Investigating diagenesis and the suitability of porcine enamel for strontium (87Sr/86Sr) isotope analysis

Population origins, animal movements, and the presence of non-local individuals have all been addressed through the analysis of strontium isotope ratios in dental tissues. There has been extensive research regarding the preservation of biogenic Sr in various human tissues: bone, tooth enamel and dentine, but little into non-human species. The applicability of this methodology to pigs in particular may be problematic with some studies considering there to be no differences between porcine and human enamel and others suggesting differences do exist. As a result it remains unclear whether porcine enamel is more susceptible to diagenetic processes and re-equilibration with diagenetic fluids from the local burial environment. Whilst several programmes of strontium isotope analysis have included pig enamel samples, very few have produced samples of allocthonous origin and the validity of the technique for reconstructing movement of pigs remains in question. This study tests the validity of using strontium isotope ratios in porcine enamel for tracking the movement of pigs in two ways. Firstly, the susceptibility of modern and archaeological pig and cattle teeth to diagenetic changes was assessed by submerging enamel samples in a solution of known strontium isotope composition for a period of up to 10 months and measuring the level of uptake as a proxy for diagenetic alteration. Secondly, the strontium isotope ratios of porcine enamel samples from five archaeological assemblages, identified as likely to contain imported, non-local pigs, were analysed to determine whether individuals that are allocthonous in origin could be identified.