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Improving Sex Estimation From Crania Using 3-dimensional CT Scans

NCJ Number
Date Published
November 2012
80 pages

This research used an innovative approach for examining endo-cranial and ecto-cranial measurements in obtaining the best identifiers of sex from such measurements.


Results of the innovative procedure found that although size is a significant component of cranial sex dimorphism, shape is also significant. The global analysis showed significant size differences in cranial length and facial breadth, as well as significant shape differences in the glabellar, zygomatic, occipital, and mastoid regions. The local analysis corroborated the global analysis. Important size-related variables captured by the discriminant analysis were bizygomatic breadth, maximum cranial length, cranial base length, and mastoid height. The shape-related variables capture differences in the projection of the glabellar region, inclination of the frontal bone, and in the angulation/orientation of the mastoid. In addition, vault thickness is a sexually dimorphic feature, with females having, on average, thicker vaults than males in the frontal region. Males have thicker vaults in the occipital region. The best model is an 11-variable model that achieved 97.3 percent accuracy. The use of only eight variables achieved 95.5 percent accuracy, and the use of three variables achieved 86.5 percent accuracy. The glabellar projection index alone achieved 82.4-percent accuracy. The accuracy percentages achieved with only the bizygomatic breadth or basion-nasion length are also indicated (83 percent and 82 percent, respectively). The accuracy rates achieved with the described method are higher than reported to date in the literature for the American population. This report also notes that the left side of the cranium results in better classification in bilateral measurement, indicating the possibility of asymmetry in sexual dimorphism. Three-dimensional skull models were constructed from computed tomography (CT) scans of crania from the William M. Bass Donated Collection housed at the University of Tennessee Anthropology Department (n=222, 141 males and 81 females). 46 figures, 8 tables, 47 references, and a listing of how research findings have been disseminated

Date Published: November 1, 2012