Thesis is submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Faculty of Science, School of Geosciences, University of the Witwatersrand, Johannesburg, 2018 / Teeth make up the bulk of hominin fossil material and are useful in taxonomic assessments. In this thesis, discriminant function, principal components and randomised CV analyses on large samples of lower second molars (n=778) from five extant reference species, both sexually dimorphic and non-dimorphic, provide estimates of ranges of size-shape variability to be expected within a single species. However, there is evidence that diet-driven tooth-size reduction and cusp simplification has expanded the ranges of shape and size variability of Homo sapiens in some populations, in areas exposed to soft, undemanding diets since the transition to agriculture and increased use of cooking, food processing and ceramics from about 12500 years ago. Molar size and shape changes are less evident in communities retaining a hunter-gatherer subsistence strategy, requiring strong dentognathic
structures with robust teeth to masticate harder, tougher foodstuffs. These factors, driving divergent variability in tooth size and shape, are unique to modern humans.
Using a novel mathematically-based landmarking methodology, developed to allow the inclusion of severely worn teeth, intra-species size-shape variability was assessed from 63 lower M2s representing nine African Plio-Pleistocene species. The first hypotheses tested in this thesis address the question of which extant hominoid species might be suitable for use as analogue species for comparisons with fossil hominin molars, and whether uniquely modern-human anomalous size-shape variability exhibited by lower second molars might disqualify modern Homo sapiens for such analyses. Secondly, where lower second molar size-versus-shape variability ratios measured for fossil species do not match those of either a sexually dimorphic or a non-dimorphic extant species, evaluations are made as to whether samples attributed to single hominin species might actually represent specimens from more than one species present in the relevant assemblages, whether sexual dimorphism may have been greater in fossil species than in extant species, and whether some individual specimens attributed to any fossil species might be misclassified.
Results of the analyses indicate that uniquely human subsistence strategy divergences are identifiable in the size-shape variability of lower second molars. Furthermore, specimens representing Australopithecus afarensis, Australopithecus africanus and Paranthropus robustus in this study exhibit very high variability and may indicate the presence of more than one species in their respective assemblages. / EM2018
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/25804 |
| Date | January 2018 |
| Creators | Dykes, Susan Jane |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (294 leaves), application/pdf |
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