Game Theory
Game Theory is often used to discuss the nature of human cooperation.
See our entries on the Prisoner's Dilemman and the Assurance Game
From the Wikipedia at http://en.wikipedia.org/wiki/Game_theory:
"Game theory is a branch of applied mathematics that studies strategic situations where players choose different actions in an attempt to maximize their returns. First developed as a tool for understanding economic behavior and then by the RAND Corporation to define nuclear strategies, game theory is now used in many diverse academic fields, ranging from biology and psychology to sociology and philosophy. Beginning in the 1970s, game theory has been applied to animal behavior, including species' development by natural selection. Because of interesting games like the prisoner's dilemma, in which rational self-interest hurts everyone, game theory has been used in political science, ethics and philosophy. Finally, game theory has recently drawn attention from computer scientists because of its use in artificial intelligence and cybernetics." (http://en.wikipedia.org/wiki/Game_theory)