Why monogamy?

Alexander (1987; Alexander et al. 1979), Betzig (1986), and MacDonald (1990) variously argue that monogamy is the result of a compromise among men after the advent of democracy whereby wealthy, powerful men receive political support from poor men in exchange for giving up their multiple wives. We advance an alternative theory and aver that the institution of marriage spontaneously emerges out of women's individual choices to marry polygynously or monogamously. If resource inequality among men is great, women choose to marry polygynously and the polygynous institution of marriage emerges. If resource inequality among men is small, women choose to marry monogamously and the monogamous institution of marriage emerges. The theory explains the historical shift from polygyny to monogamy as a result of the gradual decline of inequality among men. Computer simulations uphold the internal logical consistency of the theory, and the analysis of cross-cultural data from a large number of countries strongly supports our female choice theory and offers no support for the male compromise theory.