A Dairy Mystery

At https://phys.org/news/2020-01-ancient-dairy-mystery-modern-food.html … it begins by telling us the armies of Genghis Khan fed on dried curd as they waged war and destruction on their way across the Eurasian steppes. Dairy foods have been an ancient food source since at least 6000BC – and probably earlier. People were consuming animal milk before they developed a genetic mutation which enabled them to digest it properly. That is the mystery. The mutation meant people produced lactose, an enzyme which breaks down milk sugars. There is a 4000 year gap between the first evidence of people eating dairy foods and the first appearance of the mutation, we are told. Even in the modern world only 35% of people are lactose tolerant – mainly in Europe (and especially in NW Europe). There are other people, in sub Sahara Africa and South Asia that are also lactose tolerant, and some people in the Middle East (where dairy farming appears to have originated). Funnily enough, modern Mongolians do not have the mutation – so how do you account for the dried curd. The Mongols milk yaks, sheep, horses, camels, as well as cattle and goats, and make various forms of yoghurt which can be dried as a curd and is capable of being kept for up to 2 years without going off. Fermentation appears to be the key – in the processing of milk into yoghurt and curd (or cheeses). Microbes in guts may have evolved to break down lactose.