Elephants have tusks, two ever-growing upper incisors used to dig, uproot trees and for defence. Moreover, in each half-jaw, there are six molars, consisting of a series of transverse plates coated with enamel; these grow at the back of the mouth and then move towards the front where they wear down with use, fall out and are replaced by the next in line. This cycle takes place five times. Photo by Nancy Elera