A histological and chemical analysis of four taphonomic processes that bleach bone
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Abstract
The purpose of this study is the investigation of taphonomic processes that impact bones within the field of forensic anthropology and the establishment of novel techniques to classify these processes. Taphonomic evidence may provide context as to the origin of the remains, relocation if they have been moved from their initial location, and the length of time at which they have been exposed to the environmental conditions. This information may help the forensic anthropologist reconstruct a postmortem history. This study investigated four taphonomic processes that bleach bones, including maceration, chemical bleaching, marine bleaching, and subaerial weathering. A sample of juvenile pig (Sus scrofa) femora was examined under each condition. Programmatic analysis in the form of photography and a python script was utilized as a method of analyzing color and establishing a color matching algorithm. These findings demonstrated that maceration and chemical bleaching yielded higher overall color intensities and more consistent color intensities across red, green, and blue (RGB), indicating that the samples that underwent these processes exhibited greater levels of bleaching compared to marine bleaching and subaerial weathering, which displayed lower intensities and greater variability. This suggests that it is more challenging to distinguish between maceration and chemical bleaching, compared to the other processes. Chemical analysis employing Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy was conducted to provide information on the alteration caused by these taphonomic processes that are not visible to the naked eye. A blind study was conducted to test the efficacy of the method, and the acquired data were used to develop an algorithm for categorizing correct taphonomic process from which an unknown sample matches. The results yielded 60% accuracy in correctly identifying the unknown bone samples within the top three hits. Furthermore, the library algorithm overfit to chemical bleaching (CB) and predicted CB for 70% of matches, while maceration (M) was predicted for 0% of matches.
Histological analysis was conducted to determine if trends exist between taphonomic processes and depth of bleaching. Statistically significant difference in average depth of bleaching were consistently observed in maceration vs. chemical bleaching and marine bleaching, and marine bleaching vs. subaerial weathering. Cracking was primarily observed on the cut surface of subaerial weathering (85%) and marine bleaching (55%) cross sections but absent in macerated and chemically bleached bones. It was hypothesized that programmatic, chemical, and histological analysis can be used to characterize and match the different types of taphonomic processes that bleach bone. This investigation demonstrated that established tools can be utilized in novel ways to aid in the identification of these processes.
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2025