Similarities in pelvic dimorphisms across populations.

Abstract

The shape and size of the pelves of males and females differ, due in part, to the differing constraints of the sexes. Previous research has demonstrated that many factors impact pelvic morphology, thereby it is not surprising that there is pelvic variation within and across populations. Because of this variation, pelvic measures that are sexually dimorphic also differ by population. However, measures that are critical for reproduction should remain sexually dimorphic, regardless of circumstance. This study examines pelvic dimorphisms across six samples to determine if they are consistent. Twenty-three pelvic measurements were collected from 668 individuals from six skeletal populations. Multiple t-tests were run within samples to determine which traits were dimorphic. Further, an index value was computed for each variable to examine and to classify level of dimorphism; values were classified as high, moderate, or low. All results were compared across samples. Ten measures remained dimorphic across every population; females were consistently larger for posterior spaces of the inlet, midplane, and outlet, bi-spinous diameter, transverse diameter of the outlet, and circumference of the midplane. Males were consistently larger for anterior space of the outlet, pelvic breadth, iliac length, and pelvic depth. Index values varied across populations; however, level of dimorphism remained consistent. These findings suggest that some measures of the pelvic canal have a higher selection intensity than others. Further, variability in index values suggests that while maintaining the statistically significant presence of dimorphism, there is a degree of flexibility in the degree of dimorphism.