Sterkfontein Research Articles

Osteopathology and insect traces in the Australopithecus africanus skeleton StW 431


 
 
 We present the first application of high-resolution micro computed tomography in an analysis of both the internal and external morphology of the lumbar region of StW 431 – a hominin skeleton recovered from Member 4 infill of the Sterkfontein Caves (South Africa) in 1987. The lumbar vertebrae of the individual present a number of proliferative and erosive bony processes, which were investigated in this study. Investigations suggest a complex history of taphonomic alteration to pre-existing spinal degenerative joint disease (SDJD) as well as post-mortem modification by an unknown insect. This study is in agreement with previous pathological diagnoses of SDJD which affected StW 431 and is the first time insect traces on this hominin are described. The results of this analysis attest to the complex series of post-mortem processes affecting the Sterkfontein site and its fossil assemblages.
 
 
 
 
 Significance: 
 
 
 
 First application of high-resolution micro computed tomography of the lumbar region of StW 431, a partial skeleton of Australopithecus africanus, attests to pre-existing degenerative joint disease and identifies post-mortem modification by an unknown insect.
 The co-occurrence of degenerative pathology and insect modification may not be unique to StW 431. A combination of traditional morphoscopic analysis and non-invasive high-resolution tomography is recommended.
 
 
 

Hominin first rib discovered at the Sterkfontein Caves, South Africa

First ribs – the first or most superior ribs in the thorax – are rare in the hominin fossil record, and when found, have the potential to provide information regarding the upper thorax shape of extinct hominins. Here, we describe a partial first rib from Member 4 of the Sterkfontein Caves, South Africa. The rib shaft is broken away, so only the head and neck are preserved. The rib is small, falling closest to small-bodied Australopithecus first ribs (AL 288-1 and MH1). Given that it was recovered near the StW 318 femur excavation, which also represents a small individual, we suggest that the two may be associated. Three-dimensional geometric morphometric analyses were used to quantify the rib fragment morphology and compare it to extant hominoid and other fossil hominin ribs. While only the proximal end is preserved, our analyses show that South African Australopithecus share derived features of the proximal first rib more closely resembling A. afarensis and later hominins than great apes.

The development of a new geospatial framework for the palaeoanthropological site of the Sterkfontein Caves, Cradle of Humankind, Gauteng, South Africa

Geographical Information Systems (GIS) provide an essential element in modern paleoanthropological inquiry through their ability to integrate a diverse range of data within a multidimensional spatial framework which can be used for data storage, analysis and modeling. One of the challenges of creating such a framework is the integration of legacy and new data (collected with digital technologies) at large sites with a long history of research. The Sterkfontein Caves, located in the Cradle of Humankind, is the richest Australopithecus-bearing locality in the world and has been the focus of intense palaeoanthropological research for the past 80 years. A diverse range of spatial data has been collected over this history and future integrative research necessitates the development of a unified, cohesive 3D GIS framework. In this paper we describe three phases of work undertaken to implement such a framework and discuss the next steps in its development and utilization for spatial analyses.

What’s new from the PAST?

2003, Bob Brain wrote in this journal about the first decade of operation of PAST, the Palaeontological Scientific Trust (then known as the Palaeo-Anthropology Scientific Trust). Entitled 'A perspective on the PAST', and written in his capacity as the NGO's scientific advisor, Brain described PAST's creation at the dawn of democracy in South Africa in 1994 as an effort to 'avert a serious financial crisis at the University of the Witwatersrand that was threatening the future of palaeoanthropological research there', particularly at the world-renowned Sterkfontein Caves. Brain outlined the central role PAST played in resuscitating student training and research in palaeoanthropology at Wits, such as supporting the discovery and development of the Little Foot skeleton at Sterkfontein, through public sector financial support from Anglo-American, Standard Bank, and other corporations.

Neutron microtomography-based virtual extraction and analysis of a cercopithecoid partial cranium (STS 1039) embedded in a breccia fragment from sterkfontein member 4 (South Africa).

The Plio-Pleistocene karstic sedimentary deposits of Sterkfontein Cave, South Africa, yielded numerous fossil primate specimens embedded in blocks of indurated breccia, including the partial cercopithecoid cranium labelled STS 1039. Because the surrounding matrix masks most of its morphology, the specimen remains taxonomically undetermined. While the use of X-ray microtomography did not allow extracting any structural information about the specimen, we experimented a new investigative technique based on neutron microtomography. Using this innovative approach, we successfully virtually extracted, reconstructed in 3D and quantitatively assessed the preserved dentognathic structural morphology of STS 1039, including details of its postcanine maxillary dentition. Following comparative analyses with a number of Plio-Pleistocene and extant cercopithecoid taxa, we tentatively propose a taxonomic attribution to the taxon Cercopithecoides williamsi. Our experience highlights the remarkable potential of this novel imaging method to extract diagnostic information and to identify the fossil remains embedded in hard breccia from the South African hominin-bearing cave sites.

Geospatial subsidence hazard modelling at Sterkfontein Caves

This paper covers a GIS1 approach to identifying hazardous areas at the Sterkfontein Caves. It makes a contribution to risk assessment of land with shallow caves underneath it. The aim of the study is to ensure public safety in a concentrated area frequently visited by the public and is part of a programme to identify appropriate digital technologies for mining. The geo-hazard subsidence model includes historic subsidence occurrances, terrain (water flow) and water accumulation. Water accumulating on the surface will percolate and reduce the strength of the soil mass, possibly inducing subsidence. Areas for further geotechnical investigation are identified, demonstrating that a GIS, geospatial reclassification tool has great potential for strengthening current risk assessment approaches in mining

SURFACE WATER AND GROUNDWATER INTERACTION IN THE UPPER CROCODILE RIVER BASIN, JOHANNESBURG, SOUTH AFRICA: ENVIRONMENTAL ISOTOPE APPROACH

The interaction between surface water and groundwater is a complex process that can potentially deteriorate the quality of water, which is highly needed by communities. An environmental isotope and stream discharge based study has been conducted in the upper Crocodile River Basin, Johannesburg, which is characterized by fractured crystalline rocks and dolomitic aquifers from which groundwater is extracted for diverse economic activities. The seepage of mine water into a dolomitic aquifer in the vicinity of the Sterkfontein cave has been quantified and falls between 24 × 106 m3/y and 29 × 106 m3/y. The environmental isotope results also show that the decanting mine water extensively interacted with the shallow groundwater and streams. On the other hand, the dolomites (Malapa area) that lie away from mine areas in different dolomitic compartment contain uncontaminated and old groundwater with low 3H, which indicates long residence time, with depleted 18O and 2H indicating a recharge that took place prior to evaporation, and afterwards the recharged water circulated for long period of time. Streams also lose water into the dolomitc aquifer through sinkholes and fractures. Therefore, surface water and groundwater are intimately connected in the area.

The stratigraphy and formation history of fossil- and artefact-bearing sediments in the Milner Hall, Sterkfontein Cave, South Africa: New interpretations and implications for palaeoanthropology and archaeology

The Sterkfontein palaeokarst deposits, the richest repository of Australopithecus fossils in the world, are currently divided into six members (M1–M6) and named the Sterkfontein Formation (Partridge and Watt, 1991). In this system, it was proposed that the passages and chambers deeper than the Silberberg Grotto formed most recently and are filled with comparatively young sediments from newer openings or reworked sediments from older, upper chambers. Here we describe the geomorphology, sedimentology, fauna and archaeological evidence from six deposits excavated near the base of the system in the Milner Hall. The use of a multidisciplinary approach enabled us to clarify the complex stratigraphic history, to track artefact-bearing deposits through multiple phases of deposition, and to identify an early deposit accumulated from the Silberberg Grotto to the base of the system. We propose that the Australopithecus-bearing Member 2 deposit originally extended down to near the base of the Milner Hall. We further propose that the vertical extent of the cave system was developed prior to the opening to the landscape surface, and that at that time the groundwater level was comparable to that seen now. We therefore argue that some of the earliest palaeoanthropological material in South Africa may have been deposited into the deepest chambers of the Sterkfontein Caves.

Homortomyces gen. nov., a new dothidealean pycnidial fungus from the Cradle of Humankind

Homortomyces is introduced as a new coelomycetous genus associated with leaf spots onCombretum erythrophyllum trees growing near and around the Sterkfontein caves, Maropeng, South Africa. Based on its transversely septate, brown conidia, the presence of paraphyses, and percurrent proliferation of the conidiogenous cells, the genus resembles Stilbospora (Melanoconidaceae, Diaporthales). It is distinct in having pycnidial condiomata, conidia lacking mucoid sheaths, and becoming muriform when mature. Its morphology and phylogenetic placement based on analyses of sequence data for the large subunit nuclear ribosomal RNA gene (LSU, 28S) as well as the ITS and 5.8S rRNA gene of the nrDNA operon, show that Homortomyces represents a novel genus in Dothideomycetes, although its familial relationships remain unresolved.

A complete second metatarsal (StW 89) from Sterkfontein Member 4, South Africa

The functional anatomy of the hominin foot has played a crucial role in studies of locomotor evolution in human ancestors and extinct relatives. However, foot fossils are rare, often isolated, and fragmentary. Here, we describe a complete hominin second metatarsal (StW 89) from the 2.0–2.6 million year old deposits of Member 4, Sterkfontein Cave, South Africa. Like many other fossil foot bones, it displays a mosaic of derived human-like features and primitive ape-like features. StW 89 possesses a domed metatarsal head with a prominent sulcus, indicating dorsiflexion at the metatarsophalangeal joint during bipedal walking. However, while the range of motion at the metatarsophalangeal joint is human-like in dorsiflexion, it is ape-like in plantarflexion. Furthermore, StW 89 possesses internal torsion of the head, an anatomy decidedly unlike that found in humans today. Unlike other hominin second metatarsals, StW 89 has a dorsoplantarly gracile base, perhaps suggesting more midfoot laxity. In these latter two anatomies, the StW 89 second metatarsal is quite similar to the recently described second metatarsal of the partial foot from Burtele, Ethiopia. We interpret this combination of anatomies as evidence for a low medial longitudinal arch in a foot engaged in both bipedal locomotion, but also some degree of pedal, and perhaps even hallucal, grasping. Additional fossil evidence will be required to determine if differences between this bone and other second metatarsals from Sterkfontein reflect normal variation in an evolving lineage, or taxonomic diversity.

Palaeomagnetic analysis of the Sterkfontein palaeocave deposits: Implications for the age of the hominin fossils and stone tool industries

Palaeomagnetic analysis was conducted on speleothems from Members 1–5 at Sterkfontein Cave, South Africa. Palaeomagnetic analysis of siltstone and speleothem from the bulk of Member 4 indicate a reversed magnetic polarity that dates the deposits and its Australopithecus africanus fossils to between 2.58 and ∼2.16 Ma. Further confirmation of this age comes in the form of two short normal polarity events correlated to the Rèunion (∼2.16 Ma) and Huckleberry Ridge (∼2.05 Ma) events in speleothem capping the bulk of Member 4 and coeval with deposition of the final phase of Member 4, including A. africanus fossil Sts 5. At ∼2.16–2.05 Ma, Sts 5 is the youngest representative of A. africanus yet discovered. Palaeomagnetic analysis of the Silberberg Grotto deposits identifies a single short geomagnetic field event in flowstone overlying the StW 573 Australopithecus fossil, which is suggested to represent the Rèunion event at ∼2.16 Ma. This further supports the uranium lead age estimates of 2.3–2.2 Ma for the StW 573 fossil. Based on a reversed polarity for the deposits below the skeleton it cannot be older than 2.58 Ma. If StW 573 is considered to be a second species of Australopithecus then this indicates that two species of Australopithecus are present at Sterkfontein between 2.6 and 2.0 Ma. All of the Member 5 deposits date to less than 1.8 Ma based on a comparison of palaeomagnetic, faunal, and electron spin resonance age estimates. The StW 53 fossil bearing infill (M5A) is intermediate in age between Member 4 and the rest of Member 5 (B-C) at around 1.78–1.49 Ma. The rest of Member 5 (B-C) containing Oldowan and Acheulian stone tools and Homo and Paranthropus fossils was deposited gradually between 1.40 and 1.07 Ma, much younger than previously suggested.

The first four million years of human evolution

In one of the last paragraphs of The origin of species (1859), Darwin famously suggested that ‘Much light will be thrown on the origin of man and his history’. When he published The descent of man 12 years later, there was still no fossil evidence of our earliest evolutionary history, and

Re-appraisal of the stratigraphy and determination of new U-Pb dates for the Sterkfontein hominin site, South Africa

Sterkfontein Caves is the single richest early hominin site in the world with deposits yielding one or more species of Australopithecus and possible early Homo, as well as an extensive faunal collection. The inability to date the southern African cave sites accurately or precisely has hindered attempts to integrate the hominin fossil evidence into pan-African scenarios about human evolutionary history, and especially hominin biogeography. We have used U-Pb and U-Th techniques to date sheets of calcium carbonate flowstone inter-bedded between the fossiliferous sediments. For the first time, absolute age ranges can be assigned to the fossil-bearing deposits: Member 2 is between 2.8 ± 0.28 and 2.6 ± 0.30 Ma and Member 4 between 2.65 ± 0.30 and 2.01 ± 0.05 Ma. The age of 2.01 ± 0.05 Ma for the top of Member 4 constrains the last appearance of Australopithecus africanus to 2 Ma. In the Silberberg Grotto we have reproduced the U-Pb age of ∼2.2 Ma of for the flowstones associated with StW573. We believe that these deposits, including the fossil and the flowstones, accumulated rapidly around 2.2 Ma. The stratigraphy of the site is complex as sediments are exposed both in the underground chambers and at surface. We present a new interpretation of the stratigraphy based on surface mapping, boreholes logs and U-Pb ages. Every effort was made to retain the Member system, however, only Members 2 and 4 are recognized in the boreholes. We propose that the deposits formally known as Member 3 are in fact the distal equivalents of Member 4. The sediments of Members 2 and 4 consisted of cone-like deposits and probably never filled up the cave. The U-Th ages show that there are substantial deposits younger than 400 ka in the underground cave, underlying the older deposits, highlighting again that these cave fills are not simple layer-cakes.

U–Pb dating of calcite–aragonite layers in speleothems from hominin sites in South Africa by MC-ICP-MS

Speleothems are found in association with hominin fossil-bearing cave deposits in South Africa and can be used to provide valuable chronological constraints. Such material is generally too old for U–Th dating and, although U–Pb geochronology presents a suitable alternative, bulk U concentrations are typically too low (<0.05 μg/g) to provide useful ages. For this reason, we used a simple non-invasive beta-scanner imaging screening step to identify U-rich (≥1 μg/g) domains that could be analyzed with MC-ICP-MS techniques to provide U–Pb ages. We demonstrate the technique using samples from Sterkfontein cave that exhibit infrequent <1 cm-thick layers with U concentrations ≥1 μg/g. Relict aragonite needles are found exclusively in these U-rich layers. We analyzed material from the same flowstone suite as Walker et al. (2006) and obtained a U–Pb age of ∼2.3 Ma that agrees well with their estimate of 2.24 ± 0.09 Ma. We also obtained similar U–Pb (0.164 ± 0.026 to 0.200 ± 0.052 Ma) and U–Th (0.148 ± 0.003 Ma) ages for another sample exhibiting U-rich layers. We recognize that open-system behaviour during the partial transformation of aragonite to calcite is a potential problem and argue, on the basis of geochemistry and age consistencies, that recrystallization took place rapidly after speleothem formation and did not significantly affect the U–Pb ages.

Using Strontium Isotopes to Study Site Accumulation Processes

Strontium isotopes (87Sr/86) in tooth enamel reflect the geological subtrate on which an animal lived during tooth development. Therefore, strontium isotopes of tecth in fosil cave accumulations are potentially useful in determining whether an animal was native to the vicinity of the site or was brought in by other agents such as predators from farther afield. In this study, we tested the ability of strontium isotopes to help determine the origins of fossil rodents in Gladysvale Cave, South Africa. First, biologically available 87 Sr/86) ratios were established using modern plants recovered from three geologically distintct areas, the Malmani dolomite, the Hekpoort andesite/basalt, and the Timeball Hill shale, all of which were found to be significantly different. Strontium isotope values were then measured on tooth enamel of rodents from a moder barn ow (Tyto alba) roost in Gladysvale (67%) versus those from other geological zones. We then measured strontium isotope values of enamel from 14 fossil rodent teecth from Gladysvale Cave. The average and range of values for the fossil rodents is similar to that of the modern owl roost rodents. Fifty-seven percent of the fossil rodent probably derived from the local dolomite, while others were brought in from at least 0.8 km away. A pilot study of 87Sr/86Sr ratios of fossil rodent teeth from Swartkrans Member 1 and Sterkfontein Member 4 indicates that 81% and 55% of those rodents, respectively, are from the local dolomite subtrate. Overall, this study shows that strontium isotopes can be a useful tool in taphonomy analyses by identifying non. Local individuals, and has great potential for elucidating more of the taphonomic history of fossil accumulations in the dolomitic cave sites of South Africa.

The view from the Lincoln Cave: mid- to late Pleistocene fossil deposits from Sterkfontein hominid site, South Africa

The Lincoln-Fault cave system lies adjacent to the Sterkfontein Cave system in the Cradle of Humankind World Heritage Site, Gauteng Province, South Africa. Lincoln Cave contains a mid- to late Pleistocene fossiliferous deposit which has been dated using uranium series methods to between 252,600 ± 35,600 and 115,300 ± 7,700 years old. Although speleologists presumed that there was no connection between the Lincoln Cave and Sterkfontein Cave systems, results of excavations conducted in 1997 suggest a link between the deposits. Detailed comparisons of artifacts, fauna, hominid material, and a statistical correspondence analysis (CA) of the macromammalian fauna in the deposits strongly support this hypothesis. The recovery of Early Acheulean-type artifacts from the Lincoln Cave suggests that older artifacts eroded out of Sterkfontein Member 5 West and were redeposited into the younger Lincoln Cave deposits. The close physical proximity of these deposits, and the nature of the material recovered from them, indicates that the material was probably redeposited via a link between the two cave systems. Although faunal mixing is present, it is possible to say that large carnivorans become more scarce at Sterkfontein during the mid- to late Pleistocene, while small canids and felids appear to become more abundant, indicating that large and small carnivorans probably varied their use of the site through time. This may also reflect an increasing presence of humans in the Sterkfontein area during the mid- to late Pleistocene.

U-Pb Isotopic Age of the StW 573 Hominid from Sterkfontein, South Africa

Sterkfontein cave, South Africa, has yielded an australopith skeleton, StW 573, whose completeness has excited great interest in paleoanthropology. StW 573, or "Little Foot," was found 25 meters below the surface in the Silberberg Grotto. 238U-206Pb measurements on speleothems immediately above and below the fossil remains, corrected for initial 234U disequilibrium, yield ages of 2.17 +/- 0.17 million years ago (Ma) and 2.24(-0.07)(+0.09) Ma, respectively, indicating an age for StW 573 of close to 2.2 Ma. This age is in contrast to an age of approximately 3.3 Ma suggested by magnetochronology and ages of approximately 4 Ma based on 10Be and 26Al, but it is compatible with a faunal age range of 4 to 2 Ma.

U–Pb dating of speleothems from Sterkfontein Cave, South Africa

U–Pb dating of speleothems from Sterkfontein Cave, South Africa

Basil Cooke's contributions to our understanding of South African cave deposits and fossil fauna

Throughout his career, Basil Cooke has been a very competent hard-rock geologist, but in his research he has concentrated on the relatively recent ‘overburden’, particularly a study of animal fossils that might be preserved in it, and information they can provide about the past environment of the time. Over 100 publications, from the first one in 1938 describing the Sterkfontein Cave deposits, to his most recent paper (Cooke, 2006) on East African fossil pigs, have demonstrated Cooke's dedication to this discipline and his meticulous attention to detail. His contribution to our understanding of faunal and environmental changes in Africa during the last five million years has been enormous.

Dolomitic vegetation of the Sterkfontein Caves World Heritage Site and its importance in the conservation of Rocky Highveld Grassland

An analysis of the vegetation of the Sterkfontein Caves (i.e. the natural area surrounding the caves) is presented. Releves were compiled in 24 stratified random sample plots. A TWINSPAN classification, refined by Braun-Blanquet procedures, revealed six plant communities, also referred to as vegetation units. For each of these vegetation units the species richness was determined. Plant communities of conservation importance were identified and new associations were formally described.