Part of the show How age affects DNA and How the Body Clock Works
How long have people been cleaning their teeth ? Well, if palaeontologist Leslea Hlusko from the University of Illinois has got it right, the answer could be over 1.8 million years making it the oldest human habit yet recorded ! Indeed the teeth of our ancient relatives are often found to have curved grooves a couple of millimetres wide on their roots which, it has been suggested, were made by primitive toothpicks. But critics of this toothpick theory point out that today’s toothpick users have no such grooves. But what about if the grooves were made by something more abrasive than the wooden picks we use ? Hlusko thinks that the culprit might be grass stems. They are the right size to cause the grooves and, unlike wood, contain abrasive silica particles which are quite literally like sand-paper. Obviously the ultimate test is to try out the theory, so Hlusko spent 8 hours rubbing a tooth from a baboon, and 3 hours rubbing a grass stem against a human tooth. In both cases the grass left marks almost identical to those seen in early hominid teeth.