However, even these teeth have a limit. Over many years, the rough vegetation gradually wears them down, and they break apart and fall out.  When this happens, new teeth which have been developing at the back of the jaw move forward to take their place.  It’s a bit like adult teeth taking the place of baby teeth in humans.  However, in elephants the new teeth come from the back, not underneath.  And, more significantly, the process repeats itself up to five times over the course of an elephant’s lifetime.  This is one of the many adaptations that allow elephants to live very long lives.