On Saints and Soldiers : Rethinking the Co-evolution of Group Cooperation and Conflict

Across species, individuals form groups. In groups, individuals cooperate for progress and prosperity, and they cooperate to inflict damage on other groups. Why – what explains such co-occurrence of group cooperation and intergroup conflict? In an answer to this, prominent theories in the social, behavioural and biological sciences hold that individuals organise in groups, and that cooperation evolved, to defend against dangerous other groups. What remains open, however, is where conflict and enemy threat comes from in the first place. In this lecture I aim to answer this question – why individuals form groups and cooperate to fight other groups when there is no history of violence to revenge, and other groups pose no threat to oneself or one’s group? I discuss the results of experiments that examined two possible answers. I first examine the possibility that individuals cooperate to aggress out-groups because of evolved dislike for (members of) outside groups and communities – saints towards us and soldiers against them. My experiments disconfirm this possibility. Next, I examine the possibility that individuals cooperate to aggress out-groups to win ‘spoils of war’ that benefit themselves and their in-group – saints towards, and soldiers for us. Experiments performed in the Netherlands, China and rural parts of Africa support this possibility – individuals cooperate to make their groups strong and dangerous because they care about the groups they depend on for status, resources and opportunities. In the ultimate, group cooperation did not evolve because of conflict. Conflict evolves because of cooperation.