A strontium isotope analysis on the relationship between ritual tooth ablation and migration among the Jomon people in Japan

Distinct patterns can be discerned in the extensive ritual tooth ablation found among the human skeletal remains of the Late–Final Jomon period (ca. 3200–2800 cal BP) in Japan. Based on comparative observations of sex and grave patterns in the skeletal remains, two major patterns in ritual tooth ablation, termed type 4I and type 2C, have been assigned to locals and immigrants, respectively. In order to test this hypothesis, strontium (Sr) isotope (87Sr/86Sr) analyses were performed on human skeletal remains from the Yoshigo shell mound in Aichi Prefecture, central Japan. Plants in the surrounding area were also examined to illustrate the geographic 87Sr/86Sr distribution. The Sr isotopic variation in human tooth enamel (87Sr/86Sr = 0.70868–0.71028) was greater than that in human bones (87Sr/86Sr = 0.70871–0.70943). Individuals with higher Sr isotope ratios in their tooth enamel than seawater Sr values of 0.7092 can be identified as immigrants (36% of population). The presence of these isotopically identified immigrants between both type 2C and type 4I individuals does not support the previous hypothesis. The intra-population 87Sr/86Sr distribution of tooth enamel of type 2C individuals showed a significantly higher mean ratio than that of type 4I individuals, suggesting a higher proportion of immigrants among the former.