[The dental morphology of the Polynesians in the Cook Islands].

Abstract

The inter-island variations and biological population affinity were examined for the Cook islanders in terms of non-parametric dental characters. The materials used in the present study consisted of plaster casts for 397 people, ages 4-20, collected on Rarotonga, Mangaia and Pukapuka in the Cook Islands. The dental characters observed were 15 traits on the teeth crown. The samples have been divided into five population series on the basis of their native islands: Pukapuka, N-S group (northern-southern island crossbreedings), Rarotonga, Mangaia, and S group (southern islands except Rarotonga and Mangaia). For comparison with other ethnic populations, the samples excluding the Pukapuka are combined into one group to represent full-blood southern-Cook Island Polynesians and named "Southern Cook" here. There were no significant sex differences in the incidences of dental traits in the data used in this study, so they were combined for the statistics. A cluster analysis was carried out to compare inter-population affinities on the basis of Smith's Mean Measure of Divergence (MMD) using the frequencies of shovelling, Carabelli's cusp, protostylid, cusp 6, cusp 7, and deflecting wrinkle. The results are briefly summarized as follows: 1. The differences between the Pukapukans and other four groups in the Cook Islands were observed in the case of 11 characters. Within the samples of the four island groups making up Southern Cook, there were no definitive population differences in dental morphology. The cluster analysis based on Smith's MMD values emerged as two main clusters in the Cook Islands: one cluster consisted only of the Pukapukans, and the other consisted of the rest. The latter was divided into two subclusters. 2. The frequencies of shovelling in the Southern Cook (23%) were quite similar at the medium level (S + S.S), to those in other Polynesian groups as well as in the Micronesian groups. The Pukapukans, however, gave a fairly low percentage (10%). 3. The two populations from the Southern Cook and Pukapuka were compared with other Oceanic populations. The incidences of double shovelling were similar to those of the Guamese, but lower than those of the Hawaiians. The Carabelli's cusp, protostylid and cusp 6 showed higher frequencies than those in the Hawaiians and Guamese. On the other hand, the interstitial tubercle showed a lower percentage than those in the Hawaiians and Guamese. As far as the incidence of the deflecting wrinkle are concerned, the Southern Cook, together with the Guamese, were intermediate between the Hawaiians and Pukapukans.(ABSTRACT TRUNCATED AT 400 WORDS)