Validation Study of the Dominguez and Crowder (2012) Method for Histologically Differentiating Between Human and Non-human Cortical Bone

Species determination is an important part of forensic anthropology. Accurately differentiating between human and non-human bone is integral to the determination of medicolegal significance. When skeletal material is damaged and macromorphoscopic methods are unemployable, microscopic methods, such as histological analysis, can be used to differentiate between human and non-human bone. Current research efforts focusing on the histomorphometric differences between human and non-human bone often use discriminant function analysis to determine species origin. The Dominguez and Crowder (2012) method uses osteon area and osteon circularity measurements to differentiate between human and non-human bone via discriminant function analysis. The original authors, as well as a recent validation study, have reported accurate classification rates using this method. The Defense POW/MIA Accounting Agency (DPPA) currently has histological protocol in place that allows for osseous material of unknown origin to be marked as non-human if plexiform bone is observed, but if Haversian systems are observed the bone must be sent for DNA testing to confirm species origin. This process is costly and time-consuming, ultimately decreasing casework efficiency. The DPAA would benefit from adding a histomorphometric method to the current histology protocol that would determine whether Haversian bone is human or non-human without sending the osseous material for DNA testing, thus increasing casework efficiency. Therefore, the objective of this study was to determine the applicability of the Dominguez and Crowder (2012) method to the casework seen at the DPAA. Human and non-human bone samples were taken from the anterior quadrant of the proximal femoral midshaft. Each sample was embedded, cut into thin sections, mounted onto slides, and microscopically imaged prior to histomorphometric analysis. Osteon area and osteon circularity measurements were recorded, and mean values for each individual were plugged into the discriminant function analysis equations used in Dominguez and Crowder (2012). Overlap in non-human species was observed, but overall, the human and non-human species separated out, with the exception of the horse samples. Both horse samples included in this study misclassified as human. This result supports the need for the continuous validation of histomorphometric methods with various non-human samples to confirm applicability in different contexts. Advisor: William R. Belcher