Cole Porter, the American composer and lyricist, is credited with popularizing the phrase “the birds and the bees” to refer to sexual relations among men and women. In his 1928 hit song “Let’s Do It, Let’s Fall in Love,” Porter crooned, “And that’s why birds do it, bees do it/ Even educated fl eas do it/ Let’s do it, let’s fall in love.” Paraphrasing Porter, “the birds and the bees” became a euphemism for the way many parents and teachers approached sex education, emphasizing plant and animal reproduction and alluding to human sexuality. This phrase also illustrates two vital points about popular understandings of sex: the general acceptance that human sexuality is analogous to, or at least related to, that of animals; and the notion that men and women can apply lessons from the animal and insect kingdoms to their own mating decisions. In other words, modern understandings of human sexuality are in many ways grounded in the acceptance of human-animal kinship, an idea that became fi rmly rooted in the fi nal decades of the nineteenth century thanks to Darwinian evolutionary theory. Evolutionary theory also suggested that mate choice determined success among both individuals and species, a radical idea that inspired the fi rst scientifi c studies of sex. The relationship between evolutionary theory and scientifi c, as well as popular, understandings of sex is both foundational and generally unspoken. The methodological and ideological links between evolutionary science and sexology, however, are as old as the two fi elds themselves, tracing back to Charles Darwin and his theory of sexual selection.