"Sex change" in skeletal remains: Assessing how heat-induced changes interfere with sex estimation

The true impact of heat-induced changes in human bone regarding their sex estimation has not been comprehensively documented having a potentially negative impact on forensic anthropology. The objective of this paper was to evaluate how heat exposure affects sex estimation based on both morphological and metric features. The study focused in both low-to-medium intensity burns and high intensity burns. Selected sexually dimorphic features were analysed in 51 experimentally burnt skeletons from the 21st Century Identified Skeletal Collection. Bones were burnt to maximum temperatures between 450 °C and 1050 °C achieved after 75 to 257 min. Morphological methods tested in this study comprised the recommendations for hipbone features from Buikstra and Ubelaker (1994) and from Bruzek (2002). On the other hand, metric references tested here were the ones from Wasterlain (2000), Curate et al. (2016) and Gonçalves et al. (2013) focused on the humerus, femur, calcaneus and talus. Agreement was tested with Gwet's AC1 test and was further assessed by calculating the relative amount of perfect agreements. Results demonstrated that heat-induced changes affected not only the scoring of morphological features burnt at high temperatures but also the scoring of features burnt at lower intensities. On the other hand, metric features were only considerably affected in high intensity burns, no major changes being documented for low-to-medium intensity burns. For low-to-medium intensity burns, the Bruzek and Curate et al. methods revealed a better agreement between the pre- and post-burning scores. For high intensity burns, better agreement was obtained by using the Bruzek (2002) and Gonçalves et al. (2013) methods. As expected, heat-induced warping, fracture and metric change had a major impact on the pre- and post-observations' agreement. Contrary to what has been systematically assumed over the years, this impact is also quite substantial in bones burnt at low-to-medium burn intensities so caution is advised during the analysis of this kind of burnt skeletal material.