Morphometric data and the size factor: examining the problem using the pelvis.

Abstract

Morphometric data is inherently linked to size; however, there is no consensus for how to account for this. Some researchers adjust for size, whereas others do not, which can affect the results of a study. This study examines this problem using sexual dimorphism of the pelvis. Twenty-two pelvic measures were collected from 119 individuals from the Hamann-Todd Collection. Measures included dimensions of the false pelvis and the pelvic canal. After all the data was collected, it was compiled into 3 data sets; the first set included unadjusted data, the second set was adjusted for body size, and the third set was adjusted for pelvic size. After all adjustments, independent sample t-tests were run on each data set, to determine which measures appeared dimorphic. In each case, the measures that appeared to be sexually dimorphic differed. According to the t-test for the unadjusted data, four of the 22 measures were not dimorphic: anterior spaces of the midplane and the outlet, sacral breadth, and length of the superior pubic ramus. Using the data adjusted for body size, all pelvic measures were dimorphic. Lastly, using the data adjusted for pelvic size, five measures were not dimorphic: anterior space and transverse diameter of the inlet, inter-acetabular distance, length of the superior pubic ramus, and circumference of the inlet. These conflicting results demonstrate the intricate nature of correcting for size and the challenge comparing results across studies. Overall pelvic-size dimorphism and body-size dimorphism must be considered.