REGIONAL VARIATIONS IN THE RYUKYU ISLANDERS ON TOOTH CROWN TRAITS

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A genealogical positioning of the Okinawa main land, Miyakojima and Ishigakijima populations in East Asia and Japan was carried out by using metrical and 17 nonmetric tooth crown traits. Dental plaster casts were collected from teen-aged modern inhabitants of the Okinawa main land, Miyakojima and Ishigakijima of the Ryukyu islands.The dentition of the Ryukyu islanders were metrically examined in terms of inter island variation and biological population affinity. Measurements were taken of the tooth crown diameter of the inhabitants in Miyakojima and Ishigakijima and compared with those of another region. Mesiodistal and labio(bucco)lingual crown diameters of all anterior teeth in Miyakojima and Ishigakijima were smaller than in Okinawa. The crown diameters of all teeth in Ishigakijima were smaller than in Miyakojima.The upper and lower first molars are the largest and the most stable teeth in the mesiodistal and bucculingual crown diameters and crown area, while the upper second premol … More ar and the lower first premolar the smallest on the Miyakojima and the Ishigakijima populations. The upper and lower second premolars are proportionately the largest teeth in the crown index. The buccolingual crown diameter and crown area were larger for male than female, showing significant sex difference, premolars and molars except upper second molar, on the Miyakojima, and upper first premolar, upper second molar, lower first and second molars on the Ishigakijima populations.In Ryukyu islands, tooth sizes were correlated with geographical locations. But when compared with posterior region the sizes of Miyakojima and Ishigakijima were geographically correlated, and another not. Metrical dental characters of the Miyakojima and Ishigakijima populations were compared with these from the others. The Miyakojima populations show close affinities to the Tanegashima and Yayoi populations, and the Ishigakijima similar to the Ainu and Jomon populations.Incidences of 17 nonmetric tooth crown traits were investigated on dental plaster casts which collected from teen-age modern inhabitants of the Okinawa main land and Ishigaki island of the Ryukyu islands. The incidences of the Okinawa main land and Ishigaki islands were compared with other 11 Japanese populations and other 35 Asian-derived populations. In East Asian populations, Okinawa main land and Ishigakiisland had intermediate characters between the northeast Asian(Sinodonty)and the Southeast Asian(Sundadonty). In the Japanese populations, three Ryukyu islands were overwhelmingly similar to the migrant group(Yayoi period in north Kyusyu, the Jomon period, and the modern Hokkaido Ainu). However, the residence of Sundadonty such as Jomonese in Tanegashima on of the Yayoi period suggests a residence of Sundadonty in past Ryukyu islands and late migration on Sinodonty to Ryukyu islands. In modern Ryukyu poppulations, the Ishigaki and the Okinawa main islanders show affinities to the Yayoi period in north Kyusyu and the modern Tanegashima populations, and largely differ from the modern Hokkaido Ainu, the Jomon period and the Yayoi period in Tanegasima.Some amount of cline from north to south in the Ryukyu islands might indicate the gene flow of Sinodonty from the northward. The dental evidences shown in this study may contribute to the establishment of biological relationships between Miyakojima and Ishigakijima populations. Less