Structure and Dynamics

Discriminators who have limited tolerance for helping dissimilar others are necessary for the evolution of costly cooperation in a one-shot Prisoner’s Dilemma. Existing research reports that trust in societies decreases when agents copy markers and tolerance from more successful others. Global cooperation is possible only in highly homogenized societies. Emergent cooperative societies are not robust against mutant defectors with tolerably similar markers. Our simulation experiments compare one society where each agent has immutable binary tags at the same dimension (‘caste society’) to the other where such markers are distributed across different dimensions (‘modern society’). In both societies, the majority of population display strong parochialism. However, cooperation is significantly stable in modern societies although members are more tolerant than those in caste societies. Modern societies are characterized by loosely coupled small-sized groups with different cultural markers. In terms of efficiency, they achieve higher levels of cooperation than do societies where agents change markers rapidly before defectors attack cooperative clusters.