A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2014. / In the present thesis the use of convergence as a tool in functional analyses was investigated, with special focus on comparisons using distantly related species (“convergence approach”). Guidelines for the convergence approach were forumlated and applied in the evaluation of selected hypotheses on the contextualization of early hominins. Additionally, comprehensive reviews on water use in primates were carried out, with special focus on hominoids, including humans. The first description (and video footage) of swimming and diving behaviour in a common chimpanzee (Pan troglodytes) and an orangutan (Pongo pygmaeus) were presented here, along with swimming behaviour in other great apes (without video footage). Hypotheses on the loss of instinctive swimming in hominoids were discussed and the Saci last common ancestor hypothesis was proposed. This model suggests that the loss of swimming ability in hominoids is best explained as a consequence of phylogenetic constraints linked to the adaptation to an arboreal life in the last common ancestor of this taxon. Furthermore, several hypotheses on early hominin evolution were reviewed. It was pointed out that several of these hypotheses have similar methodological flaws in the use of analogies to corroborate specific arguments. A hypothesis on the emergence of the habitual bipedalism in early hominins was outlined, arguing that this trait did not evolve in association with a locomotory advantage or for other reasons usually presented in the literature, but as a signal to advertise unprofitability – as a warning signal in an anti-predator strategy. It was argued that fossil evidence does not allow a high resolution of inference concerning incipient traits – traits which are not optimized to fulfil a certain function after a functional change. The consideration of different lines of evidence presented in this thesis indicate that the topic “water use” must be considered in discussions on early hominin evolution. The fact that humans regularly and intensively interact with water can be considered as an indication that in some part of human phylogeny after the hominin/panin split, swimming and diving ability was specifically selected. However, contrary to the view of several proponents of the aquatic hypotheses, it was demonstrated that humans are not absolutely unique concerning their ability to learn to swim and to dive. It is therefore also conceivable that our ability to learn to swim is associated to our cognitive abilities and is not a product of specific selection in our past.

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The recently discovered site of Rising Star in the Craddle of Humankind, Johannesburg, South Africa, has yielded the single largest fossil hominin assemblage on the African continent to have been uncovered to date. Much of the anatomy of the new species, Homo naledi, has been described. With relatively human-like lower limb and strangely primitive-likeupper body, Homo naledi displays a mosaic of traits in its morphology. A small cranium for a member of the genus Homo adds to this unexpected mix of characters. [Abbreviated Abstract. Open document to view full version] / MT 2017

Swartkrans Cave, famous for abundant hominin fossils of P. robustus and the site where the first evidence of the co-existence of two hominin species was recovered, has yielded a wealth of information on early hominin behaviour. In 2005 a new program of research and excavation began at the site, and its results form the central part of this thesis. This study has focused on the early Pleistocene Member 1 deposits which include an Earlier Stone Age industry and the late Pleistocene Member 4 Middle Stone Age deposits. The thesis has four areas of focus. First the new work has resulted in clarification and new interpretations for the formation of the hominin rich Hanging Remnant deposit of Member 1, which lacks stone tools. This extensive calcified conglomerate which spans most of the north wall of the cave is now seen as a non-homogenous unit that represents material entering from at least four avens. However, this study also established that the newly exposed central portion of the Hanging Remnant and the hominin fossil-rich northwest corner infill worked by Robert Broom in the 1940s derived from the same depositional episode. Secondly, the new excavations in the Lower Bank of Member 1 have resulted in an enlargement of the previously ambiguous Earlier Stone Age assemblage. Analysis of this new assemblage, in conjunction with recently released dating results, has now confirmed that the artefacts belong to the Oldowan Industrial Complex. Thirdly, new excavations in the Member 4 deposit have resulted in the recovery of over 3,200 Middle Stone Age (MSA) stone tools and a clearer understanding of their context. The stone tool-bearing deposits of Member 4 are now understood to derive from a surface colluvium, rather than a cave infill. This MSA assemblage consists of a high number of retouched pieces that are dominated by steep-sided scrapers and denticulated scrapers with a near-absence of points. The technology of a variety of core types suggests a superior understanding of raw material flaking qualities by the tool makers. The limited types of formal tools suggest that the site was used for one or more specific activities, rather than for a range of activities by the tool makers. Fourthly, excavation of the deposits underlying the Member 4 colluvium has resulted in the discovery of two previously unknown hominin-bearing deposits. It is now established that what was originally called Member 4 is composed of three distinct deposits. The lowest of these is an east extension of the Member 1 Lower Bank (LB East Extension), which has yielded P. robustus fossils. This is overlain by a large talus cone (TCD), which also has yielded P. robustus fossils. The latter is capped by flowstone dated to ~110,000 years, followed by the MSA-tool bearing colluvium.