Spatially-resolved Ca isotope and trace element variations in modern human deciduous teeth – records of diet and physiological changes?

We present spatially-resolved Ca-isotope and trace element (esp. Sr/Ca & Ba/Ca) data in enamel of three deciduous human canines of early 20th-century Italians, firstly to investigate any physiological effects on Ca-isotope variations, and secondly to examine the utilization of Ca-isotopes to study past human weaning practices. At Royal Holloway University of London, enamel microsamples were laser-cut along the enamel-dentine junction using a 193nm laser-ablation system (RESOlution M-50), extracted and analysed for Ca isotopes (δ44/40Ca, relative to NIST 915a) by TIMS (PhoeniX-62) using double-spike technique. Trace element data were obtained on the matching, non-laser cut lingual enamel side using LA-ICPMS. The Ca-isotope profiles drop to the lowest values (~-2.5 ‰) at birth in all three individuals, indicating a likely link between physiological change and negative Ca-isotope excursions. Two individuals show an increase of 0.5 – 1‰ in enamel δ44/40Ca after birth, but the third one records a drop of 0.5 ‰ post birth. This may suggest different early-life diets between the former (formula-fed?) and the latter (breastfed?) because human milk has the lowest Ca-isotope composition. Corresponding histologicallycontrolled Sr/Ca and Ba/Ca profiles will be presented, which help to contextualize the Ca-isotope data across birth and weaning.