Milky Way

The ability to digest milk as an adult seems to have evolved just about 7,500 years ago

The ability to digest milk as an adult is much rarer than many of us would like to believe. In fact, by far the vast majority of the world’s population does not share the ability, which a new study shows originated just 7,500 years ago in Central Europe from where it spread rapidly to various parts of the world. In India, the spread of the gene varies significantly, depending on region. The gene is far more common in north India where the percentage of adults who are lactose intolerant—unable to digest the sugar found in milk—is about 27 per cent. This increases to 67 per cent in the South. Most of the North-East states seem to share the almost complete lactose intolerance that is found in East Asia.

The new study led by University College London (UCL) scientists was published in the journal PLoS Computational Biology and shows that the change that let early Europeans drink milk as adults first took place among dairy farmers who lived around 7,500 years ago in a region between the central Balkans and Central Europe. Earlier, it was believed the change first occurred in northern Europe because in places such as Scandinavia, the prevalence of lactose intolerance is under 5 per cent.

Professor Mark Thomas, UCL Genetics, Evolution and Environment, says, “Most adults worldwide do not produce the enzyme lactase and so are unable to digest the milk sugar lactose. In Europe, a single genetic change is strongly associated with lactase persistence and appears to have given people with it a big survival advantage. Since adult consumption of fresh milk was only possible after the domestication of animals, it is likely that lactase persistence co-evolved with the cultural practice of dairying. Our study simulated the spread of lactase persistence and farming in Europe, and found that lactase persistence appears to have begun around 7,500 years ago between the central Balkans and Central Europe. But contrary to popular belief, we also found that a need for dietary vitamin D was not necessary to explain why lactase persistence is common in northern Europe today.”

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Hartosh Singh Bal