INTRA-SKELETAL VARIATION IN STABLE ISOTOPES THROUGH NON-DESTRUCTIVE APPROACHES: APPLICATIONS OF THE PATTERNS OF SKELETAL REMODELING TO BIOLOGICAL ANTHROPOLOGY

Stable isotope analysis is a well-established method in biological anthropology used to deliver data on residence, diet, and life history. Samples for these analyses are often collected from the diaphyses of long bones with an assumption of an expected rate of turnover between five and ten years, depending on the skeletal element. However, the biological foundations of this assumption are still uncertain, especially concerning the intra-skeletal and intra-element variation of isotopic signatures that may relate to patterns of remodeling. Exploring these gaps in intra-element isotopic variation requires fine-grained work using multiple bones from multiple individuals, but such work is limited by the destructive nature of current mass spectrometry technology. Traditional stable isotope analysis techniques typically destroy the skeletal sample, which can be damaging for the prospect of justice, if the entire representative sample must be used, and is detrimental for the stewardship of curated skeletal collections. Destructive analyses of skeletal material can also be perceived as disrespectful and intrusive by descendants and descendant communities, and ultimately lead to the exploitation and marginalization by scientists of already marginalized communities. This project, therefore, tested a non-destructive approach using Raman Spectrometry, called Isotope Ratio Infrared Spectrometry (IRIS), to explore its application to isotopic ratio analyses in human skeletal remains for the assessment of δ¹³C and δ¹⁸O from bioapatite. Using this method as well as the traditional method of isotope ratio mass spectrometry, intra-element variation in δ¹³C and δ¹⁸O was explored in two populations, an archaeological population from Transylvania, Romania and a contemporary collection of donors to the University of Tennessee Skeletal Collection. Results suggest that, while IRIS appears promising for δ¹³C, it is not reliable for δ¹⁸O values. Results from both methods also demonstrate that intra-element variation is well within the expected ranges of intraskeletal variation, likely because bulk sampling is too coarse a method to tease apart potential differences based on the processes of remodeling. Future work must continue to search for reliable non-destructive methodologies while simultaneously ensuring all research follows ethical principles to reduce marginalization of descendant communities.

Funded by the AAFS Forensic Science Foundation Lucas Grant and the University of Tennessee Department of Anthropology's Leitner Award