In this paper, the author argues that moral systems evolved as a way to enforce cooperation between people outside of kin groups. Because cooperation within kin groups has apparent adaptive advantages, it is argued that these moral systems will be less important for societies with tight kin groups and conversely more important for those with looser kin groups. In order to test this theory, the author creates an original model that incorporates both ethnographic data and data from contemporary countries. Thus, it is postulated that historical kinship practices will influence contemporary systems. The paper concludes that there is sufficient historical evidence for this theory.

The authors of this study globally test the culture of honor hypothesis, which proposes that societies with traditional herding practices developed value systems that encourage revenge and violence. Because their livelihood depends on a mobile asset, herders are more vulnerable to theft and may be more likely to turn to violence or aggressiveness to defend their animals. The authors found dependence on herding to be significantly associated with both past and contemporary conflict and punishment.