The practice of milking cows began around 10,000 years ago, during the Neolithic period, when humans shifted from hunting and gathering to farming and domesticating animals. The initial individuals to drink milk regularly were early farmers and pastoralists in Western Europe who lived with domesticated animals like cows, sheep, and goats.
In the early stages, adults could not digest milk properly. The enzyme lactase, necessary for breaking down lactose in milk, is typically produced only in infants. As people grew older, they generally lost the ability to process lactose, leading to digestive discomfort if milk was consumed.
Over time, some populations developed a genetic adaptation known as lactase persistence, which allowed them to digest lactose throughout adulthood. This genetic trait is thought to have first appeared in southern Europe about 5,000 years ago and spread to central Europe around 3,000 years ago. This trait is now common in northern Europe, parts of Africa, and the Middle East.
Milk is now consumed in various ways, including on its own, with cereals, tea, or coffee, and used in cooking. The ability to digest milk varies by population, with over 90% of individuals in some regions experiencing lactose intolerance, reflecting historical and evolutionary changes in human diet and physiology.