DNA from a type of “chewing gum” used by teenagers in Sweden 10,000 years ago is shedding new light on the Stone Age diet and oral health, researchers said Tuesday. The wads of gum are made of pieces of birch bark pitch, a tar-like black resin, and are combined with saliva, with teethmarks clearly visible. They were found 30 years ago next to bones at the 9,700-year-old Huseby Klev archaeological site north of Sweden’s western […]