In 1891, the anthropologist Edward Westermarck proposed that early childhood association inhibits sexual attraction and that this aversion was manifested in custom and law as the basis of the universal incest taboo. Then, in 1910, in the essays later published as Totem and Taboo, Sigmund Freud challenged the "Westermarck hypothesis" on the ground that "the earliest sexual excitations of youthful human beings are invariably of an incestuous character." The incest taboo only existed, Freud argued, because of this natural propensity. Freud's challenge carried the day and became the standard view...