The 88th Annual Meeting of the American Association of Physical Anthropologists (2019)

Assessing the potential of ilium outlines, greater sciatic notch metrics, and indices of pubic/ischial length for subadult sex estimation


1College of Osteopathic Medicine, Des Moines University, 2College of Pharmacy & Health Sciences, Drake University, 3Department of Exercise Science, High Point University, 4Department of Anthropology, University of Nevada, Reno, 5Department of Anatomy, University of Pretoria

March 29, 2019 , CC Ballroom BC Add to calendar

Previous studies on subadult pelvic sexual dimorphism present varying results depending on the samples, variables, and methods applied. This study used a modern sample of subadult postmortem CT scans to investigate the utility of ilium outlines, greater sciatic notch (GSN) measurements, and indices of pubic/ischial length in subadult sex estimation. The pelves of 202 subadults (neonate to 10 years of age) were segmented and 3D surface models created. Ilium orientation was standardized and two-dimensional contour outlines were collected and subjected to elliptical Fourier and principal component analyses. GSN length, depth, and angle, along with pubic and ischial lengths, were collected from the 3D models. M/ANCOVA and discriminant function analyses (DFA) were performed on the principal components and pelvic metrics.

ANCOVA results indicate significant (p< 0.05) sexual dimorphism in components related to the ilium outline, although DFA correctly classified only 60.4% of the total sample. Systematically re-running analyses excluding the youngest age cohorts at one year intervals (e.g., including all individuals >1yr, all individuals >2yr, etc.), revealed that by the age of four, correct classification increases to 77.4%, although the sample size was limited to 31 individuals. Correct classification using GSN variables did not exceed 64% regardless of the age cohorts or variables included. The pubic/ischial indices displayed no significant sex differences. These results suggest that pelvic sex estimation is unreliable in young children, but that ilium shape may be undergoing sexual differentiation by the age of five. Larger samples of subadults in these mid-childhood ages are needed for further testing.

This project was funded as part of a National Institute of Justice (2015-DN-BX-K409).