Sufficient information is sufficient for the evolution of cooperation

Whether or not cooperation is an evolvable trait has been the subject of much discussion in evolutionary theory. Evolutionary game theory has suggested that cooperation is selected for if the genotype of a player is correlated with the phenotype of its opponent. This "inclusive fitness theory" has been criticized because it breaks down if fitness effects are non-additive. Here we present a new approach based on communication theory that shows that cooperation is selected for if the information that a player has about the opponent's phenotype exceeds the cost-to-benefit ratio of the game. We present numerical simulations of the iterated Prisoner's Dilemma (iPD) in which a player's strategy can evolve to take into account the opponent's previous move. We validate our theory for different cost-to-benefit ratios and establish the minimum amount of information that a player must have for cooperation to be beneficial. The new theory generalizes Queller's inclusive fitness rule by replacing covariance and variance by information and entropy, respectively. Because information is a non-additive concept, the theory also escapes the criticisms directed at inclusive fitness theory, and establishes that cooperation fundamentally depends on communication that distinguishes cooperators from defectors.