Abstract
Carbon deposits and soots from the Joto site in Kurashiki city, Okayama prefecture, were analyzed for the purpose of clarifying the method of cooking rice in the Yayoi period. The Joto site was chosen because the greater portion of cooking pots have carbonized grain impressions, and accordingly were clearly used for rice cooking. As a preliminary step to reconstructing the rice-cooking method, examinationswere made of the approximate number of times of use and the method of placement for each vessel. The number of times used was provisionally inferred from the frequency of marks from boiling over, and from the presence or absence of soot on the upper half of the vessel. The provisional times of use can be said to reflect the cumulative amount of received heat, and vessels with the least amount of received heat were those judged to have been used only once. As the result of examining, in order to clarify the method of placement, the scorched rice and the position of burned soot over the lower half and on the base of the vessel, it was ascertained that a ring-shaped scorched-rice trace indicates direct placement of a vessel in the flames with heat being received laterally, and a combination of a ring-shaped plus a round scorched-rice trace or a round scorched-rice trace alone indicates the combination of laterally received heat from direct placement in the flames plus heat on the vessel bottom from placement over a bed of coals. In this manner, all of the vessels in the Joto materials were seen to have been used on open fires.
In order to infer the method of cooking rice, models of the patterns of carbonized materials were devised for each of the various types of traditional rice cooking methods of rice-ferming peoples. In these ethnographic models, the attributes of the amount of boiling over, the type and frequency of scorching, the level of the water line, and the process of heating, etc., were found important for inferring the method of cooking rice. With regard to theheating process for the Joto materials, from an examination of pots used for cooking rice only once, it became clear that boiling over was taken as the signal for changing from high to low heat. Further, characteristics such as (1) high incidences of boiling over and scorched adhesions below the water line, and (2) the relatively high level of the water line itself, are in accord with those of the ethnographic models for the methods of boiling until all the moisture is absorbed, or of reducing the amount of water once the pot has boiled over. As it was indicated as well, from an analysis of the Nakazaike Minami materials, that the method of boiling until all the moisture has been absorbed had diffused to the Tohoku region in the first half of the Yayoi for everyday cooking, it is thought that this method was fairly widespread in the Yayoi period.
On the other hand, the hypothesis that "kayu (rice porridge) and zosui (rice boiled with vegetables into a gruel) were central to rice cooking in the Yayoi period" is generally accepted. While no concrete basis can be shown for this view, it is thought to come from the supposition that since per-unit rice yields were low in the Yayoi, as most farmers could therefore not eat much rice they boiled it soft to increase the volume. In contrast to this, as a result of this examination of Yayoi cooking pots, the conclusion that the practice of boiling until all the moisture is absorbed was widespread in the Yayoi period suggests that the amount of rice in the Yayoi diet was greater than currently supposed in the mainstream hypothesis.
