No human societies exist without social norms, that is, without normative standards of behavior that are enforced by informal social sanctions. In fact, the ability to develop and enforce social norms is probably one of the distinguishing characteristics of the human species.

DEFINE: Clarifies what social norms are: normative behavioral standards enforced by informal sanctions. Builds on: "Unaffected bystanders punish norm violators even without personal stakes"

Ernst Fehr, Third-Party Punishment and …, loc. 4