Haplotype diversity and linkage disequilibrium at human G6PD: Recent origin of alleles that confer malarial resistance

The frequencies of Low-activity alleles of glucose-6-phosphate dehydrogenas e in humans are highly correlated with the prevalence of malaria. These "de ficiency" alleles are thought to provide reduced risk from infection by the Plasmodium parasite and are maintained at high frequency despite the hemop athologies that they cause. Haplotype analysis of "A-" and "Med" mutations at this Locus indicates that they have evolved independently and have incre ased in frequency at a rate that is too rapid to be explained by random gen etic drift. Statistical modeling indicates that the A- allele arose within the past 3840 to 11,760 years and the Med allele arose within the past 1600 to 6640 years. These results support the hypothesis that malaria has had a major impact on humans only since the introduction of agriculture within t he past 10,000 years and provide a striking example of the signature of sel ection on the human genome.