Papers by Pan Lei
Anthropological Science, 2012
ABSTRACT A bi-level nasal floor, although present in most Pleistocene and recent human samples, r... more ABSTRACT A bi-level nasal floor, although present in most Pleistocene and recent human samples, reaches its highest frequency among the western Eurasian Neandertals and has been considered a fea-ture distinctive of them. Early modern humans, in contrast, tend to feature a level (or sloping) nasal floor. Sufficiently intact maxillae are rare among eastern Eurasian Pleistocene humans, but several fos-sils provide nasal floor configurations. The available eastern Eurasian Late Pleistocene early modern humans have predominantly level nasal floors, similar to western early modern humans. Of the four observable eastern Eurasian archaic Homo maxillae (Sangiran 4, Chaoxian 1, Xujiayao 1, and Chang-yang 1), three have the bi-level pattern and the fourth is scored as bi-level/sloping. It therefore appears that bi-level nasal floors were common among Pleistocene archaic humans, and a high frequency of them is not distinctive of the Neandertals.
Objectives: The aim of this study is to compare the degree and patterning of inter-and intra-indi... more Objectives: The aim of this study is to compare the degree and patterning of inter-and intra-individual metameric variation in South African australopiths, early Homo and modern humans. Metameric variation likely reflects developmental and taxonomical issues, and could also be used to infer ecological and functional adaptations. However, its patterning along the early hominin postcanine dentition, particularly among South African fossil hominins, remains unexplored. Materials and Methods: Using microfocus X-ray computed tomography (mXCT) and geometric morphometric tools, we studied the enamel-dentine junction (EDJ) morphology and we investigated the intra-and inter-individual EDJ metameric variation among eight australopiths and two early Homo specimens from South Africa, as well as 32 modern humans. Results: Along post-canine dentition, shape changes between metameres represented by relative positions and height of dentine horns, outlines of the EDJ occlusal table are reported in modern and fossil taxa. Comparisons of EDJ mean shapes and multivariate analyses reveal substantial variation in the direction and magnitude of metameric shape changes among taxa, but some common trends can be found. In modern humans, both the direction and magnitude of metameric shape change show increased variability in M 2-M 3 compared to M 1-M 2. Fossil specimens are clustered together showing similar magnitudes of shape change. Along M 2-M 3 , the lengths of their meta-meric vectors are not as variable as those of modern humans, but they display considerable variability in the direction of shape change. Conclusion: The distalward increase of metameric variation along the modern human molar row is consistent with the odontogenetic models of molar row structure (inhibitory cascade model). Though much remains to be tested, the variable trends and magnitudes in metamerism in fossil hominins reported here, together with differences in the scale of shape change between modern humans and fossil hominins may provide valuable information regarding functional morphology and developmental processes in fossil species.
The appearance of the earliest members of the genus Homo in South Africa represents a key event i... more The appearance of the earliest members of the genus Homo in South Africa represents a key event in human evolution. Although enamel thickness and enamel dentine junction (EDJ) morphology preserve important information about hominin systematics and dietary adaptation, these features have not been sufficiently studied with regard to early Homo. We used micro-CT to compare enamel thickness and EDJ morphology among the mandibular postcanine dentitions of South African early hominins (N ¼ 30) and extant Homo sapiens (N ¼ 26), with special reference to early members of the genus Homo. We found that South African early Homo shows a similar enamel thickness distribution pattern to modern humans, although three-dimensional average and relative enamel thicknesses do not distinguish australopiths, early Homo, and modern humans particularly well. Based on enamel thickness distributions, our study suggests that a dietary shift occurred between australopiths and the origin of the Homo lineage. We also observed that South African early Homo postcanine EDJ combined primitive traits seen in australopith molars with derived features observed in modern human premolars. Our results confirm that some dental morphological patterns in later Homo actually occurred early in the Homo lineage, and highlight the taxonomic value of premolar EDJ morphology in hominin species.
The geographical and climatic patterning in craniofacial morphology among recent hominids has bee... more The geographical and climatic patterning in craniofacial morphology among recent hominids has been regarded as relatively reliable evidence of environmental adaptation and natural selection, which is largely attributed to thermoregulation. However, the relative influence of genetic and environmental factors on craniofacial features is unclear. Our study employed 3D laser scanning techniques to evaluate the association between geographical (latitude), climatic (annual temperature) factors, and 3D craniofacial measurements in 18 recent populations through bivariate correlation analysis. Significant correlations were found among braincase surface area, zygomatic bone surface area, cranial-facial index (facial surface area relative to braincase surface area) and local temperature, and a clear latitudinal gradient was also found in variation of braincase surface area. No significant correlations were found between zygomatic bone surface area, cranial-facial index and latitude. Our analysis supports the idea that the braincase functions as a radiator and is closely related to direct sunlight. We also suggest that absolute/relative craniofacial surface area varies consistently with predictions derived from Bergmann's Rule. The mosaic craniofacial traits of American Indians may reflect retention of cold-derived, ancestral features, as well as a response to a slightly warmer climate. Because different craniofacial regions preserve environmental/genetic signatures differentially, caution is suggested when craniofacial anatomy is used for phylogenetic reconstruction and functional-morphological analysis.
Endocasts are important materials used for the study of human brain evolution, and allow examinat... more Endocasts are important materials used for the study of human brain evolution, and allow examination of the external features of brain anatomy from the inside the cranium. Studies examining brain asymmetries in fossil hominids are usually limited to scoring of differences in hemisphere protrusion rostrally and caudally, or to comparing the width of the hemispheres. In the present study, using 3D laser scanning, we examined asymmetries of the hemisphere volumes and surface areas in the Zhoukoudain (ZKD) Homo erectus, dated to 0.4-0.8 Ma. Compared with modern endocasts, we found that the absolute hemisphere volumes and surface areas exhibited no significant asymmetries in the ZKD or in modern specimens. However, the relative hemisphere volumes against surface areas differed between the two groups. When comparing the relative sizes between the left and right hemispheres, the ZKD specimens exhibited a greater variation than in the modern humans; there were no differences in the two hemispheres in the ZKD specimens, while in the modern endocasts the left hemisphere was significantly greater than the right hemisphere. These data suggest that brain asymmetries originated from relative brain sizes rather than absolute brain volumes during human evolution. These anatomical changes are likely related to the origin of human brain lateralization.
Thesis Chapters by Pan Lei
This thesis consists of two individual projects and six chapters, which are based on the examinat... more This thesis consists of two individual projects and six chapters, which are based on the examination
of dental inner structure of lower postcanine dentition in a number of fossil and modern specimens,
through which a comprehensive study has been done using micro-computed tomography and computer-
assisted paleonanthropology tools. We first documented and assessed the taxonomical value of enamel
thickness and 3D whole-crown enamel thickness distribution patterns in a number of earliest members
of the genus Homo in South Africa, and looked into the taxonomic relavence of EDJ morphology along
postcanine dentition, and discussed the possible adaptive/developmental factors that account for the
variation of EDJ morphology we observed here.
The first three chapters (Introduction, Materials and Methods) provide an overview of the objectives
of this thesis, and review previous studies. Also, they provide a detailed introduction of fossil materials ,
sites and a background of computer-aided method (micro-XCT) to analyze the dental inner structure. The
Results chapter comprises of two independent research papers, in different stages of submission and
publication. The Results and Discussion chapters offer an extensive summary of enamel thickness, EDJ
geometric morphometrics and 3D-EDJ metameric variation between species, and compare the results
with a number of morphological and developmental studies, and provide an outlook of future study. The
last chapter reaches the conclusive points of this thesis, it highlights the taxonomical value of premolar
EDJ, and emphasizes the mosaic features of the dentition of South African early Homo.
P r F r e d e r i c k GRI NE P r B r u n o MA URE I L L E P r F r é d é r i c V A Y S S E 1 2 / 0... more P r F r e d e r i c k GRI NE P r B r u n o MA URE I L L E P r F r é d é r i c V A Y S S E 1 2 / 0 9 / 2 0 1 6 Acknowledgement I would like to express my deepest appreciation to the supervisor of my doctoral studies, Professor Jos é Braga, at the Laboratoire d'Anthropologie Molé culaire et Imagerie de Synthè se, not only for accepting me as a PhD student three years ago, but for his continuous support throughout my doctoral study. He kindly provided me with many opportunities to participate in research projects, fieldwork and collaborations. His enthusiasm, persistance and dedication in research have a deep influence on me and my future academic career. Jean Dumoncel, our engineer and technician, particularly assisted me during my doctoral studies, he helped me with the geometric morphometric analyses I employed in this thesis. He kindly taught me how to use the programs he developed, patiently helped me when I encountered difficulties with the statistical analyses. I would like to thank Clé ment Zanolli, for including me in his research projects, for providing micro-CT data of modern humans and Neanderthals, Clé ment and I also had many fruitful discussions on the study sample, the interpretations of the results, and on my career choice. I thank Amé lie Beaudet for helping me with principals of enamel thickness measurements and geometric morphometrics, and she was always there when I had difficulties with the French language and administrations. I would like to express my gratitude to these colleagues and instututions which helped with the micro -CT scans and data collection: Firkkie de Beer and Jakobus Hoffman (South African Nuclear Energy Corporation), Benjamin Duployer and Christophe Tenailleau (UMR 5085 CNRS), Song Xing (IVPP); for the permissions and assistance to study the materials, I thank Francis Thackeray (Wits University), Stephany Potze (Ditsong National Museum of Natural History), Anna Oettlé (University of Pretoria) and Catherine Thè ves (UM R 5288 CNRS). Also, I would like to especially thank Francis for his kind support when I tried t o apply for a post-doc position. During my doctoral studies I was fortunate to receive valuable support from many senior scholars, I thank Roberto Macchiarelli for his insights on the Neanderthal taxonomy and chronology; Maria Martinón-Torres for her kind acceptance of collaboration; Wu Liu and Xiujie Wu for information on Chinese fossil hominins and for their advice on pursuing a career; Laurent Bruxelles for his interpretation of the Kromdraai stratigraphy and Sterkfontein cave systems. I deeply appreciate the reviewers of my doctoral dissertation for their efforts to improve the quality of the manuscript, I will benefit from their valuable comments and suggestions during my future academic career.
Uploads
Papers by Pan Lei
Thesis Chapters by Pan Lei
of dental inner structure of lower postcanine dentition in a number of fossil and modern specimens,
through which a comprehensive study has been done using micro-computed tomography and computer-
assisted paleonanthropology tools. We first documented and assessed the taxonomical value of enamel
thickness and 3D whole-crown enamel thickness distribution patterns in a number of earliest members
of the genus Homo in South Africa, and looked into the taxonomic relavence of EDJ morphology along
postcanine dentition, and discussed the possible adaptive/developmental factors that account for the
variation of EDJ morphology we observed here.
The first three chapters (Introduction, Materials and Methods) provide an overview of the objectives
of this thesis, and review previous studies. Also, they provide a detailed introduction of fossil materials ,
sites and a background of computer-aided method (micro-XCT) to analyze the dental inner structure. The
Results chapter comprises of two independent research papers, in different stages of submission and
publication. The Results and Discussion chapters offer an extensive summary of enamel thickness, EDJ
geometric morphometrics and 3D-EDJ metameric variation between species, and compare the results
with a number of morphological and developmental studies, and provide an outlook of future study. The
last chapter reaches the conclusive points of this thesis, it highlights the taxonomical value of premolar
EDJ, and emphasizes the mosaic features of the dentition of South African early Homo.
of dental inner structure of lower postcanine dentition in a number of fossil and modern specimens,
through which a comprehensive study has been done using micro-computed tomography and computer-
assisted paleonanthropology tools. We first documented and assessed the taxonomical value of enamel
thickness and 3D whole-crown enamel thickness distribution patterns in a number of earliest members
of the genus Homo in South Africa, and looked into the taxonomic relavence of EDJ morphology along
postcanine dentition, and discussed the possible adaptive/developmental factors that account for the
variation of EDJ morphology we observed here.
The first three chapters (Introduction, Materials and Methods) provide an overview of the objectives
of this thesis, and review previous studies. Also, they provide a detailed introduction of fossil materials ,
sites and a background of computer-aided method (micro-XCT) to analyze the dental inner structure. The
Results chapter comprises of two independent research papers, in different stages of submission and
publication. The Results and Discussion chapters offer an extensive summary of enamel thickness, EDJ
geometric morphometrics and 3D-EDJ metameric variation between species, and compare the results
with a number of morphological and developmental studies, and provide an outlook of future study. The
last chapter reaches the conclusive points of this thesis, it highlights the taxonomical value of premolar
EDJ, and emphasizes the mosaic features of the dentition of South African early Homo.