Strontium isotope evidence of migration and diet in relation to ritual tooth ablation: a case study from the Inariyama Jomon site,Japan

Ritual tooth ablation was extensively practiced among Jomon (Japanese Neolithic) societies in their final phase (ca. 3000-2300 BP). This tradition includes two different tooth ablation patterns, type 4I and type 2C, referring to extraction of the mandibular incisors and canines, respectively. However, the reason for this difference is unclear. Previous carbon and nitrogen stable isotope analysis of human remains from the Inariyama shell mound revealed that type 4I individuals were more dependent on terrestrial resources and type 2C individuals on marine resources. To test this hypothesis, we performed strontium (Sr) isotope (⁸⁷Sr/⁸⁶Sr) analyses on the same skeletal remains and on modern plants around the site. Because Sr isotope ratios of plants differ according to the local geology and seawater has a consistent Sr isotope ratio, the Sr isotope ratios of tooth enamel can reveal both migration and diet. Comparing Sr isotope ratios in plants and seawater with those of tooth enamel, we identified four possible immigrants. Type 4I locals had significantly higher Sr isotope ratios than type 2C locals. The ratios of the type 4I and type 2C locals were close to those of terrestrial plants and seawater, respectively, suggesting that type 4I locals had incorporated much Sr from terrestrial resources and type 2C locals from marine resources. These results support the hypothesis that ritual tooth ablation reflects dietary differences throughout an individual’s life, and they suggest possible occupational differentiation among the Jomon people.     

利用X-CT和数字图像相关法对遗址反复干湿导致的劣化机制进行基础研究

此研究是以石材和土壤所构成的考古遗址为主要研究对象。在确定石材和土壤的渗透性下,通过数字体积相关法(DVC)和数字图像相关法(DIC)对干湿劣化的环境条件进行定量的评估,并提出控制这种劣化发生的环境调整方法。 为了收集基本数据,通过DIC及X射线成像技术分析从湿润到干燥的过程中丰浦硅砂的位移量实验,并在实验中,使用DIC计算样品在收缩应力下的变形分布。此外,本次实验以铁粉作为示踪剂添加至样品中,并以铁粉作为参考点计算丰浦硅砂特定范围的移动量,借此评估铁粉作为示踪剂的适用性及精确性。结果表明,通过拍摄干燥前后样品的X射线图像,并用DIC进行分析可以计算出干燥前后的变形分布。在样品中添加示踪剂也被发现有助于分析样品局部区域的移动方向及移动量。因此通过此基本数据的检验,相信将来通过X射线计算机断层扫描(X-CT)及数字体积相关法(DVC)的应用,可以用来阐明反复干湿风化的劣化机制。     

Patterns of social identity in relation to tooth ablation among prehistoric Jomon foragers from the Yoshigo site,Aichi prefecture,Japan

This study documents and interprets patterns of identity in relation to tooth ablation patterns at Yoshigo, a Late/Final Jomon period (3500–2500 yBP) site. Two patterns of tooth ablation are observed among the Yoshigo people: both (2) mandibular canines or four (4) mandibular incisors were extracted during life and formed a basis for identity differentiation. Three hypotheses are tested regarding these groups: (1) tooth ablation groups will be unrelated to postmarital residence; (2) tooth ablation groups will be associated with age‐based achievements; (3) tooth ablation groups will be associated with occupational specialisation. Biodistance, demographic and stable isotope analyses were performed on skeletal remains recovered from Yoshigo (3500–2300 BP) to test these hypotheses. Within‐group variation expressed by cranial and dental measurements was not significantly different between tooth ablation groups. This indicates that tooth ablation practices were not related to migration. Previous biodistance findings do, however, suggest that tooth ablation groups represent closely related individuals, possibly kin‐based networks. Demographic analysis of age‐at‐death and tooth ablation suggests that tooth ablation styles were achieved at different ages. Stable isotope analysis indicates that the tooth ablation groups consumed similar foods. Based on isotopic findings from other sites and archaeological evidence for food sharing among Jomon people, these results suggest that dietary variability between tooth ablation groups was homogenised by cooperative food sharing. The totality of these findings support the hypothesis that the identities associated with tooth ablation were unrelated to migratory patterns, and instead, possibly reflect kin‐based social units, where achievement or age acted as a determinant of membership. Copyright © 2010 John Wiley & Sons, Ltd.     

Strontium isotope analysis to reveal migration in relation to climate change and ritual tooth ablation of Jomon skeletal remains from western Japan

A gradual population increase accompanying climate cooling has been evinced as having occurred in western Japan during the Middle (ca. 5000–4000 years BP) to Late-Final Jomon period (ca. 4000–2300 years BP). We test the hypothesis that this population change paralleled increasing human migration. We also test the archaeological hypothesis that types of ritual tooth ablation can be used to distinguish between locals and immigrants during the Late-Final Jomon period. We measured strontium isotope ratios in human skeletal remains from the Middle Jomon Ota and the Late-Final Jomon Tsukumo sites located in the Sanyo region of western Japan. Tooth enamel and bone were analyzed, and modern plant samples were collected in the areas surrounding the two sites to make a map of environmental strontium isotope ratios. The biosphere strontium isotope ratios correlated well with the underlying geology, enabling us to put forth a hypothesis of immigrants’ origins. There were no migration pattern differences between the Middle and Late-Final Jomon groups, indicating that the gradual population increase was caused by an increase in the indigenous population. All the Tsukumo individuals are locals, and this finding indicates that types of tooth ablation did not distinguish between locals and immigrants. Alternative hypotheses for the presence of different tooth ablation types in the Jomon society should be explored.     

Carbon and nitrogen stable isotope analysis on the diet of Jomon populations from two coastal regions of Japan

We report on a stable isotope paleodietary reconstruction of Jomon populations in Japan during the Middle to Final Jomon period (ca. 5000–2300 years BP), focusing on dietary differences within and among populations and between regions. Carbon and nitrogen isotope analysis was performed on human and faunal bone collagen from six coastal sites along the Inland Sea in the Sanyo (Ota, Funamoto, and Tsukumo) region and along Mikawa Bay and the Pacific Ocean in the Tokai (Kawaji, Yoshigo, and Inariyama) region. We found that carbon and nitrogen isotope ratios were positively correlated, indicating that the Jomon people consumed a mixed diet of marine (shellfish and marine fish) and terrestrial (C₃ plants and terrestrial mammals) protein. In the Ota samples (n = 25, during the Middle Jomon period, 5000–4000 years BP), sex was one of the main reasons for the intra-population dietary variation. Ota males consumed greater amounts of marine food, while Ota females consumed greater amounts of terrestrial food; these dissimilar diets may have been related to the sexual division of labor. Significant inter-population dietary differences were found, which may have been related to differences in age or site location. Notably, the two coastal regions showed clear isotopic differences. Nitrogen isotope ratios of individuals from the Sanyo region were significantly higher than ratios of individuals from the Tokai region. The individuals in the Sanyo region might have consumed a diet high in aquatic foods, particularly high trophic level marine fish, whereas the individuals in the Tokai region might have consumed a lot of marine shellfish. Another possible reason for the regional isotopic difference might have been different baseline of nitrogen isotope ratios of the marine ecosystems.     

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.