Morphological relationship between the mandible and teeth : its functional and evolutionary significance

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To examine when, how, and to what extent the developing dentition within the mandible is interrelated with external mandibular growth, a series of three comparative studies were undertaken. First, an interpopulation comparison was made between prehistoric Jomon and modern Japanese. Second, sex comparisons were conducted in two cercopithecine primates(hamadryas baboon and Japanese monkey). Finally, interspecies comparisons were carried out among four primate species including modern humans. Through the above studies, some suggestions were made : 1) the relatively large size of the anterior teeth is indicated as the common source of the high anterior corpi of the modern Japanese and the male baboons relative to the Jomon and the female baboons, respectively. 2) both interpopulation and interspecies differences in the placement patterns of the incisor and canine crypts within the developing mandible can be accounted for by the size balance between the developing teeth and mandibular available space. 3) species-specific characteristics of the mandibular symphysis, including the inclination, are largely independent of the adult canine size, and its interspecies differences are consistently maintained throughout growth. The results thus indicate the importance of understanding the spatial conditions of the developing teeth in interpreting mandibular morphology.