Cooperation, not ruthlessness, turns out to be the winning strategy in evolution, and this BBC Horizon film narrated by Richard Dawkins sets out to show why. It builds its case around the prisoner's dilemma, a game theory puzzle in which two players choose to cooperate or betray each other without knowing the other's move, and uses computer tournaments to test which strategies survive repeated rounds. The winner is tit for tat: cooperate first, then simply mirror whatever the other player did last time. Dawkins connects the math to real biology, drawing on examples from the animal kingdom where individuals or species that help each other outcompete those that only look out for themselves. The film treats this as a challenge to the popular reading of Darwin as pure dog-eat-dog competition, arguing instead that stable cooperation can be the more successful long-term strategy, in nature and in human affairs like business and diplomacy. It closes with the game theory finding stated plainly: reciprocity beats aggression when the same players keep meeting again.