Improving sex estimation from crania using a novel three-dimensional quantitative method

Abstract

This study utilizes an innovative 3D approach to discover metric variables that obtain the highest classification rates for sex estimation from the cranium. Models were constructed from 222 cranial CT scans of U.S. Whites from the Bass Donated Collection. These models were used to create a statistical bone atlas that captures the primary shape variation in the skull and facilitates rapid computer-automated analyses. The bone atlas showed that important size-related sex variables are bizygomatic breadth, maximum cranial length, cranial base length, and mastoid height. Shape-related variables capture sex differences in the projection of the glabellar region, inclination of the frontal, and cranial base flexion. In addition, vault thickness is highly dimorphic, with females having on average thicker vaults in the frontal region, and males having thicker vaults in the occipital region. Cross-validated linear discriminant analysis obtained >95% accuracy (97.5% with 11 variables and 95.5% with eight variables).

Keywords: cranial base; cranium; forensic anthropology; forensic science; geometric morphometrics; sex estimation; sexual dimorphism; statistical atlas; three-dimensional analysis; vault thickness.