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Title: The comparative anatomy and evolution of the human vocal tract
Author: Clegg, Margaret
ISNI:       0000 0001 3558 8287
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 2001
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During the course of human evolution a major re-organisation of the upper respiratory tract, or vocal tract, appears to have taken place. This re-organisation is easily observed when humans and other mammals are compared. All mammals, including nonhuman primates, are reported as having larynges positioned high in the neck, with the epiglottis and soft palate in close approximation. Human adults, on the other hand, have a low laryngeal position with the epiglottis and soft palate widely separated. This thesis sets out to investigate inter and intra specific variation in, and relationships between, various hard and soft tissue features of the vocal tract in humans (n=20), great apes (n=3) and several other non-human primates (n=18), comprising 13 Macaca mulatta, 2 Colobus guereza, 1 Hylobates muelleri, 1 Leontopithicus rosalia and 1 Hapalemur sp. The main aim of the thesis is to gain a better understanding of how the shape and size of the human vocal tract correlates with speech abilities and when these abilities evolved during human evolution. This thesis also aims to extend our knowledge of the anatomy and morphology of the larynx, vocal tract and hyoid bone. The morphology and ossification of the hyoid bone are little documented. This thesis attempts to rectify this by a full analysis of the morphology and ossification of human (n=l 15) and African ape (n=90) hyoid bones. The functional disadvantage of a low larynx is explored through analysis of historic demographic data on mortality from choking on food in England and Wales over a period of 100 years. This thesis questions commonly held assumptions regarding the morphology of the vocal tract and the possible selection pressures resulting in the descent of the human larynx. This thesis offers no support for the hypothesis that the ability to produce speech sounds was the main selection pressure for a low larynx. A more parsimonious explanation is that the lower larynx and consequent longer vocal tract in humans is a response to changes elsewhere in the cranium. The evidence from mortality statistics shows that choking to death on food is a rare event. Almost all cases appear to be culturally mediated, rather than caused by our general method of swallowing. This thesis presents evidence that the Kebara hyoid falls within the range of human variation for hyoid bone dimensions and morphology. It also produces equations based on regression analysis of cranial measurements for the prediction of hyoid bone morphology. A model of laryngeal descent in early hominins is proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Human anatomy & human histology