Although Darwin did note that in a handful of species the roles were reversed – with females being competitive and males being choosy – he considered these insignificant anomalies. Darwin’s explanation for the constancy of his gendered sex roles was that it all boils down to fundamental differences between sperm and eggs. Sperm are mobile, he noted, while eggs are sedentary; and in this disparity lay the foundations for ‘active’ masculinity and ‘passive’ femininity.
