The contemporary study of Jewish genetics has a long prehistory dating to the eighteenth century. Prior to the era of genetics, studies of the physical makeup of Jews were undertaken by comparative anatomists and physical anthropologists. In the nineteenth century the field was referred to as “race science.” Believed by many race scientists to be a homogeneous and pure race, Jews occupied a central position in the discourse of race science because they were seen as the control group par excellence to determine the relative primacy of nature or nurture in the development of racial characteristics. In the nineteenth century, claims of Jewish homogeneity prompted research that sought to explain morphological differences among Jews, chief among them the difference between Sephardim and Ashkenazim. I examine some of these original debates here with a view to placing them in their historical and cultural contexts.