鎌倉市由比ヶ浜中世集団墓地遺跡から出土した人骨4点、犬骨3点について、東京大学総合研究博物館においてゼラチン抽出を行い、加速器質量分析装置(AMS)を用い、炭素・窒素安定同位体比と放射性炭素年代を測定した。測定された年代値をOxCal4.4（Bronk Ramsey, 2009）を用い較正、さらにIntCal20（Reimer et al. 2020）をMarine20（Heaton et al. 2020）も用い補正を行った結果、人骨の年代は、概ね13C後半から14C前半、犬骨についても13-14Cの範囲に収まった。炭素・窒素安定同位体比からは、当遺跡に埋葬された中世鎌倉人が米(水稲)と淡水魚を主食糧としていた様子が窺えた。一方、イヌについては、個体によるヴァリエーションが人骨に比べ遥に大きいことも確認できた。鎌倉では中世の人骨・犬骨出土例が数多く知られるが、それらについて放射性炭素年代や炭素・窒素安定同位体比が測定された事例は意外に少ない。それだけに、本研究は、今後、中世における人と家畜の食性を考える上で重要な意味をもつ。
Gelatin was extracted from 4 human bones and 3 dog bones excavated from the Yuigahama Medieval Mass Cemetery in Kamakura City and was measured and radiocarbon dated. After calibration using OxCal4.4 (Bronk Ramsey, 2009) and IntCal20 (Reimer et al. 2020) and Marine20 (Heaton et al. 2020), the ages of the bones were determined as follows: Human bones were generally in the late 13C to early 14C range, and the dog bones were also in the range of 13-14C. Stable isotope ratios of carbon and nitrogen suggest that the medieval Kamakura people buried at this site ate mainly rice (paddy rice) and freshwater fish. On the other hand, it was also confirmed that dog bones have much greater variation among individuals than human bones. Although many human bones and dog bones from the Middle Ages are known to have been unearthed in Kamakura, there are surprisingly few cases in which radiocarbon dates and carbon/nitrogen stable isotope ratios have been measured. Therefore, this study has important implications for future consideration of dietary habits for humans and livestock in the Middle Ages.