Genetics of Tooth Size

This paper summarises the findings of a genetic study of tooth size in a group of Australian Aboriginals. Measurements were obtained from a total of 392 dental casts collected as part of a longitudinal growth study of Aboriginals living at Yuendumu, a settlement town in the Northern Territory of Australia. Family data were compiled from genealogical records gathered over a number of years. The custom of polygyny practised by the Yuendumu people enabled the analysis of associations between both full-siblings and half-siblings.

Similarities between related individuals were expressed in terms of correlation coefficients. Values of average correlations for both mesiodistal and buccolingual dimensions conformed with the theoretical correlations expected assuming autosomal polygenic inheritance. No evidence of sex chromosomal involvement was found. Heritability estimates for permanent tooth size were derived and the contribution of common environment to the observed phenotypic variability estimated. Results obtained from full-sibling, half-sibling and parent-offspring data suggested that approximately 50 to 60 per cent of the total variability of permanent tooth size could be attributed to additive genetic effects, while an additional 14 per cent was due to common environment.

Although the genetic contribution to tooth size variability is high, the findings have indicated that non-genetic factors also play an important role in the determination of this metric character.