A Tale of Two Haplotypes: The EDA2R/AR Intergenic Region Is the Most Divergent Genomic Segment Between Africans and East Asians in the Human Genome

The study investigated the EDA2R/AR intergenic region on the X chromosome, which is highly divergent between African and East Asian populations. It involved analyzing 52 SNPs within this region across 3,000 X chromosomes from 65 human populations. The research identified two predominant haplotypes: the a-haplotype, which is common in African populations and likely arose before their diversification, and the ß-haplotype, which is frequent in non-African populations and likely originated in East Africa before the out-of-Africa migration. Rare haplotypes found in African hunter-gatherer populations suggest a diverse ancestral haplotype pool. The study suggests demographic changes and positive selection shaped the predominance of these haplotypes, with evidence of purifying selection against recombinants. Additionally, the study found an association between the region and androgenic alopecia (AGA), with the ancestral allele of SNP rs12558842 on the ß-haplotype being a risk allele for AGA, and the derived allele on the a-haplotype being protective.