Using Solar Radiation as a Means for Understanding Skeletal Decomposition Through Physical Changes Caused by Bone Weathering
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Bone weathering has often been used in forensic, archaeological, and paleoanthropological sites to better understand the context in which remains are found. In forensic settings bone weathering is used to estimate the postmortem interval of deceased individuals. The application of bone weathering as a tool for estimating time since death stems from Behrensmeyer’s 1978 study on bone bed assemblages in Africa. Previous research has looked at weathering in varying climates using animal remains, but none have used human skeletal remains nor have they attempted to quantify the underlying variables that are associated with weathering. The present research represents a quantitative analysis of solar radiation as a variable of weathering using human skeletal remains. Donations (n=19) from the Willed Body Donation Program at the Forensic Anthropology Center at Texas State were separated into two groups. The groups consisted of individuals exposed to solar radiation (n=9) and individuals unexposed to solar radiation (n=10).
Upon initial skeletonization of the remains, weekly observations for signs of weathering were conducted. Once weathering characteristics were marked as present; solar radiation, ADD and calendar day required for the onset of weathering were calculated. Data were analyzed using Mann-Whitney U, Kruskal-Wallis, and Pearson’s Correlation. The median values were reported due to the non-normal distribution of the data. The median value for the appearance of bleaching was 51366.4 W/m2 for total solar radiation, 997 ADD, and 47 calendar days. Weathering rates were not significantly different between long bones and flat/irregular bones (p=0.158) and among different groups of bone (p=0.985). The Pearson’s Correlation indicates that solar radiation is significantly correlated with ADD (p=0.000) and the number of calendar days (p=0.000) observed when bleaching appeared. It also became apparent while conducting observations that new definitions for weathering characteristics were needed to clarify and standardize descriptions of features associated with weathering. Results from this research in conjunction with similar studies on the different weathering variables will impact not only forensic settings but will aid in better understanding the circumstances and conditions affecting human remains in the archaeological and paleoanthropological record.