The monograph is devoted to one of the key problems of globalization - the growing ethnocultural fragmentation of society, occurring against the backdrop of a systemic crisis of modern nations. To explain this phenomenon, the concept of ethno- and national genesis is proposed, which substantiates the historically long coexistence of an ethnos and a nation, understood as ontologically different communities in which the individual participates simultaneously. Nation and ethnic group have coexisted since the emergence of early states, differ in the mechanisms of sociogenesis, dynamics of development and are associated with different spheres of existence for the nation and ethnic group.