The man known only as 12011 lived in Poland between 5,450 and 7,500 years ago. He was a hunter-gatherer. He died roughly between the ages of 40 and 45. Beyond that, the details of his life are a mystery. We don’t know what his voice would have sounded like. We don’t know what he liked or disliked. We don’t know why he died.

We do, however, know which bacteria were living on his teeth.

Microbes grew inside his mouth just as they do on yours. They created a layer of plaque on his teeth, which eventually hardened into tartar—a substance that’s structurally similar to concrete. In tartar, bacteria become locked in a mineral cage of calcium phosphate, which is so tough