This thesis investigates the morphology of internal tooth structures of fossils attributed to the genus Homo and explores the implications for the systematics of the earliest members of our genus. The origins and evolution of the genus Homo are poorly understood, and one of the major unresolves issues concerns the relationship between the species Homo habilis and other taxa. The enamel-dentine junction (EDJ) is useful for studies of hominin systematics because its morphology contains taxonomically important information that may otherwise be lost due to the effects of occlusal dental wear. Few studies focus on the EDJ morphology of early Homo due to a lack of microtomographic scans that preserve adequate contrast between dental tissues. This thesis presents the first analysis of new scans of important H. habilis specimens from Olduvai Gorge in Tanzania, including the type specimen OH 7. Overall EDJ shape is quantified using landmark-based geometric morphometric methods, revealing that a number of H. habilis specimens retain a very primitive EDJ morphology, largely within the range of Australopithecus. Conversely, H. habilis specimen OH 16 shows a suite of derived traits, particularly in the premolars, suggesting considerable variability within the species hypodigm. Analysis of the mandibular premolar EDJ of the species Homo naledi reveals a distinctive and remarkably consistent morphology that differs in several key traits from those of comparative taxa, including H. habilis and H. erectus. However, two specimens from sites in South Africa show H. naledi-like traits, suggesting a possible phylogenetic link with much earlier hominins. Finally, the thesis also investigates the EDJ expression of mandibular molar accessory cusps, outlining a scoring system for these traits at the EDJ. There are taxon-specific patterns in accessory cusp expression, with early Homo molars frequently displaying a lingual accessory cusp but no distal accessory cusp. However, the EDJ reveals a number of developmental complexities. This is well-illustrated by three Olduvai H. habilis first molars; each has a lingual accessory cusp, but the form of the trait clearly differs in each, raising questions over the use of accessory cusps for taxonomy. This thesis demonstrates the importance of studying the EDJ of fossil hominin teeth alongside the outer enamel surface and improves our understanding of the dental morphology of early Homo.:Acknowledgements............i
Bibliographical Data............iii
Summary............1
Zusammenfassung............8
Chapter 1............15
Chapter 2............29
Chapter 3............57
Appendix............81
Supplementary Information – Chapter 1............82
Supplementary Information – Chapter 2............95
Supplementary Information – Chapter 3............265
Co-author contributions............279
Certificate of exclusive authorship – Chapter 3............282
Declaration of independent work............284
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:76712 |
| Date | 24 November 2021 |
| Creators | Davies, Thomas William |
| Contributors | Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/acceptedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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