The paper requires that equilibrium behavior for two person symmetric games be resistant to genetic evolution. In particular the paper assumes that the evolution of genotypes selecting a behavioral rule can be described according to some generalization of the replicator model. This paper defines an equilibrium concept, 'evolutionary equilibrium', which is defined as the limit of stationary points of the evolutionary process as the proportion of the population that mutates goes to zero. Then the set of evolutionary equilibria, as defined in the paper, is a nonempty subset of the set of perfect equilibria (and thus of the set of Nash equilibria) and a superset of the set of regular equilibria and the set of ESS
