Sexual dimorphism of pelvic morphology variation in live humans

Abstract

This study represents the comparison of the morphology variation in different planes of female and male pelvis. Anthropological literature represents two different views of the pelvic morphology variation. On the one hand, the variation is considered lower in females than in males. On the other hand, some empirical findings demonstrated no differences in the pelvic morphology variation between sexes. Moreover, some measures of female pelvis demonstrate higher coefficients of variation. Taking into account that previous findings were based on linear measures, it seems important to analyze pelvic proportions and the variation of the inlet, middle, and outlet planes. The study was based on the retrospective pelvimetry of threedimensional computer tomography of 176 live males and 212 females. Anterioposterior diameters and transverse diameters were measured in four planes, and their ratios were calculated in order to evaluate proportions and variances. The Levene’s test for the equality of variances was used to evaluate the observed variation in male and female pelvis morphology. The results confirmed well established sexual dimorphism in the pelvic linear measures – the anteroposterior diameters of the midplane and the outlet. In addition, this study identified higher variation in the transverse diameter of the inlet in females. The proportions demonstrated no differences in variation in all the planes but the midplane including bispinous diameter (F=11.34; p<.01). It seems important that the female pelvis cavity demonstrated lower variance than the male pelvis cavity in the midplane including bispinous. This finding supports the view of selective pressure on the female pelvis and its intensity in the midplane.