> Those of African heritage commonly have Sickle Cell Anemia. While it is a crippling illness it gives one resistance to malaria; in much of Africa that enables one to live longer than those with healthy blood cells.
That's not quite right. Being heterozygous for the sickle-cell trait produces reduced symptoms from malaria (but not immunity), while being homozygous for the trait produces sickle cell disease and and, consequently, greater vulnerability to malaria (since malarial infection, in addition to its other effects, frequently produces sickle cell crises in persons with sickle cell disease.)
That's not quite right. Being heterozygous for the sickle-cell trait produces reduced symptoms from malaria (but not immunity), while being homozygous for the trait produces sickle cell disease and and, consequently, greater vulnerability to malaria (since malarial infection, in addition to its other effects, frequently produces sickle cell crises in persons with sickle cell disease.)