Game Theory: Evolutionary

Evolutionary game theory studies how strategies spread in a population when payoffs determine reproductive or imitation success. There are no rational, calculating players — only strategies that do well or poorly and thus grow or shrink in share. The central solution concept is the evolutionarily stable strategy (ESS): a strategy that, once predominant, cannot be invaded by a small fraction of mutants. It explains cooperation, aggression, and conventions (e.g. driving on one side) as emergent from payoff structure and dynamics. For founders, the lens is "what behaviour would be stable if everyone copied successful players?" — that's often what you get in the long run, even without perfect rationality.

Identify the payoff structure: who does well when others do what? The strategy that does best when prevalent is a candidate ESS. To change the game, shift payoffs (e.g. make cooperation more rewarding) or change who interacts with whom (structure). Don't assume rationality; assume imitation of success.

Evolutionary game theory: strategies spread by success; no rationality required. ESS: strategy that can't be invaded. Use it to explain conventions, norms, and industry equilibria. To change behaviour, change payoffs or structure so a better ESS emerges.