Evidence for still ongoing convergence evolution of the lactase persistence T-13910 alleles in humans

A single nucleotide variant, C/T-13910, located 14 kb upstream from the lactase (LCT) gene has been shown to be completely correlated with lactase persistence (LP) in Northern Europeans. Here we analysed the allelic background of the alleles carrying the critical variant in 1611 DNA samples from 37 populations. Our data shows that the T-13910 variant is found on two different highly divergent haplotype backgrounds in the global populations. The first is the most common LP haplotype (LP H98) present in all populations analyzed, whereas the others, originating from the same ancestral allelic haplotype (LP H8-H12) are found in geographically restricted populations living west of the Ural, north of the Caucasus. The global distribution pattern of the LP T-13910 H98 supports the Caucasian origin of this allele. Age estimates based on different mathematical models would evidence that the common LP T-13910 H98 allele (~ 5000-12000 years) is relatively older than the other geographically restricted LP alleles (~ 1400-3000 years). Our data of global allelic haplotypes of the lactose tolerance variant would imply that the T-13910 allele has been independently introduced more than once and there is a still ongoing process of convergent evolution of the LP alleles in humans.