In the 1940s, the scientist J. B. S. Haldane linked many human red blood cell disorders with the tropical regions where malaria occurs. Haldane hypothesized that the widespread presence of these red blood cell disorders as well as traits that protect individuals from malaria were the result of natural selection. Haldane’s hypothesis was later confirmed by the research of A. C. Allison. The resistance to malaria carried by individuals in areas where malaria is widespread is the result of