A number of animal species from different lineages live socially. One of the features of social living is the formation of dominance hierarchy. Despite its obvious benefit in the survival probability of the species, the hierarchical structureitself poses psychological and physiological burden leading to the chronic activation of stress related pathways. Considering these apparently conflicting observations, here we propose that social hierarchy can act as a selective force in the evolution of social species. We also discuss its role on social psychology.