著者

小山 修三 杉藤 重信 Shuzo Koyama Shigenobu Sugito

出版者

国立民族学博物館

雑誌

国立民族学博物館研究報告 = Bulletin of the National Museum of Ethnology (ISSN:0385180X)

巻号頁・発行日

vol.9, no.1, pp.1-39, 1984-03-31

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This paper applies techniques of computer simulation to theanalysis of Jomon demographic patterns. The computer programsare based on the following assumptions: (1) Population grows exponentially,with the equation Nt=No*evt; (2) there is an upperlimit to population size in a given area, termed carrying capacity(K); and (3) at the level K, population growth stops. In this program,we divided Japan into nine regions, such that when populationreaches the level K, the surplus migrates to other areas, according toprobablistic models.In dealing with carrying capacity, we initially assign the constantM, a hypothetical population maximum for an area; subsequentlyM is converted to K as a consequence the impact of climate andtechnology.Pollen analysis indicates significant climatic change during theJomon Period. This was precipitated by a warming trend, whichbegan after the last glacial, and continued until about 6000 B.P.,followed by a cooling trend which lasted until about 2000 B.P.This climatic wave caused significant change in the vegetation of theJapanese archipelago. In the East during the warming trend,coniferous forests were replaced by deciduous Fagus-Quercus forests,comprised of a variety of nut-bearing trees, which constituted animportant food source for the Jomon people. However, the nutbearingtrees are sensitive and often succumb in cold weather. Basedon these facts, we assume that carrying capacity increased during thewarming trend and decreased during the cooling trend in the regionsof East Japan. In West Japan, however, Yasuda [1980] suggeststhat during the warming trend the environment deteriorated owing todry summers. So here we assume that carrying capacity declinedduring the warming trend and then remained constant.The technology of Jomon food production, including the toolelements used for hunting, fishing and gathering, are well known froman early stage in East Japan. Thus we assume that although tools musthave been refined and systematized as Eastern Jomon technologydeveloped, they were not powerful enough to influence carryingcapacity, because the system did not prevent population decline in thecooling period. By contrast, farming, the true technological innovation,introduced from the Asian continent to Kyushu, changedJomon society into an agricultural one. In this simulation we stipulatethat when rice is introduced into a region it not only doubles theratio of population growth but also increases carrying capacity(five times).The results were compared with earlier estimates [KOYAMA 1978]based on the number of sites. Both data coincide well, especiallywith respect to the population curve throughout the Jomon period.In the East this curve shows a sharp increase of population until theMiddle Phase, where a rapid decline is observed (Late Phase). Inthe West population remained almost constant throughout the entireperiod. During the Jomon, the distribution of pupolation was highin the East, whereas in the Yayoi it was high in the West—representinga complete reversal between the two periods.