ABSTRACT
From central Nigeria eastward throughout sub-Saharan Africa and in Madagascar, hemoglobin S is the only abnormal variant found in high frequencies. Other hemoglobin variants are reported from the Congo Republic, Uganda and Angola, but none attain appreciable frequencies. The ability of hemoglobin S to replace other hemoglobin variants is due to the great fitness of the AS heterozygote. From northern Mozambique to the central Sudan, the frequencies of hemoglobin S and the glucose-6-phosphate dehydrogenase (G6PD) deficiency vary enormously. In the dry grassland and semi-desert regions of Tanzania and Kenya, the hemoglobin S frequencies among the pastoralists are almost zero, and their G6PD deficiency frequencies are also very low. In Rhodesia the frequency of hemoglobin S is very low, and malaria is present, although more epidemic than endemic. Because of the widespread presence of hemoglobin S in central Africa, one is tempted to associate this abnormal hemoglobin with the expansion of the Bantu peoples.
