Date of Award
Doctor of Philosophy (PhD)
Characteristic patterns of dental wear form through the use of the dentition for non-masticatory manipulative behaviors. The use of “teeth-as-tools” or the dentition as a “third hand” for manipulative behaviors emphasizes the importance of the human dentition in our otherwise extrasomatic tool-kit. The extreme pattern of anterior dental wear found in many Neandertals, together with their large anterior teeth, has led researchers to suggest that the unique craniofacial morphology of Neandertals is the result of functional adaptation to the habitual use of the dentition for manipulative tasks. However, decades of research investigating the adaptive significance and biomechanical properties of Neandertal and modern human craniofacial morphology has not convincingly demonstrated whether non-masticatory behavior was a significant selective force during the Late Pleistocene. Studies addressing non-masticatory behavior among Late Pleistocene archaic and modern humans through the direct study of dental wear are equally equivocal in this regard. The few studies that have attempted to systematically quantify non-masticatory dental wear among Neandertals and early modern humans are constrained by different analytic methods that prevent cross-study comparisons, contain small early modern human samples, and/or differ in conclusion as to the implied patterning and magnitude of behavioral shifts in the Late Pleistocene.
The aims of this thesis are to address non-masticatory manipulative shifts in the Middle to Late Pleistocene through the analysis of non-masticatory dental wear using both macroscopic and microscopic techniques. Scaled macrowear gradients, enamel chipping, and instrumental cutmarks on labial tooth surfaces were documented to understand differences in degree, magnitude, and repetition of non-masticatory behaviors between morphologically and temporally partitioned groups of Middle and Late Pleistocene humans. Data from Middle and Late Pleistocene fossils are studied directly rather than using recent human groups as proxies for Pleistocene behavioral variation.
Changing technological, cultural, and socioeconomic organization during the Middle to Upper Paleolithic Transition is often used to explain craniodental structural reduction across the morphological transition from archaic to fully modern human morphology during the Late Pleistocene. The results of this thesis challenge this view by documenting a high degree of wear among both archaic and modern human groups in the Pleistocene. Archaic humans benefit from having large anterior dentitions to withstand a lifetime of anterior tooth-use, but there is little evidence from anatomy or dental wear to indicate that the forces exerted, or non-masticatory activities engaged in, differed greatly from those of early modern humans. Instead, a high degree of anterior versus posterior dental wear is characteristic of hunter-gatherers generally. Thus, explanations relying on technological innovation as a means of relaxing selection on the body/dentition for manipulative tasks fall short in this regard. Anterior dental reduction (and craniofacial reduction, generally) occurred despite evidence suggestive of persistent use of the dentition for manipulative tasks throughout the Pleistocene and into the Holocene by modern humans. It is implausible that anterior tooth-use or extreme dental wear would have produced selective pressure on craniodental anatomy in humans since most problems related to extreme tooth-use among hunter-gatherers will affect individual morbidity late in life but not necessarily affect reproductive fitness. There is a paradox in that anterior dental reduction occurred among early modern humans despite high-levels of anterior tooth use. Therefore, we are left with another example of how modern humans are derived with respect to Middle and Late Pleistocene archaic humans.
Chair and Committee
Kari L. Allen, Glenn C. Conroy, Fred H. Smith, David S. Strait
Willman, John Charles, "The Non-Masticatory Use of the Anterior Teeth Among Late Pleistocene Humans" (2016). Arts & Sciences Electronic Theses and Dissertations. 906.