According to Alexander's [Alexander, R. D. (1987). The biology of moral systems. New York: Aldine de Gruyter] theory of morality, human social groups became large as a result of between-group competition over preferred habitats and resources, but although larger social groups are more successful in competition, they also experience more pressures to fission. Morality unites a society by limiting infringements upon the rights of other society members, so if larger societies are indeed more likely to split, then those that remain intact may be expected to have more effective inviolable moral rules, such as those imposed by moralizing gods. Cross-cultural analyses support this line of thought: more competition between societies is found in environments rich in resources and larger societies tend to occupy these environments; large societies engage in external conflicts at higher rates and are more often characterized by beliefs in moralizing gods. An additional explanation is briefly discussed, and we speculatively picture the historical chain of events giving rise to a belief in moralizing gods.