‘Evolutionary biology’ applies game theory to evolutionary scenarios. In evolutionary game theory we can equate behaviour as strategy, and fitness as utility. Anything — be it a gene or an organism — which can replicate itself and determine strategic behaviour in a game is known as a replicator, and these tend to settle into evolutionarily stable dynamics. Standard game theory puzzles, such as the Hawk-Dove Game, the Prisoner's Dilemma, and Chicken can be applied to evolutionary scenarios. Cooperation within family groups has developed to protect all copies of a gene, and its strength is modulated by the degree of relationship between individuals. Social and cultural replicators — or memes — have also evolved.