Just as human digestive anatomy does not reflect the trend found in the great apes, similarly humans have dental and oral anatomy that sets them apart from nearly all of the other primates. In the great apes, prominent canine teeth are the rule, and they play a role in display, defence and in feeding. The remaining teeth are however strikingly similar to human teeth, for example, bonobo teeth and human teeth look almost identical, as pictures in the book 'Bonobo: The Forgotten Ape' reveal(10). This suggests a very similar diet or dietary strategy and thus evolution. In contrast to the other great apes, the human canine tooth is no longer prominent and resembles the size and shape of the incisors. Because of this similarity, human canines are known as "incisiform" canines, and it has been suggested(8) that they function as extensions of the incisors and by analogy perform the same function.
Incisiform canines that are large and spatulate are found in herbivores. The Dusky Titi monkey whose diet is 54% fruit, 28% leaves and 17% insect(11) also has incisiform canines(27). According to Pilbeam(8) "absolutely and relatively large incisors are correlated with food procurement tasks (what must be done to obtain bite-sized portions), such as biting into large fruits with hard rinds." A depiction in Dental Functional Morphology by Peter W. Lucas (p. 130), shows the functioning of incisors in primates as either removing the flesh of fruits, or stripping leaves from branches. Furthermore, humans have in common with animals that regularly suction-feed; a small mouth, a smooth and vaulted palate, a smooth and round tongue that can be shaped to fit tightly against the palate, a closed parabolic upper tooth row without long canines and diastemas, and a descended larynx(27). The human mouth is superbly adapted to scooping out and pulverising juicy fruits.
The dental and oral anatomy of humans is entirely consistent with that of a frugivorous great ape, with the addition of canine teeth further adapted to a biting plus suction fruit diet. Canine teeth still develop from a structure that is pointed, but juicy fruits have probably played such a significant role in human evolution that selection in favour of thick enamel outgrowths has taken place, so that they have evolved to form an incisor like “canine”.