Visualizing shape transformation between chimpanzee and human braincases

The quantitative comparison of the form of the braincase is a central issue in paleoanthropology (i.e., the study of human evolution based on fossil evidence). The major difficulty is that there are only few locations defining biological correspondence between individual braincases. In this paper, we use mesh parameterization techniques to tackle this problem. We propose a method to conformally parameterize the genus-0 surface of the braincase on the sphere and to calibrate the parameterization to match biological constraints. The resulting consistent parameterization gives detailed information about shape differences between the braincase of human and chimp. This opens up new perspectives for the quantitative comparison of "featureless” biological structure

A Geometric Morphometric Analysis of Heterochrony in the Cranium of Chimpanzees and Bonobos

Despite several decades of research, there remains a lack of consensus on the extent to which bonobos are paedomorphic (juvenilized) chimpanzees in terms of cranial morphology. This study reexamines the issue by comparing the ontogeny of cranial shape in cross-sectional samples of bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) using both internal and external 3D landmarks digitized from CT scans. Geometric morphometric methods were used to quantify shape and size; dental-maturation criteria were used to estimate relative dental age. Heterochrony was evaluated using combined size-shape (allometry) and shape-age relationships for the entire cranium, the face, and the braincase. These analyses indicate that the bonobo skull is paedomorphic relative to the chimpanzee for the first principal component of size-related shape variation, most likely via a mechanism of postformation (paedomorphosis due to initial shape underdevelopment). However, the results also indicate that not all aspects of shape differences between the two species, particularly in the face, can be attributed to heterochronic transformation and that additional developmental differences must also have occurred during their evolution.Anthropolog

Modern human brain growth and development (contribution to brain evolution in hominids)

Le cerveau est un tissu mou, qui ne se fossilisent pas. Pour en déduire l'évolution du cerveau humain, il est donc essentiel d'étudier les preuves indirectes sur la morphologie endocrânienne. Pour faire des déductions sur le cerveau des endocrâne fossiles, il est essentiel de comprendre la relation entre le cerveau et endocrâne des humains actuelles. Dans cette thèse, l'endocrânne versus l'ontogénie du cerveau est caractérisé par l'imagerie médicale et des méthodes morphométriques. La thèse analyse les corrélations des ces deux structures et comment ils interagissent au cours de la croissance et le développement. Les modèles de taille et de change de forme de l'endocrâne et le cerveau sont étroitement corrélés au cours de l'ontogenèse précoce, mais pas à la fin de cours de l'ontogenèse. Inférences cerveau-endocrâne des hominidés fossiles immatures sont donc plus fiables que dans des spécimens adultes.The brain is a soft tissue, which does not fossilize. To infer human brain evolution, it is therefore essential to study the indirect evidence left in the form of endocranial morphology. Before inferences on the brain can be drawn from fossil endocrania, however, it is vital to understand the relationship between brain and endocranium in living humans. In this PhD thesis, human endocranial versus brain ontogeny is characterized with medical imaging and morphometric methods. The thesis analyzes how these two structures correlate and interact during growth and development. Patterns of size and shape change of the endocranium and the brain are closely correlated during early ontogeny, but not during late ontogeny. Brain-endocast inferences in immature fossil hominins are thus more reliable than in adult specimens.PARIS-Museum Hist.Naturelle (751052304) / SudocSudocFranceF

Evolution et développement du crâne de primates strepsirrhiniens

Les récents progrès de la génétique du développement et de l'analyse du phénotype ont engendré un regain d'intérêt considérable pour l'étude de l'évolution du développement (evo-devo). Cette thèse présente une étude des relations entre ontogénèse et phylogénèse dans le sous-ordre des primates strepsirrhiniens. Ici, on s'intéresse au complexe cranio-mandibulaire, dont la croissance et le développement sont analysés à l'aide d'un ensemble d'outils dédiés de géométrie morphométrique. Une analyse comparative de l'ontogénie du crâne et de la mandibule est conduite sur un ensemble de dix espèces de strepsirrhiniens et de deux espèces d'haplorrhiniens. Les haplorrhiniens et les strepsirrhiniens diffèrent largement dans la direction, la position, et la longueur de leurs trajectoires ontogénétiques. Chez les lémuriens malgaches, il y a une plus grande diversité de direction, de position et de longueur des trajectoires ontogénétiques que chez les loriformes. De plus, on observe des différences importantes de grade allométrique parmi les espèces de lémuriens, et une plus faible variabilité au sein des loriformes. Une analyse comparative est conduite sur un échantillon de primates Eocènes adapiformes et de strepsirrhiniens actuels. Au sein des adapinés, une augmentation de taille via transposition allométrique caractérise la lignée des Leptadapis. Enfin, les adapiformes adapinés et notharctidés ont des trajectoires ontogénétiques plus longues en terme de quantité de changement de forme que les espèces de strepsirrhiniens actuels. Une tendance au raccourcicement des trajectoires ontogénétiques caractérise l'évolution des strepsirrhiniens. Ceci est lié à un contexte général d'augmentation de l'encéphalisation au cours de leur histoire évolutiveDue to recent advances in developmental genetics and phenotypic analysis, evolutionary developmental (evo-devo) studies regained considerable interest, and led to fundamental changes in our understanding of how ontogeny and phylogeny are related. This thesis investigates the relationship between ontogeny and phylogeny in strepsirrhine primates. Here, the focus is on cranial diversity, which is analyzed from a developmental perspective, and with a new set of geometric morphometric tools. A comparative geometric morphometric analysis of cranio-mandibular development is conducted in ten strepsirrhine and two haplorrhine species. Haplorrhines and strepsirrhines differ widely in ontogenetic trajectory direction, length and position. Within the strepsirrhines, divergence between taxon-specific ontogenetic trajectories and allometric grade shifts are more pronounced in lemurs than in lorises. The insights obtained from the evolutionary developmental analysis of extant taxa are used for a comparative analysis of Eocene fossil strepsirrhine taxa belonging to the infraorder Adapiformes. Among the adapine adapiforms, an increase in size via allometric grade shift has occurred in the Leptadapis lineage, which suggests phyletic gigantism in this genus. Adapiforms exhibit longer ontogenetic trajectories than extant strepsirrhines. A trend toward a shortening of ontogenetic trajectories has occurred in the evolutionary history of strepsirrhines. This can be related to a context of general increase in encephalization in this lineageMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Exploring Late Pleistocene hominin dispersals, coexistence and extinction with agent-based multi-factor models

© 2022Toward the end of the Pleistocene, archaic humans in Eurasia such as the Neanderthals and Denisovans were completely replaced by anatomically modern humans dispersing from Africa. The causes underlying the replacement and extinction processes remain controversial, especially regarding the relative importance of random events, and anthropogenic and environmental factors. Here, we use the most comprehensive agent-based modeling framework to date for exploring Late Pleistocene human population dynamics under realistic time-evolving environmental conditions. Model simulations suggest multiple out-of-Africa dispersals. Most of these resulted in only partial replacement of Eurasians and long-term coexistence of spatially structured archaic and modern populations in Eurasia. Moreover, a comparison of empirical and model data suggests that the best-documented extinction process – that of the Neanderthals – did not have a single overarching cause, but spatially and temporally diverse causes and mechanisms, such as environmental fluctuations, and asymmetry in resource exploitation efficiency and reproductive rates. When viewed in isolation, various population properties have central importance for replacements, but their true importance can only be understood in comparison and with interactions with other properties.11Nsciescopu

Different in death: different in life? Diet and mobility correlates of irregular burials in a Roman necropolis from Bologna (Northern Italy, 1st-4th century AD)

The study of migration within the Roman Empire has been a focus of the bioarchaeological and biogeochemical research during the last decade. The possible association of diet and sex, age, and funerary treatment during the 1st-4th centuries AD have been extensively explored in Britain, and Central-Southern Italy. Conversely, no knowledge is available about these processes for the North of the Italian Peninsula. In the present work we analyse a set (N=16) of Roman inhumations from Bologna (Northern Italy, 1st-4th c. AD), some of which are characterized by unusual features (prone depositions, transfixion of the skeleton by iron nails). Analysis of strontium, oxygen, nitrogen, and carbon isotopes is used to test for the possible correlation between funerary treatment, geographic origin, and diet. Here we provide the first biogeochemical data for a Northern Italian Imperial sample, wherein our results show no clear association between these variables, suggesting that funerary variability, at least in the analysed context, was shaped by a variety of heterogeneous factors, and not a representation of vertical social differences or differential geographic origin

Visualizing Shape Transformation between Chimpanzee and Human Braincases

The quantitative comparison of the form of the braincase is a central issue in paleoanthropology (i.e. the study of human evolution based on fossil evidence). The major difficulty is that there are only few locations defining biological correspondence between individual braincases. In this paper, we use mesh parameterization techniques to tackle this problem. We propose a method to conformally parameterize the genus zero surface of the braincase on the sphere and to calibrate the parameterization to match biological constraints. The resulting consistent parameterization gives detailed information about shape differences between the braincase of human and of chimp. This opens up new perspectives for the quantitative comparison of “featureless” biological structures