School of Geosciences (ETDs)

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Browsing School of Geosciences (ETDs) by Author "Beaudet, Amélie"

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    Cranial orientation and the lateral semicircular canal in primates: implications for palaeobiological reconstructions and the evolution of locomotor repertoires
    (University of the Witwatersrand, Johannesburg, 2023) Pestana, Christopher; Benoit, Julien; Beaudet, Amélie
    The lateral semicircular canal and its predicted relation to head posture have been used in reconstructions of locomotion and posture of contemporary and extinct species, and in the evolution of bipedalism. Inferences of head posture in fossil species sometimes assume that the lateral semicircular canal is held near the earth’s horizontal when the head is at rest. Despite the physiological importance of the vestibular system, the relationship between head posture and lateral semicircular canal orientation in primates has not been explored on a statistically significant sample, using phylogenetically corrected methods. This study tests the hypothesised relationship between lateral semicircular canal orientation and head posture in primates, and investigates potential links to locomotor categories. This study finds that lateral canal orientation is not significantly correlated to positional repertoires. Significant differences in canal orientation are detected between terrestrial and arboreal species. Neutral head posture distinguishes several locomotor categories, and explains a moderate proportion of the variance in positional behaviour. Brain mass is found to correlate with positional behaviour when correcting for the effects of the phylogeny. The implications of the evolution of head posture in fossil species are discussed.
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    Reconstructing locomotor behaviour of Southern African plio-pleistocene cercopithecoids: evidence from functionally-related inner structural arrangement of the trabecular bone
    (University of the Witwatersrand, Johannesburg, 2023-07) Babutsi, Mosarwa; Beaudet, Amélie; Zipfel, Bernhard; Jakata, Kudakwashe
    Because of their abundance in African Plio-Pleistocene hominin-bearing sites and their stratigraphic association with fossil hominins, cercopithecoids represent a relevant “control group” for contextualising hominin evolution. often considered as ecological and biochronological indicators, particularly their ecological sensitivity is valuable in reconstructing southern African hominin bearing site’s palaeoenvironment and environmental changes. Since biomechanical loadings on trabecular bone produced throughout locomotor activities shape the structure of the skeleton, particularly at locomotor key joints, the expectation is that investigation of the trabecular bone of fossil cercopithecoids key joints like femur, humerus, Tibia and calcaneus would provide further evidence for eloquent discreet disparity in their locomotor behaviour and reconstructing their paleohabitats. This study used trabecular bone, described as meshwork or sponge with porous network within long bones joints and inside footbones contains red bone marrow. Its preferred orientation in is the basis of Wolff’s law, relating bone structures and its ability to adapt to mechanical load alignment in the direction of loading stress, as such recoding informative locomotor signals. Forty one (41) fossil cercopithecids from the Cradle of Humankind World Heritage sites that include Sterkfontein, Swartkrans, Makapansgat, Taung and Bolt’s Farm as well as forty (40) extant cercopithecoids specimens were scanned using a micro-focus X-ray computed tomography (CT) scanner. Trabecular bone parameters that include trabecular bone fabric anisotropy, volume fraction, thickness and spacing were quantified in ImageJ. These Plio-Pleistocene cercopithecoids recorded more arboreal locomotor signals with occasional terrestrial locomotion, suggesting transitional palaeoenvironment from long trees with cool climatic conditions to a more open grass land savanna type with dry climatic conditions believed contributed significantly to extinct of archaic humans and the emergence of the successful Homo.