HUMAN EVOLUTION Vol. 1 - N. 1 (23-39) - 1986 P.W. Lucas Department of Anatomy National University oJ Singapore Kent Ridge Singapore 0511 R.T. Corlett Department o[ Botany National University of Singapore Kent Ridge Singapore 0511 D.A. Luke Unit of Anatomy in relation to dentistry Anatomy Department Guy's Hospital Medical School St Thomas Street London SE1 9RT Sexual Dimorphism of Tooth Size in Anthropoids We have examined the size of the canine and postcanine teeth of cebid and catarrhine primates in relation to each other, to jaw size and to body weight. We have found that the canine size of males is large enough to be limited by jaw shape and size. A large contribution of P4 to the postcanine row is associated with smaller canines in males. Neither factor seems to limit canine size in females. The females of a small number of species possess enlarged canines. Much of the variation of the postcanine row can be described by the ratio of tbe (nominal) crown areas of M1 to M3. This ratio is monomorphic which conforms with the general lack of dietary dimorphism in primates. A brief discussion of the evolution of canine size is offered with a new suggestion to account for canine reduction in male hominids. Introduction In general, skulls of cebid and catarrhine primates can be sexed by examining the canine teeth. Less often, the lower anterior premolar is also obviously sexually dimorphic. The rest of the dentition appears to be shape monomorphic. Complications arise immediately following measurement because the size of any tooth very often depends on sex. This is presumed to reflect overall size differences between the sexes. Thus a tooth should be described as sexually dimorphic only if it possesses a different shape in each sex or, alternatively, is of a size in one sex that is out of proportion with neighbouring teeth. Neither of these possibilities can be dealt with through the comparison of individual measurements. A stereotyped procedure has gradually developed in physical anthropology to ~sub- tract~ size from structures, usually prior to any further analysis. For living species, this usually involves correction for body weight. In this review, we have tried to formulate a different approach and to restrict our analysis to those measurements that can usually be found in fossils to increase its relevance to palaeontology. These measurements have been assembled into dimensionless variables whenever possible and the interrelationships between these variables have been investigated. Materials and Methods Dental, mandibular and ecological data have been collected for 78 species of primates, although complete data could be obtained on only approximately half of these. In addition, a small sample of canine and mandibular measurements was made on 20