Assessing life history from commingled assemblages: the biogeochemistry of inter-tooth variability in Bronze Age Arabia

Stable isotopes represent a remarkable means of assessing the life histories of individuals in the archaeological record, primarily by taking advantage of multiple skeletal tissues that form and remodel throughout life. However, this methodological tool also has the potential to provide crucial information on the life histories of individuals represented only by commingled, fragmentary, and otherwise isolated human skeletal remains, particularly when more traditional methods of evaluation are not possible. In this study, a sequential analysis of radiogenic strontium (87Sr/86Sr) and stable oxygen (δ18O) isotopes of associated molars from the in situ mandibular or maxillary fragments of 19 commingled individuals from multiple Bronze Age tombs in the United Arab Emirates was undertaken in order to examine temporal changes in mobility at the level of the individual. The majority of individuals display little difference in inter-tooth isotope ratios, suggesting a general lack of residential mobility between early childhood and late adolescence, an unexpected result given abundant evidence (artifactual and written) for a population actively engaged in both regional and interregional trade in the third millennium BC. However, two individuals from the Emirate of Fujairah demonstrate disparate inter-tooth 87Sr/86Sr values - likely indicative of some migration event - which calls into question the supposed cultural isolation of the region during the second millennium BC.