An analysis of sexual dimorphism using geometric morphometrics of the femur and tibia: the use of GM in assessing sex of fragmented remains
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This project analyzes the sexual dimorphism of the femur and tibia using geometric morphometrics. The study sample includes 250 individuals of known sex and age at death with complete, non-damaged, non-pathological skeletal remains from the William M. Bass Donated Skeletal Collection at the University of Tennessee, Knoxville. Ages range from 19-96 for males (mean=56.92 years) and 29-97 for females (mean=59.48 years). A combination of landmarks and semi-landmarks were collected on the proximal and distal epiphyses of each bone using a Microscribe, which helps capture the overall size and shape variation present in the sample. Only individuals from one population, White, where analyzed in order to eliminate population variation bias. Classification rates for males and females for the proximal femur were 80.8% and 78.4% respectively, for the distal femur 92.6% and 89.6% respectively, for the proximal tibia 80.8% and 83.2% respectively, and the distal tibia 81.6% and 80.8% respectively, all with a p<0.0001. These rates created a classification model for which epiphysis gave the most accurate assessment of sex: the distal femur, followed by the proximal tibia, then the distal tibia, and lastly the proximal femur. This study indicates the knee joint is the most dimorphic, followed by the ankle and then the hip. The results fall in line with another study indicating the knee is more sexually dimorphic in a modern White population (Spradley and Jantz 2011), though in contrast to their results this study found the distal femur was more dimorphic than the proximal tibia. This method indicates that in comparison to standard measurements, geometric morphometrics may provide a more reliable method for sex estimation when used, specifically on the knee. Certain landmarks were then selected based on the standard taphonomic process of coffin wear and postmortem damage (Pokines and Baker 2014) for exclusion to determine the usability of the method on fragmented or damaged skeletal remains. When combinations of landmarks were removed, the distal femur still possessed the highest classification rates with over 80% accuracy.