 So far our discussion has focused on how game theory has been used to illustrate some ostensible functions of morality and the role social norms play in it. However, game theory has also been utilized to identify particular norms that might be important, as well as to identify important characteristics of norms. And, where the previous analysis relied primarily on the tools of non-cooperative game theory, here it is evolutionary game theory that has been especially illuminating. Particularly influential in this regard was the work of Robert Axelrod and colleagues in the early 1980s on the evolution of cooperation, along with the subsequent work of Robert Boyd, Peter Richerson, and various collaborators (see Axelrod 2006 and Boyd &amp; Richerson 2005 for summaries of the relevant work). By analyzing the performance of various fixed strategies in repeated social dilemmas they were able to illustrate the important role that conditional strategies and the willingness to sanction bad behavior play in allowing cooperation and other prosocial behaviors to not only emerge, but become optimal from the standpoint of the individual. More specifically, they showed that in environments where individuals have a long-run interest in bringing about mutually advantageous outcomes but a short-term interest in exploiting others for maximum gain, it is essential that (i) individuals not leave themselves vulnerable to repeated exploitation, and (ii) at least some individuals be willing to punish exploitative behavior.