Evolution of Norms in a Multi-Level Selection Modelof Conflict and Cooperation

We investigate the evolution of social norms in a game theoretical model of multi-level selection and mutation. Cooperation is modelled at the lower level of selection by means of a social dilemma in the context of indirect reciprocity, whereas at the higher level of selection conflict is introduced via different mechanisms. The model allows the emergence of norms requiring high levels of cognition. Results show that natural selection and mutation lead to the emergence of a robust yet simple social norm, which we call stern-judging. Stern-judging is compatible with expectations that anthropologists have regarding the Pleistocene hunter gatherer communities. Perhaps surprisingly, it
also fits very well recent studies of the behaviour of reputation-based e-trading. Under stern-judging, helping a good individual or refusing help to a bad individual leads to a good reputation, whereas refusing help to a good individual or helping a bad one leads to a bad reputation. The lack of ambiguity of stern-judging, where implacable punishment is compensated by prompt forgiving, supports the idea that simplicity is often associated with evolutionary success.