Hawks, Doves, and Perissodus microlepis. Undermining the selected effects theory of function.

The selected effects theory is supposed to provide a fully naturalistic basis for statements about what biological traits or processes are for without appeal to final causes or intelligent design. On the selected effects theory, biologists are allowed to say, for instance, that hindwing eyespots on butterfly wings serve to deflect predators' attacks away from vital organs because a similar fitness-enhancing effect explains why eyespots themselves were favoured by natural selection and persisted in the population. This is known as the explanatory dimension of the selected effects theory.