A Human Skeleton of the Satsumon Period from the Shimodanosawa Site, Akkeshi-cho, Eastern Hokkaido

Abstract

The Satsumon culture flourished throughout Hokkaido from about the 8th century to the 13th century A.D. before the emergence of the Ainu in recent times. Human skeletal remains of this period, however, have rarely been discovered.
In 1966, the archaeological excavation team directed by Mr. S. Sawa of the Kushiro City Museum unearthed human skeletal remains from a grave pit of the Satsumon period at the Shimodanosawa site, Akkeshi-cho, eastern Hokkaido (Fig. 1). This skeletal material, consisting of the skull and parts of the post-cranial skeleton, was intensively examined for this study.
The age and sex of these remains were judged from the morphological evidence to be an adult female.
Although PENROSE's shape distance based on seven cranial measurements showed that the Shimodanosawa individual was slightly closer to the modern Tohoku Japanese than to the Hokkaido Ainu (Tables 1 and 3), the same distances based on 13 mesiodistal tooth-crown diameters showed that the Shimodanosawa was far closer to the Hokkaido Ainu than to the modern Japanese (Tables 2 and 4). Moreover, a likelihood ratio analysis of cranial nonmetric traits indicated that the Shimodanosawa remains were far more likely to have come from the Ainu population than from the modern Japanese population (Table 5). Noticeable, as to the nonmetric traits of the Shimodanosawa skull, was the occurrence of a well-defined third occipital condyle, which is known to be relatively frequent in the Ainu but extremely rare in the Japanese (Fig. 3). The shoveling of the upper central incisors was slight in the Shimodanosawa as it is in the Ainu and the Jomon.
With regard to the post-cranial bones of the Shimodanosawa remains, such traits as the ponticulus posterior of the atlas, the narrow and deep intercondylar notch, as well as the pilastered shaft of the femur, and the transversely flattened shaft of the tibia are all believed to appear more frequently in the Ainu than in the Japanese population.
Therefore, taking all the results obtained from this study into consideration, it can be concluded that the total morphological pattern of the Shimodanosawa skeletal remains is substantially not different from that of the Hokkaido Ainu of recent times.