1Department of Anthropology, Georgia State University, 2Department of Computer Science, Georgia State University
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The sexual dimorphism of Australopithecus has been investigated previously using resampling methods. These have provided measures of sexual dimorphism relative to extant hominoids. However, craniofacial measures have rarely been subjected to resampling methods to provide a measure of dimorphism, partially due to the fragmental nature of the fossils. Here we compare the craniofacial sexual dimorphism of Australopithecus africanus (n = 22) and Australopithecus robustus (n = 9) to Pan paniscus (n = 45), Pan troglodytes (n = 44) and Homo sapiens (n = 91). Because of the lack of completeness of fossil specimens, we focus on compatible subsets. In previous resampling tests of the postcranium, males regularly exceed females, yielding dimorphism measures greater than one. However, in the craniofacial region, this pattern may not always hold. Therefore, an absolute measure of dimorphism was included to avoid the loss of information when calculating geometric mean values. Australopithecus robustus exhibits the greatest geometric mean of dimorphism measures among the taxa examined. For extant taxa, the average of geometric means for Pan troglodytes exceeds Pan paniscus, and both are higher than those for Homo sapiens. However, the standard deviation for Pan troglodytes is pronounced; the geometric mean of absolute dimorphism measures for Australopithecus robustus falls within one standard deviation of Pan troglodytes. Pan paniscus exhibits a narrow range of values for the geometric mean of absolute dimorphism measures. Australopithecus africanus exhibits an average of geometric means between those obtained for the two species of Pan.
This study was supported by the Fulbright Foundation, the Belgian American Educational Foundation and the Vice President for Research at Georgia State University.