Evolutionary game theory is mathematical expression of Darwin’s theory. This theory explained e.g., evolution of aggressivity (Hawk-Dove game), evolution of cooperation (Prisoner’s dilemma). These models, as many others, are described by a payoff matrix. Solutions are then thought in the form of evolutionarily stable strategies, or Nash equilibria. Evolutionarily stable strategies, in contrast to the Nash equilibria, are stable with respect to invasion by small quantities of mutants playing a different strategy, realized in biology by a different pheno/genotype.