Lactase persistence in humans is a fascinating topic that intersects biology, anthropology and history. The term ‘lactase persistence’ refers to the continued activity of the enzyme lactase throughout adult life. Lactase is responsible for breaking down lactose, the primary sugar in milk, into glucose and galactose, which can then be absorbed by the body. In most mammals, lactase activity declines after weaning, leading to lactose intolerance. However, in some human populations, lactase activity persists into adulthood, enabling the digestion of lactose.