Frontier Research Institute for Interdisciplinary Sciences
Tohoku University

The Ryukyu Islands in the southwestern Japanese Archipelago are an island region where diversified cultures and communities have developed. In particular, this region is geographically divided into the Northern (including Amami and Okinawa islands) and Southern Ryukyu (including Miyako and Yaeyama islands), and significant cultural differences have been identified in the prehistoric period. Differences in population phylogeny or differences in adaptation to each island's environment have been proposed as contributing factors, but no conclusions have been reached. Recent population genetics and linguistic studies have presented new possibilities, but verification based on archaeological data remains elusive.

The present study focuses on the "environmental adaptation," one of the hypotheses for the factors that led the culture of prehistoric Southern Ryukyu to have different characteristics from that of northern (middle) Ryukyu, and approaches the reasons for the occurrence and establishment of the adze made of shell sherd (shell adze), a material culture unique to Southern Ryukyu. The shell adze was previously considered strong evidence for a migration from the other southern regions, but recently it has been found that the shell adze was used regionally with the stone adze, and the possibility that it was produced in an environmentally adaptive process has been pointed out. In this project, based on collaboration with dentistry (Dr. Yuka Hatano), mathematical science (Dr. Kohei Tamura), and archaeology (Dr. Kaishi Yamagiwa), focus specifically on use marks and morphology to determine the relationship between shell and stone adzes in their manufacture and use in the southern Ryukyus and test the validity of environmental adaptations. In addition, combining conventional archaeological data (chronology, associated material culture, and similarities between regions), we will examine the relationship and origin with surrounding regions, such as Northern (Central) Ryukyu, Taiwan and Philippines.