The evolution of war and its cognitive foundations

Abstract

Coalitional aggression evolved because it allowed the participants to promote their fitness by gaining access to disputed, reproduction-enhancing resources that would otherwise be denied to them. Few species engage in coalitional aggression, even though the social conditions that would favor its evolution seem to be widespread. Why? Forming coalitions to exploit these opportunities requires individuals to solve highly complex and specialized information processing problems involving cooperation, coordination, and social exchange. The difficulty of evolving cognitive mechanisms capable of solving these problems—especially when the individuals involved are not kin—may explain why multi-individual coalitions are phylogenetically rare. We propose that humans and a few other cognitively pre-adapted species have evolved specialized cognitive programs that govern coalitional behavior, which constitute a distinctive coalitional psychology. To derive a preliminary map of this psychology, we started with a task analysis of the adaptive information-processing problems that arise during coalitional aggression. This exercise can shine light on our evolved psychology because algorithms that motivate and organize coalitional aggression would need design features that solve these problems well to be favored by selection. These problems include decisions about when to form a coalition or join one, when to initiate an attack, and how to allocate the costs and benefits that result from coalitional action. The risk contract of war identifies circumstances under which natural selection would favor decisions to initiate an attack. When the conditions of this model are met, mortality rates will not negatively impact the fitness of males in the winning coalition. This outcome has implications for the design of computational systems that motivate coalitional attacks; it may explain why warfare is so favored an activity among men, despite its risks to the participating individuals' welfare.