The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

A Head for Cranial Analysis: 3D Investigation of Endo- and Ectocranial Sex Dimorphism


1Anatomy Department, Lincoln Memorial University DeBusk College of Osteopathic Medicine, 2Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, 3Anthropology Department, University of Tennessee

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A novel 3D method was used to explore size and shape sex dimorphism in modern American crania and improve sex estimation using endo- and ectocranial measurements.

Three-dimensional models were constructed from cranial CT scans from the William Bass Donated Collection (n=222). These models were used to create statistical bone atlases of the endo- and ectocranium. A bone atlas is a template that captures the primary shape variation in a skeletal element and facilitates computer-automated measurements and shape analyses from large datasets. An exploratory analysis of the atlas principal components was used to pinpoint areas of high sexual dimorphism. Linear and angular measurements were extracted, focusing on areas highlighted by the PCA. Linear discriminant analysis with variable selection was used to determine the most effective discriminators.

Results indicate that, while size is a significant component of cranial sex dimorphism, shape plays a role, as well. The PCA showed significant size differences in cranial length and facial breadth and shape differences in the glabellar, zygomatic, occipital, and mastoid regions. Important size-related variables captured by the discriminant analysis were bizygomatic breadth, maximum cranial length, cranial base length, and mastoid height. Vault thickness is also a sexually dimorphic feature, with females having thicker vaults than males in the frontal region, and males having thicker vaults in the occiput. An 11-variable model achieved 97.3% and eight variables classified 95.5%. Glabella projection index alone achieved 82.4%, bizygomatic breadth 83%, and basion-nasion length 82%. These accuracy rates are higher than those currently reported for the American population.

This research was funded by the National Institute of Justice (Award Number 2008-DN-BX-K182).

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