Dental plaque holds far more than just a gross reminder to keep brushing your teeth. New research shows that buried within plaque is a history of the bacteria, food, and other microscopic particles that crossed the teeth that its come to coat. While plaque may have less to say about those with good oral hygiene today, an international group of researchers has found that it could reveal quite a bit about our ancestors: on the teeth of several 1,000-year-old skeletons, researchers were able to determine health and dietary information and to analyze the bacteria that once existed in their mouths. The most interesting — but not especially staggering finding — is that it was possible to reconstruct the whole genome of a bacteria living in a Medieval nuns mouth and reveal that it lacked antibiotic resistance genes found in modern strains, Matthew Collins, a University of York professor involved with the research, writes in an email to The Verge.