Scientists have spent decades studying ancient paintings on cave walls that depict animals being milked in an attempt to find evidence of dairy consumption. They have even found traces of dairy fat in pots. But scientists have never been able to determine if one specific human ate or drank dairy until now.

Modern technology has recently allowed archaeologists to test ancient remains for proteins specific to milk, and they can even tell you which animal the milk came from!

But how? You guessed it. By their teeth! Archaeologists have removed hardened dental plaque, called calculus, from our ancestors’ teeth and test it for these proteins. Fortunately for us, many ancient people didn’t brush their teeth. Unfortunately for our ancient ancestors, the lack of proper oral care coupled with the sugars naturally present in dairy probably meant a lot of tooth decay and pain. Over time, plaque built up on their teeth and hardened into calculus, locking in the dairy proteins and preserving them for us to find six thousand years later.

A study done at a gravesite in Sudan revealed that goat milk was being ingested over 4,000 years ago. Other studies in Africa have shown that sheep’s milk was also consumed, while evidence in Europe suggests our ancient ancestors also farmed cows.

This discovery doesn’t just prove that ancient humans drank milk from animals. It also provides a glimpse into the development of farming and dairying as humans transitioned from hunter-gatherers to a more agricultural society.