Figure 1. Multiple origins of the beta globin Glu6Val (β^s, sickle) mutation within the African continent.

Malaria selection pressure led to the emergence of the sickle mutation at four distinct locations in sub-Saharan Africa, which are distinguishable by flanking DNA polymorphisms that define beta globin SCA haplotypes from Senegal (SEN), Benin (BEN), Cameroon (CAM), and Central African Republic (CAR). An additional sickle mutation occurred in the Arabian-Indian region, not shown.