Ancient Dental Plaque Reveals When Ancient Humans First Drank Milk

When did we first begin drinking milk as humans? Drinking milk is a relatively unusual trait for adult mammals, which is why our milk-drinking habits have long puzzled researchers. Now, scientists have taken a closer look  and have found the answers in the form of calcified dental plaque on ancient human teeth.

Previous studies have shown that mutations which enable adults to drink milk are under the strongest selection of any in the human genome. These mutations cause the intestinal enzyme, lactase, to continue to be produced long after weaning occurs. Yet this lactase persistence is only prevalent in some populations around the world, such as in Northern Europe. In most people of the world, the lactose cannot be properly digested.

What's interesting is that some dairy products, such as cheese, have had their lactose content reduced or removed through processing. The lactose ends up in the whey in the case of cheese. If it's so easy to remove milk sugars, though, why is the mutation under such strong selection?

In this case, the researchers examined human dental calculus, a mineralized form of dental plaque, in ancient human teeth. The scientists detected a milk protein, beta-lactoglobulin, in the ancient remainds.

"It is only within the last several thousand years that genetic mutations arose in Europe, East Africa and the Arabian Peninsula that allowed lactase to persist into adulthood, a genetic trait that enables lifelong milk consumption," said Dallas Swallow, one of the researchers, in a news release.

The discovery of the milk proteins will, in theory, allow scientists to unite different lines of evidence and compare genetic traits and cultural behaviors of specific individuals who lived thousands of years ago.

The findings are published in the journal Scientific Reports.