In a new analysis of thousands of teeth from ancient skeletons buried at a site near Naples, Italy, archaeologists have discovered that people were using their mouths to help with their work -- occupations that likely involved processing hemp into string and fabric. We all use our teeth as tools -- to open bottles, hold pieces of paper, or even smoke a pipe. When we do this, we open ourselves up to the possibility of cracking our teeth but also create microscopic grooves and injuries to the enamel surface. Since teeth don't remodel like bones do, these tiny insults remain...