On Mar. 10, 2025, new research shows positive selection at the 2q21.3 locus in Europeans and Africans has long been tied to lactase persistence (LP) and milk-drinking and is a textbook example of convergent evolution and gene–culture coevolution.

However, the selection may not have been driven by LP alone. research has identified a high-frequency East Asian–specific haplotype at this locus, which came from Neanderthals and has been under positive selection. While this haplotype might be linked to LP, it is highly unlikely that the selection would have been for this reason. Instead, changes in immune function likely explain the selection in East Asians, thus indicating that selection was either for different reasons in different populations or selection was similarly not for LP in other populations.

Positive selection at the 2q21.3 enhancer region for lactase gene (LCT) expression in Europeans and Africans has long been attributed to selection for lactase persistence (LP), the capacity of adults to digest lactose in milk, presumably because of the benefits associated with milk consumption.

“The frequency of LP exhibits significant variation among global populations, spanning a range from 5% to almost 100%. Notably, the highest frequencies are found in people of Northern European descent and some populations from West Africa, East Africa, and the Middle East.”

The study show that an East Asian–specific haplotype that was introgressed from Neanderthals has experienced positive selection beginning 25 to 28 thousand years ago and that there is suggestive evidence associating this haplotype with LP in East Asians. The study was published in the Proceedings of the National Academy of Sciences.