Samuel Bowles and Herbert Gintis bring together a wide range of evidence in their discussion on the origin and nature of human cooperation and society. Humans are cooperative, not only for mutual gain, but also altruistically. We care for one another. This entails not only the welfare of each other, but also in the upholding of norms that are part of the particular culture we live in. How did the peculiar behavior evolve?
The most common explanations invoke kin and reciprocity. Kin relationships can and do underlie altruistic behavior among many species. Reciprocity is rare among animals, but could in principle be invoked for some types of altruism. But Bowles and Gintis conclude that these do not sufficiently explain human cooperative behavior. Social preferences such as cooperating with unrelated people even in cases when reciprocity is unlikely, and the propensity to punish free-riders and cheats even when doing so is costly, require other explanations.
The discussion is exhaustive, and in parts exhausting. The authors recapitulate very technical treatments of models and simulations, primarily relating to evolutionary theory and game theory approaches to cooperation. However, the reason is that they wish to show that the effects of kin and reciprocity cannot quantitatively account for the full extent of human cooperation. It is one thing to argue the qualitative effects, but another to show that the numbers add up. Bowles and Gintis goes through the formulae and numbers in detail, which is necessary, but heavy going for an amateur.
The authors argue that more is required to explain the evolution of human cooperation. Their answer is the co-evolution of institutions and group-mindedness, where culture and group competition act as critical factors. The driving force was the between-group competition that operated during Homo sapiens early evolution. This included the survival (or not) of groups of people in the harsh environment by inventing and maintaining the appropriate tools (in a wide sense) to deal with the challenges. It also included the inter-group competition and conflicts that could determine which one survived and which not.
Bowles and Gintis write that the "individual motives and group-level institutions that account for cooperation among humans include not only the most elevated, including a concern for others, fair-mindedness, and democratic accountability of leaders, but also the most wicked, such as vengeance, racism. religious bigotry and hostility towards outsiders." The ability to be good as well as evil has been our blessing and curse since our species evolved. It is our heritage.