G6PD deficiency: a polymorphism balanced by heterozygote advantage against malaria

Very few people would doubt nowadays that Darwinian selection pervades not only the macroevolution of organisms, but also the microevolution of the human species. As a convincing example, many biology teachers, and certainly most haematologists, will choose sickle cell and malaria, and the reason is clear. Homozygous sickle cell anaemia (SS) is a serious inherited (autosomal recessive) disease that, left untreated, reduces life expectancy greatly; therefore, AS heterozygotes must have a remarkable advantage to balance the loss of homozygotes and enable this genetic polymorphism to persist.