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

Tansies in the field: an odontometric assessment of orthodox perspectives on ontogenetic canalization, dental field theory, and sex dimorphism


1Anthropology, California State University, Bakersfield, 2Department of Integrative Biology, University of California, Berkeley

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Over the last 70 years a consensus has emerged that dental development in humans is characterized by a greater degree of developmental buffering among females than males, that odontogenesis is characterized by a series of developmental fields which correspond broadly to tooth type by jaw, and that expression of sex dimorphism is uniformly expressed across adequately nourished human populations. This study tests these assumptions through assessment of mesiodistal and buccolingual dimensions of all permanent teeth except third molars among 2746 living individuals of 15 ethnic groups from South Asia.Bartlett’s chi-square indicates that most ethnic groups follow the expected pattern of greater variability among males, but a consistent minority displays the opposite pattern with greater variability among females relative to males. Dahlberg asserted that earlier developing “key” teeth within a dental field were less variable than later developing “distal” teeth, with one exception, the mandibular incisors in which the developmental field was held to have been reversed. Results obtained not only provide no support for wholesale reversal of the mandibular incisor field, but also indicate that sporadic reversals are common in all fields and corroborate Bartlett’s chi-square in demonstrating that reversals are equally common among females as males. Two-way ANOVA confirms that the two most important determinants of relative tooth size are position within a dental field and sex dimorphism, but ANOVA also reveals that expression of sex dimorphism differs in both the degree of expression and, to a lesser extent, in patterning throughout the dentition.

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