- vol.18, pp.134-143, 2007-03 (Released:2010-06-10)
During the past several decades, many medieval skeletons were excavated from archaeological sites in the Yuigahama area, Kamakura, Japan. The excavations yielded more than 5,000 individuals in varying states of preservation from the Zaimokuza, Seiyokan, Yuigahama-minami and Chusei Shudan Bochi sites. Medieval Kamakura was an ancient capital of the Kamakura Shogunate, and a lot of people lived in Kamakura with high population density. The human skeletons excavated from the Zaimokuza site are reported to be humans dead by competition at the end of the Kamakura Shogunate, but a detailed study on dating of the human skeletons has not made yet. In this study, we measured ^<14>C ages, together with carbon and nitrogen isotope ratios, of human skeletal remains excavated from the Yuigahama-minami site and Chusei Shudan Bochi site. The δ^<13>C and δ^<15>N were not different between human skeletal samples of both sites, while the ^<14>C ages were different between them: The human bones of the Yuigahama-minami site are 100 year younger than those of the medieval collective-cemetery site. All of ages of human skeletons from both of the sites are older than the latest Kamakura period. The δ^<13>C and δ^<15>N values of the medieval Kamakura people are higher than those of terrestrial mammals, indicating that they exploited some amount of marine fish and/or mammals with higher δ^<13>C and δ^<15>N as protein sources. Therefore, the ^<14>C ages obtained for human skeletons could be order than the true ages. ^<87>Sr/^<86>Sr isotopic ratios of human skeletons of the Yuigahama-minami site tend to be higher than those of the Chusei Shudan Bochi site. Soils, plants and animals feeding on them in a given locality have ^<87>Sr/^<86>Sr values that generally mirror underlying bedrock composition, and thus ^<87>Sr/^<86>Sr ratios of human skeletons are useful tools for assessing migration in prehistory. The result obtained in this study suggests that Yuigahama-minami humans and Chusei Shudan Bochi humas lived in different areas. More skeleton samples should be analyzed for determining detailed ^<14>C ages of humans excavated from the Yuigahama sites, and for estimating migration of prehistory of the medieval Kamakura humans.