An evolutionary stable strategy describes tactics employed by individual organisms when competing with one another for a given resource. These tactics can be behavioral or structural, and the organism does not consciously choose them, but adopts them as a natural consequence of evolution. Both structures and behaviors are heritable (capable of being inherited), and as some are successful and some fail, only the better ones are passed on. It is important to differentiate between a strategy employed by an individual, such as displaying brighter-colored feathers, and a strategic decision an individual might consciously make, such as going to medical school, because only heritable strategies get passed on to offspring. Decisions such as going to medical school, however strong in a family, are not heritable.

The idea of evolutionary stable strategy (ESS) was first conceived by the British biologist John Maynard Smith in 1974. The idea...