◯Soichiro KUSAKA (Tokai University), Mai TAKIGAMI (National Museum of Nature and Science), Kazuhiro SAKAUE (National Museum of Nature and Science)
１．Purpose of research
In order to establish a new academic field, "integrated bioarchaeology", this project aims to clarify prehistoric diet and migration, which is necessary for integrating past food ecology and social organization. We will receive research materials from other groups, conduct dating, carbon and nitrogen isotope analysis, and strontium isotope analysis of the materials, and provide feedback to each group on the results of these analyses. The group will conduct similar analyses of human remains excavated at each site, and will also conduct research on chronological and regional differences. This project will clarify the food ecology of prehistoric peoples and contribute to research purpose A "Analysis of Prehistoric Human Societies in the Japanese Archipelago" by integrating the results of the other research groups' studies on prehistoric societies.
The objective of this project is to contribute to the reconstruction of prehistoric societies by studying the diet, migration, and chronology of prehistoric people. Reconstruction of the protein source by carbon and nitrogen isotope analysis of collagen from archaeological bones. Carbon isotope analysis of hydroxyapatite in paleoanthropic bones will be used to estimate the energy source. Strontium isotope analysis of teeth will be used to detect the migrated human. By applying this method to multiple archaeological sites, we will reconstruct the dietary practices of prehistoric societies, their migrations, and their transitions.
２． Summary of Research Results
In this study, a stable isotope ratio mass spectrometer (IRMS) was installed at Tokai University. The preprocessing equipment of an elemental analyzer that can measure the carbon and nitrogen content of organic materials such as collagen, and a GasBench that can measure carbon isotope ratios from the carbon dioxide gas of hydroxyapatite. Due to the recent global shortage of semiconductors, delivery of the mass spectrometer took place in December. After that, a trial run was conducted to learn how to use the instruments.
The carbon and nitrogen stable isotope ratios of the materials are reported against the value of the International Standards, which is an internationally established standards for isotope ratios. Since the amount of the international standards is limited, the working standard is used in ordinary measurements. For this reason, a new working standard was developed for carbon and nitrogen isotope measurements. First, the isotope ratio of the material alanine was measured. Alanine was dissolved in ultrapure water, and small amounts of alanine with high 13C and 15N contents were added. After stirring, alanine showing the desired high carbon and nitrogen isotope ratios was obtained by lyophilization. In the future, we plan to determine the value of the working standard by simultaneously measuring the international standard and the working standard.
Regarding material collection, we visited the Anjo City Museum of History in Aichi Prefecture to examine the Horiuchi shell mound material from the Late Jomon period. We collected five human skeletal remains and five animal bones. In the future, we plan to proceed with collagen extraction to reconstruct the diet. Furthermore, in collaboration with Group A01, we conducted dietary analysis and dating of human bones from the Kawaji shell mound in Aichi Prefecture, and presented the data at the annual meeting of an anthropological society in Japan. Variations in carbon and nitrogen isotope ratios were observed along the chronological sequence. Burial subgroups were found in the grave site, and the burial positions varied according to the age.
The types of tooth ablasion also varied with age, making this an interesting case study that can trace changes in diet and ritual customs. In addition, 20 radiocarbon dates were obtained from human bones excavated from the Tsukumo shell mound in Okayama Prefecture on consignment. We plan to analyze the data after additional measurements in the next fiscal year.
In the collection of the National Museum of Nature and Science, we attempted to date Human Bones No. 1 and No. 2 from the Kurawa Site on Hachijojima Island. Unfortunately, we could not proceed to dating because we could not recover collagen from the skull fragments. In collaboration with Group B04, we have again conducted dating of human collagen from the Aoya Kamijichi site. In previous experiments, the collagen was in poor condition and the expected age was not obtained. This year, we extracted the collagen by adding ultrafiltration pretreatment and conducted radiocarbon dating. Analysis of the dating data is currently underway. In addition, we have also reconstructed two cranial bones from the Aoya Kamijichi site, Cranial No. 1 and No. 8. In addition, Sr isotope measurements were made on the tooth enamel of the Aoya Kamijichi human bones. Preliminary data have been obtained, and further analysis is expected to allow us to examine human migration in combination with genetic data. Some of these results from the Aoya Kamijichi site were reported at the Tottori Yayoi no Okoku Symposium "The Truth about the Japanese People: The People of the Aoya Kamijichi Site Revealed" held on March 16.
Takigami participated in the organization of the Kasasagi Meeting, a meeting for young researchers.
3．Future Research
In the next fiscal year, we will continue to investigate the diet and age of human skeletal remains by stable isotope analysis. We will also collect data from other shell mound sites in Aichi Prefecture, and study the changes in diet during the Late–Final Jomon Period. We will also examine the age of human bones excavated from the Yoshigo shell mound, which have already been radiocarbon dated. We will proceed with dating of human remains excavated from the Tsukumo shell mound. For the mass spectrometer, we will construct an environment in which we can measure the carbon and nitrogen isotope ratios of collagen by repeatedly measuring the working standard. We also plan to improve the elemental analyzer so that it can measure even small amounts of samples.
We will also continue our joint research with Group B04 on the diet, age, and migration of human remains from the Aoya Kamijichi site. In particular, we will analyze the data of radiocarbon dating of ultrafiltrated samples and interpret the obtained Sr isotope ratio data.