中国ナシ(納西)族の歯冠形態の特徴 : 東アジア民族集団との比較

Abstract

The purpose of this study is to assess what might be diagnostic of the Naxi dental characteristics and to demonstrate the ethnic relationships of the Naxi among Asian populations. Plaster models were taken from 80 male and 80 female students, 16 to 19 years of age, of the Naxi tribe middle high school in Lijiang, Yunann, China. Nineteen nonmetrical traits of tooth crown were classified using the Arizona State University Dental Anthropological System and counted with the individual count method. The frequencies of 19 traits in the Naxi were compared with those of 24 East Asian populations. Nine crown traits that indicated high frequencies were UI1 Shoveling, UI1 Double-shovel, UC Canine medical ridge, LP2 Premolar lingual cusp variation, U and L1,2 Odontome, LM1 Deflecting wrinkle, LM1 Protostylid, LM1 Cusp5 and LM2 4-Cusp. Those showing low frequencies were UI1^2 Winging, UI2 Interruption groove, UC Tuberculum dentale, UC Canine distal accessory ridge, UM1 Cusp 5, UM1 Carabelli's trait, LM1 Distal trigonid crest, LM1 Cusp 6 and LM2 Y groove pattern. On comparing the eight crown traits that indicated significant differences between Sinodonts which is typical of Northeast Asia, and Sundadonts which is typical of Southeast Asia, the Naxi tribe had three Sinodont-like traits: Double-shovel, Cusp 5 and Y groove pattern, and four Sundadont-like traits: Winging, Shoveling, Deflecting wrinkle and 4-Cusp. Two major clusters were found by cluster analysis on Ward method among the 25 East Asia populations including the Naxi tribe, based on the 19 crown traits. The one macro-cluster contains all northern peoples and Naxi (Sinodonts), and the other all Southeast Asia and Jomon (Sundadonts). The Sinodonty cluster was divided into two subclusters, one was the Han, Japanese and the south China group, and the other the Chaoxian, the Man and the Da furs group including the Naxi. The multidimentional scaling analysis showed that the Naxi tribe was distant from the Sundadonts and closed to the Dufurs, the Chaoxian, the Man and the Yami. The Naxi tribe showed affinities, in terms of nonmetric crown traits, with Northeast Asians rather than with Southeast Asians. The Naxi tribe was the closest to the Da furs among the populations compared here.