Evolutionarily minded psychologists and philosophers routinely invoke gradualism when theorising about human cognition, assuming human cognitive evolution evolved via a series of gradual phenotypic steps from an ancestral trait to the trait of interest. I argue this assumption is neither theoretically required nor empirically well supported. Evolutionary biology provides clear cases where major phenotypic shifts occur rapidly, and there is no principled reason to exempt cognition from this pattern. Acknowledging this leads to a more nuanced view of what makes explanations of human psychology evolutionarily plausible, and of what a successful evolutionary approach to psychology should aim to provide.
Rachael L. Brown (Thu,) studied this question.