Human monogamy in mammalian context

Monogamy has been argued to have played an important role in human evolution1-5 and, across animals more generally, evolutionary transitions to highly cooperative societies have been far more likely to occur in monogamous species6-8, raising the possibility that this may also have been the case for humans. However, the extent to which we can consider monogamy to be the species-typical human mating system is subject to debate9-11. Here, I provide comparative context on human mating behaviour by comparing the distribution of sibling types (full siblings versus half-siblings) across >100 human societies with equivalent data from 35 nonhuman 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 cross-cultural diversity in marriage and mating practices, the overall high frequency of full siblings is consistent with the characterisation of monogamy as the modal mating system for humans.