Dental sexual dimorphisms in some extant hominoids and ramapithecines from China: A quantitative approach

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., 19851. 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 Siuapithecus 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.

Size and shape dimorphism in great ape mandibles and implications for fossil species recognition

“…troglodytes and Pongo p. abelii). In this, as in other studies (e.g., Lieberman et al, 1985;Oxnard et al, 1985), none of the patterns of size dimorphism are significantly correlated at the generic level; nor does the magnitude of rank correlations show any systematic pattern according to phylogenetic affinity at that level. Pongo and Gorilla share a similarly high degree of mandibular size dimorphism compared to Pan (see also Wood et al, 1991), but it is evident that they differ in many aspects of their dimorphism patterns (Fig.…”

“…Shape dimorphism patterns in the distal femur also failed to differentiate Australopithecus afarensis from any extant hominoid, leading Lague (2002) to conclude that such patterns have little phylogenetic value. Likewise, while some studies Lieberman et al, 1985;O'Higgins et al, 1990;O'Higgins and Dryden, 1993) suggested that extant great apes are characterized by distinctive patterns of dental dimorphism, others (e.g., Wood et al, 1991) argued that pattern differences among hominoids are relatively subtle, and outweighed by the similarities. Lockwood (1999) observed greater similarity in facial dimorphism patterns between Australopithecus africanus and modern humans as compared to extant hominoids, while also noting unique dimorphism patterns in A. africanus.…”

Sexual dimorphism in primate evolution

“…It has been suggested that there is a "field effect" of sexual dimorphism in the dentition, centered on the canine teeth, such that teeth closer to the canines tend to be more dimorphic than those farther away (Garn et al, 1966). Others have suggested that different taxa share different patterns of sexual dimorphism in the teeth (Lieberman et al, 1985;Oxnard, 1987). It appears, however, that noncanine tooth size dimorphism is largely a correlate of body mass dimorphism (Cochard, 1985;.…”

Mixture Analysis and its Preliminary Application in Archaeology

“…In almost all archaeological publications, only statistical results are available (e.g. Oxnard et al, 1985;Lieberman et al, 1985;Oxnard, 1987;Wood & Xu, 1991;Wood et al, 1991), but not the original (raw) data. Cheek teeth were chosen for analysis as they are both relatively durable and common, and they have a degree of sexual dimorphism too small for detection by more conventional techniques, but are still large enough in many cases for mixture analysis to detect with a good sample size.…”

“…These teeth have been the focus of lively debate in palaeoanthropology in the past decade (Wu & Oxnard, 1983a,b;Lieberman et al, 1985;Oxnard, 1987;Kelly & Etler, 1989;Wood & Xu, 1991). One interesting and important feature is that these teeth show considerable size variation.…”