Why do humans drink cow milk?

The Smithsonian’s magazine recently shared a study of Neolithic farmers’ teeth that reveals humans have been drinking milk for at least 6,000 years. This era saw the rise of farming in what is now England. But for those lactose tolerant historians, farming areas within Northern Europe had yet to develop to continue breaking down lactose sugars in adulthood. So why do humans consume dairy?  

Lactose sugar is found in dairy products. When the lactose sugar enters the body, the lactase enzyme breaks the sugar down so it is easily digestible. Originally, only infants could consume milk, but this lactose tolerance would disappear around the age of weaning from breastmilk. The further into adulthood, the less tolerance humans had for lactose in dairy. It created gastrointestinal discomforts such as abdominal pain, diarrhea, gas and uncomfortable bloating. While this is still the case for many who consume too much lactose, people who were a part of ancient farming groups insisted on consuming dairy and changed how we see dairy. This would have given them the symptoms common with lactose intolerance, but their persistence created a tolerance. Many people with lactose intolerance can tolerate more lactose products if dairy is slowly introduced to the diet, but this went further. Eventually, farming communities developed a genetic mutation that allowed lactase to break down lactose sugars past infancy, meaning more reliance on dairy consumption was possible for farming groups.  

Yet this ability took thousands of years to develop. To enjoy cow’s milk—seen as the preferred milk amongst those groups studied—farmers processed their milk before consumption. It is believed that milk was turned into cheese, fermented foods and yogurts, which have less lactose than milk. If these people lived today, they could enjoy foods with most or all lactose conveniently removed, but they had to get creative.  

There are other studies which date milk consumption back further despite lactose intolerance. Ancient remnants in pottery show Mediterranean people may have consumed milk 9,000 years ago while genetic testing in Africa suggests dairy consumption became prominent around 10,000 years ago.   

The rise of dairy consumption began with the domestication of livestock. Pastoral farming created a more stable food supply than hunting (and the constant moving of following your food source). With a readily available ingredient like milk, these farmers learned of its nutrition and versatility in their diet. Milk was too good to pass up despite its gastrointestinal discomforts, so ancient dairy farmers invented lactose-friendly creations until biology began to catch up.   

Today’s population that can consume milk without the effects of lactose intolerance can thank their dairy farming ancestors. And when reaching for a gallon of milk—lactose-free or regular—remember that people have always loved the taste of milk. Even when milk consumption was not genetically in their favor, humans have strived to make dairy a part of their diet. Some things never change.