In 1995, Roger Bannister, the first man to break four minutes in the mile, gave new life to an old debate. He argued that Black runners had “certain anatomical advantages” that made them all but unbeatable on the track and the roads. Some condemned his remarks. Bannister had, they said, failed to acknowledge the role of culture. Nature or nurture? commentators asked and asked again. The disagreement between the two sides hid a larger consensus: that the Black athlete constitutes a coherent scientific classification, a classification that, in a society that values the natural above the social sciences (and all sciences above the humanities), enters the collective consciousness in biological form. Chapter 1 tells the longer story of that consensus and how science and science writers used a naturalized male/female binary to naturalize a Black/white racial binary – a rhetorical move that the movement to bar trans athletes from competing in women’s and girls’ divisions has borrowed and reversed.