Morphological variation of major human populations based on nonmetric dental traits.

The patterns of inter- and intra-regional variation among 12 major geographical groups from around the world were investigated based on 15 nonmetric dental traits. The R-matrix method was applied using a pooled within-group variance-covariance matrix estimated with the maximum likelihood method (tetrachoric correlation matrix) and the threshold value for each trait estimated by univariate probit analysis. Using average heritability rates that range from 0.40 to 1.00, the inter-regional variation represented by Fst falls between 7.19% and 16.23% of the total variance. This range of variation is compatible with those obtained by genetic, craniometric, and odontometric data. Subsaharan Africans show the largest intra-regional diversity among the groups compared. The degree of intra-regional variation shows, moreover, rough clinalities from subsaharan Africa to peripheral regions. The relationship between regional variation and geographic distance from subsaharan Africa supports serial bottlenecks and the founder effect of ancient populations originating in Africa. The variation of East/Northeast Asians is relatively large, suggesting a complex population history such as possible earlier divergence and multiple migrations from outside sources. The present findings are in agreement with both the recent African model for the origin of anatomically modern humans and the current scenario for human migration history suggested by genetic analyses.