https://www.scientificamerican.com/article/ancient-teeth-unlock-plague-secrets/

Nearly 4,000 years ago, a woman and a man were buried together just east of the Volga River in modern-day Russia, with a secret locked away in the pulp of their teeth.

The bodies were uncovered just a few years ago, the teeth pulled and sent westward to the Max Planck Institute in Germany, where Maria Spyrou was working on a Ph.D. in paleogenetics. When she subjected the pulp to a bevy of genetic tests, she found something surprising: an ancestor of the bacteria responsible for the Black Death.