Race is often defined by its reference to biology, blood , genes, nature or essence. Yet these concepts are often left unexamined. Integrating material from the history of science, science studies, and anthropological studies of kinship and new reproductive technologies, as well as from studies of race, this work explores the meaning of such terms and interrogates the relationship between nature and culture in ideas about race. Exploring the interconnection between nature and culture in making persons what they are, this work argues that these ideas of biology and nature that underwrite racial discourse are more complex than they seem.