Le site de Malapa a livré les restes de deux homininés, associés aux restes d’autres animaux et datés à 1,98 Ma. Le degré de conservation restes osseux est remarquable dans le contexte des ensembles fossiles plio-pléistocènes retrouvés en grotte. Cela indique une combinaison de processus taphonomiques unique et non-observée dans les sites contemporains de la région. Une approche combinant analyses paléontologique, physique et spatiale des homininés et de la faune associée a été choisie afin d’interpréter la taphonomie de l’ensemble fossile, avec une attention toute particulière portée aux homininés. Des techniques de tomographie et micro-tomographie assistées par ordinateur, combinées à un logiciel de reconstruction virtuelle ont été appliquées afin de créer un modèle en 3 dimensions de la grotte et des deux squelettes d’Au. sediba. La position initiale dans laquelle les homininés ont été enfouis a été reconstruite. Les résultats indiquent que la majorité du matériel osseux a été accumulée par l’intermédiaire d’un aven-piège. Les carcasses se sont accumulées sous la forme d’un cône de débris, dans une partie profonde du système karstique présentant un accès très limité voire inexistant pour les charognards. Les deux individus ne sont peut-être pas entrés dans la grotte au même moment. Lorsque l’enfouissement a eu lieu, leur décomposition était achevée (disparition et/ou dessiccation des parties molles). Leurs os présentent des indices d’intempérisation, suggérant une période d’exposition avant l’enfouissement d’au moins plusieurs mois. Les insectes sont les principaux agents ayant modifié les restes. Les indices de momification naturelle avant l’enfouissement pour MH1 et MH2 suggèrent la préservation possible de matière organique (peau). / The cave deposits at Malapa have yielded the remains of two extremely well-preserved hominins (Australopithecus sediba) and associated fauna, dated to 1.977-1.8 Ma. The state of preservation of the hominins and some of the non-hominin material is remarkable in the context of Plio-Pleistocene fossil assemblages accumulated in caves, and indicates a unique combination of taphonomic processes, not yet observed in contemporaneous cave deposits in the region. A comprehensive approach, including palaeontological, physical, and spatial analyses of the hominins and associated fauna was undertaken to determine, describe and interpret the taphonomy of the faunal material, with particular reference to hominins. An innovative combination of Computed-Tomography (CT), micro-CT scanning and virtual reconstruction techniques was applied to create a 3D model of a selected area of the Malapa cave, with renderings of the two near-complete Au. sediba skeletons. The original burial position of the hominins was reconstructed. The results indicate that the majority of the faunal material recovered was most likely accumulated via a natural death trap. Their bodies came to rest in a deep area of the cave system with restricted access to scavengers. Results show that both individuals did probably not enter the cave system at the same time. They reached skeletonization and were slightly weathered before final burial, indicating several years of exposure before burial. Insects proved to be the primary modifiers of the hominin remains. Evidence of natural mummification before burial for MH1 and MH2 suggests the possible preservation of soft tissue.

Human evolution has been linked to climate change multiple times in the literature. One of the more well-known theories is the ‘savannah’ theory, which states that walking upright became an advantageous character when climate in Africa changed causing drier environments, changing woodlands to savannahs. Human ancestors could cross open fields more easily when walking upright, therefore it was thought that climate change could be a driving factor in the change to bipedal locomotion. Five hominin species were the basis of the study presented here, showing that change towards bipedal locomotion was a mosaic process with gradual change. A review of the relevant literature shows that the timing of change in fossils to bipedal locomotion and climate change do not coincide in the interval 6-3 Ma, therefore suggesting that climate change did not drive human evolution in this case. Changes towards open landscapes with C4 grass dominance peaked at the Pliocene-Pleistocene boundary (2.6 Ma), while the first hominin species already walked completely bipedally before 3.5 Ma.

abstract: Dietary diversity is an important component of species’s ecology that often relates to species’s abundance and geographic distribution. Additionally, dietary diversity is involved in many hypotheses regarding the geographic distribution and evolutionary fate of fossil primates. However, in taxa such as primates with relatively generalized morphology and diets, a method for approximating dietary diversity in fossil species is lacking. One method that has shown promise in approximating dietary diversity is dental microwear analyses. Dental microwear variance has been used to infer dietary variation in fossil species, but a strong link between variation in microwear and variation in diet is lacking. This dissertation presents data testing the hypotheses that species with greater variation in dental microwear textures have greater annual, seasonal, or monthly dietary diversity. Dental microwear texture scans were collected from Phase II facets of first and second molars from 309 museum specimens of eight species of extant African Old World monkeys (Cercopithecidae; n = 9 to 74) with differing dietary diversity. Dietary diversity was calculated based on food category consumption frequency at study sites of wild populations. Variation in the individual microwear variables complexity (Asfc) and scale of maximum complexity (Smc) distinguished groups that were consistent with differences in annual dietary diversity, but other variables did not distinguish such groups. The overall variance in microwear variables for each species in this sample was also significantly correlated with the species’s annual dietary diversity. However, the overall variance in microwear variables was more strongly correlated with annual frequencies of fruit and foliage consumption. Although some variation due to seasonal and geographic differences among individuals was present, this variation was small in comparison to the variation among species. Finally, no association was found between short-term monthly dietary variation and variation in microwear textures. These results suggest that greater variation in microwear textures is correlated with greater annual dietary diversity in Cercopithecidae, but that variation may be more closely related to the frequencies of fruit and foliage in the diet. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2015

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