Three-dimensional molar enamel distribution and thickness in Australopithecus and Paranthropus |
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Authors: | Olejniczak A J Smith T M Skinner M M Grine F E Feeney R N M Thackeray J F Hublin J-J |
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Institution: | Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany. olejniczak@eva.mpg.de |
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Abstract: | Thick molar enamel is among the few diagnostic characters of hominins which are measurable in fossil specimens. Despite a long history of study and characterization of Paranthropus molars as relatively 'hyper-thick', only a few tooth fragments and controlled planes of section (designed to be proxies of whole-crown thickness) have been measured. Here, we measure molar enamel thickness in Australopithecus africanus and Paranthropus robustus using accurate microtomographic methods, recording the whole-crown distribution of enamel. Both taxa have relatively thick enamel, but are thinner than previously characterized based on two-dimensional measurements. Three-dimensional measurements show that P. robustus enamel is not hyper-thick, and A. africanus enamel is relatively thinner than that of recent humans. Interspecific differences in the whole-crown distribution of enamel thickness influence cross-sectional measurements such that enamel thickness is exaggerated in two-dimensional sections of A. africanus and P. robustus molars. As such, two-dimensional enamel thickness measurements in australopiths are not reliable proxies for the three-dimensional data they are meant to represent. The three-dimensional distribution of enamel thickness shows different patterns among species, and is more useful for the interpretation of functional adaptations than single summary measures of enamel thickness. |
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Keywords: | hominin evolution microtomography enamel distribution |
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