The evolution of peace

Abstract

While some species have affiliative and even cooperative interactions between individuals of different social groups, humans are alone in having durable, positive-sum, interdependent relationships across unrelated social groups. Our capacity to have harmonious relationships that cross group boundaries is an important aspect of our species’ success, allowing for the exchange of ideas, materials, and ultimately enabling cumulative cultural evolution. Knowledge about the conditions required for peaceful intergroup relationships is critical for understanding the success of our species and building a more peaceful world. How do humans create harmonious relationships across group boundaries and when did this capacity emerge in the human lineage? Answering these questions involves considering the costs and benefits of intergroup cooperation and aggression, for oneself, one's group, and one's neighbor. Taking a game theoretical perspective provides new insights into the difficulties of removing the threat of war and reveals an ironic logic to peace—the factors that enable peace also facilitate the increased scale and destructiveness of conflict. In what follows, I explore the conditions required for peace, why they are so difficult to achieve, and when we expect peace to have emerged in the human lineage. I argue that intergroup cooperation was an important component of human relationships and a selective force in our species history in the past 300 thousand years. But the preconditions for peace only emerged in the past 100 thousand years and likely coexisted with intermittent intergroup violence which would have also been an important and selective force in our species’ history.

The evolution of intergroup cooperation

“…From around 2 Ma, early humans' ability to use culture to construct niches [ 51 ] has complicated how the evolution of intergroup cooperation depends on ecological context. Recent work suggests that the establishment of peaceful intergroup interactions requires cultural institutions such as social norms that dictate non-aggression [ 52 ].…”

Long-distance social relationships can both undercut and promote local natural resource management

“…For example, long-distance relationships can advance neocolonialism and extractivism perpetuated by the Global North against the Global South [104]; this is sometimes encapsulated in the relationship between international aid organizations and local common-pool resources, with organizations gaining benefits like projects, contracts and substantial employment opportunities by leveraging the challenges encountered in local NRM [105]. On the other hand, long-distance relationships regularly move people [31] and money [106] across borders, and their presence can be a segue to trade [107], peace [108] and large-scale collective action [109]. In short, the relevance of long-distance relationships to local, regional and even international NRM is, in our opinion, worthy of further study.…”

Dyadic inter-group cooperation in shotgun hunting activities in a Congo Basin village

“…The human capacity to maintain relatively harmonious, interdependent relationships across group boundaries is one of the many ways in which cooperative behaviour is unique in our species (Barth, 1969 ; Boyd & Richerson, 2021 ; Robinson & Barker, 2017 ). Chimpanzees and bonobos, for instance, are intolerant towards neighbours, and interactions tend to be aggressive (Glowacki, 2022 ; Pisor & Surbeck, 2019 ; Wrangham & Glowacki, 2012 ). While some observations of the latter species suggests that scope for inter-group cooperation may be phylogenetically deep in our evolutionary lineage (Lucchesi et al, 2021 ; Pusey, 2022 ), the scale, duration and diversity of cooperation between human groups is unprecedented.…”