As ethnicity increasingly becomes part of the politicization of culture, a decision people take to depict themselves or others symbolically as bearers of a certain cultural identity, historians have turned to ethnicity in the past, particularly in the early Middle Ages. In studies of ethnicity, the recent focus on categorization represents a reaction to constructivism as a sociological and anthropological theory, which tends to reduce culture to narrative discourse, process, and identity. In Eastern Europe, both before and after the demise of the Communist regimes, the study of ethnicity (especially of Slavic ethnicity) was dominated by an obsessive preoccupation with formal elements—phenotype, language, or culture. In studies of ethnogenesis in the United States, the emphasis is typically laid on “agency,” and the topic is regarded as quite appropriate for a critique of assimilationist and integrationist Eurocentrism. Moreover, ethnogenesis is sometimes regarded as a form of resistance to oppression.