Decoupling of sexual dimorphism in the human bony pelvis and its relationship to differential selective pressures

Abstract

Obstetrics and locomotion have opposing demands on the form of the human bony pelvis. Previous work has identified sexual dimorphism in the posterior spaces (PS) and non‐dimorphism in the anterior spaces (PS). This study tests the hypothesis that the AS is more influenced by locomotion, and the PS is more influenced by obstetrics. Landmarks (k = 43) were collected on articulated male (N=102) and female (N=104) pelves. Euclidean Distance Matrix Analysis was used to define distances in each space. MANCOVAs were used to test for effects of sex and body mass for each space. A significant effect of sex and a non‐significant effect of body mass would indicate that the distances are influenced more by obstetrics, while the reverse would indicate that distances are influenced by locomotion.Results from the MANCOVAs on both the AS and PS distances identified highly significant effects of both sex (p<0.001), and body mass (p<0.001), demonstrating that there are morphological adaptations related to locomotion and obstetrics in both spaces. However, a comparison of the relative proportion of variance attributed to sex and body mass demonstrated that there was a stronger influence of sex in the PS, and a stronger influence of body mass in the AS. These results suggest that decoupling of sexual dimorphism in the human bony pelvis facilitates morphological adaptations related to differential selective pressures within the pelvis.Grant Funding Source : NSF DDIG (#0925468), Sigma Xi GIAR (#G2009100302)