Sexual Dimorphism in the Craniofacial Skeleton of Modern Humans

Abstract

Sexual dimorphism is a major component of infraspecific variation in nonhuman primates. Among humans, differences in the pattern and degree of sexual dimorphism may provide a means for discriminating between populations. In this paper we explore the variance dimorphism, sex-specific size and shape differences, and between-population differences in patterns of sexual dimorphism in a sample of Romano—British (n = 47) and modern African (n = 53) crania. Shape coordinates, uniform components of variation and centroid size were derived for nine midsagittal landmarks obtained from lateral radiographs of the skull. No evidence was found for size-variance or shape-variance dimorphism in either population. Significant sexual size dimorphism was detected in the Romano—British sample alone. No significant sexual dimorphism in uniform components of variation was found in either sample. Multivariate analyses of variance for the effect of sex on shape coordinate pairs detected significant variation in the African sample, particularly in those landmarks that measure the amount of prognathism. Although the discriminant functions derived from the shape coordinate pairs correctly reallocated 81% of specimens to their sex, this value was not found to differ significantly from that of randomized data. The results of this study suggest that the consistency in patterns of between-population sexual dimorphism warrant caution when extrapolating from one sample to others for the purposes of sex discrimination.