Nomological mechanisms of anthropoid nasomaxillary diversity.
Item
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Title
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Nomological mechanisms of anthropoid nasomaxillary diversity.
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Identifier
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AAI9946199
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identifier
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9946199
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Creator
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McMahon, James Michael.
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Contributor
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Adviser: Timothy Bromage
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Date
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1999
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Language
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English
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Publisher
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City University of New York.
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Subject
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Anthropology, Physical | Biology, Anatomy | Biology, Biostatistics
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Abstract
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The primary objectives of this thesis were (1) to formulate an integrated theoretical, operational and analytical approach to the study of craniofacial diversity, and (2) test specific hypotheses regarding the evolutionary and developmental mechanisms responsible for nasomaxillary diversity among extant anthropoid primates.;Craniofacial diversity derives from variation of underlying genetic and cellular activities during development (proximate causal mechanisms). Nomological distal causal mechanisms (NDCMs) are law-based processes that determine which proximate mechanisms are expressed and which are repressed. Three NDCMs were explored: neoDarwinian selection, physiological acclimation and biological constraints.;Morphometric 3D landmark data were collected from 300 adult female specimens representing 37 species of extant anthropoids, and from infant specimens representing a subset of 27 species. Methods were developed to deal with the problems of phylogenetic effects and scale adjustment in cross-taxonomic comparative analyses. A multi-level covariance structure analytic technique was devised to test specific hypotheses regarding the affects of growth constraints, body size, brain form, olfaction, locomotion, and mastication on nasomaxillary form. The analysis permitted an examination of the independent effects of selection, acclimation and constraints on nasomaxillary form and form variation.;It was found that much of the diversity in the anteroposterior dimension of the nasomaxillary complex (e.g., anterior facial length, maxillary arch length, facial prognathism, nasal bone length, etc.) among anthropoids can be accounted for through an integrated growth process involving both structural and functional components. Brain growth and form interact with the chondrocraniurn (specifically the spheno-ethmoidal complex), which in turn determines the vector of facial growth. The extent of facial growth acts to maintain the orientation of the occlusal plane within functional limits required for proper mastication. Forces generated during mastication also appear to influence nasomaxillary form, via both selectional and acclimational mechanisms. These results support the hypotheses of Weidenreich, Enlow, Hylander, and others. Neither olfaction nor locomotion appear to substantially affect nasomaxillary form among anthropoids.;The results indicate the primary importance of structural and functional growth constraints and the relationship between brain growth and chondrocranial development in the evolution of anthropoid nasomaxillary diversity.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
