Regional estimation by oxygen isotope ratio analysis using tooth enamel of Japanese individuals

In the field of forensic sciences, human teeth are used to identify individuals in cases involving unidentified bodies. In recent years, isotope analysis of tooth enamel has been increasingly employed to estimate birth year and place of birth. The enamel is formed between the prenatal period and childhood, and after the tooth crown is complete, it does not undergo additional growth. Therefore, the oxygen isotope composition of the enamel bioapatite is significantly influenced by the environmental conditions during these periods, including dietary habits and tap water consumption. In this study, we aimed to predict the places of birth of 65 Japanese individuals, whose places of birth were known, by analysing the oxygen isotope ratios in carbonates in the enamel bioapatite. The oxygen isotope ratio in bioapatite varied from a maximum value of −3.4‰ to a minimum of −8.76‰, indicating lower and higher values in cold and warmer areas, respectively. Furthermore, a correlation was observed between the oxygen isotope ratios and the latitudes and average annual temperatures of the place of residence during enamel formation (correlation coefficients: −0.84 and 0.81, respectively). Oxygen isotope analysis of enamel bioapatite can help in determining the environmental conditions in the place of residence during enamel formation. Overall, oxygen isotope analysis can be useful in predicting the place of residence during the enamel formation of individuals in Japan.