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Drinking milk

In some parts of the world, certain adults cannot drink large amounts of milk because they are unable to digest lactose, the sugar found in milk. Drinking fresh milk causes discomfort and diarrhoea, but they can eat dairy products treated to break down lactose - like yoghurt. In other parts of the world most people have a version of a gene (allele) that allows them to digest lactose in adulthood. This characteristic probably spread through some populations thousands of years ago, as their ancestors began farming cattle.

Ancient carving of domestic cattle from Mamallapuram, India.
Ancient carving of domestic cattle from Mamallapuram, India.
Nicky Lewis

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