Maternal placentophagy, the consumption of the placenta or "afterbirth" by the mother following parturition, is an ubiquitous behavior among eutherian mammals, including non-human primates. Here we report on a cross-cultural survey of 179 human societies regarding the consumption, treatment, and disposal of human placenta, in addition to accompanying cultural beliefs and perceptions about the organ. The conspicuous absence of cultural traditions associated with maternal placentophagy in the cross-cultural ethnographic record raises interesting questions relative to its ubiquitous presence among nearly all other mammals, and the reasons for its absence (or extreme rarity) among prehistoric/historic and contemporary human cultures.