At his death at age one hundred in 2005, Ernst Mayr was hailed as the greatest evolutionary biologist of the twentieth century. His definition of species, published in 1942 in Systematics and the Origin of Species and known as the “biological species concept,” is familiar to every tenth grader: “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.” That definition, together with Mayr’s and Theodosius Dobzhansky’s theory of speciation, enabled the integration of modern genetics and Darwinian evolutionary theory. In this paper I will argue that it imported racism into the heart of modern genetics as well