Intra- and inter-individual variation in δ13C and δ15N in human dental calculus and comparison to bone collagen and apatite isotopes

Abstract

There are mixed opinions on the suitability of dental calculus for paleodietary reconstruction using stable isotope analysis. We examine δ13C and δ15N values of calculus samples from two regions, central California in the USA and Sai Island in the Sudan. When atomic C/N ratios are less than 12 in calculus, results show positive correlations at both the regional and individual level between stable isotopes of bone collagen and calculus, suggesting these materials track similar dietary behaviors. Correlations are still positive but lower between δ13C values of calculus and bone apatite. Stable isotope ratios of calculus show between 30% and 50% greater variation than bone, are typically enriched in 15N (mean = 2.1‰ higher), and are depleted in 13C relative to bone collagen (mean = 0.8‰ lower) and apatite (mean = 6.4‰ lower). Calculus from multiple teeth was analyzed separately for seven individuals to examine intra-individual variation. Results show that within an individual δ13C varies up to 1.8‰, and δ15N up to 2.1‰, which may explain some of the weak bone-calculus correlations previously reported in the literature. When atomic C/N ratios are greater than 12, calculus correlates more poorly with bone collagen, suggesting these samples should be treated with caution.