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Molar enamel thickness in the chacma baboon, Papio ursinus (Kerr 1792)
F E Grine1, M A Spencer, B Demes
1Department of Anthropology, Stony Brook University, Stony Brook, New York 11794, USA. fgrine@notes.cc.sunysb.edu
American Journal of Physical Anthropology
|July 19, 2005
Summary
Human molars show thicker enamel on later teeth, but this study in baboons suggests it
Area of Science:
- Primate dental morphology
- Paleoanthropology
- Biomechanics
Background:
- Modern humans display increasing relative enamel thickness from M1 to M3.
- Functional hypotheses link this gradient to increased occlusal forces on distal molars.
- Alternative explanations suggest enamel thickness relates to crown size reduction.
Purpose of the Study:
- To test the functional hypothesis of bite force by examining relative enamel thickness in baboons (Papio ursinus).
- To investigate the relationship between molar size and enamel thickness in a species with increasing M1-M3 crown size.
- To assess the implications for interpreting molar enamel thickness in hominin evolution.
Main Methods:
- Comparative analysis of relative enamel thickness across the molar row (M1-M3) in Papio ursinus.
- Measurement of enamel thickness relative to crown size.
- Evaluation of biomechanical factors, including temporomandibular joint position and muscle force potential.
Main Results:
- No significant difference in relative enamel thickness was found along the molar row in Papio ursinus.
- This contrasts with the distalward gradient observed in modern humans.
- Baboons, despite having a different bite force potential, do not show a similar enamel thickness gradient.
Conclusions:
- The findings support the hypothesis that increased enamel thickness in human distal molars is primarily a consequence of crown size reduction, not functional demands related to bite force.
- This suggests that the thicker enamel of distal molars in humans and fossil relatives may not be a homologous trait driven by the same developmental processes.
- Reinterpretations of dental enamel thickness in phylogenetic analyses may be necessary, considering potential differences in developmental origins.
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