Modeling Protein Diagenesis in Ancient Bone: Towards a Validation of Stable Isotope Data

Abstract

Modern mammalian bone was experimentally inoculated with soil bacteria to induce protein diagenesis. The protein relics extracted from these bones were compared with degraded protein from archaeological human bone. Protein identification was done by gel electrophoresis and amino acid analyses, whereby non-proteinogenetic amino acids were especially monitored. We present a model for microbial collagen break-down and the resulting consequences for stable isotopic data and thus paleodiet reconstruction. While bacteria produce a shift in δ¹³C towards lighter values as a result of selective amino acid consumption, an overall enrichment of δ¹⁵N in the range of a trophic level effect was detected. A metho for an estimation of in vivo δ¹³C values in collagen is suggested by correction of diagenetically altered amino acid profiles. Since a shift in δ¹⁵N should largely be the result of peptide bond cleaving, no such estimations are possible.