Kent Academic Repository Full text document (pdf) Citation for published version Imbrasas, Mykolas Dovydas (2018) Performance of 2D geometric morphometric analysis in hominin taxonomy and its application to the mandibular molar sample from Lomekwi, Kenya. Master of Research (MRes) thesis, University of Kent,. DOI Link to record in KAR https://kar.kent.ac.uk/76756/ Document Version UNSPECIFIED Copyright & reuse Content in the Kent Academic Repository is made available for research purposes. Unless otherwise stated all content is protected by copyright and in the absence of an open licence (eg Creative Commons), permissions for further reuse of content should be sought from the publisher, author or other copyright holder. Versions of research The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record. Enquiries For any further enquiries regarding the licence status of this document, please contact: [email protected] If you believe this document infringes copyright then please contact the KAR admin team with the take-down information provided at http://kar.kent.ac.uk/contact.html Performance of 2D geometric morphometric analysis in hominin taxonomy and its application to the mandibular molar sample from Lomekwi, Kenya Mykolas Dovydas Imbrasas Student No. 17905401 School of Anthropology and Conservation University of Kent Project supervisor – Dr. Matthew Skinner Submitted November 2018 Acknowledgements I would like to thank Matthew Skinner for introducing me to the world of hominin dentition, and for providing detailed instruction regarding the current techniques (geometric morphometrics, micro-CT scanning, and software used for visualizing 3D data) used in studies of hominin tooth morphology. I would also like to thank Matthew Skinner for his support and guidance throughout this research and beyond it. I would like to thank Tracy Kivell for providing me with the opportunity to work with fossil hominin hands, which was a welcomed change of scenery from teeth. Lastly, I would like to thank my parents for their financial and moral support throughout this year. Abstract The Lomekwi area, situated west of Late Turkana, Kenya, has yielded numerous hominin fossil specimens, mostly isolated teeth, dated to between 3.5 to 3.2 million years ago. The isolated dental remains from Lomekwi have been tentatively attributed to Kenyanthropus platyops, whereas a number of specimens (KNM-WT 8556 and KNM-WT 16006) have been referred to as Australopithecus afarensis. However, the type specimens of K. platyops do not have sufficient dental material preserved, which does not allow the direct comparison of the isolated Lomekwi teeth to the dentition of K. platyops. In this study, 2D geometric morphometric (GM) data of the occlusal enamel surface of the crown have been used to compare the crown morphology of eleven mandibular molars from Lomekwi to specimens attributed to Au. afarensis (n=26), Au. africanus (n=35), and Au. anamensis (n=11). The current study also compared the performance of 2D GM data to traditional crown morphology measurements (cusp areas and mesiodistal and buccolingual dimensions) in classifying molars to their correct taxon by use of a canonical variate analysis (CVA), and finding differences between taxa in MANOVAs and permutational MANOVAs. The results showed that the Lomekwi sample was not exclusively linked to any of the comparative Australopithecus taxa, and exhibited some degree of morphological uniqueness. With regards to the data type comparisons, 2D GM data has been shown to be able to more accurately classify specimens to their correct taxonomic groups, and find a larger number of significant differences between taxa than traditional crown morphology measurements. Table of Contents CHAPTER 1: INTRODUCTION,AIMS, AND LITERATURE REVIEW ............................................................... 1 1.1 Introduction ................................................................................................................................... 1 1.2 Lomekwi and Kenyanthropus platyops ........................................................................................... 2 1.3 Geometric morphometrics ............................................................................................................. 3 1.4 Aims .............................................................................................................................................. 6 1.5 Literature review ......................................................................................................................... 10 CHAPTER 2: METHODS COMPARISON ................................................................................................... 35 2.1 Materials and methods ................................................................................................................ 35 2.1.1 Materials............................................................................................................................... 35 2.1.2 Methods ............................................................................................................................... 36 2.2 Results ......................................................................................................................................... 49 2.2.1 First molars ........................................................................................................................... 49 2.2.2 Second molars ...................................................................................................................... 58 2.2.3 Third molars .......................................................................................................................... 66 2.2.4 Au. afarensis molars .............................................................................................................. 75 2.2.5 Summary .............................................................................................................................. 82 CHAPTER 3: COMPARATIVE ANALYSIS OF THE LOMEKWI MANDIBULAR MOLARS ............................... 86 3.1 Materials and methods ................................................................................................................ 86 3.1.1 Materials............................................................................................................................... 87 3.1.2 The Lomekwi sample ............................................................................................................. 87 3.1.3 Methods ............................................................................................................................. 100 3.2 Results ....................................................................................................................................... 102 3.2.1 Determination of the position of isolated Lomekwi molars.................................................. 102 3.2.2 Assessing to which known Australopithecus taxa the Lomekwi molars are most similar ...... 113 3.2.3 Assessment of whether the Lomekwi sample exhibits morphological uniqueness ............... 129 CHAPTER 4: DISCUSSION ..................................................................................................................... 139 4.1 Taxonomic signal in traditional measurements of crown morphology ........................................ 139 4.2 Challenges to 2D GM assessement of crown morphology........................................................... 141 4.3 Tooth position ambiguity ........................................................................................................... 144 4.4 Taxonomy of Lomekwi ............................................................................................................... 145 4.4.1 Similarities to Australopithecus ........................................................................................... 145 4.4.2 Lomekwi as its own taxon ................................................................................................... 150 4.5 Lomekwi molars that could be considered as morphological outliers ......................................... 152 4.6 Future directions........................................................................................................................ 156 CHAPTER 5: CONCLUSION ................................................................................................................... 158 Appendix ............................................................................................................................................ 160 Landmarked teeth .............................................................................................................................. 173 Bibliography........................................................................................................................................ 187 R code ................................................................................................................................................. 196 CHAPTER 1: INTRODUCTION, AIMS, TERMINOLOGY, AND LITERATURE REVIEW 1.1 Introduction Teeth constitute a major part of the hominin fossil record (Guatelli-Steinberg, 2016). Teeth are compact, strong, and made of mineralized tissue, which renders them relatively resilient to weathering, and allows them to be found