Unpublished draft

Evolution of cooperation

The evolution of cooperation is the study of the mechanisms by which natural selection favors behaviors that benefit others at a cost to the actor. Martin Nowak organized the known mechanisms into five rules in a 2006 Nature review.

The five mechanisms

  1. Kin selection. Cooperation spreads among relatives when the benefit, weighted by relatedness, exceeds the cost — Hamilton’s rule.
  2. Direct reciprocity. Repeated encounters between the same two individuals allow “I help you, you help me” strategies such as tit-for-tat.
  3. Indirect reciprocity. Helping builds a reputation, and others help individuals with good reputations.
  4. Network reciprocity. In spatially structured populations, cooperators cluster and protect each other from defectors.
  5. Group selection. Groups with more cooperators outcompete