Lewis H. Morgan's Systems of Consanguinity and Affinity of the Human Family (1871) is credited with inventing the anthropological study of “kinship” from a comparative perspective (Trautmann 1987). Since Émile Durkheim's critique of 1898, Morgan is also said to have reduced kinship to biology in keeping with Anglo-American cultural assumptions about “blood relations” given in nature. Yet, on closer inspection, Morgan's “consanguinity” proves to be fraught with contradictions. Debates about the degenerative effects of mixing bloods in marriage—consanguinity with affinity—encompassed not only miscegenation but also “consanguineous marriages,” such as Morgan's own marriage to his first cousin (his mother's brother's daughter) in 1851.