The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

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


1Department of Anthropology, University of Alaska Fairbanks, 22Research Centre in Evolutionary Anthropology and Palaeoecology, John Moores University

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Twenty years ago Edward Harris proposed a new approach using principal components analysis to compare mesiodistal and buccolingual crown diameters in humans. A major goal, like other researchers (e.g., Penrose), was to remove overall “size” from the measurements – which is ineffective for biological affinity and phylogenetic analyses. 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 overall size predictors in multiple linear regression to calculate PC 1 residuals; these, and other uncorrected components where then used in the analysis. The approach was subsequently used by many to quantify population differences at global to local in scale.

Tooth size apportionment analysis, like many quantitative methods, was “in style” before something else gained attention. Here we demonstrate that it is still effective, by comparing 32 MD and BL measurements in 12 (n=712) and 18 (n=1251) samples from sub-Saharan and North Africa, respectively. Plotting of the first three components (50% of variance) shows clear sample separation between regions. Relative to sub-Saharan samples, 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.

We thank Heather Edgar, Helen Liversidge, and Loren Lease for the invitation to this symposium in honor of Ed Harris. Thanks also go to everybody at the institutions from which JDI collected the odontometric data. Funding was provided to JDI by the National Science Foundation (BNS-0104731), Wenner-Gren Foundation (#7557), National Geographic Society (#8116-06), Institute for Bioarchaeology, ASU Research Development Program, Hierakonpolis Expedition, and American Museum of Natural History.

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