Kanazawa (2009) proposes a ‘‘first law of intergroup conflict, ’’suggesting that polygyny and its impact on access to reproductive women provides ‘‘the ultimate cause’’ for civil war. This controversial claim is supported by an empirical analysis at odds with most existing studies of civil wars. We reconsider the influence of polygyny in a more conventional statistical model. We fail to find evidence that ethnic groups with polygyny engage more frequently in civil wars, although it is possible to find results indicating that civil wars may be more common in states with legal polygamy. We detail how these findings seem at odds with Kanazawa’s theory and argue that misogyny seems a more plausible source of insights into the context for civil war and peace. We then show that civil wars are less common when women’s rights are better established and that legal polygamy has no discernable residual effect once women’s rights are considered.