Sickle cell trait is apparently an adaptation for the prevention of Malaria. Sickle cell trait is a condition in which the red blood cells are abnormally shaped, if they inherit two faulty copies of the gene for the oxygen-carrying protein hemoglobin. The faulty gene persists because even carrying one copy of it confers some resistance to malaria. As a result, the frequencies of sickle cell carriers are high in malaria endemic areas.
