I'm guessing you brush twice a day or aspire to. Our ancestors were a little less diligent. But that's a good thing for scientists. Because ancient, plaque-coated teeth are like time capsules, preserving early evidence of cavities or even plague DNA. Now researchers have turned to thousand-year-old teeth from a convent cemetery outside Frankfurt, Germany. And they cleaned 'em, much like your dentist does. "We used the same dental tools, and we collected the calculus from the teeth." That's molecular anthropologist Christina Warinner of the University of Oklahoma. Inside that calculus—or plaque—she and her colleagues found tiny bits of pork, bread wheat and cabbage, identified by their DNA. Along with the bugs behind strep throat, bacterial meningitis and an oral strain of gonorrhea. And don't be too quick to judge. "Nearly all of us still have gonorrhea in our mouth." Their study is in the journal Nature Genetics. Some of those bugs were antibiotic resistant too. Because long before penicillin, some microbes produced natural antibiotics to attack rivals. "Your mouth is like a battlefield of bacteria." So chew on that.