The battle of the brides: Co-wife competition and aggression across 19 cultures

The dominant account of women's intrasexual competition holds that women prefer indirect over direct aggression, a prediction supported by experimental studies drawn largely from young women in WEIRD settings competing over low or hypothetical stakes. The present analysis examines co-wife competition as a theoretically motivated high-stakes test case, using systematic analysis of the eHRAF World Cultures database. Ethnographic records from 19 cultures spanning five world regions were coded using a four-domain scheme covering causes, modes, resolution strategies, and prevention strategies, developed inductively and refined. Competition for the husband's sexual attention and general preference was the dominant cause (73.7%), followed by material resource competition (36.8%). Physical aggression between co-wives was the most frequently documented competitive mode, confirmed in 63.2% of cultures. Resolutions varied, with the most frequent being the husband's intervention or relationship dissolution (both 47.4%). The prevention domain revealed that spatial separation of wives was the most common structural response to co-wife hostility (57.9%), indicating that polygynous households are routinely organized to deter anticipated conflict. These findings support the conclusion that direct female aggression is a common, and often the dominant mode of co-wife competition under high-stakes conditions, occurring in addition to indirect strategies rather than replacing them, and running counter to the prevailing view that women rarely aggress directly.