Sokendai Review of Cultural and Social Studies


A Chronology of the Irrigation and Cultivation of
Paddy in the Eastern Part of Shikoku:
A Local Case Study Using Carbon-14 Dating


Department of Japanese History,
School of Cultural and Social Studies,
SOKENDAI (The Graduate University for Advanced Studies)

Key words:

Carbon-14 dating, Yayoi period chronology, calibrated chronology, irrigated paddies, settlement scenery, Tokushima

We conducted a carbon-14 dating-based survey on settlement sites in Tokushima, the eastern part of Shikoku, to determine the date of introduction of paddy farming in the area.

We used the carbon-14 dating method to date materials, including deer bones, mollusk shells, carbonized material adhering to pottery, and products made of wood, such as piles, from the Mitani and Sho-Minami Kuramoto sites in Tokushima City. Consulting archaeological findings obtained from excavations and surveys, we ascertained calibrated dates for the items from the early Yayoi period as it occurred in Tokushima.

We dated the Tokushima convex rimmed pottery IV-2 back to a period in the first part of early Yayoi (concurrent with the Itazuke IIa phase), a 40–50-year period in 700–600cal BC; the Tokushima I-1 (concurrent with the Itazuke IIa phase) to a 50-year period following IV-2; the Tokushima I-2 (concurrent with the Itazuke IIb phase) to a 100-year period in 600–500cal BC; the Tokushima I-3 (first half) (concurrent with Itazuke IIb phase) to a 100-year period in 500–400cal BC; and the Tokushima I-3 (latter half) (concurrent with Itazuke IIc phase) to a 50-year period in 400–350cal BC.

Based on this timeframe, we reproduced the scenery of the village sites during the introduction of wet rice agriculture in Tokushima. Looking at each stage with the calibrated chronology as a frame of reference, it is clear that the population did not switch to practicing rice farming exclusively soon after the introduction of rice agriculture; instead, they experimented for around 40 to 50 years with rice farming alongside their traditional means of subsistence like hunting, fishing, and stockpiling grains and beans. Thereafter, they relocated their settlements in search of land suitable for creating irrigated paddies, and gradually developed these while monitoring the state of the rivers. This situation continued for approximately 50 years, as their population increased to considerably more than before. Around 600cal BC, they started to attempt major reshaping of the land, began the full-fledged creation of irrigated paddies, and started to reside in settlements consisting of two to three pit dwellings. While evidence suggests that the people were oriented toward irrigated paddy-field farming at this time, there is evidence to show that they also made dry fields and engaged in a variety of different kinds of agriculture. Given that this trend continued for around 200 years until 400cal BC, it is apparent that the full-fledged effort to implement irrigated paddy field agriculture did not result in an immediate change in the structure of settlements; rather, the social changes accompanying rice farming must have been rather slow to take effect. A major change in the settlements occurred during the 50-year period before 350cal BC in the following stage. The scale of the settlements expanded markedly, with each living area invariably having at least two pit dwellings, and the settlement as a whole having around ten. From this, we surmised that the size of the population had reached more than double that of the previous period.