Size does matter: Variation in tooth size apportionment among major regional North and sub-Saharan African populations

Abstract

In the 1980s Edward Harris proposed an approach using principal components analysis to compare mesiodistal and buccolingual crown diameters in humans. A major goal was to remove overall "size" from the measurements - which is ineffective for biological affinity. Relative size, however, is important, i.e., to assess how it is apportioned along the tooth rows. To get at such data, Harris utilized three size predictors in multiple linear regression to calculate PC 1 residuals, which were then used with other uncorrected components in analysis.
Here we demonstrate that it is still an effective method, by comparing 32 MD and BL measurements in 12 (n=712) and 18 (n=1251) samples from sub-Saharan and North Africa. Plotting of the first three components (50% of variance) shows clear separation between regions. North Africans are characterized by: 1) small LI1s, and BL dimensions of the UM1, LI2, and LM1, and 2) large MD diameters of the UM2 and LM1, and BL diameters of the LM2 and LM3. Comparisons of North Africans only show the ability to distinguish among samples from the Maghreb, Egypt, and Nubia. In other words, basic crown diameters can be successfully used for affinity estimation, if relative size, a.k.a., "shape" is accounted for.