A population has adopted an evolutionarily stable strategy (ESS) in regards to cooperation or defection. If a new mutant strategy appears that causes an opposite behavior from the norm, which of the following will result?
A. The mutant strategy will not be able to increase in numbers in the population under the influence of natural selection.
B. Antagonistic pleiotropy will allow an equilibrium in which both strategies are maintained in the population.
C. The members of the population using the original strategy will act with aggression toward those exhibiting the mutant strategy.
D. The evolutionarily stable strategy will be displaced because of natural selection in favor of the mutant strategy.
E. Natural selection will maintain the mutant strategy because the variation in strategy may be useful in future environments.

An evolutionarily stable strategy (EES) can be defined as a strategy that is competitively superior to others strategies and cannot be replaced or invaded by any other strategy through natural selection, resulting in punishment for those who deviate from it. Thus, an EES may confer a higher reproductive/adaptive fitness than alternative strategies when it is adopted by most members of the population. Individuals having an ESS are 'spiteful' because they act not only to increase their payoffs but also to decrease the payoffs of their competitors. An EES is resistant to low levels of mutation when all individuals in the population have the same strategy. In game-theoretical terms, an ESS is a strategy such that if all the members of a population adopt this strategy, then no mutant strategies could invade the population under natural selection. In consequence, when all individuals of a population adopt an EES, mutant phenotypes cannot invade and displace the ESS.