Temporal and genealogical variation of human tooth root number in Japanese archipelago and its peripheral regions

2022 Fiscal Year Final Research Report

• Project/Area Number: 16K07536
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Physical anthropology
• Research Institution: Nagasaki University
• Principal Investigator: Manabe Yoshitaka 長崎大学, 医歯薬学総合研究科(歯学系), 名誉教授 (80131887)
• Co-Investigator(Kenkyū-buntansha): 小山田 常一 長崎大学, 医歯薬学総合研究科(歯学系), 准教授 (00244070) ; 西 啓太 長崎大学, 医歯薬学総合研究科(歯学系), 助教 (60823292)
• Project Period (FY): 2016-04-01 – 2023-03-31
• Keywords: 歯根数 / 時代的変異 / 地域的変異 / 非計測的形質 / 系統間変異 / 小進化 / 歯根融合傾向 / 歯根退化の方向性

Outline of Final Research Achievements

In order to clarify the morphological variation of human tooth roots, temporal and regional variations in the number of tooth roots over approximately 10,000 years from the Jomon period, the Yayoi period, the Kofun period, the medieval period, the early modern period to the modern period in various region of the Japanese archipelago were investigated and analyzed.
There was clear inter-lineage variation in molar root numbers between native and immigrant populations in the Japanese archipelago.
In addition, regarding the temporal variation in each lineage, the temporal fusion of the tooth roots of the maxillary and mandibular molars in the immigrant populations from the Yayoi period to the modern period among past over the past 2,500 years, were recognized. It was speculated that the molar roots of modern Japanese will tend to fuse more strongly in the future, and the number of molar roots will decrease with the times.

Free Research Field

歯の人類学

Academic Significance and Societal Importance of the Research Achievements

本研究におけるヒトの歯根数の時代的変異かつ地域的変異に関する総括的研究は，形質人類学の分野において集団間の系統関係の分析における歯の形態学的特徴の有用性を示すものであり，歯の形態変異をもとに集団の系統関係を探ることが可能であることを示すものである。また過去2500年間の日本列島人の歯根の退化融合傾向が明らかになったことにより，現代日本人の歯根形態の進化の方向性とその変化速度の推移を推定することが可能となったことから，顎顔面領域の進化の観点から歯科医療分野の将来にも大きく貢献できるものと考えられる。