Our findings support the latter hypothesis: that frequencies of the G6PD c.202T allele in Kilifi are a result that frequencies of the G6PD c.202T allele in Kilifi are a result of historic selection for heterozygous girls through a survival advantage against severe malaria balanced by the increased loss from severe malaria anaemia of both G6PD c.202T hemizygous boys and homozygous girls with G6PD deficiency. The gene discussed is G6PD; the disease is anemia (phenotype).