Postcanine megadontia
[5] The shift towards postcanine megadontia dates back to about 4-5 million years ago with the discovery of Ardipithecus ramidus in the Middle Awash region of Ethiopia.
[6] Distinctive features in A. ramidus such as dentition with reduced canines, the skull, hindlimb and forelimb suggest it to be near the split between the chimpanzee and hominin lineages.
[7] It was the origin of Australopithecus africanus, found in several regions of South Africa (Taung, Sterkfontein, Makapansgat) 2-3 million years ago that first demonstrated the enlargement of the pre-molars and molars.
[10] P. boisei was known for massive facial and dental bones and structure, primarily larger mandibles, molars, and premolars, which was an adaptation allowing them to consume hard plant foods with the ability of high force chewing.
[18] The development and evolution of this trait was characterized by a thick coating of enamel surrounding the molars and premolars, mitigating the detrimental effects of the tough diet.
[25][26] The enlargement of the teeth affected by postcanine megadontia, without a difference in the arrangement or number of cusps that compose them, imparted an increased ability for grinding and crushing matter compared to modern day humans.
[28] For example, the large transverse dimensions of corpses of Homo floresiensis from the Liang Bua cave on Flores Island in Indonesia suggest that these early hominids had postcanine megadontia and a diet with great masticatory stress.
[29] However, as Homo evolved, the amount of masticatory stress involved in eating decreased as “behavioral adaptations for extraoral food processing” were further developed.
Thus, tool making Liang Bua corpses would have a comparatively smaller transverse dimensions of the skull, meaning their “mascilatory functional morphology” deviates greatly from the Pleistocene Homo.
However, calculations made using biomechanical models does not necessarily perfectly predict the efficiency of different mandibular compositions in resistance to bending forces.
In postcanine Megadontia specimens, the cross sectional area is on average much larger than modern hominids which implies greater shear stress resistance.
[32] It is theorized that tooth enlargement is due to several different gene mechanisms, none of them fully understood, and that selection acts on molars and pre-molars as a singular unit rather than on individual teeth.
[30] Compared to present day humans, early hominids such as Paranthropus aethiopicus and Australopithecus garhi[34] had significantly larger dental morphology in their molars and premolars and smaller incisors.
