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J Forensic Sci, July 2010, Vol. 55, No. 4 doi: 10.1111/j.1556-4029.2010.01374.x Available online at: interscience.wiley.com
PAPER PHYSICAL ANTHROPOLOGY Joan A. Bytheway,1 Ph.D. and Ann H. Ross,2 Ph.D.
A Geometric Morphometric Approach to Sex Determination of the Human Adult Os Coxa
ABSTRACT: Sex determination of the human skeleton is best assessed from the os coxa. The present study explored the possibility of using three-dimensional landmark coordinate data collected from various landmarks located over the entire bone to determine whether there were significant sex differences local to the landmarks. Thirty-six landmarks were digitized on 200 African American and European American male and female adult human os coxae. MANCOVA results show that sex and size have a significant effect on shape for both European Americans (Sex, F = 17.50, d.f. = 36, 63, p > F = 0.0001; Size, F = 2.56, d.f. = 36, 63, p > F = 0.0022) and African Americans (Sex, F = 21.18, d.f. = 36, 63, p > F = 0.0001; Size, F = 2.59, d.f. = 36, 63, p > F = 0.0005). The discriminant analysis shows that sexing accuracy for European Americans is 98% for both males and females, 98% for African American females, and 100% for African American males. KEYWORDS: forensic science, forensic anthropology, sex determination, os coxa, geometric morphometrics, discriminant function analysis
The os coxa is the most reliable bone of the human skeleton to determine sex and when used alone it can achieve approximately 90% accuracy (1–4). Sex determination using the os coxa can be accomplished through visual observation of anthroposcopic characteristics or metric analysis of linear measurements (5) and both methods have shown high accuracy percentages. For example, _ ¸ can’s (6) metric analysis on a modern Greek populaSteyn and Is tion showed that most measurements were ‘‘highly repeatable’’ and when all variables are present, the average accuracy is 95.4%. Phillip Walker (7) found that visual observation of the greater sciatic notch produces ‘‘about the same proportion of correct sex assignments’’ as using metric methods. There have been a number of observed pelvic features used over the years that have been successful in determining sex. Traditionally, the pelvic inlet (8,9) was used. The female pelvic inlet increases in diameter during puberty. Its shape changes from a preadolescent elliptical form to a more open, rounded aperture. Males retain the more elliptical, constricted aperture. This change in the female pelvic inlet initially was believed to be the result of the increase of hormonal activity (9). More recent studies (10–17) attribute pelvic inlet or pelvic canal change to ‘‘functional adaptations to certain modes of locomotion’’ and maternal–fetal size relationships (16). In addition to the pelvic inlet, features such as the subpubic angle, pubic symphysis height, and the shape of the obturator foramen (18,19) were used. With growth, the female subpubic angle becomes more obtuse than in the male. The pubic symphysis becomes shorter and the obturator foramen becomes more triangular (20). One problem using the subpubic angle is that although sex assessment can be made without complete articulation of the pelvis, 1 College of Criminal Justice, Forensic Science, Sam Houston State University, Huntsville, TX 77341-2525. 2 Department of Sociology and Anthropology, North Carolina State University, Raleigh, NC 27695-8107. Received 12 Mar. 2009; and in revised form 2 June 2009; accepted 6 June 2009.
2010 American Academy of Forensic Sciences
it is best assessed when it is. Therefore, it could be argued that using only one side does not result in the most accurate evaluation (20). Because of the frequent fragmentary nature of pelvic remains articulation is not always possible. The second problem exists when observing the pubic symphysis height. With the f