Sexual dimorphism at the proximal tibia: a geometric morphometric analysis
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In the past few decades, an area of skeletal research focusing on shape analyses has gained popularity in the field of physical anthropology, and subsequently forensic anthropology. Known as geometric morphometrics, this type of analysis allows the researcher to place the morphological shape of bones into a statistical framework to answer questions on a variety of topics, including sexual dimorphism. Sex assessment from the long bones has been traditionally conducted using traditional morphometric methods (Iscan and Miller-Shaivitz 1984; Steyn and Iscan 1997), and as a result, relies mainly on size differences and has not considered how joint morphology and shape affect sex. For this project, a geometric morphometric analysis of the proximal tibia in a modern Caucasian American population was conducted using a sample of 100 male and 100 female tibiae from the William M. Bass Donated Skeletal Collection at the University of Tennessee at Knoxville. The proximal tibia's effectiveness as an indicator of sex in a modern American population was evaluated via generalized Procrustes, principal components, and discriminant function analyses. Principal components revealed a lack of separation between males and females in terms of proximal tibia shape. The discriminant function analysis was successful at discriminating males from females, but cross-validation yielded a low total accuracy rate of 58%. The shape of the proximal tibia contributes to sexual dimorphism in a Caucasian American population, but is only slightly useful in a discriminant function. Further research should be conducted on different populations and using different skeletal landmarks.