that, to the extent that we accept pluralism, we should not accept what I call (in Chap. 5) “between-discipline pluralism,” which seeks to restrict the applicability of the selected effects theory to some branches of evolutionary biology. Third, I advocate a specific version of the selected effects theory, the generalized selected effects theory, which I described earlier (in Chap. 3). In closing, I outline three outstanding problems for most theories of function. The first is function indeterminacy. Typically, there are a number of different activities associated with the performance of a function and most theories of function do not have the resources to specify which of those activities, precisely, constitutes an item’s function. Second, in many cases, a trait not only has a function, but it has an appropriate rate of functioning. For example, the heart not only has the function of beating, but it has the function of beating at a certain rate. How should we specify the appropriate rate of function? Third, for many traits that have functions, we can distinguish between appropriate and inappropriate situations for the performance of those functions. How should we modify our theories to take this into account?