Cranial Sexual Dimorphism in Hispanics Using Geometric Morphometrics
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Hispanics comprise the second largest population group in the US. Further, 63% of U.S. Hispanics are of Mexican origin with 37% foreign born (Motel and Patten, 2012). Sex estimation is an important component of the forensic anthropological profile and is considered population specific in that human groups differ in size. Sexual dimorphism in the cranium has been explored in American Whites and Blacks (Kimmerle et al., 2008), but little is understood concerning sexual dimorphism in Hispanics; the fastest growing US population (Martinez and Ariosto, 2011). A better understanding of sexual dimorphism among US population groups will facilitate more accurate sex estimation techniques within forensic anthropological practice.
Therefore, the purpose of this thesis is to explore cranial size and shape sexual dimorphism in Hispanics when compared to American Blacks and American Whites using geometric morphometric methods. Landmark data for American Blacks (N=75) and Whites (N=384) was obtained from the Forensic Anthropology Data Bank. The Hispanic sample was obtained from multiple sources, including two populations from Mexico (n=128), the Forensic Databank (n=93), the Pima County Office of the Medical Examiner (n=227), the Maxwell Museum of Anthropology (n=10) and the Texas State Donated Skeletal Collection (n=5). All individuals used in this research have 20th century birth years. A total of 35 landmarks were chosen to maximize sample size and represent overall craniofacial morphology.
A MANOVA indicates no significant differences in the expression of sexual size dimorphism among the groups, however significant sex-specific differences in size among the groups were detected. Shape differences using the Procrustes coordinates in a canonical variates analysis demonstrate differences in the areas of the cranium that provide the most information of differentiation between the sexes. In the American Black sample, cranial differences between sexes lied mainly in the posterior and superior vault shape, with some differences also arising from the nasal and orbit area. The Hispanic sample differed mainly in vault shape, including the posterior, superior and lateral vault, as well as the basicranium and the glabellar region. The differences in the American White sample were focused in the midface (nasal, cheek and orbit areas) and the basicranium.