 The revised conceptions of race and genetics worked off this evolutionary story, where the idea was that racial categories represented human groups with unique genetic profiles tied to those different selection histories (Hardimon 2017). A Black person, the thought went, came from African ancestry, while a White person came from European ancestry. In turn, the Black person was likely to have a different genetic profile when it came to melanin production (which controls skin shade) than the White person, and the Black person was more likely to be a carrier for sickle-cell anemia (a blood disorder that also offers some resistance to malaria) while the White person was more likely to be a carrier for cystic fibrosis (a respiratory disorder that also offers some resistance to cholera) (Spencer 2018). Proponents of these newer ideas about race and genetics were eager to say that they were not in the business of ranking races; they were just tracing different racial histories and the modern phenotypic results of them (entry:  the social dimensions of scientific knowledge).