The Isotopic Taphonomy of Human Remains

The Isotopic Taphonomy of Human Remains The Isotopic Taphonomy of Human Remains We propose to examine the isotopic change in different tissues of human remains after burial in environmental conditions relevant to forensic investigation. Isotopic ratios of carbon, nitrogen, oxygen, hydrogen, strontium and lead (d13C, d15N, d18O, dD, 87Sr/86Sr, 207Pb/206Pb, 208Pb/206Pb) record diet, birthplace and travel history, valuable information when trying to identify human remains of unknown origin. Evaluating the preservation fidelity of tissues for pre-mortem isotopic values is essential if these tools are to be routinely applied in forensic cases of unidentified individuals. There are 8,855 open cases of unidentified human remains in the NamUs database system.1 Forensic osteological evaluation and DNA technology can lead to identificaitons, but there are limitations to these techniques. Familial DNA reference samples or known osteological characteristics are needed to match to a particular set of remains. Extracted DNA and osteological classification of sex, age and ethnicity do not provide information about an individuals birthplace or past travel history. However, isotopic measurements of hair, teeth and bone have resolved selected forensic cases by identifying the birthplace or travel history of decedents. However, basic research into the taphonomy and preservation of isotopic signals in a forensic context is lacking. Archaeological taphonomic studies have laid the groundwork, but there are specific issues in modern humans and forensic contexts that have not been evaluated. The proposed research addresses the following questions: 1) What is the intra-individual isotopic heterogeneity? 2) What is the fidelity of the isotopic record in different tissues during decomposition? 3) What are recommendations for tissue sampling, storage and isotopic analysis of unknown human remains? Ten subjects would be analyzed, six at the ARF facility in Tennessee and four at FARF in Texas. Every effort would be made to obtain subjects that are non-local, for maximum discordance of isotopic composition with local environmental conditions. Detailed postmortem histories of subjects, as well as pre-mortem travel and geographic life histories will be known. The subjects will be evenly divided between men and women, and subjects will include maximum racial diversity within the constraints of donor availability. Samples would include hair, teeth, and skeletal elements including metacarpal/phalange, femur and rib. Hair will be cut from the head, and only the most recent section will be analyzed. 15 mg of enamel will be mechanically removed with a Dremel tool, while bone biopsies will be sampled with a commercial bone biopsy surgical kit. Samples for isotopic analysis will be taken at receipt of the subject, and after decomposition in either surficial or shallow burial conditions. A detailed sampling strategy is attached.