The Impact of Intergroup Social Ties on Coalitionary Aggression

Intergroup coalitionary aggression is a vast and sensitive topic.  Here I will limit the discussion to the impact of mutually supportive intergroup ties on aggression in small scale societies. Unlike our closest primate relatives, chimpanzees and bonobos, humans form strong intergroup ties which can mitigate coalitionary aggression and make peace possible. However, such bonds can also be used to build to larger alliances that take such conflicts to a new level of magnitude, supported by cultural and linguistic proficiencies. First, I will compare intergroup ties between humans, chimpanzees and bonobos and explore some of the possible evolutionary developments that contributed to the human disposition to form mutually supportive external bonds. Then I will discuss the impact of social ties on coalitionary action. Intergroup ties can reduce coalitionary aggression of the nature proposed in the ‘imbalance of power hypothesis’ used to account for chimpanzee intergroup attacks, as well as human motivations such as marriage by capture and revenge. However, when social ties are expanded into institutions to bind and motivate larger coalitions into communities or tribes, new incentives enter the picture that ramp up coalitionary competition: These include rallies to dehumanize the enemy, adoption of sacrosanct values, concern with honor, reputation and balance of power, as well as coalitionary action to unite groups against a common enemy. Fortunately, intergroup social ties can also provide a basis to restore peace.