Genotyping of urinary JC virus (JCV) DNAs is a useful means of elucidating the origin of ethnic populations. We previously reported JCV genotypes in eastern China and Mongolia. To gain a comprehensive picture of JCV genotypes in China, we collected urine samples at three northwestern sites along the Silk Road: X'ian, Lanzhou and Urumqi. DNA was extracted from urine samples, and used to amplify the 610-base-pair region (IG region) of the viral genome. For each geographical site, we determined 16 to 24 IG sequences, from which a neighbor-joining phylogenetic tree was constructed to classify detected JCV isolates into distinct genotypes. (1) The northeastern-Asian genotype (CY) was mainly detected at X'ian and Lanzhou. This finding suggested that these two sites were colonized mainly by northeastern Asians. (2) The northeastern-Asian (CY) and central/western-Asian genotype (B1-b) were mainly detected at Urumqi. This suggested that Urumqi was colonized by both northeastern and central Asians. (3) In addition, several minor JCV genotypes were detected at these sites. These included a genotype (B1-c) prevalent in Europe and western Asia and a genotype (Af2) prevalent in Africa and western Asia. Significant admixture of human populations may have occurred in areas along the Silk Road that was used in ancient times to transport goods between China and Europe.
We performed metrical studies of the mandibular crown components of molar teeth in Japanese. Materials used were 140 dental plaster casts (75 males and 65 females). The mandibular first and second molars (M1 and M2) were measured using sliding calipers. Sex differences were greater in the talonid dimensions than in the trigonid dimensions, and were greater in M2 than in M1. Those of the molar reduction were also noted in the talonid dimensions. Although the trigonid mesiodistal diameter was significantly larger in M2 than in M1 (P<0.01), the talonid dimensions were significantly larger in M1 than in M2 (P<0.01). The variability of the crown dimensions was higher in M2 than in M1, especially in the talonid dimensions. This result related to the fact that the talonid developed later than the trigonid in both ontogeny and phylogeny. Allometric relationships between the trigonid or talonid component to total crown size showed that males had negative allometry in the trigonid and positive allometry in the talonid, while females showed isometry in both crown components. These results indicated that the talonid was more variable under the influence of the total size variation, and related to sex difference in tooth size.
The basal tubercle and its related traits on the basal part of the lingual surface of maxillary central incisors vary in developmental grades. Although a well-developed basal tubercle was observed in fossil humans, much attention to this trait has not been paid in modern humans. We compared five morphological traits on the lingual surface of maxillary incisors among seven Pacific populations. Results showed that the South-Pacific populations examined in this study especially Fijians and New Guinea Highlanders had a well-developed basal tubercle, but with a low frequency of shovel-shaped incisors. On the contrary, Japanese and Kiribatian populations of this study had a high frequency of shovel-shaped incisors, but a low frequency of tubercle-shaped incisors. It was suggested that the basal tubercle is one of the key dental traits in characterizing Pacific populations.
Dental arch sizes and shapes of Papua New Guinea (PNG) Highlanders (Wabag, Enga Province, 26 males and 26 females) were measured using photographs of dental casts and compared with those of five populations in the Pacific region (Fiji, Samoa, Kiribati, Australia, Japan). The dental arch breadths of the Wabag males and females were the largest among the six groups. The Wabag males had the shortest lengths and the Wabag females were in the middle range among the six groups. As a result, the dental arches of the Wabag people proved to be short and broad. Principal component analyses based on arch measurements showed that the Wabag people were close to Fijians suggesting that these two Melanesian populations had similar dental arch forms.