ABSTRACT
Whether we should use the experimental or the comparative method depends on the question we ask. Our problem concerns the function of sex; we ask how the distribution of sexuality among multicellular animals is to be explained. This offers little purchase for the experimental method: we can perform experiments to elicit sexuality in the laboratory, but these will identify only proximate causes, while we are interested in function, or ultimate causation. More generally, we can sometimes perform experiments which test the validity of the axioms on which rival hypotheses rest, but it is difficult in this way either to exclude hypotheses or to investigate their generality. The more powerful technique for these purposes is the comparative method, which allows us to examine the relationship between theoretical predictions and the patterns in nature whose explication is our ultimate goal.
