著者

本庄 総子

出版者

史学研究会 (京都大学大学院文学研究科内)

雑誌

史林 = The Journal of history (ISSN:03869369)

巻号頁・発行日

vol.103, no.1, pp.7-40, 2020-01

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マクニール・モデルとは、集団間に支配・被支配が成立する背景を、疫病への免疫力格差によって説明する理論型である。本稿では、この理論を踏まえつつ、日本古代における疫病の構造的理解を目指す。日本古代の疫病には大きく分けて二つのタイプがある。一つは、国外からの伝播ではないかと推定される大宰府発生の疫病である。このタイプは、非常に高い致死性をもつが、発生は稀である。もう一つは、京から伝播するタイプの疫病で、比較的致死性は低いが、頻繁に発生し、京から徒歩一〇日圏内からやや西に偏る範囲に伝播する。両タイプとも、飢饉の結果として発生するだけでなく、さらなる飢饉の誘因ともなった。奈良時代以前の疫病は、大きな被害を被った場合でも、一定期間内に復興が見込めたが、平安時代の最初期、復興に遅延が生じるようになった結果、疫癘間発という疫病の連鎖が発生し、律令国家の掌握する人口と田地に大きな損害を与えた。According to William H. McNeil the determining factor separating the rulers and the ruled is the gap in their level ofimmunity to pestilence or epidemics. This gap is the product ofthe discrepancies between the population and the degree ofits contact with outsiders. It has been claimed that because there was little contact with the outside world in ancient Japan, immunity to pestilence was weak and the society was subject to severe outbreaks ofharmf ul pestilence. Certainly, it is true that the view that invasive pestilence originated from abroad was deeply rooted in Japan, and religious rites were developed to protect the capital from disease. In addition, it is highly likely that the epidemics that struck in Tenpyô 7 and 9 (735 and 737) did spread from abroad, and were responsible for a remarkable level of harm seldom seen in the history ofepidemics in Japan. However, it was generally the case that epidemics in ancient Japan were centered instead on the capital and spread from there. The area within tendays ofwalking from the capital (however tending toward the west) was the typical target area. And in addition, when an epidemic struck, areas within the capital with the greatest population density were severely struck, and the Kinki region around the capital was struck next. Generally speaking, it has often been the case that outbreaks of an epidemic are triggered by lowered levels ofresistance due to famine, but in the case of ancient Japan, it was frequently the case that famine brought on epidemic instead. Because ancient Japan operated on the principles ofan agricultural society, paddy land where rice could be grown was invested with the greatest share oflabor, and when a labor shortage was caused by an epidemic, the paddies were left to ruin and further famine and epidemic ensued. In ancient Japan the harmful effects of famine and epidemics were closely linked. Even so, after the outbreak of an epidemic during the years roughly corresponding to the Nara period, the fixed level of the population was usually maintained after recovery was achieved. Some theories suppose that a great population increase occurred in the meantime However, from the beginning of the 9th century, there was a slowdown in the recovery rate following the outbreak of an epidemic. Even in the years ofabundant crops recovery from epidemics continued to be incomplete. In the 30 years before and after the turn of the century outbreaks of pestilence struck frequently throughout Japan and there was no stopping the series of famines and epidemics. As a result, population decline and ruined fields greatly increased. Because the populace and paddy lands were the fundamental capital for the ritsuryo-governed state ofancient Japan, one can say that the very foundations of the ritsuryo state itselfwere being undermined by the frequent outbreak of epidemics. Furthermore, as ifoperating in concert with these, in the first halfofthe 9th century, it was often the case that local officials did not provide accurate reports ofthe outbreaks ofthese epidemics. In order to reduce the amount of tax collected by the central government, local officials would attempt to over-estimate the damage caused by an epidemic. The central government at first tried to strictly restrain this tactic, but by the middle of the 9th century it had lost its fervor to police local officials. The rise ofthe risk ofepidemic due the concentration ofthe populace shook the foundations of the society but also had the effect of increasing mobility. As the McNeil model views regions with concentrated populations with many interactions as naturally dominant, it is an argument characterized by anticipated harmony, but given concentrated disturbance of the dominant area by epidemics, it is necessary to reevaluate the historical significance possessed by pestilence.