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Conjoining uncooperative societies facilitates evolution of cooperation


Social structure affects the emergence and maintenance of cooperation. Here, we study the evolutionary dynamics of cooperation in fragmented societies, and show that conjoining segregated cooperation-inhibiting groups, if done properly, rescues the fate of collective cooperation. We highlight the essential role of intergroup ties, which sew the patches of the social network together and facilitate cooperation. We point out several examples of this phenomenon in actual settings. We explore random and non-random graphs, as well as empirical networks. In many cases, we find a marked reduction of the critical benefit-to-cost ratio needed for sustaining cooperation. Our finding gives hope that the increasing worldwide connectivity, if managed properly, can promote global cooperation.

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Fig. 1: From spite to cooperation by conjoining cliques.
Fig. 2: Super-promoters of cooperation.
Fig. 3: Rich clubs and bipartite graphs.
Fig. 4: Conjoining random graphs and empirical networks.


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This work was supported by the James S. McDonnell Foundation (B.F.), NSF grant 1715315 (B.A.) and the John Templeton Foundation (M.A.N.). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. B.F. thanks S. Rytina for insightful and stimulating conversations.

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Correspondence to Babak Fotouhi.

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Fotouhi, B., Momeni, N., Allen, B. et al. Conjoining uncooperative societies facilitates evolution of cooperation. Nat Hum Behav 2, 492–499 (2018).

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