Stupid Question ™
April 20, 2000
By John Ruch
Q: Why did humans start drinking cows’ milk?
A: Probably the same reason you’re asking about it: Humans are nothing if not curious.
Humans have consumed the milk of nearly every large mammal, but the first daring sip was probably from a goat or sheep, which were domesticated at least 9,000 years ago.
Cattle were domesticated about 1,000 years later, but eventually produced more milk for the buck. The earliest evidence of cow-milking is 6,000-year-old artwork from Egypt and Mesopotamia (which depict cheese- and butter-making, so milking was already far along).
However, none of these animals were domesticated for milk. Goats were probably tamed to keep them from eating crops. Cattle were possibly tamed for sacrifice and as tokens of wealth; the Egyptians used milk as a sacrificial-ritual substance and a medicine long before they used it for food.
Milk is loaded with nutrients, and is highly portable in the form of cheese, yogurt and butter. But it became an important food only as populations moved from hunting and gathering to agriculture in less-fertile places.
Cows would turn dry grass into useful milk. (Meat farming came later, in good pastures.) And their milk helped provide the calcium missing from the cereal-based diet of early agriculture.
Thus, people in poor areas (northern Europe and central Africa and Asia) with a taste for milk would be healthier and reproduce more.
But first, they had to breed themselves into a freakish line of adult babies. If you’re a grown-up who can digest milk, you’re a genetic weirdo compared to most people on this planet.
Milk contains lactose, which is digested only after being broken down by the enzyme lactase. After infancy (or, in humans, sometime during childhood), mammals’ lactase production is genetically switched off, since they’re supposed to be done nursing. Without the lactase, lactose ferments in the gut, producing gas and diarrhea.
Genetic freaks whose lactase didn’t shut off were favored in groups that consumed dairy products, eventually evolving entire lines of lactose-tolerant adults. But the majority of humanity remains normal and lactose-intolerant.
While about 85 percent of American whites can drink milk without side effects, 70 percent of American blacks can’t.
Mediterranean, Asian and Native American populations are 75-100 percent lactose-intolerant, are as 90 percent of Africans.
Milk-drinking by modern, industrial-world adults is simply a cultural artifact and social custom that is nutritionally unnecessary. In fact, the high protein, fat and cholesterol content of milk can be problems in the US diet.