Abstract

Monogamy has been argued to have played an important role in human evolution and, across animals more generally, evolutionary transitions to highly cooperative societies have been far more likely to occur in monogamous species, raising the possibility that this may have also been the case for humans. However, the extent to which we can consider monogamy to be the typical human mating system is subject to debate. Here, I provide comparative context on human mating behaviour by comparing the distribution of sibling types (full siblings versus half-siblings) across more than 100 human societies with equivalent data from 34 non-human mammal species. While cross-culturally variable, rates of full siblings in humans cluster closely with rates seen among socially monogamous mammals and fall consistently above the range seen in non-monogamous mammals. Although the human data is demonstrative of considerable cross-cultural diversity in marriage and mating practices, the overall high frequency of full siblings is consistent with the characterization of monogamy as the modal mating system for humans.