Continuing Franz Boas' work to establish anthropology as an academic discipline in the US at the turn of the twentieth century, Alfred L. Kroeber re-defined culture as a phenomenon sui generis. To achieve this he asked geneticists to enter into a coalition against hereditarian thoughts prevalent at that time in the US. The goal was to create space for anthropology as a separate discipline within academia, distinct from other disciplines. To this end he crossed the boundary separating anthropology from biology in order to secure the boundary. His notion of culture, closely bound to the concept of heredity, saw it as independent of biological heredity (culture as superorganic) but at the same time as a heredity of another sort. The paper intends to summarise the shifting boundaries of anthropology at the beginning of the twentieth century, and to present Kroeber?s ideas on culture, with a focus on how the changing landscape of concepts of heredity influenced his views. The historical case serves to illustrate two general conclusions: that the concept of culture played and plays different roles in explaining human existence; that genetics and the concept of Weismannian hard inheritance did not have an unambiguous unidirectional historical effect on the vogue for hereditarianism at that time; on the contrary, it helped to establish culture in Kroeber's sense, culture as independent of heredity.