A Morphometric Outline Analysis of Ancestry and Sex Differences in Cranial Shape

Forensic anthropological techniques that utilize nonmetric cranial traits to estimate sex and ancestry have historically been criticized for their subjectivity and qualitative nature. Nonmetric traits, however, continue to be valuable tools in identifying remains in forensic investigations. In this study, geometric morphometric analyses of cranial outlines were performed to quantitatively assess population and sex variation in modern human cranial shapes and to verify group differences in previously reported qualitative traits. Elliptical Fourier analysis was conducted on two-dimensional images of the left lateral, posterior, and superior cranial views from 198 U.S. Black and White crania. Results reveal significant sex and population differences in cranial shape that generally coincide with traditional qualitative descriptions. Although sex classification was relatively low (70.2%), ancestry classification was higher (92.4%), indicating that outline analyses that incorporate multiple nonmetric traits into a single statistical analysis may provide a more objective and accurate means of ancestry classification.