Credit: CC0 Public Domain

As in many other socially-living species, humans form coalitions to gain advantage in conflicts or to seek or maintain social status. However, studying coalition formation in human societies is complicated by the formal institutions—such as businesses, courts, and governments—that structure social relationships and conflict resolution. But even in small-scale human societies with a relative lack of such formal institutions, there is scant research on the details of coalition formation. Daniel Redhead, from the Max Planck Institute for Evolutionary Anthropology, and Chris von Rueden, from the University of Richmond, have now published a new study that describes coalition formation over a period of eight years among men in Tsimané Amerindians living in Amazonian Bolivia.

In two Tsimané communities, the authors describe the inter-personal conflicts that tend to arise between men, and the individual attributes and existing relationships that predict the coalitional support men receive in the event of conflicts.

Conflicts that arise between men concern disputes over access to forest for slash-and-burn horticulture, as well as accusations of theft, laziness, negligence, domestic abuse, and sexual affairs.

Men tend to reciprocate coalitional support

Key findings are that men who are kin or who exchange food and labor are more likely to subsequently provide support to each other in the event of a conflict. Men tend to reciprocate coalitional support over time, and an ally of a man's current ally is likely to become a future ally. The authors also find evidence that men who share a common adversary become allies, though this finding did not hold consistently across the eight years of the study.

In reference to the impact of these findings, Redhead, said: "Coalition formation among men is multiply determined in the Tsimané, and likely in other human societies. Importantly, the social network analyses we used show that properties of the network, not just the individual, affect coalition formation."

Higher status men more likely to provide coalitional support

Furthermore, Tsimané men who are physically formidable or who have more informal influence in their community are more likely to provide coalitional support to others. Evidence was mixed that they receive more coalitional support. These higher status men are hubs of their community's coalitional support network, and there is little indication that this network is partitioned into clearly separable coalitions that divide the community.

"In the Tsimané, men who have higher informal status strategically deploy coalitional support to build up a diverse, community-wide following. In many cases, both disputants in a conflict will report the same higher status man as having provided coalitional support, which points to the often blurry line between coalitional support and conflict mediation," von Rueden said. "Politics is the art of persuading enough people you have their interests at heart. In less egalitarian societies where there is more privately available wealth and community sizes are larger, status is less contingent on providing direct support to a broad swath of community members, there is greater homophily by , and coalitional divides within a community are more likely to be pronounced."

Redhead and von Rueden focus their study on men because they at present lack longitudinal data on women's coalition formation. However, there is reason to analyze coalition networks separately by gender, given evidence of gender differences in how men and women build and leverage their social relationships, particularly in societies like the Tsimané where there is a pronounced gendered division of labor.

More information: Daniel Redhead et al. Coalitions and conflict: A longitudinal analysis of men's politics, Evolutionary Human Sciences (2021). DOI: 10.1017/ehs.2021.26

Provided by Max Planck Society