伊豆諸島三宅島における初期農耕の成立と環境適応

An early agricultural society was established in the Izu Islands by the middle of the Yayoi period(ca.100 BC). A large scale village dating to this period was recently excavated at Ozato-higashi on Miyake Island. This site produced a large quantity of barley phytoliths from the artifact bearing strata. Although rice paddy fields cannot be utilized on the volcanic loam soils of Miyake Island, the presence of barley agriculture in dry fields was confirmed at Ozato-higashi. Compared with mainland sites of the same time period, Ozato-higashi produced many tools such as saddle querns and grinding stones that would appear to be linked with food processing. Another characteristic of the site is its almost total lack of fishing tools despite its coastal location. Ozato-higashi appears to have been a permanent residential village with a main emphasis on dry field farming. Furthermore, the presence of a large quantity of faunal remains at the nearby Middle Yayoi site of Kokomanokoshi suggests that rather than mere seasonal adaptations, a division of labour between villages was already in existence. On the main islands of Japan, this was the time in which full-scale agricultural villages based on wet rice cultivation were being established. The same was true of the Izu Islands, but here the evidence of sites such as Ozato-higashi shows that there was a flexibility to adapt to the more difficult local environmental conditions. The formation of a society having such an adaptive flexibility meant the end of the society which had carried out incipient cultivation from the latter half of the Jomon period.

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