She lived on an island in the Baltic Sea around 3,700 B.C. She was lactose intolerant and may have suffered from gum disease, and she had recently dined on a meal that included ducks and hazelnuts.

More than 700 species of microbes live in your mouth and they include bacteria, fungus, and more. Some are helpful, and some harmful. Don’t run for your toothbrush or mouthwash just yet. As long as ...