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Keywords:

  • dental dimensions;
  • multivariate statistics;
  • canonical variates analysis;
  • sexual dimorphisms;
  • humans;
  • chimpanzees;
  • gorillas;
  • orangutans;
  • ramapithe cines;
  • Gorilla;
  • Pan;
  • Pongo;
  • Homo

Abstract

Studies of sexual dimorphism in the dental dimensions of some extant and fossil hominoids have been carried out by means of univariate statistical methods [Oxnard et al., 1985]. The study reported here extended these studies with multivariate statistical methods (canonical variates analyses). The extant genera studied were Gorilla, Pan, Pongo, and Homo. The fossil teeth interpolated were those of the recently discovered ramapithecines from Yunnan Province, China. For both extant and fossil species, the lengths and breadths of all maxillary and mandibular teeth were used except for the third molar, which was excluded because of its absence in so many human subjects. The nature of sexual dimorphism in the dentition of extant apes and humans was assessed, and the positions of the fossil teeth within the multivariate results for the extant forms was examined. Among the apes, the greatest sexual dimorphism was seen in Gorilla; the least was seen in Pan. Three different patterns of sexual dimorphism were apparent among the three ape species. The maxillary and mandibular patterns were different in Gorilla and Pan but more similar in Pongo. The African apes showed greater differences between variances for each sex and of each jaw; these features may have evolved most recently. The conventional notion that sexual dimorphism is mainly due to size and size-related shape effects along a single continuum or axis was rejected. The interpolation of the fossil data placed Sivapithecus close to each of the more dimorphic apes, especially Pongo, but also showed that it had higher order differences from the extant forms studied. Ramapithecus was most similar to Homo. These results have implications both for the role of sexual dimorphism in the evolution of higher primates and for the phylogenetic relationships among them.