New methods for old challenges: A sampling protocol for sequential stable isotope analysis (δ13C and δ15N) of dentine collagen in high-crowned teeth

Intra-tooth or sequential stable isotope analyses are nowadays widely implemented in zooarchaeological research. Sequential isotopic analyses have been mainly restricted to the mineral fraction of the enamel, while a wider implementation in dentine collagen has been generally eluded, despite conforming an essential organic compound for paleodietary studies. In high-crowned teeth, dentine grows oblique to the vertical axis of growth and some challenges arise when trying to isolate dentine increments during a sequential sampling. Previous sampling strategies slice the whole dentine thickness and provide sequences where isotopic variation is largely attenuated. In this study, we show a new proposal for performing carbon and nitrogen isotope analyses of dentine collagen which better fits dentine's growth. We implemented it in mandibular second molars of an experimental modern sheep flock. Our sampling largely reduces the isotopic “damping” of previous approaches and provides short time-span samples. Sequential δ¹³C values obtained in dentine tissue yielded similar resolution to those obtained in enamel tissue of the same individuals. This proposal, especially suitable for caprine and other bovid species, broadens the implementation of dentine collagen signatures in the field of stable isotope analyses in zooarchaeology.