The Origins of Virtue is a nonfiction book by British popular science writer Matt Ridley. The central thesis of the book is that altruistic behavior—the selfless action and mentality of helping other people—was developed among certain individuals and passed down to their next of kin; essentially, that altruism could be genetically inherited. The book's premise could be considered an example of sociobiology theory, an interdisciplinary field that studies the dynamics between a living organism and their social environment.

Another major theme in the book is the development of morality. Instead of expressing philosophical theories and concepts pertaining to morality—which is the approach many writers take when attempting to dissect the subject—Ridley looks at it from a sociobiological point of view. Ridley believes that the same mechanism that allows altruism to be passed down from generation to generation via genetic traits applies to one's "moral compass." While the question of moral judgment does lean more towards sociology than biology, Ridley attempts to argue that one's perception of right and wrong can be influenced by genetic traits.

Ridley explains that his theory is based on the concept of prisoner's dilemma, an example of game theory which posits that two individuals will not cooperate despite personal rewards for doing so. In the book, Ridley states that human society developed to where it is now because of altruism and that our human ancestors learned early on that cooperating was more beneficial to themselves as individuals and to the group as a whole. In a way, cooperating was a win-win situation from a micro and macro perspective.

The other theme in the book, which is closely related to the overall thesis, is the concept of tit-for-tat. Ridley used computer generated models of tit-for-tat systems to observe how individuals will cooperate with others if there is an equal exchange of benefits. Those that do not offer a benefit in return will be excluded from the group. In this sense, Ridley's theory of cooperation is not purely "selfless" because, in the tit-for-tat model, the actors are both seeking personal rewards from the cooperation rather than cooperating out of true selflessness and generosity. Lastly, Ridley concludes the book by proposing—without any political rhetoric or political ideology endorsement—that society should scale down to a local form of governance, because the altruism theory can only be applied in a small group.