East Asian human gene that allows adult humans to digest sugars in milk likely came from Neanderthals
A small team of computational and evolutionary biologists from the University of Chinese Academy of Sciences, Zhongshan Hospital and the Max Planck Institute for Evolutionary Anthropology, reports that unique lactase genes carried by about 25% of East Asian people may have been inherited from Neanderthals.
In their study in Proceedings of the National Academy of Sciences, the group compared the genes of thousands of people of African, East Asian and European descent against one another and then against Neanderthal genes.
Prior research has shown that many people of European descent carry genes that allow them to easily digest the sugars (lactose) present in milk, in sharp contrast to people of East Asian descent, who tend to have a high percentage of lactose intolerance. However, in this new effort, the research team found unique versions of the lactase gene in some East Asian people along with evidence that they may have come from interbreeding between humans and Neanderthals thousands of years ago.
The researchers compared thousands of genomes collected from people of known European, African or East Asian descent, looking for commonalities between people who were lactose intolerant and those who were not. They found that approximately 25% of the East Asian samples studied carried versions of lactase genes not found in the genes of African or European people.
That led them to then compare those lactase genes from East Asians with genes from Neanderthals. They found that the genes in the East Asian samples likely came from the Neanderthals. This was because the genes showed up in the early humans before they had begun to drink the milk of domesticated animals such as cows, which ruled that out as a source of selection.
Exploring how the Neanderthals might have developed the lactase genes, the team found evidence that they may have provided some degree of protection against infections, a finding that would also explain why the genes persisted in East Asians long after the disappearance of the Neanderthal.
More information: Xixian Ma et al, Neanderthal adaptive introgression shaped LCT enhancer region diversity without linking to lactase persistence in East Asian populations, Proceedings of the National Academy of Sciences (2025).
Journal information: Proceedings of the National Academy of Sciences
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