It has now been sufficiently established that even in the tribal condition people were differentiated into social ranks. We have traced the beginning of nobility to leadership and have found, in both ancient and mediaeval society, new noble families forming by the side of the old. Social distinctions were well developed long before the founding of cities. When a community, whether a tribe or a city, is far enough advanced to begin the conquest of neighbors, “it has already differentiated into royal, noble, free, and servile families.”[250] This was true of Sparta. In her “the conquerors nevertheless, notwithstanding great differences among themselves, remain sharply separated in social function from the conquered.... The conquerors became a religious, military, and political class, and the conquered an industrial class.”[251] Even in the case of Sparta, however, which is perhaps our best example of the exclusiveness of a ruling city, there is evidence of mingling between the conquering Spartans and the conquered Laconians before the former became exclusive.[252] In like manner there was much mixing of the invading “Aryans” with the natives of India—the more intelligent of the natives rising to the higher classes and the less gifted of the invaders sinking to the lower—before the crystallization of the castes.[253] We find the same mingling of conquerors and conquered in varying degrees in ancient Ireland,[254] in England under the Normans,[255] and throughout the Roman empire in the period of Germanic settlements.[256] It becomes doubtful, therefore, whether a nobility was ever formed purely by the superposition of one community upon another. The effect of conquest was rather to accentuate existing class distinctions, and by a partial substitution of strangers in place of native nobles to stir up antagonism between the classes. Even where the differences between the social ranks seem to be racial, it would be hazardous to resort to the race theory in explanation; for such a condition could be produced in the course of generations by different modes of life, education, nurture, and marriage regulations of the nobles and commons respectively.[257]