Sex Estimation from the Greater Sciatic Notch of the Human Pelvis: A Geometric Morphometric Approach
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It is widely agreed that the human pelvis holds the greatest degree of sexual dimorphism and is the most useful bone for estimating sex in skeletal remains. It is also commonly believed that the greater sciatic notch holds a great deal of sexual dimorphism and can be used to estimate sex. Yet despite the crucial nature of estimating sex from skeletal remain when creating a biological profile, methods considered common today rely rather heavily on the experience of the anthropologist and on the presence of more complete innominate bones. Following earlier research by the author, this project examines the usefulness of two forms of geometric morphometric (GM) approaches to estimating sex from the portion of the innominate most likely to survive over time, the greater sciatic notch. These methods, originally tested on American White and American Black samples from the Terry Collection at the Smithsonian Institution, have now been applied to a Mexican sample from skeletal collection at the School of Medicine, National Autonomous University of Mexico (UNAM). The first GM approach uses a 3D digitizer to collect the coordinate points of three landmarks on the greater sciatic notch; the most anterior point on the posterior border near the posterior inferior iliac spine, the base of the ischial spine, and the deepest point of the notch. Geometric dimensions are calculated from these coordinate points and constitute one data type for GM analyses. The second type of data is formed by coordinate data of semilandmarks that describe the shape of the greater sciatic notch. Multivariate statistics were used to examine the effects of population group, sex, and the interaction between population group and sex on the variation among individuals and populations. Discriminant function analyses were used to examine the ability of the two data types to estimate population group, given the significant effect of population group, as well as their ability to estimate sex. While both data types provided low classification rates for population group, both data types provided relatively high classification rates for sex, ranging from 83.8% to 100% accuracy. This study determined that estimating sex from the greater sciatic notch is not only possible, but reliable when using either notch dimension or notch shape data. The use of notch dimension data is the more practical of the two methods, but the reliability of the method is supported by the high classification rates of the notch shape data. Forensic anthropology and bioarchaeology are equally benefited from this new method of estimating sex from the greater sciatic notch of unidentified skeletal remains.