The evolution of democratic peace in animal societies

Abstract

A major goal in evolutionary biology is to elucidate common principles that drive human and other animal societies towards war or peace. One idea proposed to account for differences between human societies is the "democratic peace" hypothesis, which suggests autocracies are more warlike than democracies because leaders can pursue fights for private gain. Given that animals can make autocratic or democratic collective decisions, we consider whether the logic of democratic peace may apply across taxa. We adapt the classic Hawk-Dove model to consider conflict decisions by groups rather than individuals, finding support for the democratic peace hypothesis without mechanisms involving complex human institutions. We suggest that the degree to which collective decisions are shared may explain variation in the intensity of intergroup conflict in nature.