Haldane's hypothesis was confirmed by A. C. Allison, who showed that the geographical distribution of the sickle‐cell mutation in the beta hemoglobin gene (HBB) was limited to Africa and correlated with malaria endemicity, and individuals who carried the sickle‐cell trait were resistant to malaria (Allison, 1954). The gene discussed is HBB; the disease is malaria.