Milk wasn't on the Stone Age menu, says a new study which suggests the vast majority of adult Europeans were lactose intolerant as recently as 7,000 years ago.

While cow's milk is a mainstay in the diet of modern-day Europeans, their ancestors weren't able to digest the nutritious dairy product after childhood, according to DNA analysis of human skeletons from the Neolithic period.

The study was led by Joachim Burger of the Institute of Archaeology at Mainz University in Germany.

The findings supports the idea that milk drinkers became widespread in Europe only after dairy farming had become established there—not the other way around.

Most mammals lose their ability to digest milk after being weaned, but some humans can continue to benefit from the calcium-rich, high-energy liquid.