A quantitative assessment of the supraorbital region in modern Melanesian crania
Vinyard, Christopher J.
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The supraorbital region in modem Homo sapiens has been a topic of continued debate concerning its relationship within the larger craniofacial context and regarding a functional and/or structural explanation of supraorbital expression. A morphometric examination of the supraorbital region in a sample of eighty modem Melanesian crania was conducted to examine these two areas of ongoing discussion. A battery of quantitative dimensions, including measurements taken from CT scanning, were taken on the cranial sample and analyzed using both bivariate and multivariate statistical procedures. The results indicated that the supraorbital region in modem Melanesian crania is intricately related to other metric craniofacial dimensions. The supraorbital region is not realistically considered outside of the craniofacial context. The most pervasive influence upon supraorbital development is craniofacial size. Other interrelationships (between specific supraorbital dimensions) and relationships (with other craniofacial variables) exhibit smaller levels of explained variation. The lateral supraorbital heights are differentiated from both medial supraorbital height and supraorbital projections. The lateral heights are linked to upper facial and frontal breadths and contrasted to frontal length and lower facial breadth dimensions. Conversely, supraorbital projections are associated with frontal lengths and contrasted with frontal and upper facial breadths. Medial supraorbital height is hypothesized to be directly related to the development of the frontal sinus. A second focus of this project was the testing of several hypotheses taken from the functional and/or structural models used to account for the supraorbital region. Among the biomechanical models, only the hypothesis derived from the neuro-facial torsion model was supported throughout the supraorbital region. The lateral supraorbital region was linked to temporalis muscle size following the prediction of the bent beam model. However, no other hypotheses derived from this model were supported. Support for the hypotheses derived from the spatial model was found throughout the hypothesis testing. No support for the influence of prognathism upon supraorbital development was offered. A relationship was exhibited between longer crania and larger supraorbitals. The observation that several hypotheses received support in this section highlights the probability that the supraorbital region is influenced by multiple non-mutually exclusive factors.