Atsushi Rokutanda

Nonmetric tooth crown traits in the ami tribe, taiwan aborigines: comparisons with other east asian populations

The frequencies of occurrence of 17 tooth crown traits in the living Ami tribe, which inhabits the east coast of Taiwan, were investigated and compared with other East Asian populations based on Turners (1987) Mongoloid dental variation theory. Principal coordinate analysis based on Smiths mean measure of divergence using frequencies of the 17 traits suggests that the Ami tribe together with the Yami tribe and the Bunun tribe is included in the sinodont group typical of the Chinese mainland and northeast Asia. In light of these results and the estimated distribution of sinodonty and sundadonty in the past and the present, we speculate that the gene flow from Chinese mainlanders to native sundadonts, who seem to have migrated northward to Taiwan, contributed significantly to the formation of the living Taiwan aboriginal groups, sinodonts. Among the aboriginal tribes of Taiwan, the Ami have characteristics intermediate between those of the Yami and the Bunun. The relative positions of these tribes in East Asian populations suggests that the extent of sinodontification and of genetic isolation is one of the causes of the intertribal variation.

Non-metric tooth crown traits of the Thai, Aka and Yao tribes of Northern Thailand

A survey was made of Thai tribe members, who cultivate rice paddies in the flatlands of northern Thailand, and of the Aka and Yao tribes, who farm with the slash-and-burn method in a mountainous region of northern Thailand. Plaster casts of the upper and lower jaws of tribe members were taken. Seventeen non-metric traits of their tooth crowns were classified and compared with other Mongoloid populations in various regions and periods. It was observed that the Thai tribe had the Sundadont characteristics, typical of South-East Asians, but the Aka and Yao tribe had more Sinodont than Sundadont characteristics, typical of North-East Asians. The regional and temporal variations of crown morphology in South-East Asia suggest earlier setting of the Thai tribe than the Aka and Yao tribes in this region. Moreover, comparison of the tooth morphological and linguistic classifications contradicts the traditional theory of the genealogy of the Thai language family. On the subject of the origin of modern South-East Asians, it is suggested that there has not been a gene flow of Sinodonty into Sundadonty of the principal ethnic groups in Neolithic South-East Asia.

Morphological and anthropological aspects of human triangular deciduous lower first molar teeth

The crown and root morphology, and bilateral occurrence of human deciduous lower first molars that exhibited a triangular occlusal outline, taken from excavated samples of Japanese, Jomonese and Iraqi origin, were investigated. The crowns of triangular teeth had smaller mesiodistal and larger buccolingual diameters than normally shaped deciduous lower first molars. An elongated buccolingual diameter was derived from the buccal projection of the distobuccal cusp and lingual projection of the portion between the metaconid and distolingual cusp. In this analysis, all triangular deciduous lower first molars in which root morphology could be observed were accompanied by additional distolingual roots. Correlation between the right- and left-hand sides of this trait was high.

Mitochondrial DNA analysis of Yayoi period human skeletal remains from the Doigahama site

We analyzed the mitochondrial DNA extracted from 14 human skeletal remains from the Doigahama site in Japan to clarify the genetic structure of the Doigahama Yayoi population and the relationship between burial style and kinship among individuals. The sequence types obtained in this study were compared with those of the modern Japanese, northern Kyushu Yayoi and ancient Chinese populations. We found that the northern Kyushu Yayoi populations belonged to the groups that include most of the modern Japanese population. In contrast, most of the Doigahama Yayoi population belonged to the group that includes a small number of the modern Japanese population. These results suggest that the Doigahama Yayoi population might have contributed less to the formation of the modern Japanese population than the northern Kyushu Yayoi populations. Moreover, when we examined the kinship between individuals in the Doigahama site, we found that the vicinal burial of adult skeletons indicated a maternal kinship, although that of juvenile skeletons did not. The vicinal burial style might have been influenced by many factors, such as paternal lineages, periods and geographical regions, as well as maternal lineages. In addition, skeletons considered to be those of shamans or leaders had the same sequence types. Their crucial social roles may have been inherited through maternal lineage.