Population genomics on the origin of lactase persistence in Europe and South Asia

The C to T mutation at rs4988235 located upstream of the lactase (LCT) gene is the primary determinant for lactase persistence (LP) that is prevalent among Europeans and South Asians. Here, we review evolutionary studies of this mutation based on ancient and present-day human genomes with the following concluding remarks: the mutation arose in the Pontic Steppe somewhere between 23,000 and 5960 years ago, emigrated into Europe and South Asia in the Bronze Age via the expansion of the Steppe ancestry, and experienced local hard sweeps with their delayed onsets occurring between 5000 and 3280 years ago. We also argue that the G to A mutation at rs182549 arose earlier than 23,000 years ago, the intermediate CA haplotype ancestral to the LP-related TA haplotype is still represented by samples from Tuscans, admixed Americans and South Asians, and the great majority of G to A mutated descendants have hitchhiked since the C to T mutation was favored by local selection.