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modern · 1920 to 2004
Animals do not calculate, yet they play strategies. Maynard Smith showed that natural selection is a game, and that evolution settles on strategies no mutant can invade.
Facts reviewed 2026-07-11.
John Maynard Smith was a British biologist, originally trained as an aeronautical engineer, who brought the tools of game theory into evolutionary biology and transformed both fields. Working in part with the mathematician George Price, he saw that the logic of strategic interaction did not require conscious minds; it only required that some behaviors reproduce more successfully than others.
The move was radical. Game theory had assumed rational players choosing strategies. Maynard Smith replaced the rational chooser with natural selection, and the strategies with heritable behaviors, and found the mathematics still worked.
In a 1973 paper in Nature with George Price, Maynard Smith introduced the evolutionarily stable strategy, or ESS: a behavior that, once common in a population, cannot be invaded by any rare alternative. It is an equilibrium concept, like Nash's, but driven by reproductive success rather than reasoning. A strategy is stable not because players choose it but because selection preserves it against mutants.