種子島住民の歯の形質に関する人類学的研究

Abstract

A series of field survey were undertaken among the inhabitants of Tanegashima islanders of Kagoshima Prefecture to examine their teeth as to the possible manifestation of ethnological characteristics and of age changes. Since the geographical situation of this island has suggested the existence of close communication with neighboring islands such as Okinawa and Formosa, data obtained from these regions were compared with those of Tanegashima islanders. Chronological comparison was also made between the teeth of Tanegashima islanders and those of the remains of Yayoi era inhabitants excavated from Hirota site of the island by Yamada et al.. Measurement was conducted on 133 plaster models of upper and lower jaws taken from inhabitants of Minami-tanegashima-machi and macroscopic observation was done on the morphology of crown of respective tooth of jaws. Results were summarized as follows. 1) No appreciable difference was noticed with every values of mesurement among the Japanese subjects of this and other regions and there existed rather close similarities between Tanegashima inhabitants and the inhabitants of Kyushu region and aborigines of Formosa. 2) Occurrence of the shovel shaped teeth and double-shovel shaped teeth in anterior teeth and occurrence of the spinal process in the upper anterior teeth were respectively infrequent as compared to the Japanese of other regions, and development of the distal accessory-ridge found on the lingual surface of canine teeth was weaker in the inhabitants of Tanegashima than in the common Japanese. 3) With regard to the groove types in the occlusal surface of upper premolar teeth no particular difference was detected to exist between the present subjects and the Japanase subjects in Kyushu region. However, when comparison was made of the above traits with the remains of Yayoi era, certain retrogressive trend was apparent in the teeth of Tanegashima inhabitants. 4) The cuspal types and the occlusal groove types in the lower premolar teeth of Tanegashima islanders were generally similar to those found in the inhabitants of Kyushu region. Howevrer, comparison between Tanegashima islanders and Yayoi era remains revealed that the latter showed greater trend of first premolar to have bicuspid and greater trend of second premolar to have teicuspid. On the other hand, the groove types of occlusal surface in Tanegashima islanders showed stronger trend toward retrogression as compared to Yayoi era inhabitants. 5) The cuspal types found in the upper molars in Tanegashima inhabitants were almost similar to those found in the common Japanese, showing a greater trend toward retrogression compared to Yayoi era inhabitants. Occurrence of the upper second molar having mesiodistally compressed crown was more frequently seen in the inhabitants of Tanegashima than in the common Japanese, and this phenomenon showed an inverse correlation with the occurrence of cuspal types. 6) Although no significant difference in the physical traits of lower molars crowns existed between Tanegashima inhabitants and the common Japanese, occurrence of Dryopithecus pattern in both first and second molars was slightly more frequent in the former than in the latter, and in first molar the frequency of Dryopithecus pattern nearly equaled that in Yayoi inhabitants. 7) To sum up the whole data of present study, the physical traits of teeth in Tanegashima islanders were generally similar to those found in the Japanese of Kyushu region and its neighboring districts. Some regional deviation, however, existed with regard to several traits of tooth crown studied. Comparison between Tanegashima inhabitants and Yayoi era inhabitants further revealed certain chronological difference present with regard to some parts of these physical traits.