🧑 Human

Homo sapiens is the mammal species to which we belong. Like all mammals, humans feed their babies on milk from the mammary glands. What sets humans apart is that they milk other animals, such as cows, buffaloes, goats, sheep, camels and mares, and turn their milk into cheese, butter, kefir and hundreds of other products.

Dairying is ancient. The earliest direct traces of milk are fat residues in pottery from the Near East and southeastern Europe dating to the 7th millennium BC; cattle, sheep and goats had been domesticated there even earlier, by the 8th millennium BC. In Europe milk has been widely used since the Neolithic: about 7,000 animal fat residues have been found in pottery from more than 550 sites.

To digest the milk sugar lactose, the body needs the enzyme lactase. In most people its activity declines after infancy: according to the US National Library of Medicine, about 65% of people have a reduced ability to digest lactose, but among people of northern European descent only about 5% do. The ability to keep lactase active throughout life is called lactase persistence. It is one of the traits most strongly shaped by natural selection over the last 10,000 years, yet early Neolithic Europeans barely had it: it spread noticeably only in the Bronze Age and later.

Why it matters to you. Digesting lactose less well does not mean milk is off limits. According to EFSA, most such people tolerate up to 12 g of lactose at a time, roughly a glass of milk, with no symptoms or only minor ones. Cheese and yoghurt are often better tolerated, because much of the lactose is broken down during fermentation. And babies should not be given cow's milk as a main drink before the age of one (NHS).