This book attempts to create an evolutionary theory of fairness. Sharing food is commonplace in the animal kingdom because it insures animals that share against hunger. Anthropologists report that hunter-gatherer societies which survived into the 20th century shared on a very egalitarian basis. What can such information tell us about the sense of fairness with which modern man is born? Using game theory as a basic tool, the book argues that fairness norms should be seen as a device for selecting an efficient equilibrium in the human game of life. Evolutionary arguments are then used to argue that the deep structure of this device resembles the original position formulated by John Rawls in his Theory of Justice. Such an evolutionary framework allows problems over welfare comparison and norm enforcement to be tackled in a manner that resolves the long debate between utilitarianism and egalitarianism.