Using a multiproxy analysis of springbok fossils to track 2 million years of vegetation changes experienced by hominins in southern Africa.

Abstract

A causal link between climatic changes and hominin evolution is an established one, yet the exact dynamics of this relationship is debated. Key climatic changes, such as the intensification of the Northern Hemisphere Glaciation, the onset of the Walker Circulation and the Mid-Pleistocene Revolution, have been linked to palaeoenvironmental changes that catalysed hominin evolutionary events in Plio-Pleistocene Africa. Climate-induced faunal turnover has not been found in East Africa, largely due to local buffers of large-scale climatic and environmental changes. Away from the dynamic landscapes of East Africa, southern Africa is thought to be more vulnerable to the effects of climate change. Southern Africa, as a major locale of hominin evolution and associated behavioural advancements, (with the appearance and disappearance of Australopithecus africanus, Australopithecus sediba, Paranthropus robustus and the emergence the Homo genus) requires greater understanding of the underlying catalysts for paleoenvironmental change and resultant pressures subjected upon the fauna (including hominins). A holistic palaeoenvironmental and palaeovegetational context for these hominin advancements remains elusive. This research aims to contribute to that holistic palaeoenvironmental signal for southern Africa between 2.0 to 0.8 Ma. As herbivorous, mixed-feeding antelopes, the abundant springbok (genus Antidorcas) adapt their diet according to the prevailing vegetation conditions. Via a multi- method analysis of Antidorcas diets, this enables inferences to be made regarding the prevailing palaeovegetational trends and habitat availability in the landscape, through this crucial temporal period. In this thesis, the taxonomic identity of the Antidorcas genus represented at the Cradle of Humankind is initially established. Antidorcas dental specimens from multiple hominin sites in South Africa from the temporal range, 2.8-0.8 Ma, are subject to a multi- method analysis. Dental metrics allow inferences into Antidorcas phylogenetic adaptations and establishes the baseline of dietary capabilities. Dental use-wear analysis provides the lifetime (mesowear) and end of life (microwear) dietary signals, supplemented by the early years signal from stable isotope analysis (carbon and oxygen). Further palaeoenvironmental conditions, such as precipitation levels (oxygen isotopes) and exogenous grit/dust particles (use-wear) is inferred from use-wear and isotope analysis. This research concludes that there is limited evidence for the presence of A. australis as a distinct species in the fossiliferous deposits of the Cradle of Humankind. All Antidorcas species show mixed-feeding dietary preferences through time, with the ancestral, Antidorcas recki, tending more towards browsing and Antidorcas bondi showing some tendencies towards grazing. Antidorcas display no obvious turnover point within the lineage but rather gradual adaptation and speciation. An underlying palaeoenvironmental trend of increased aridity and open grasslands is apparent with a marked shift around c. 1.7 Ma. Around 1.7 Ma Antidorcas dietary changes display high inter- and intraspecific variation, implying increased palaeoenvironmental instability and habitat heterogeneity. These behavioural adaptations (via dietary inferences) coincide with climatic changes around 1.7 Ma, such as the onset of the Walker Circulation. This in turn may be linked to the appearance of the southern African Homo genus and associated hominin Acheulean toolkit.