Date of Award

6-1978

Degree Type

Thesis

Degree Name

Master of Arts

Major

Anthropology

Major Professor

Fred H. Smith

Committee Members

Richard L. Jantz, William M. Bass

Abstract

Analysis of the temporomandibular region in Homo sapiens neanderthalensis reveals diagnostic morphological differences in comparison to the morphological pattern typically expressed in the temporomandibular joint region of Homo sapiens sapiens. The temporomandibular joint region in Neandertals is characterized by a (1) thickened tympanic ring, petrosal area, mandibular fossa roof, and temporal squama; (2) pronounced postglenoid process; (3) more oval external auditory meatus, directed anteriorly and superiorly, positioned relatively higher on the temporal bone; (4) wide shallow glenoid fossa; (5) formation of the glenoid fossa wall; and (6) prominently developed articular eminence. This thesis concentrates on the morphological variations expressed in the glenoid fossa and its immediate surroundings of Homo sapiens neanderthalensis in comparison to the total morphological pattern present in Homo sapiens sapiens in an attempt to understand the possible significance of the differences expressed.

The primary focus of this thesis is directed toward the basic question: Do the mandibular fossa and postglenoid process exhibit the morphological pattern they do in Neandertals as (1) an adaptive response to stress generated during the habitual use of the anterior dentition for nonmasticatory purposes, or (2) a secondary response to the general neurocranial growth pattern characteristic of Neandertals? In order to propose a possible explanation for the variations expressed in the temporomandibular joint region in Neandertals in comparison with modern man, the joint region in modern man is carefully reviewed within the framework of the functional matrix theory. Analysis of the gross aspects of hard tissue morphology alone suggests the Neandertal glenoid fossa and postglenoid process may be adapted to withstanding stress generated during the functioning of the mandible for masticatory and nonmasticatory purposes. However, a review of the temporomandibular joint as a diarthrodial joint, functional requirements of a diarthrosis, principles of biomechanical functioning, and morphology of the soft tissues contributing to joint formation indicate the functional components of the temporomandibular joint include only the articular eminence and mandibular condyle.

The mandibular fossa and postglenoid process are not functional components of the temporomandibular joint. Stress generated during mandibular functioning is transmitted through the mandibular condyle and articular eminence and not the mandibular fossa as evidenced by the morphology of the fossa roof, composition, vascular/avascular pattern of the articular disk, and functional movements of the articular disk.

Analysis of the temporomandibular joint embryogenesis and general cranial and neurocranial development also strengthens the hypothesis that the form of the mandibular fossa seen in Homo sapiens sapiens does not have a functional adaptive significance. Interpreted within the framework of the functional matrix theory the morphology and configuration of the central and posterior portions of the temporomandibular joint in Homo sapiens sapiens and Homo sapiens neanderthalensis appear to be a secondary response to the extrinsic and intrinsic factors responsible for general cranial growth and configuration. From this analysis it appears the morphology and configuration of the mandibular fossa and postglenoid process of the temporomandibular joint are not functional prerequisites to efficient biomechanical functioning of the temporomandibular joint and thereby do not have a direct adaptive basis.

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