" Every gene in every human body has passed through thousands of penises over thousands of generations of human evolution. Equally, every gene has passed down through thousands of eggs inside female ancestors who chose to copulate with particular males. In sexually reproducing species, copulation is the genetic gateway from one generation to the next, which is what makes it so important evolutionarily, physically, and psychologically. "

― Geoffrey Miller , The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature