The macrovertebrate fossil assemblage from the Name Chamber, Sterkfontein: taxonomy, taphonomy and implications for site formation processes

The Name Chamber contains some of the deepest fossiliferous deposits in the Sterkfontein Caves, at ~20 metres below the surface deposits of Members 4 and 5. Recent excavations complemented by detailed studies of the geological context, as well as of the microfaunal and lithic (i.e. Oldowan artefacts) assemblages, have shed some light on the complex history of sediment accumulation in that part of the Sterkfontein karstic system. The Name Chamber has a long and intricate history of deposition that is of particular value for understanding the redistribution of Oldowan-bearing sediments from Member 5 into the deep chamber below. Recognizing sediment movement and sources through multidisciplinary investigations is of key importance to reconstructing primary lithic assemblages and ultimately the behavioural proxies associated with them. Here, we present the results of a taxonomic and taphonomic analysis of the macrofaunal assemblage recovered during excavations of the decalcified sediments of the Western Talus in the Name Chamber. The taxonomic composition of the faunal spectrum is similar to that of Member 5 East Oldowan, with an overrepresentation of medium-sized bovids and the occurrence of taxa associated with grasslands. The taphonomic features of the fossil remains are characteristic of a mixed assemblage with indications of contributions by carnivores, slope wash and gravity collecting bones from the catchment surface (including carnivore-gnawed and butchery-marked specimens). The results independently corroborate lithic and microfaunal analyses and support the hypothesis of multiple origins for the sediments of the Name Chamber, with a main contribution from Member 5 East Oldowan (notably illustrated in the Name Chamber assemblage by the identification of several cut-marked remains and a bone tool), shortly after it accumulated at about 2.18 Ma. There is also indication of a minor contribution from Member 4 but no evidence for a noticeable contribution from Post-Member 6 (L/63 Infill).Palaeontological Scientific Trust [publication costs

A study of newly discovered lithics from earlier Stone Age deposits at Sterkfontein, Gauteng province, South Africa

The need to expand the current lithic Plio-Pleistocene assemblages at Sterkfontein and to understand how these assemblages have been incorporated into the cave deposits is of key importance to archaeological research on the Oldowan and Early Acheulean of South Africa. The greater the archaeological sample size the more accurately inferences can be made regarding the behaviour and technological practices of local hominid groups. An accurate understanding of depositional processes influencing these assemblages allows inferences to be made regarding the post-depositional movement of elements within the assemblage. The first objective of this research is to expand the assemblages representing the earliest stone tool technologies found at Sterkfontein. The first assemblage researched here is the Dump 21 collection, a small number of artefacts found recently just south of the Sterkfontein Member 5 West breccia and the former Extension Site of John Robinson. This material had been removed from a cave deposit by lime miners and dumped where it was found. This dump may have been created up to a century ago and was concealed by vegetation. The technological attributes exhibited on the cores and flakes of Dump 21 were compared to the current Sterkfontein Early Acheulean of Member 5 West. Parallel patterns in core types and flaking patterns, as well as raw material utilisation, suggest analogous technological intention and therefore identical depositional origins. The second assemblage analysed here was excavated from the Name Chamber and yielded large quantities of quartz dominated small flaking debris. Comparisons of raw material profiles and technological attributes of artefacts <20mm in size indicate the Name Chamber artefacts originated within the Oldowan assemblage, with a large proportion of <10mm and some <20mm material being winnowed out of the Member 5 East Oldowan breccia at some stage. The second objective of this research was to more clearly understand the processes involved in the formation of the Name Chamber deposit, examination of the geology and stratigraphy of the Name Chamber was undertaken. Three depositional events have been isolated. The first deposit filled the existing Sterkfontein chambers prior to the opening of the caves to the surface. The second and third deposits have entered the Name Chamber through a shaft that appears to articulate with the deepest portions of the Member 5 East area of the site, forming fauna-rich talus slopes within the chamber. The changing internal structure of this shaft has influenced the size profile and destination of the sediments accumulated in the three current talus deposits fed by the shaft

The underground central deposits of the Sterkfontein Caves, South Africa

Ph.D., Faculty of Science, University of the Witwatersrand, 2011Work on Sterkfontein cave deposits has generally focussed on clarifying the life histories of interned hominin remains. Less attention has been paid to the depositional context of the fossils and the specific stratigraphic processes involved in the formation of deposits, and their interaction within the cave system. Also lacking is an understanding of the complex processes influencing the distribution and integrity of the faunal and artefact assemblages. This research applied a broad-spectrum multidisciplinary approach to investigate a previously unexamined area of the caves with a particularly rich depositional history. The underground central deposits represent several infills of important fossil and artefact-bearing sediments. These sediments have accumulated into one of the deepest central areas of the Sterkfontein cave system creating a confluence area with a complex formation history. Three excavations (STK-MH1, STK-MH2 and STK-EC1) uncovered seven deposits. These deposits document a depositional history ranging from the earliest introduction of allogenic sediments (STK-MH1 T4), to the commercial exploitation of the caves through mining and tourism (STK-MH1 T1, STK-MH2). The stratigraphic sequence for the underground central deposits exhibits multiple formation processes including deposition (through numerous processes), erosion, collapse, diagenetic modification, deformation and displacement. The detailed stratigraphic history of these deposits was elucidated utilising sedimentological, fabric, stratigraphic, taphonomic and taxonomic analyses. As well as deciphering the complex formation history of this important area, this research attempted to identify the influence of cave sedimentation processes on faunal distribution and assemblage integrity. Faunal assemblages are prone to extensive modification caused by sedimentation and re-sedimentation processes mixing and distributing deposits through the caves. Varying sedimentological properties within fossil-bearing sediment gravity flows can cause the destruction of primary context taphonomic evidence, the concentration of fossils representing multiple stratigraphically distinct facies, and deposit-wide fossil distributions based on element size and shape. In addition to these processes, it was found that different skeletal elements change shape in different ways through breakage, thereby changing the specific mobility of the fossils and their potential distribution through the sediment body. Not identifying or not accounting for these post-depositional processes can lead to non-representative sampling, and to the misinterpretation of taphonomic and taxonomic data

Preliminary paleohistological observations of the StW 573 ('Little Foot') skull

Numerous aspects of early hominin biology remain debated or simply unknown. However, recent developments in high-resolution imaging techniques have opened new avenues in the field of paleoanthropology. More specifically, X-ray synchrotron-based analytical imaging techniques have the potential to provide crucial details on the ontogeny, physiology, biomechanics, and biological identity of fossil specimens. Here we present preliminary results of our X-ray synchrotron-based investigation of the skull of the 3.67-million-year-old Australopithecus specimen StW 573 ('Little Foot') at the I12 beamline of the Diamond Light Source (United Kingdom). Besides showing fine details of the enamel (i.e., hypoplasias) and cementum (i.e., incremental lines), as well as of the cranial bone microarchitecture (e.g., diploic channels), our synchrotron-based investigation reveals for the first time the 3D spatial organization of the Haversian systems in the mandibular symphysis of an early hominin

Preliminary paleohistological observations of the StW 573 ('Little Foot') skull.

Numerous aspects of early hominin biology remain debated or simply unknown. However, recent developments in high-resolution imaging techniques have opened new avenues in the field of paleoanthropology. More specifically, X-ray synchrotron-based analytical imaging techniques have the potential to provide crucial details on the ontogeny, physiology, biomechanics, and biological identity of fossil specimens. Here we present preliminary results of our X-ray synchrotron-based investigation of the skull of the 3.67-million-year-old Australopithecus specimen StW 573 ('Little Foot') at the I12 beamline of the Diamond Light Source (United Kingdom). Besides showing fine details of the enamel (i.e., hypoplasias) and cementum (i.e., incremental lines), as well as of the cranial bone microarchitecture (e.g., diploic channels), our synchrotron-based investigation reveals for the first time the 3D spatial organization of the Haversian systems in the mandibular symphysis of an early hominin

Plants, people and fire: Phytolith and FTIR analyses of the post-Howiesons Poort occupations at Border Cave (KwaZulu-Natal, South Africa)

Border Cave is a well-known South African Middle and Early Later Stone Age site located in KwaZulu-Natal. The site has exceptional plant preservation, unparalleled in the African Middle Stone Age archaeological record. This study focuses on the phytolith and FTIR analysis of two Members (2 BS and 2 WA) of the under-documented post-Howiesons Poort occupations dating to ∼60 ka. These members contain complex successions of vertically overlapping, interdigitating light brown sediments, plant bedding and combustion features of various sizes. The complexity and distinctiveness of these deposits provide an excellent opportunity for the study of plant exploitation strategies and their associated human behaviour. Our taphonomic assessment inferred, through the variability of phytolith properties and minerals composing archaeological layers, that specific occupations suffered more physical weathering than others, for example in the form of trampling. The preservation of fragile and highly soluble phytoliths (eudicot leaf phytoliths) and the high frequencies of articulated phytoliths indicates that some bedding deposits experienced little disturbance after their deposition. Not all bedding layers dating to ⁓60 ka show, from a phytolith perspective, the same plant composition, which could be explained in terms of changes in human preference for the use of plants over time to construct bedding or because distinct types of living floors are represented. Finally, the systematic application of phytoliths and FTIR to the complex archaeological sequence of Border Cave confirm these analyses can be used in the future to identify bedding deposits not visible to the naked eye, and behavioural patterns obscured by diagenetic or biased processes during sampling.publishedVersio

Shape analysis of the StW 578 calotte from Jacovec Cavern, Gauteng (South Africa)

The fossiliferous deposits within the lower-lying Jacovec Cavern in the locality of Sterkfontein yielded valuable hominin remains, including the StW 578 specimen. Because StW 578 mainly preserves the calotte, the taxonomic status of this specimen has been a matter of discussion. Within this context, here we employed high-resolution microtomography and a landmark-free registration method to explore taxonomically diagnostic features in the external surface of the StW 578 calotte. Our comparative sample included adult humans and common chimpanzees as well as one Australopithecus africanus specimen (Sts 5). We partially restored the StW 578 calotte digitally and compared it to extant specimens and Sts 5 using a landmark-free registration based on smooth and invertible surface deformation. Our comparative shape analysis reveals morphological differences with extant humans, especially in the frontal bones, and with extant chimpanzees, as well as intriguing specificities in the morphology of the StW 578 parietal bones. Lastly, our study suggests morphological proximity between StW 578 and Sts 5. Given the intimate relationship between the brain and the braincase, as well as the integration of the hominin face and neurocranium, we suggest that cranial vault shape differences between StW 578 and extant humans, if confirmed by further analyses, could be either explained by differences in brain surface morphology or in the face. Besides providing additional information about the morphology of the Jacovec calotte that will be useful in future taxonomic discussion, this study introduces a new protocol for the landmark-free analysis of fossil hominin cranial shape.Significance:• We provide further information on the enigmatic fossil specimen StW 578.• We introduce a new approach for the morphological study of fossil hominin crania.• We highlight morphological similarities between StW 578 and ‘Mrs Ples’

The atlas of StW 573 and the late emergence of human-like head mobility and brain metabolism

Functional morphology of the atlas reflects multiple aspects of an organism’s biology. More specifically, its shape indicates patterns of head mobility, while the size of its vascular foramina reflects blood flow to the brain. Anatomy and function of the early hominin atlas, and thus, its evolutionary history, are poorly documented because of a paucity of fossilized material. Meticulous excavation, cleaning and high-resolution micro-CT scanning of the StW 573 (‘Little Foot’) skull has revealed the most complete early hominin atlas yet found, having been cemented by breccia in its displaced and flipped over position on the cranial base anterolateral to the foramen magnum. Description and landmark-free morphometric analyses of the StW 573 atlas, along with other less complete hominin atlases from Sterkfontein (StW 679) and Hadar (AL 333-83), confirm the presence of an arboreal component in the positional repertoire of Australopithecus. Finally, assessment of the cross-sectional areas of the transverse foramina of the atlas and the left carotid canal in StW 573 further suggests there may have been lower metabolic costs for cerebral tissues in this hominin than have been attributed to extant humans and may support the idea that blood perfusion of these tissues increased over the course of hominin evolution.The DST-NRF for sponsoring the Micro-XCT facility at Necsa, and the DST-NRF and Wits University for funding the microfocus X-ray CT facility in the ESI. The Ghent University Special Research Fund (BOF-UGent) for the financial support of the Centre of Expertise UGCT (BOF.EXP.2017.0007), the Sterkfontein excavations and MicroCT scanning work have been provided by National Research Foundation and by PAST.http://www.nature.com/srepam2021Anatom

Frontal sinuses and human evolution

The frontal sinuses are cavities inside the frontal bone located at the junction between the face and the cranial vault and close to the brain. Despite a long history of study, understanding of their origin and variation through evolution is limited. This work compares most hominin species’ holotypes and other key individuals with extant hominids. It provides a unique and valuable perspective of the variation in sinuses position, shape, and dimensions based on a simple and reproducible methodology. We also observed a covariation between the size and shape of the sinuses and the underlying frontal lobes in hominin species from at least the appearance of Homo erectus. Our results additionally undermine hypotheses stating that hominin frontal sinuses were directly affected by biomechanical constraints resulting from either chewing or adaptation to climate. Last, we demonstrate their substantial potential for discussions of the evolutionary relationships between hominin species