Human Skeletal Remains of the Yayoi Period from the Iwatsubo Cave Site in Gunma Prefecture, Kanto District

Abstract

A full description of seven human skeletal remains of the early middle Yayoi period, excavated in 1980 and 1982 at the Iwatsubo cave site, Manba-cho, Tano-gun, Gunma Prefecture, Japan is given. These are the first well-preserved human skeletal remains of the Yayoi period from an inland site in the Kanto district. Comparative analyses with east Japan Jomon, east Japan Kofun, northern Kyushu Yayoi and recent Kanto populations were made. The inventory and osteological measurements of the Iwatsubo remains are shown in Tables 1 to 8.
Recent morphological and genetical studies have resulted in a consensus view that the recent Japanese are genetically greatly influenced by immigrants from the Asian Continent since the Yayoi period. Whether the people of the Iwatsubo site retained skeletal features characteristic of Jomon populations or possessed those of the immigrants is the major focus of this paper.
Two of the Iwatsubo specimens (both are adult female) are relatively complete and showed considerable morphological similarities with the Jomon series. These include a broad and low facial skeleton, straight upper orbital margins, prominent and broad nasal bones and long, flat and weakly curved clavicle shafts in Iwatsubo 1, long forearm bones, pilastric femora, long tibiae, and megaperonic fibulae in both Iwatsubo 1 and 2. Iwatsubo 1 and 2, however, differ from the average Jomon conditions in their higher estimated stature and larger circumferences of major long bones. Therefore, although Iwatsubo 1 and 2 are thought to have been direct decendants of Jomon populations, some unknown new environmental factors may have affected their statures and robusticity of long bones.
The other Iwatsubo specimens are less informative because of their poor preservation or infant status.