Methodological and Archaeological Implications of Intra-tooth Isotopic Variations (δ13C, δ18O) in Herbivores from Ain Ghazal (Jordan, Neolithic)

Tooth enamel is considered very stable against post-mortem alteration and therefore is a preferred study material for isotopic analyses in the context of palaeoecology. The range of isotopic variation within one given tooth has important implications for the sampling procedure especially if microsamples are used. Thus, the awareness of intra-tooth isotopic variability is undeniable for the study of palaeoclimate as well as for the reconstruction of palaeodiet and the inferred use of ecological niches in the past. In Neolithic tooth enamel (Bovidae and Equidae from Ain Ghazal, Jordan) carbonate was analysed for δ13C and δ18O in order to trace intra-tooth variation. Up to 13 enamel samples were taken per tooth from crown to root in horizontal layers with a drill. The variation of isotopic values is higher in equid than in bovid tooth enamel. Results for δ13C in a given tooth vary within a range up to 2·9 per mil (PDB) in equid enamel, but remain within the frame of either C3or C4feeders, and do not indicate a clear shift from C3or C4plant consumption for a given individual. Results for δ18O vary up to 6·9 per mil (PDB) within one given tooth in equids. This approach offers several methodological perspectives. First, the sampling of many individuals of one species at a given site over a longer time period should permit a comparison of stable isotope variations, both synchronically and diachronically. From the high time resolution possible via intra- and inter-tooth isotopic variability we may better monitor seasonality or reconstruct climatic changes. Information on short-term climatic variation could provide important arguments for the discussion of cultural developments at a given archaeological site. Here we emphasize the methodological aspect and its implications. A better understanding of the site of Ain Ghazal and its development reflected in settlement size, artefacts, and architecture will be possible, however, here we present preliminary data.