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Challenging the antiquity of the Cradle of Humankind, South Africa: Geochronological evidence restricts the age of Eurotomys bolti and Parapapio to less than 2.3 Ma at Waypoint 160, Bolt's Farm
Abstract
Waypoint 160 is a paleocave at Bolt's Farm in the 'Cradle of Humankind,' South Africa. It is known for the novel murid taxa Eurotomys bolti, argued to be morphologically intermediate between Eurotomys pelomyoides from Langebaanweg (∼5.1 Ma) and the earliest Otomyinae from Makapansgat Limeworks (∼3.0-2.6 Ma). Based on the presence of this specimen, an age of ∼4.5 Ma was inferred for Waypoint 160, making it far older than other Cradle sites. This biochronological age was used to argue that Parapapio and Cercopithecoides fossils from Waypoint 160 were the oldest in the region. Here, we provide a detailed sedimentological context for the in-situ deposits at Waypoint 160. We have identified interior cave deposits, in contrast to other sites at Bolt's Farm. Petrography confirms that one unit (facies D) contains in-situ microfaunal fossils, indicating the likely provenience of the E. bolti specimen. Palaeomagnetic analysis shows four periods of magnetic polarity in the sequence. Using U-Pb ages as chronological pins, we argue that the upper part of the sequence records a polarity change at the end of the Olduvai subChron (1.78 Ma). The lower part of the sequence records a polarity shift from normal to reversed that likely relates to the Feni subChron (2.16-2.12 Ma), based on a basal flowstone U-Pb age of 2.269 ± 0.075 Ma. Together this points to a depositional window of ∼500 ka, with the Parapapio and E. bolti tentatively attributed to the micromammal fossil-bearing layers dating to ∼2.27-2.07 Ma. This has significant implications for other biochronological dates in South Africa, as E. bolti is now less than ∼2.27 Ma, younger than the oldest Otomyinae at Makapansgat Limeworks and thus not ancestral to them. This chronology for Waypoint 160 challenges the presence of older, early to mid-Pliocene deposits >3.20 Ma in the Gauteng portion of the Cradle.
Bolt’s Farm is the name given to a series of non-hominin bearing fossil sites that have often been suggested to be some of the oldest Pliocene sites in the Cradle of Humankind, South Africa. This article reports the results of the first combined Uranium-Series and Electron Spin Resonance (US-ESR) dating of bovid teeth at Milo’s Cave and Aves Cave at Bolt’s Farm. Both tooth enamel fragments and tooth enamel powder ages were presented for comparison. US-ESR, EU and LU models are calculated. Overall, the powder ages are consistent with previous uranium-lead and palaeomagnetic age estimates for the Aves Cave deposit, which suggest an age between ~3.15 and 2.61 Ma and provide the first ages for Milo’s Cave dates to between ~3.1 and 2.7 Ma. The final ages were not overly dependent on the models used (US-ESR, LU or EU), which all overlap within error. These ages are all consistent with the biochronological age estimate (<3.4–>2.6 Ma) based on the occurrence of Stage I Metridiochoerus andrewsi . Preliminary palaeomagnetic analysis from Milo’s Cave indicates a reversal takes place at the site with predominantly intermediate directions, suggesting the deposit may date to the period between ~3.03 and 3.11 Ma within error of the ESR ages. This further suggests that there are no definitive examples of palaeocave deposits at Bolt’s Farm older than 3.2 Ma. This research indicates that US-ESR dating has the potential to date fossil sites in the Cradle of Humankind to over 3 Ma. However, bulk sample analysis for US-ESR dating is recommended for sites over 3 Ma.
Initial radioactive disequilibrium amongst intermediate nuclides of the U decay chains can have a significant impact on the accuracy of U–Pb ages, especially in young samples. For samples that can reasonably be assumed to have attained radioactive equilibrium at the time of analysis, a relatively straightforward correction may be applied. However, in younger materials where this assumption is unreasonable, it is necessary to replace the familiar U–Pb age equations with more complete expressions that account for growth and decay of intermediate nuclides through time. DQPB is software for calculating U–Pb ages while accounting for the effects of radioactive disequilibrium among intermediate nuclides of the U decay chains. The software is written in Python and distributed as both a pure Python package and a stand-alone graphical user interface (GUI) application that integrates with standard Microsoft Excel spreadsheets. The software implements disequilibrium U–Pb equations to compute ages using various approaches, including concordia intercept ages on a Tera–Wasserburg diagram, U–Pb isochron ages, Pb*/U ages based on single aliquots, and 207Pb-corrected ages. While these age-calculation approaches are tailored toward young samples that cannot reasonably be assumed to have attained radioactive equilibrium at the time of analysis, they may also be applied to older materials where disequilibrium is no longer analytically resolvable. The software allows users to implement a variety of regression algorithms based on both classical and robust statistical approaches, compute weighted average ages and construct customisable, publication-ready plots of U–Pb age data. The regression and weighted average algorithms implemented in DQPB may also be applicable to other (i.e. non-U–Pb) geochronological datasets.
Sterkfontein is the most prolific single source of Australopithecus fossils, the vast majority of which were recovered from Member 4, a cave breccia now exposed by erosion and weathering at the landscape surface. A few other Australopithecus fossils, including the StW 573 skeleton, come from subterranean deposits [T. C. Partridge et al. , Science 300, 607–612 (2003); R. J. Clarke, K. Kuman, J. Hum. Evol. 134, 102634 (2019)]. Here, we report a cosmogenic nuclide isochron burial date of 3.41 ± 0.11 million years (My) within the lower middle part of Member 4, and simple burial dates of 3.49 ± 0.19 My in the upper middle part of Member 4 and 3.61 ± 0.09 My in Jacovec Cavern. Together with a previously published isochron burial date of 3.67 ± 0.16 My for StW 573 [D. E. Granger et al. , Nature 522, 85–88 (2015)], these results place nearly the entire Australopithecus assemblage at Sterkfontein in the mid-Pliocene, contemporaneous with Australopithecus afarensis in East Africa. Our ages for the fossil-bearing breccia in Member 4 are considerably older than the previous ages of ca. 2.1 to 2.6 My interpreted from flowstones associated with the same deposit. We show that these previously dated flowstones are stratigraphically intrusive within Member 4 and that they therefore underestimate the true age of the fossils.
The region ∼40 km north-west of Johannesburg, South Africa, known locally as the Cradle of Humankind, is of global significance as the caves preserve Plio-Pleistocene faunal and early hominin fossils. Despite a long history of research, there is still a need to contextualise and date the remarkable collection of fossils. An important but understudied palaeontological site, Bolt's Farm, may provide a key to addressing this as it preserves a series of >20 separate eroded palaeocave remnants occurring across a 1 km length of hillside. This is in contrast to highly concentrated deposits representing a single site, as is the case at the majority of the sites in the region. Historically, a lithostratigraphic approach to South African palaeocaves made reconstruction and comparison within, and between, deposits difficult or impossible. Here, we present a sequence stratigraphic approach and simple facies model for three palaeocave remnants at Bolt's Farm collectively termed the Aves Cave Complex (ACC), and a chronology based on combined uranium lead (U-Pb) dating, of basal and capping flowstones, and palaeomagnetic analysis. Results indicate that these currently discrete localities, formed together from a single entry dating to the end of the Gauss Normal Polarity Chron between 3.03 and 2.61 Ma, making ACC one of the oldest directly dated fossil deposits in the Cradle. The ACC contains the earliest occurrence of a key biochronological species, Metridiochoerus andrewsi, in the region. This work reinforces the model that clastic sedimentation and flowstone precipitation do not occur concurrently in Cradle caves; rather their mutually exclusive formation is driven by allocyclic changes in hydroclimate. This research contributes to understanding how Bolt's Farm developed the unprecedented high density of palaeokarst observed today, by offering the first evidence that currently discrete localities were once connected as a single cave system.
The time scale for marine magnetic anomalies for the Late Cretaceous through Neogene (C-sequence) and Middle Jurassic through Early Cretaceous (M-sequence with deep-tow extension) has been calibrated through magnetostratigraphic studies to biostratigraphy, cycle-stratigraphy and selected radioisotope-dated levels. The majority of the geomagnetic polarity time scale for the past 160 Myr is constructed by fitting spreading rate models to these constraints. The status of the geomagnetic polarity time scale for each geologic period is summarized in the appropriate period chapters.
This chapter incorporates some of the discussions from the Geomagnetic Polarity Time Scale chapters in GTS2004 and GTS2012 by J.G. Ogg and A.G. Smith. The derivation of age-models for the C-sequence and the M-sequence of polarity chrons are new to GTS2020.
Bolt’s Farm is a Plio-Pleistocene fossil site located within the southwestern corner of the UNESCO Hominid Fossil Sites of South Africa World Heritage Site. The site is a complex of active caves and more than 20 palaeokarst deposits or pits, many of which were exposed through the action of lime mining in the early 20th century. The pits represent heavily eroded cave systems, and as such associating the palaeocave sediments within and between the pits is difficult, especially as little geochronological data exists. These pits and the associated lime miner’s rubble were first explored by palaeoanthropologists in the late 1930s, but as yet no hominin material has been recovered. The first systematic mapping was undertaken by Frank Peabody as part of the University of California Africa Expedition (UCAE) in 1947–1948. A redrawn version of the map was not published until 1991 by Basil Cooke and this has subsequently been used and modified by recent researchers. Renewed work in the 2000s used Cooke’s map to try and relocate the original fossil deposits. However, Peabody’s map does not include all the pits and caves, and thus in some cases this was successful, while in others previously sampled pits were inadvertently given new names. This was compounded by the fact that new fossil bearing deposits were discovered in this new phase, causing confusion in associating the 1940s fossils with the deposits from which they originated; as well as associating them with the recently excavated material. To address this, we have used a Geographic Information System (GIS) to compare Peabody’s original map with subsequently published maps. This highlighted transcription errors between maps, most notably the location of Pit 23, an important palaeontological deposit given the recovery of well-preserved primate crania ( Parapapio , Cercopithecoides ) and partial skeletons of the extinct felid Dinofelis . We conducted the first drone and Differential Global Positioning System (DGPS) survey of Bolt’s Farm. Using legacy data, high-resolution aerial imagery, accurate DGPS survey and GIS, we relocate the original fossil deposits and propose a definitive and transparent naming strategy for Bolt’s Farm, based on the original UCAE Pit numbers. We provide datum points and a new comprehensive, georectified map to facilitate spatially accurate fossil collection for all future work. Additionally, we have collated recently published faunal data with historic fossil data to evaluate the biochronological potential of the various deposits. This suggests that the palaeocave deposits in different pits formed at different times with the occurrence of Equus in some pits implying ages of <2.3 Ma, whereas more primitive suids ( Metridiochoerus ) hint at a terminal Pliocene age for other deposits. This study highlights that Bolt’s Farm contains rare South African terminal Pliocene fossil deposits and creates a framework for future studies of the deposits and previously excavated material.
The Cradle of Humankind (Cradle) in South Africa preserves a rich collection of fossil hominins representing Australopithecus, Paranthropus and Homo1. The ages of these fossils are contentious2–4 and have compromised the degree to which the South African hominin record can be used to test hypotheses of human evolution. However, uranium–lead (U–Pb) analyses of horizontally bedded layers of calcium carbonate (flowstone) provide a potential opportunity to obtain a robust chronology5. Flowstones are ubiquitous cave features and provide a palaeoclimatic context, because they grow only during phases of increased effective precipitation6,7, ideally in closed caves. Here we show that flowstones from eight Cradle caves date to six narrow time intervals between 3.2 and 1.3 million years ago. We use a kernel density estimate to combine 29 U–Pb ages into a single record of flowstone growth intervals. We interpret these as major wet phases, when an increased water supply, more extensive vegetation cover and at least partially closed caves allowed for undisturbed, semi-continuous growth of the flowstones. The intervening times represent substantially drier phases, during which fossils of hominins and other fossils accumulated in open caves. Fossil preservation, restricted to drier intervals, thus biases the view of hominin evolutionary history and behaviour, and places the hominins in a community of comparatively dry-adapted fauna. Although the periods of cave closure leave temporal gaps in the South African fossil record, the flowstones themselves provide valuable insights into both local and pan-African climate variability. Climate-driven periodicity of flowstone accretion between 3.2 and 1.3 million years ago in Cradle of Humankind caves reveals that the presence of hominin fossils reflects accumulation in open caves during intermittent, substantially drier phases.
Interannual variability of African rainfall impacts local and global communities, but its past behaviour and response in future climate projections are poorly understood. This is primarily due to short instrumental records and a lack of long high-resolution palaeoclimate proxy records. Here we present an annually resolved 91,000 year Early Pleistocene record of hydroclimate from the early hominin-bearing Makapansgat Valley, South Africa. Changes in speleothem annual band thickness are dominated by precession over four consecutive orbital cycles with strong millennial-scale periodicity. The frequency of interannual variability (2.0-6.5 yr oscillations) does not change systematically, yet its amplitude is modulated by the orbital forcing. These long-term characteristics of interannual variability are reproduced with transient climate model simulations of water balance for South Africa from the Late Pleistocene to Recent. Based on these results, we suggest that the frequency of interannual variations in southern African rainfall is likely to be stable under anthropogenic warming, but that the size of year-to-year variations may increase. We see an orbitally forced increase in the amplitude of interannual climate variability between 1.8 Ma and 1.7 Ma coincident with the first evidence for the Acheulean stone tool technology.
Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa.
ELife digest
Species of ancient humans and the extinct relatives of our ancestors are typically described from a limited number of fossils. However, this was not the case with Homo naledi. More than 1500 fossils representing at least 15 individuals of this species were unearthed from the Rising Star cave system in South Africa between 2013 and 2014. Found deep underground in the Dinaledi Chamber, the H. naledi fossils are the largest collection of a single species of an ancient human-relative discovered in Africa.
After the discovery was reported, a number of questions still remained. Not least among these questions was: how old were the fossils? The material was undated, and predictions ranged from anywhere between 2 million years old and 100,000 years old. H. naledi shared several traits with the most primitive of our ancient relatives, including its small brain. As a result, many scientists guessed that H. naledi was an old species in our family tree, and possibly one of the earliest species to evolve in the genus Homo.
Now, Dirks et al. – who include many of the researchers who were involved in the discovery of H. naledi – report that the fossils are most likely between 236,000 and 335,000 years old. These dates are based on measuring the concentration of radioactive elements, and the damage caused by these elements (which accumulates over time), in three fossilized teeth, plus surrounding rock and sediments from the cave chamber. Importantly, the most crucial tests were carried out at independent laboratories around the world, and the scientists conducted the tests without knowing the results of the other laboratories. Dirks et al. took these extra steps to make sure that the results obtained were reproducible and unbiased.
The estimated dates are much more recent than many had predicted, and mean that H. naledi was alive at the same time as the earliest members of our own species – which most likely evolved between 300,000 and 200,000 years ago. These new findings demonstrate why it can be unwise to try to predict the age of a fossil based only on its appearance, and emphasize the importance of dating specimens via independent tests. Finally in two related reports, Berger et al. suggest how a primitive-looking species like H. naledi survived more recently than many would have predicted, while Hawks et al. describe the discovery of more H. naledi fossils from a separate chamber in the same cave system.
DOI: http://dx.doi.org/10.7554/eLife.24231.002
In spite of the increasing number of papers on cave sediments published during the last few decades, no one has focused from a sedimentological point of view on the processes that take place specifically within the coastal karst areas of carbonate islands. The objective of the present investigations is to deal with the sedimentary processes that take place inside two littoral caves of Mallorca (western Mediterranean), characterizing the different facies existing in the particular geological, geochemical, and hydrological setting that represents this very specific cave sedimentary environment. The recent exploration of extensive underwater galleries and chambers into some outstanding coastal caves of the island, has permitted the recognition of important accumulations of present-day sedimentary infillings in their drowned passages. Both the Pirata-Pont-Piqueta cave system and the Cova de sa Gleda have floors covered by muddy and/or sandy sediments which, in a wide sense, fit into two well-differentiated categories. On one hand we have allochthonous reddish mud sediments (mainly siliciclastic) and on the other hand autochthonous yellowish carbonate mud or sands. The mixing of both materials is also frequent as well as the accumulation of large blocks and debris due to the breakdown of roof and cave walls. A series of 21 manual cores was obtained by scuba-divers in both caves, in order to collect the full thickness of sedimentary fill. Soil samples at the entrance of the two caves, as well as rock samples of the walls of both sites, were also obtained for a later comparison. Several sedimentary facies can be distinguished, which include coarse-grained deposits (entrance facies and breakdown blocks), fine-grained siliceous sediments (silts and muddy deposits with very variable organic matter content), carbonate deposits composed of calcite raft accumulations and/ or weathering-released limestone grains, and mixed facies including diverse proportions of the other sediment types. There are also some relict deposits composed of siliceous red silts, which are affected by polygonal desiccation cracks. In all the cases, the siliciclastic elements (quartz and feldspars, mainly) are related to rain events supplying dust of Saharan origin. The deposits and facies described herein correspond to different sedimentary environments that can be individualized inside the caves (collapse entrances, breakdown chambers, fully drowned passages and chambers, pools with free water surface.), and reflect very specific hydrological, geochemical, and mechanical processes related to the coastal nature of the studied karst caves.
Palaeontological and geological research at the Gladysvale Cave during the last decade has concentrated on de-roofed deposits located outside the Main Chamber. This area has been termed the Gladysvale External Deposit (GVED) and consists of fossil-rich calcified and decalcified sediments. Here we report on the recent analysis of both the faunal material and the geological context of this deposit. The faunal assemblage, excavated from the decalcified sediments contains 29 mammal species including taxa rare or absent in the Witwatersrand Plio-Pleistocene fossil record (e.g. Pelorovis and Kobus leche). Carnivores and porcupines are identified as accumulating agents of the bones. No new hominin findings can be reported from this deposit, and no cultural remains have been recovered. Geologically the calcified and decalcified breccias represent part of a large talus cone that is relatively unexposed. Uniquely for a cave fill in the Witwatersrand hominin-bearing sites, the sediments are horizontally stratified and form a number of flowstone bound sequences. The dating of the in situ cemented sediments is based on electron spin resonance (ESR) and palaeomagnetism. Recent results indicate that the deposits are of Middle-Pleistocene age.
The Drimolen palaeocave system has been actively excavated since the 1990s and has produced a demographically-diverse record of Paranthropus robustus, early Homo, and a substantial record of early Pleistocene bone tools; all recovered from the Main Quarry, a single fossil bearing deposit within the system. Early surveys identified an isolated solution-tube 55 meters west of the Main Quarry filled with decalcified matrix and fossils (the Drimolen Makondo). Recent excavations into the Makondo have started to address the geology, depositional history, and faunas of the deposits; particularly whether the Makondo represents a distant uneroded part of the Main Quarry infill, or deposits in-filled into a separate entrance within the same system. We present the first description of fossil macromammalian faunas from the Makondo, excavated 2013-2014. A total of 531 specimens were recovered, 268 (50.5%) of which are taxonomically identifiable. The resulting list is diverse given the sample size and includes primate and carnivore taxa frequently recovered at other terminal Pliocene and earlier Pleistocene localities, as well as more rarely encountered species and elements like the first postcranial remains of the hunting hyaenid (Chasmaporthetes ?nitidula) from the Cradle. While some of the Makondo fauna overlaps with taxa recovered from the Main Quarry, there are key differences between the described samples that may reflect differences in the age of the deposits and/or taphonomic processes between these deposits at Drimolen.
Karst aquifers require transport of clastic sediments for the conduit system to remain open and thus to continue to be an eligible route for ongoing speleogenesis. Sediments are injected into the aquifer by sinking surface streams and through sinkholes, vertical shafts, open fractures, and other pathways from the land surface. Transport of clastic sediments tends to be episodic with sediment loads held in storage until moved by infrequent flood events. Although the overall mix of clastics depends on material available in the source area, distinctly different facies are universally recognizable depending on the flow dynamics within the conduit system. The facies are most clearly recognized when the source areas provide a wide variety of particle sizes from clays to boulders. In order of decreasing prevalence, one can distinguish (i) channel facies: usually well-sorted and often well-stratified silt through gravel carried as bedload at intermediate flow levels, (ii) slackwater facies: mostly clay and silt, carried as suspended load and deposited from floodwaters backfilled into the conduit system, (iii) thalweg facies: coarse gravel- to cobble-sized material, well-winnowed, forming armoring on underground streams that moves only during flood flow, (iv) backswamp facies: fine-grained sediments derived from the insoluble residue of the limestone, deposited under phreatic conditions with little lateral transport, and (v) diamicton facies: masses of unsorted, unstratified clays through boulders carried as a slurry during flood events.
The tufa deposits of the Ghaap Plateau escarpment provide a rich, yet minimally explored, geological archive of climate and environmental history coincident with hominin evolution in South Africa. This study examines the sedimentary and geochemical records of ancient and modern tufas from Buxton-Norlim Limeworks, Groot Kloof, and Gorrokop, to assess the potential of these sediments for providing reliable chronologies of high-resolution, paleoenvironmental information. Chronometric dating demonstrates that tufa formation has occurred from at least the terminal Pliocene through to the modern day. The stable isotope records show a trend toward higher, more variable δ18O and δ13C values with decreasing age from the end of the Pliocene onwards. The long-term increase in δ18O values corresponds to increasingly arid conditions, while increasing δ13C values reflect the changing proportion of C3/C4 vegetation in the local environment. Analysis of the Thabaseek Tufa, in particular, provides valuable evidence for reconstructing the depositional and chronological context of the enigmatic Taung Child (Australopithecus africanus). Collectively, the results of the present study demonstrate the potential of these deposits for developing high-precision records of climate change and, ultimately, for understanding the causal processes relating climate and hominin evolution.
The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 (‘Little Foot’) in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling. Much of the existing chronology based on uranium–lead dating and palaeomagnetic stratigraphy has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence. Earlier dating with cosmogenic nuclides suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking. Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 ± 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it. The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa. We also date the earliest stone tools at Sterkfontein to 2.18 ± 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans and Wonderwerk.
Karst aquifers demand continuous transport of clastic sediments if the conduit system is to remain open. Sediments are injected into the aquifer by sinking surface streams and through sinkholes, vertical shafts, open fractures, and other pathways from the land surface of sufficient aperture to permit gravity- and inwash-driven transport. Much transport of clastic sediments tends to be episodic with sediment loads held in storage until moved by infrequent flood events. Although the overall mix of clastic material depends on material available in the source area, distinctly different facies are recognizable depending on the flow dynamics within the conduit system. The facies are most clearly recognized when the source areas provide a wide variety of particle sizes from clays to boulders. In order of decreasing stream power, one can distinguish (i) diamicton facies: masses of unsorted, unstratified clays through boulders carried as a slurry during high energy flood events, (ii) thalweg facies: coarse gravel to cobble size material, well winnowed, forming armoring on underground streams that moves only during flood flow, (iii) channel facies: usually well sorted and often well stratified silt though gravel carried as bedload at intermediate stream powers, (iv) slackwater facies: mostly clay and silt carried as suspended load and deposited from floodwaters backfilled into the conduit system, (v) backswamp facies: mostly clay derived from the insoluble residue of the limestone, deposited under phreatic conditions with little lateral transport.
Deposits yielding australopithecines, other fossil mammals and an
industry recalling the Oldowan are succeeded by an Acheulian assemblage,
overlain by flood plain silts with abundant spreads of later artifacts.
The structure is dominated by an asymmetric anticline.
Palaeoenvironments are reconstructed and the nature of the raw materials
and of the tool makers themselves are briefly discussed.
Since 2006, the HRU team has systematically prospected the fossiliferous area of Bolt's Farm located near the Sterkfontein Caves in the Cradle of Human kind World Heritage Site (Gauteng Province, South Africa). To date, Bolt's Farm has yielded more than 30 fossiliferous sites. In this article, new sites discovered in 2010 are presented. Some of them show great potential regarding the Plio-Pleistocene fauna thus far processed from ex situ calcified sediment dumpsites. The material from one of these sites, Milo's Pit A, is currently being prepared but preliminary results suggest a Pliocene age for this locality based on the presence of a third molar attributable to Stage I Metridiochoerus andrewsi / Metridiochoerus shawi. This would make Milo A the second oldest site in the Cradle of Humankind after Waypoint 160, also located on Bolt's Farm.
Reddish mud-rich sediments are common in several karst areas, in the form of red surface soils and clastic cave infillings. The origin and significance of red surface soils have been much debated over recent years, while clastic mud-rich sediments in cave environments have received less attention from geoscientists. The genetic relationship between these two materials still remains uncertain. Because these sediments are mainly composed of fine-grained materials, their study has been generally focused on the clay fraction only. This paper compares the clay fraction of red surface soils and mud-rich cave sediments in the Montagnola Senese karst massif. Previous studies have demonstrated that, in this area, red cave muds originate from the erosion of the similarly red surface soils, that were subsequently re-deposited in the cave environment. Despite these well-established genetic relations, notable differences in the clay fraction of these two materials have been recognized in the present study. These differences are likely to be attributable to the different grades of pedogenetic weathering that affected the two materials. This study demonstrates that the genetic relationship between mud-rich cave sediments and red surface soils can be misinterpreted when only the clay mineral fraction is considered.
Ocean Drilling Program Site 1085 provides a continuous marine sediment record off southern South West Africa for at least the last three and half million years. The n-alkane partial derivative(13) C record from this site records changes in past vegetation and provides an indication of the moisture availability of SW Africa during this time period. Very little variation, and no apparent trend, is observed in the n-alkane delta C-13 record, suggesting stable long-term conditions despite significant changes in East African tectonics and global climate. Slightly higher n-alkane delta C-13 values occur between 3.5 and 2.7 Ma suggesting slightly drier conditions than today. Between 2.5 and 2.7 Ma there is a shift to more negative n-alkane delta C-13 values suggesting slightly wetter conditions during a similar to 0.2 Ma episode that coincides with the intensification of Northern Hemisphere Glaciation (iNHG). From 2.5 to 0.4 Ma the n-alkane delta C-13 values are very consistent, varying by less than +/- 0.5 parts per thousand and suggesting little or no long-term change in the moisture availability of South West Africa over the last 2.5 million years. This is in contrast to the long-term drying trend observed further north offshore from the Namib Desert and in East Africa. A comparison of the climate history of these regions suggests that Southern Africa may have been an area of long-term stability over the last 3.5 Myrs. (C) 2011 Elsevier B.V. All rights reserved.
Five fabrics were identified in Alpine and Irish caves on the basis of morphological and microstructural characteristics, and related to growth mechanisms and growth environment. Columnar and fibrous fabrics grow when speleothems are continuously wet, and from fluids at near equilibrium conditions (low supersaturation; SIcc < 0.35), through the screw dislocation mechanism. The highly defective microcrystalline fabrics form at the same supersaturation range as columnar fabric but under variable discharge and the presence of growth inhibitors. Dendritic fabrics, which have the highest density of crystal defects, develop in disequilibrium conditions (high supersaturation) under periodic very low-flow-regime periods that result in prolonged outgassing. Cave calcareous tufa forms in disequilibrium conditions. Only the calcite crystals of fabrics formed at low supersaturation seem to precipitate near-isotopic-equilibrium conditions.
This interdisciplinary book interprets early human evolution in the context of the local ecology and specific habitats. It assesses carefully the possible role of climate change in driving early human evolution. Bringing an ecological and biogeographic perspective to recent fossil finds, the book provides a new synthesis of ideas on hominid evolution. It will be a valuable resource for researchers in physical, biological, or paleoanthropology, evolutionary biology or biogeography.
The Early Pleistocene site of Swartkrans in South Africa’s Cradle of Humankind World Heritage Site has been significant for our understanding of the evolution of both early Homo and Paranthropus, as well as the earliest archaeology of southern Africa. Previous attempts to improve a faunal age estimate of the earliest deposit, Member 1, had produced results obtained with uranium-lead dating (U–Pb) on flowstones and cosmogenic burial dating of quartz, which placed the entire member in the range of >1.7/1.8 Ma and <2.3 Ma. In 2014, two simple burial dates for the Lower Bank, the earliest unit within Member 1, narrowed its age to between ca. 1.8 Ma and 2.2 Ma. A new dating program using the isochron method for burial dating has established an absolute age of 2.22 ± 0.09 Ma for a large portion of the Lower Bank, which can now be identified as containing the earliest Oldowan stone tools and fossils of Paranthropus robustus in South Africa. This date agrees within one sigma with the U–Pb age of 2.25 ± 0.08 Ma previously published for the flowstone underlying the Lower Bank and confirms a relatively rapid rate of accumulation for a large portion of the talus.
We define 17 African land mammal ages, or AFLMAs, covering the Cenozoic record of the Afro-arabian continent, the planet’s second largest land mass. While fossiliferous deposits are absent on the eroded plateau of the continent’s interior, almost 800 fossil genera from over 350 locations have now been identified in coastal deposits, karst caves, and in the Neogene rift valleys. Given a well-developed geochronologic framework, together with continuing revision to the fossil record—both stimulated by the story of human evolution in Africa—and also to compensate for the variation in fossil ecosystems across such great distances, the AFLMAs are biochronological units defined by type localities, and not biozones to be recognized by the occurrence of certain genera. Disparities are notable: Africa is the highest of all continents, but almost every Paleogene locality was formed at sea level; the fossil record of its great rainforest ecosystem remains virtually unknown; and the Paleogene fauna is relatively isolated, whereas the Neogene begins with open exchange with Laurasia following the Tauride collision, with a simultaneous opening of the East African rift valleys in which the newly revolutionized fauna is abundantly preserved. Notably, the continent-wide and comprehensive documentation of the African mammalian record reveals an unparalleled rate of transformation in the hominin lineage, unmatched by any other group, in response to the Neogene expansion of the open-country ecosystem.
Dating the Drimolen hominins
Fossil hominins from South Africa are enriching the story of early human evolution and dispersal. Herries et al. describe the geological context and dating of the hominin-bearing infilled cave, or palaeocave, at a site called Drimolen in South Africa (see the Perspective by Antón). They focus on the age and context of a recently discovered Homo erectus sensu lato fossil and a Paranthropus robustus fossil, which they dated to ∼2.04 million to 1.95 million years ago. This makes Drimolen one of the best-dated sites in South Africa and establishes these fossils as the oldest definitive specimens of their respective species ever discovered. The age confirms that species of Australopithecus, Paranthropus , and early Homo overlapped in the karst of South Africa ∼2 million years ago.
Science , this issue p. eaaw7293 ; see also p. 34
We review the ages of Quaternary magnetic polarity reversals and magnetic excursions. Improvements in radioisotopic ⁴⁰Ar/³⁹Ar dating of reversals and excursions reflect the use of multi-collector mass spectrometers, along with ultra-low backgrounds, laser-based incremental heating methods, and adoption of 28.201 Ma for the Fish Canyon sanidine (FCs) standard age (Kuiper et al., 2008). These improvements have brought ⁴⁰Ar/³⁹Ar ages of reversals and excursions into close correspondence with astrochronological ages based on the correlation of δ¹⁸O data to LR04 (Lisiecki and Raymo, 2005) and, in a few cases, correlation to ice-core chronologies. Ages of two polarity reversals, the Matuyama-Brunhes boundary and base Olduvai, are at odds with ages given in popular geomagnetic polarity timescales. Sedimentary records of the Laschamp and Iceland Basin excursion are numerous and widespread, and attest to global manifestation and global synchronicity of these excursions. Records of other Quaternary excursions are less numerous. The Blake excursion (∼115 ka) has been recorded in North Atlantic sediments, Chinese loess, Indian Ocean volcanics, and Spanish speleothems. The Santa Rosa excursion (∼932 ka) has been recorded in North Atlantic and Phillipine Basin sediments, as well as in volcanic rocks from New Mexico and Galapagos. The Punaruu excursion (∼1115 ka) has been observed in sediments from the North Atlantic and California Margin as well as in volcanic rocks on Tahiti. Uniformity of individual excursion ages, using astrochronological, ⁴⁰Ar/³⁹Ar and U–Th methods, argues for synchronous global manifestation of excursions, strengthening the usefulness of magnetic excursions (and reversals) in Quaternary stratigraphy.
The Sterkfontein Caves is currently the world's richest Australopithecus-bearing site. Included in Sterkfontein's hominin assemblage is StW 573 ('Little Foot'), a near-complete Australopithecus skeleton discovered in Member 2 in the Silberberg Grotto. Because of its importance to the fossil hominin record, the geological age of StW 573 has been the subject of significant debate. Three main hypotheses have been proposed regarding the formation and age of Member 2 and by association StW 573. The first proposes that Member 2 (as originally defined in the type section in the Silberberg Grotto) started to accumulate at around 2.58 Ma and that the unit is contained within the Silberberg Grotto. The second proposes that Member 2 started forming before 3.67 ± 0.16 Ma and that the deposit extends into the Milner Hall and close to the base of the cave system. The third proposes a 'two-stage burial scenario', in which some sediments and StW 573 represent a secondary and mixed-age accumulation reworked from a higher cave. The stratigraphic and sedimentological implications of these hypotheses are tested here through the application of a multiscale investigation of Member 2, with reference to the taphonomy of the StW 573 skeleton. The complete infilling sequence of Member 2 is described across all exposures of the deposit in the Silberberg Grotto and into the Milner Hall. Sediments are generally stratified and conformably deposited in a sequence of silty sands eroded from well-developed lateritic soils on the landscape surface. Voids, clasts and bioclasts are organized consistently across and through Member 2 conforming with the underlying deposit geometry, indicating gradual deposit accretion with no distinct collapse facies evident and only localized intra-unit postdepositional modification. The stratigraphy and sedimentology of Member 2 support a simple single-stage accumulation process of Member 2 and a primary association between the sediments of Member 2 and the StW 573 'Little Foot' skeleton.
South Africa contains a wealth of palaeokarst deposits that have yielded hominin fossils and Early Stone Age archaeology. Despite the complex nature of deposition within many of these caves there has been a dearth of detailed geoarchaeological studies undertaken on these sites. Many sites in South Africa have been interpreted using an overly simplistic Member System based on simplified sedimentological attributes, rather than chronostratigrahic units. Many of the defined Members thus identify different, but contemporary geological processes occurring in the caves. This has caused serious confusion in reconstructing the life histories of palaeocaves and the ages of the fossil remains interned within them. It is critical to uncover new sites that have not been extensively altered by decades of data collection and destructive mining techniques employed early in their discovery. Although unmined sites present their own problems with regards to extensive colluvium cover and access to fossil-bearing units, analysing strata that is found in-situ enhances overall confidence of interpretations drawn. A wealth of geoarchaeological and 3D visualisation techniques can now be employed to aid in the understanding of cave life histories, as well as their excavation. In this paper we present the first attempt to integrate and publish data from a range of such methods on South African fossil bearing palaeokarst using the newly discovered Drimolen Makondo deposit as a case study. This includes the use of ground penetrating radar, 3D visualisation through photogrammetry and multi-scale 3D scanning, micromophology and petrography, palaeomagnetism, mineral magnetism, synchrotron radiation, electron spin resonance, uranium-lead dating and biochronology. Our analysis has allowed us to successfully uncover the full extent of this new ∼2.61 Ma fossil bearing palaeokarst deposit and to visualise and interpret its chronostratigraphy.
The Cradle of Humankind in South Africa, recognized as World Heritage by UNESCO since 1999, contains fossil sites which have yielded hominid remains and/or non-human primates (Cercopithecoidea). Robert Broom was the first to prospect for fossils at Bolt's Farm Cave System (or BFCS), and this since 1936. Research only became regular in 2006 with the creation of the HRU (Hope (Human Origins and Past Environment) Research Unit). BFCS is best known for yielding remains of large cats. Yet some fossils of Cercopithecoidea discovered at BFCS are considered to be references in palaeoprimatology: BF42 (Cercopithecoides williamsi) and BF43 (Parapapio broomi). Waypoint 160 at BFCS yielded the oldest remains of nonhuman primates in the Cradle of Humankind which are dated to the Pliocene. For more information about the geological and palaeoenvironmental context, excavations were conducted since 2011 in some loci based on the surveys carried out by members of HRU. The present challenge is to obtain the maximum amount of data concerning palaeobiodiversity, including the microfauna which must be extracted from the breccia by acid preparation techniques, study of the conditions of fossilization and the preservation of fossils, as well as the determination of the ages of the fossils.
Paleomagnetic directions provide the basis for use of paleomagnetism in chronological and tectonic reconstructions and for constraining past geomagnetic field behavior over a variety of timescales. Crucial to paleomagnetic analysis is the separation and quantification of a characteristic remanent magnetization (ChRM), which relates to a process of interest, from other remanence components. Principal component analysis (PCA) of stepwise demagnetization data is employed routinely in these situations to estimate magnetic remanence directions and their uncertainties. A given ChRM is often assumed to trend toward the origin of a vector demagnetization diagram and prevailing data analysis frameworks allow remanence directions to be estimated based on PCA fits that are forced to pass through the origin of such diagrams, a process referred to as “anchoring.” While this approach is adopted commonly, little attention has been paid to the effects of anchoring and the influence it has on both estimated remanence directions and their associated uncertainties. In almost all cases, anchoring produces an artificially low uncertainty estimation compared to an unanchored fit. Bayesian model selection demonstrates that the effects of anchoring cannot typically be justified from a statistical standpoint. We present an alternative to anchoring that constrains the best fit remanence direction to pass through the origin of a vector demagnetization diagram without unreasonably distorting the representation of the demagnetization data.
The geologic, environmental, and taphonomic context of the Taung Australopithecus africanus skull has been the subject of speculation and sporadic research since its first publication. In order to refine our contextual knowledge of this important hominin fossil, systematic excavations of the Taung fossil site at the Buxton Limeworks, in the Taung district of what is now the North West Province of South Africa, were conducted from 1988 to 1993. The excavations began on the Hrdlička pinnacle, where Aleš Hrdlička had found fossiliferous deposits in 1925. A separate set of deposits, closer to the reconstructed position of the 1924 Australopithecus discovery and more consistent with the historical record of the Taung discovery, was uncovered on the quarry floor, 42 m southwest of and 6 m lower than the nearest Hrdlička deposits. The fossils of these three distinct deposits, known as the ‘Dart deposits,’ are sparsely distributed, representing different taphonomic conditions and most likely older than most previous discoveries. There are 16 cercopithecid fossils and four bovid fossils, along with eggshell, turtle shell, brachiopods, and reed casts. They provide the most immediate context for the depositional conditions of the Taung Australopithecus juvenile.
Citation for this article: McKee J. K., and K. L. Kuykendall. 2016. The Dart deposits of the Buxton Limeworks, Taung, South Africa, and the context of the Taung Australopithecus fossil. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1054937.
Although individual suid specimens from other sites have been described, only Makapansgat has been treated comprehensively, but much new material has come to light in the past three decades. The University of California African Expedition worked several sites of different ages at Bolt's Farm and the material recovered includes a virtually complete, slightly compressed, skull of Phacochoerus modestus (=P. antiquus Broom 1948) from Pit 3, associated with Antidorcas recki, and also several cranial and dental fragments from Pit 14 that belong to the typical Makapansgat Potamochoeroides shawi. Bolt's Farm was the source of a cranial specimen described by Broom as "Notochoerus meadowsi'(=Metridiochoerus andrewsi). Other discoveries, from Swartkrans, the Sterkfontein Type site and Makapansgat, are described. -from Author
Proboscidean remains are very rare in the Transvaal cave breccias and the few specimens recovered are generally fragmentary but deserve description because of their potential value in correlation and dating. The best specimen is the back half of a left lower molar from Pit 7 of the University of California African Expedition's work at Bolt's Farm. It was regarded by Maglio as representing Elephas ekorensis but closer examination suggests that there are some more progressive characters and it most likely represents Elephas recki brumpti. Makapansgat has furnished 14 fragmentary fossils, six of them tusk or root remains. Particularly interesting is the occurrence of a pair of cones from a molar of Anancus. -from Author
Analyses are presented of the mammalian component of rich microfaunal fossil breccia collections mainly of owl pellet origin from the Transvaal Plio-Pleistocene australopithecine sites Kromdraai, Sterkfontein and Makapansgat Limeworks, with briefer references to Swartkrans, Langebaanweg and the Makapansgat Cave of Hearths. Rodent incisors show Cryptomys robertsi to be a distinct extinct species occurring with C. hottentotus, and indicate a relationship between Mystromys, the Cricetomyidae and certain fossil Cricetodontidae. The fossil assemblages are generally similar to modern ones but elephant shrews (several species) and dormice are relatively commoner, and Mystromys has declined in favour of the murid Mastomys. Crocidura and Saccostomus are abstracted from the older fossil sites, appearing only in the more recent Cave of Hearths. Mystromys darti Lavocat has been rediscovered in abundance in in situ Rodent Corner breccia at Makapansgat, yet it is totally absent from other parts of the Limeworks deposit. It is referred to a new genus Stenodontomys, with a second species from Langebaanweg. Another extinct cricetid previously known under a manuscript name as Mystomys cookei, common to Makapansgat, Taung and the Krugersdorp district sites, is formally described for the first time also under a new generic name, Proodontomys. On microfaunal evidence Makapansgat is definitely older than the Krugersdorp sites, of which Kromdraai is perhaps the oldest and Swartkrans the youngest. Certain extinct fossils link Makapansgat to Langebaanweg (Stenodontomys), Kromdraai (Macroscelides proboscideus vagans) and Taung (Gypsorhychus). Suggestions that Taung is significantly younger than other australopithecine sites are not supported. - from Author
This paper presents a review of, and new data concerning, the age of Australopithecus in southern Africa. Current dating suggests that Makapansgat Limeworks is the oldest hominin deposit in southern Africa, with Australopithecus africanus dating to between 3.0 and 2.6 Ma. The Taung Child A. africanus fossil from Taung is most likely penecontemporary with the Makapansgat material between 3.0 and 2.6 Ma. A. africanus from Sterkfontein Member 4 is estimated to date to between 2.6 and 2.0 Ma, with the Sts 5 specimen dating to around 2.0 Ma. The A. africanus deposits from Gladysvale are most likely contemporaneous with the Sterkfontein group with an age between 2.4 and 2.0 Ma. The potential second species of Australopithecus, StW 573 from the Silberberg Grotto at Sterkfontein, is most likely dated to between 2.6 and 2.2 Ma. As such, StW 573 is contemporary with A. africanus fossils from Member 4 and suggest that two contemporary Australopithecus species occurred at Sterkfontein between ~2.6 and 2.0 Ma. Based on the presence of Equus the A. africanus fossils from Jacovec Cavern also likely date to Australopithecus sediba-bearing deposits of Malapa date to 1.98 Ma and suggests that three different species of Australopithecus occur in South Africa between 2.3 and 1.9 Ma. Given these dates, A. africanus represents the oldest southern African hominin species being found in two temporally distinct groups of sites, Makapansgat/Taung and Sterkfontein/Gladysvale, and A. sediba is the youngest species at ~1.98 Ma. However, if StW 53 is also Australopithecus, as some have suggested, then this genus survives to younger than 1.8 Ma in South Africa. Australopithecus thus lasted for a significant period of time in southern Africa after the genus is last seen in eastern Africa (Australopithecus garhi at ~2.5 Ma). This new dating indicates that the South African Australopithecus fossils are younger than previously suggested and are contemporary with the earliest suggested representatives of Homo (~2.3 Ma) and Paranthropus (2.7–2.5 Ma) in eastern Africa.
Barton Springs is the fourth largest spring in Texas (Brune, 1981). It is the major discharge point for a segment of Cretaceous Edwards Limestone karst aquifer. Water from Bartom Springs is a significant component of the water resource of Austin, the 21st largest city in the United States. Barton Springs is also a heavily used recreational spot, and it is the sole home of the Barton Springs Salamander (Eurycea sosorum), an endangered species that is extremely vulnerable to changes in water quality (Mahler and Lynch, 1999).
Waypoint 160 is a breccia occurrence in a dolomite solution cavity on Bolt's Farm on the southern margin of the Cradle of Humankind World Heritage site in South Africa. The calcified breccia has yielded microfauna that has been dated between 4.0 and 4.5 million years. Here we present the first evidence for Parapapio, an extinct monkey, from Waypoint 160. This site is of particular interest as Parapapio is associated with Pliocene or Pleistocene hominids in Africa, for example at Sterkfontein, Taung, Kromdraai, Swartkrans and Makapansgat in South Africa, as well as at Lothagam in East Africa.
The time of deposition of the Makapansgat Limeworks site in South Africa, containing several hominid fossils, has an important bearing on hominid phylogeny in Africa. Hence, in an attempt to determine this age, a palaeomagnetic analysis of the site has been performed and the results are reported here. Member 3 (from which most of the important hominid fossils have been recovered) appears to have an age greater than 2.90 Ma and possibly greater than 3.06 Ma but less than 3.32 Ma. Previously it has not been possible to delineate the age of this important member with any degree of accuracy. The most likely position for the underlying Member 2 is in that section of the Gauss normal epoch predating the Mammoth event and having age limits of 3.06-3.32 Ma.