著者

高橋 遼平 タカハシ リョウヘイ Ryohei TAKAHASHI

出版者

総合研究大学院大学

巻号頁・発行日

2012-09-28

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現在の琉球列島の食文化に家畜ブタは必要不可欠な存在だが、その起源は不明瞭である。文献史実では琉球列島への最古の家畜ブタ導入は14世紀頃とされ、それ以前は琉球列島に固有の野生イノシシであるリュウキュウイノシシが狩猟されていたと考えられてきた。しかし近年では琉球列島や周辺地域を対象とした考古学・動物考古学研究から、12世紀以前の先史時代にイノシシ・もしくは家畜ブタ(以下Sus属と省略)が外部諸地域から導入されていた可能性が指摘されている。本論文では先史時代の琉球列島へ外部地域からSus属が導入された時期や地域・経路を解明するため、琉球列島の現生及び先史時代遺跡から出土したSus属の歯や骨を用いて形態解析とancient DNA (aDNA) 解析を行った。本論文は全6章から構成される。第1章では家畜ブタや様々な家畜動物の起源や拡散に関する動物考古学研究や分子系統学研究を概観した。また本章では琉球列島の形成史や先史時代文化に関する研究も概観した。第2章には解析に使用した遺跡資料と現生資料、そして解析手法を記載した。琉球列島は地質学・考古学的に北部圏、中部圏、南部圏の3つに区分される。本論文ではこれらのうち中部圏と南部圏の先史時代遺跡から出土した資料を解析した。さらに本論文では現生リュウキュウイノシシの遺伝的変異の程度を確認するため、現生個体のmtDNA D-loop領域を解析した。第3章では沖縄本島の野国貝塚群(約7200 - 4400年前)を含む中部圏の遺跡から出土したSus属の歯や骨を用いて形態・aDNA解析を行った。野国貝塚群から出土した下顎第三臼歯 (M3) の計測値を現生リュウキュウイノシシや沖縄諸島の他の遺跡資料(約4800 - 1400年前)と比較した結果、野国貝塚群から出土したSus属のM3のサイズ分布は、現生リュウキュウイノシシや他の遺跡資料とは異なり小さい事が判明した。また野国貝塚群から出土した下顎骨から得られたmtDNA D-loop領域の塩基配列情報をデータベースから取得した世界のSus属と比較した結果、野国貝塚群から現生リュウキュウイノシシと遺伝的に異なる系統に属するSus属の配列タイプを検出した。第4章では琉球列島南部圏に属する石垣島の大田原遺跡(約4100 - 3800年前)と神田貝塚(約1600 - 900年前)、宮古島のアラフ遺跡(約2800 - 800年前)と長墓遺跡(約1900 - 1400年前)から出土したSus属の骨を用いてaDNA解析を実施した。この結果石垣島の遺跡から出土したSus属は全て現生リュウキュウイノシシと遺伝的に近縁であった。一方宮古島のアラフ遺跡と長墓遺跡からは、現生リュウキュウイノシシと遺伝的に異なる系統に属する個体が検出された。第5章では現生リュウキュウイノシシの遺伝的変異の程度を検討した。リュウキュウイノシシの生息する全7島のうち6島由来の113個体を用いたmtDNA解析の結果、これらは全て遺伝的に近縁であり、他のアジアのSus属系統と近縁な配列タイプは現生集団から検出されなかった。第6章では研究結果をまとめ、先史時代の琉球列島を舞台としたSus属の導入について考察した。琉球列島中部圏では約7200 - 4400年前、南部圏でも約2000年前に琉球列島の野生イノシシであるリュウキュウイノシシとは形態・遺伝的に異なる特徴を持つSus属が存在した事が判明した。この結果から1) 先史時代の琉球列島には遺伝的に異なる野生イノシシが複数系統存在した、2) 先史時代の琉球列島へ人類が近隣地域からSus属を導入していた、という2仮説が考えられた。しかし仮説1で示すように先史時代の琉球列島に複数の野生イノシシ系統が混在していた場合、a) 現在は生息地域ごとに異なるイノシシ系統が生き残っている可能性が高いが、113個体の現生リュウキュウイノシシを解析しても遺伝的に異なる系統は確認されなかった。b) また複数のイノシシ系統は、アジア大陸と琉球列島が地続きであった可能性のある約8万年前より古い時期に渡来し、遺跡が形成された時期まで多型を維持していた事になる。しかしシミュレーションによる推定の結果、複数のイノシシ系統がどちらか1系統に固定する事なく約7万5000年間維持される確率は低い(1%以下)。従って本研究では琉球列島にかつて複数系統の野生イノシシがいたという仮説1は支持されなかった。以上の結果から本研究では、先史時代の琉球列島やその周辺地域でSus属を伴う人類の移動が生じていたという仮説2が支持された。野国貝塚群が属する琉球列島中部圏とアラフ遺跡や長墓遺跡が属する南部圏の間では物質文化交流が12世紀頃まで生じていなかったとされるため、中部圏と南部圏では異なるSus属の導入経路があったと考えられる。先史時代の琉球列島中部圏は考古学的に九州との交流が指摘されている。しかし野国貝塚群から出土したSus属は、九州等のニホンイノシシやアジア大陸の野生イノシシよりも小さいM3を持つうえ、リュウキュウイノシシよりもさらに小型であるため、これらの地域の野生イノシシが直接導入されたとは考えにくい。野国貝塚群のSus属は、家畜化の影響を受けて M3が矮小化していた可能性も考えられる。アラフ遺跡や長墓遺跡が属する琉球列島南部圏の先史時代文化は、フィリピンやミクロネシア等を含む海外諸地域に影響されていた可能性がある。島嶼部東南アジアやオセアニアでは、約3300年前以降に人類が家畜ブタを伴って移動や交流をしていた事が知られているため、琉球列島南部圏のSus属の導入はこれらの先史時代人類の移動や交流による可能性も考えられる。 本論文では先史時代の琉球列島に複数のSus属の導入経路が存在した可能性を示した。また本研究成果は先史時代の東アジアや東南アジア、オセアニアにおけるSus属を伴う人類の移動や交流に琉球列島が含まれていた可能性をも示している。 Although domestic pigs play an important role in traditional food resources in the Ryukyu Islands, southern Japan, the origin of domestic pigs in the Ryukyu Islands is not clear yet. From historical evidence, the oldest date for the introduction of domestic pigs to the Ryukyu Islands was in the 14th century AD. It has been believed that there were no domestic pigs in Ryukyu before this introduction (earlier than 14th century AD), rather people hunted Ryukyu wild boar, one of the subspecies of wild boar that inhabits the Ryukyu Islands. Recent archaeological and zooarchaeological studies in the Ryukyu Islands and surrounding areas, however, suggest that there is a possibility that wild boar or domestic pigs (Sus) may have been introduced to the Ryukyu Islands in the prehistoric times, which is earlier than the 12th century AD according to archaeological chronology. In this thesis, I analyzed tooth samples and ancient DNA (aDNA) derived from bone of Sus excavated from prehistoric sites in the Ryukyu Islands as well as the modern Ryukyu wild boar samples, and investigated morphologically and molecular phylogenetically whether external introduction of Sus into the Ryukyu Islands took place during prehistoric times.This thesis consists of six chapters.Chapter one describes previous archaeological and molecular phylogenetic studies concerning the origin and dispersal over the world of various domestic animals including domestic pigs. In this chapter, I also reviewed previous studies on the formation of the Ryukyu Islands as well as prehistoric culture of the Ryukyu.Chapter two describes archaeological and modern samples, and methods of analyses used in this thesis. Based on geological and archaeological knowledge, the Ryukyu Islands can be divided into three cultural regions, North, Central, and South regions. Of these three cultural regions, for the following analyses, I used archaeological samples from prehistoric sites in Central and South cultural regions. Furthermore, nucleotide sequences of mtDNA D-loop region of modern Ryukyu wild boar were determined to investigate the extent of genetic variation among present population of Ryukyu wild boar.In Chapter three, I analyzed morphological and molecular phylogenetic characteristics of Sus tooth samples and aDNA from bones excavated from the sites in Central region, including Noguni shell middens (ca.7200 - 4400 years ago) on Okinawa main Island. Measurements of lower third molars from Noguni shell middens were compared with those of Sus remains from later sites in the Okinawa Islands (ca.4800 - 1400 years ago) as well as modern Ryukyu wild boar. Based on measurements of lower third molars, Sus samples from the Noguni shell middens were distinctly smaller than those from modern Ryukyu wild boar and other ancient sites in the Okinawa Islands. In addition to morphological analysis, nucleotide sequences of ancient mtDNA D-loop region from mandibles of the Noguni shell middens were compared with those of Sus in other parts of the world collected from a database. Phylogenetic analysis using aDNA sequence types showed that some sequence types from the Noguni shell middens made a different cluster from modern Ryukyu wild boar, suggesting a presence of the different genetic Sus lineage from modern Ryukyu wild boar at that time.In Chapter four, aDNA analysis was carried out by using Sus bone samples excavated from Ohtabaru site (ca.4100 - 3800 years ago) and Kanda shell midden (ca.1600 - 900 years ago) in Ishigaki Island, Arafu site (ca.2800 - 800 years ago) and Nagabaka site (ca.1900 - 1400 years ago) in Miyako Island, which belonged to South cultural region. All aDNA sequence types from prehistoric sites in Ishigaki Island were genetically close or identical to those of modern Ryukyu wild boar. However, sequence types from Arafu site and Nagabaka site were in different lineages from modern Ryukyu wild boar but had rather close relationship to other Asian Sus lineages: the similar situation was observed as in Noguni samples.In Chapter five, I investigated the extent of genetic variation among present population of Ryukyu wild boar to find out whether the different lineage detected from ancient samples still exist among the present populations. Ryukyu wild boar inhabits seven islands in the Ryukyu Islands. Phylogenetic studies based on the mtDNA analysis of 113 Individuals from six of the seven islands show all individuals are genetically close to each other, and no sequence type is either identical or similar to other Asian Sus lineages. Chapter six discusses the possibility of the external introduction of Sus into the prehistoric Ryukyu Islands. In the present study, some Sus samples from prehistoric sites in the Central (ca.7200 - 800 years ago) and South cultural regions (ca.2000 years ago) had different morphological / genetic characteristics from modern Ryukyu wild boar. Concerning the origin of these Sus population from the prehistoric sites in Ryukyu, I propose two possible hypotheses: first, there were at least two genetic lineages of wild boar inhabited the prehistoric Ryukyu Islands; second, introduction of Sus to the Ryukyu Islands by human took place during prehistoric times. I distinguish these hypotheses as follows.In the case of former hypothesis, a) It is very likely that some surviving population has different genetic characteristic from those of other habitats (islands). However, multiple lineages of wild boar were not found in 113 individuals from present populations. b) Furthermore, if multiple lineages of wild boar really existed in the prehistoric Ryukyu Islands, they must have migrated from Asian Continent to Ryukyu at the time when land bridge connected these regions, which is earlier than 80,000 years ago. Based on estimation using simulation, probability for coexistence of multiple Sus lineages for the period of 75,000 years was calculated and it reveals to be lower than 1%. These results indicate that it is unlikely that multiple lineages of wild boar coexisted in the prehistoric Ryukyu Islands. Thus, the latter hypothesis that prehistoric introduction of Sus into the Ryukyu Islands by human was supported by my study. It has been suggested that the South cultural region had no archaeological links with North and Central regions until historic time, ca. 12th century AD. This archaeological evidence infers a possibility of more than one introduction pathways of Sus from outside of the Ryukyu directly to the Central or South Cultural regions during prehistoric times. In the case of Noguni shell middens, some cultural factors of prehistoric Central regions were considered to be related to Jomon culture in Kyushu. This archaeological evidence suggests that Sus population was introduced from main land Japan or from the Asian Continent via Kyushu region. In this case the transported Sus cannot be hunted wild boar because the size of wild boar in both mainland Japan and Asian Continent is much larger than those of Noguni shell middens. There is a possibility that lower third molars of Sus from Noguni shell middens were reduced in size as the consequence of domestication. In contrast, prehistoric culture of South cultural region including Arafu and Nagabaka sites were considered to be related to those of Island Southeast Asia such as the Philippines as well as Micronesia. Since it is revealed that prehistoric human dispersal and peopling in Island Southeast Asia and Oceania was accompanied by domestic pigs and other animals, introduction of Sus population to South cultural region of Ryukyu might be involved in such prehistoric interaction of humans. In this thesis I conclude multiple pathways of Sus introduction to the Ryukyu Islands existed during prehistoric times. Furthermore, present study indicates the possibility that cultural interaction and movement of prehistoric human took place between the Ryukyu Islands and surrounding areas, accompanied by Sus.

著者

Kanji MIYABE Ryohei TAKAHASHI Youki SHIMAZAKI

出版者

(社)日本分析化学会

雑誌

Analytical Sciences (ISSN:09106340)

巻号頁・発行日

vol.31, no.10, pp.1019-1025, 2015-10-10 (Released:2015-10-10)

参考文献数

40

被引用文献数

3 18

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We developed moment analysis of affinity kinetics by chromatographic capillary electrophoresis (MKCCE) method for the kinetic study of intermolecular interactions. Association and dissociation rate constants of the interaction in a micellar electrokinetic chromatography (MEKC) system between thymol and sodium dodecylsulfate micelle were determined by the MKCCE method. It is a method based on the moment theory for the kinetic study of intermolecular interactions under the conditions that neither immobilization nor chemical modification of molecules is required. In CCE mode, experimental conditions are controlled so that the migration of solute-micelle complex is stopped and only solute molecules migrate in a capillary. Mass transfer behavior of solute molecules in the CCE system is analogous to that in a chromatographic system. However, because it was difficult in practice to really perform CE experiments under the CCE conditions, CE data were measured with changing experimental conditions, i.e., applied pressure, under the conditions that the migration velocity of solute-micelle complex was around zero. The rate constants could be analytically determined from the CE data. In the MKCCE method, it is not necessary to fit elution curves numerically calculated to those experimentally measured for the determination of the rate constants. Regarding the interaction between thymol and SDS micelles, association equilibrium constant and association and dissociation rate constants were determined as 6.35 × 103 dm3 mol−1, 5.6 × 104 dm3 mol−1 s−1, and 8.7 s−1, respectively. It was demonstrated that the MKCCE method was effective for the kinetic study of intermolecular interactions.