Speleology and magnetobiostratigraphic chronology of the GD 2 locality of the Gondolin hominin-bearing paleocave deposits, North West Province, South Africa

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

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.

The Thorny Issue of African Porcupines: a New Mandible of Hystrix makapanensis from Olduvai Gorge (Tanzania) and Rediagnosis of the Species

Several porcupine taxa are reported from the middle Miocene to the early Holocene in the Old World. Among these, five species of the subfamily Hystricinae occurred in Africa approximately in the last 6 Ma: the extinct Hystrix makapanensis, Hystrix leakeyi, and Xenohystrix crassidens and the still living Hystrix africaeaustralis and Hystrix cristata. The large-sized H. makapanensis is reported from numerous sites in East and South Africa between the early Pliocene and Early Pleistocene. In this paper, we describe a new mandible of H. makapanensis from the world-renowned Tanzanian paleontological and archeological site of Olduvai Gorge (HWK West; lowermost Bed II; ca. 1.8-1.7 Ma). The discovery of the new mandible triggered a comprehensive review of the entire African record of H. makapanensis. In particular, we describe or re-analyze the samples from South Africa (Makapansgat Limeworks, Gondolin, Kromdraai, Swartkrans, and Sterkfontein), Tanzania (Olduvai and Laetoli), Ethiopia (Omo Shungura and Hadar), and Kenya (Chemeron), enriching the quantity of specimens confidently referable to this species and above all improving the information on its craniodental anatomy. On this basis, we: (1) propose an emended diagnosis of H. makapanensis; (2) point out the morphological and biometric differences between H. makapanensis and other African Hystricinae (also in terms of body mass); and (3) broaden the knowledge on the geographical and chronological distribution of this extinct species.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10914-021-09588-z.

Fossil mammals from the Gondolin Dump A ex situ hominin deposits, South Africa

The Gondolin palaeokarstic system, located in the UNESCO Fossil Hominids of South Africa World Heritage Site, has been sporadically excavated since the 1970s. Sampling of ex situ dumpsites in 1997 recovered the only two fossil hominin specimens recovered thus far from Gondolin. While one partial mandibular molar (GA 1) remains unattributed, the complete mandibular second molar (GA 2) represents the largest Paranthropus robustus Broom, 1938 tooth identified to date. While subsequent excavations and research at Gondolin has clarified the geological, temporal, taphonomic, and palaeoecologic context for the in situ deposits, this paper presents the first comprehensive description of the fossil assemblage 'associated' with the two ex situ hominins. Analysis of 42 calcified sediment blocks and naturally decalcified sediments excavated from three cubic metres of the Dump A deposits reinforce that the dump contains a heterogeneous aggregation of materials from across the Gondolin sedimentary deposits. A total of 15,250 individual fossil specimens were processed (via sifting or acetic-acid mediated processing of calcified sediment blocks), yielding a faunal record that largely mirrors that described from either (or both) the GD 1 and GD 2 in situ assemblages but includes representatives of four novel mammal groups (Families Cercopithecidae, Felidae, Herpestidae, Giraffidae) not recorded in either in situ sample. While basic assemblage characteristics including primary taphonomic data is presented, analysis and interpretation is limited by the ex situ origin of the sample. Ultimately, these results reinforce that the substantial mining-mediated obliteration of palaeokarstic deposits at Gondolin continue to obscure a clear association between the Gondolin Dump A hominins and any of the sampled and dated in situ deposits.

A two-million-year-long hydroclimatic context for hominin evolution in southeastern Africa

The past two million years of eastern African climate variability is currently poorly constrained, despite interest in understanding its assumed role in early human evolution^1-4. Rare palaeoclimate records from northeastern Africa suggest progressively drier conditions^2,5 or a stable hydroclimate⁶. By contrast, records from Lake Malawi in tropical southeastern Africa reveal a trend of a progressively wetter climate over the past 1.3 million years^7,8. The climatic forcings that controlled these past hydrological changes are also a matter of debate. Some studies suggest a dominant local insolation forcing on hydrological changes^9-11, whereas others infer a potential influence of sea surface temperature changes in the Indian Ocean^8,12,13. Here we show that the hydroclimate in southeastern Africa (20-25° S) is controlled by interplay between low-latitude insolation forcing (precession and eccentricity) and changes in ice volume at high latitudes. Our results are based on a multiple-proxy reconstruction of hydrological changes in the Limpopo River catchment, combined with a reconstruction of sea surface temperature in the southwestern Indian Ocean for the past 2.14 million years. We find a long-term aridification in the Limpopo catchment between around 1 and 0.6 million years ago, opposite to the hydroclimatic evolution suggested by records from Lake Malawi. Our results, together with evidence of wetting at Lake Malawi, imply that the rainbelt contracted toward the Equator in response to increased ice volume at high latitudes. By reducing the extent of woodland or wetlands in terrestrial ecosystems, the observed changes in the hydroclimate of southeastern Africa-both in terms of its long-term state and marked precessional variability-could have had a role in the evolution of early hominins, particularly in the extinction of Paranthropus robustus.

The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa

New ages for flowstone, sediments and fossil bones from the Dinaledi Chamber are presented. We combined optically stimulated luminescence dating of sediments with U-Th and palaeomagnetic analyses of flowstones to establish that all sediments containing Homo naledi fossils can be allocated to a single stratigraphic entity (sub-unit 3b), interpreted to be deposited between 236 ka and 414 ka. This result has been confirmed independently by dating three H. naledi teeth with combined U-series and electron spin resonance (US-ESR) dating. Two dating scenarios for the fossils were tested by varying the assumed levels of ²²²Rn loss in the encasing sediments: a maximum age scenario provides an average age for the two least altered fossil teeth of 253 +82/–70 ka, whilst a minimum age scenario yields an average age of 200 +70/–61 ka. We consider the maximum age scenario to more closely reflect conditions in the cave, and therefore, the true age of the fossils. By combining the US-ESR maximum age estimate obtained from the teeth, with the U-Th age for the oldest flowstone overlying Homo naledi fossils, we have constrained the depositional age of Homo naledi to a period between 236 ka and 335 ka. These age results demonstrate that a morphologically primitive hominin, Homo naledi, survived into the later parts of the Pleistocene in Africa, and indicate a much younger age for the Homo naledi fossils than have previously been hypothesized based on their morphology.

DOI:http://dx.doi.org/10.7554/eLife.24231.001

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

The first hominin from the early Pleistocene paleocave of Haasgat, South Africa

Haasgat is a primate-rich fossil locality in the northeastern part of the Fossil Hominid Sites of South Africa UNESCO World Heritage Site. Here we report the first hominin identified from Haasgat, a partial maxillary molar (HGT 500), that was recovered from an ex situ calcified sediment block sampled from the locality. The in situ fossil bearing deposits of the Haasgat paleokarstic deposits are estimated to date to slightly older than 1.95 Ma based on magnetobiostratigraphy. This places the hominin specimen at a critical time period in South Africa that marks the last occurrence of Australopithecus around 1.98 Ma and the first evidence of Paranthropus and Homo in the region between ∼2.0 and 1.8 Ma. A comprehensive morphological evaluation of the Haasgat hominin molar was conducted against the current South African catalogue of hominin dental remains and imaging analyses using micro-CT, electron and confocal microscopy. The preserved occlusal morphology is most similar to Australopithecus africanus or early Homo specimens but different from Paranthropus. Occlusal linear enamel thickness measured from micro-CT scans provides an average of ∼2.0 mm consistent with Australopithecus and early Homo. Analysis of the enamel microstructure suggests an estimated periodicity of 7–9 days. Hunter–Schreger bands appear long and straight as in some Paranthropus, but contrast with this genus in the short shape of the striae of Retzius. Taken together, these data suggests that the maxillary fragment recovered from Haasgat best fits within the Australopithecus—early Homo hypodigms to the exclusion of the genus Paranthropus. At ∼1.95 Ma this specimen would either represent another example of late occurring Australopithecus or one of the earliest examples of Homo in the region. While the identification of this first hominin specimen from Haasgat is not unexpected given the composition of other South African penecontemporaneous site deposits, it represents one of the few hominin localities in the topographically-distinct northern World Heritage Site. When coupled with the substantial differences in the mammalian faunal communities between the northern localities (e.g., Haasgat, Gondolin) and well-sampled Bloubank Valley sites (e.g., Sterkfontein, Swartkrans, Kromdraai), the recovery of the HGT 500 specimen highlights the potential for further research at the Haasgat locality for understanding the distribution and interactions of hominin populations across the landscape, ecosystems and fossil mammalian communities of early Pleistocene South Africa. Such contextual data from sites like Haasgat is critical for understanding the transition in hominin representation at ∼2 Ma sites in the region from Australopithecus to Paranthropus and early Homo.

Brief communication: beyond the South African cave paradigm--Australopithecus africanus from Plio-Pleistocene paleosol deposits at Taung

Following the discovery of the "Taung Child" (Australopithecus africanus) in 1924 in the Buxton-Norlim Limeworks near Taung, the fossil-bearing deposits associated with the Dart and Hrdlička pinnacles have been interpreted as the mined remnants of cave sediments that formed within the Plio-Pleistocene Thabaseek Tufa: either as a younger cave-fill or as contemporaneous carapace caves. When combined with the Plio-Pleistocene dolomitic cave deposits from the "Cradle of Humankind," a rather restricted view emerges that South African early hominins derived from cave deposits, whereas those of east and central Africa are derived from fluvio-lacustrine and paleosol deposits. We undertook a sedimentological and paleomagnetic analysis of the pink-colored deposit (PCS) from which the "Taung Child" is purported to have derived and demonstrate that it is a calcrete, a carbonate-rich pedogenic sediment, which formed on the paleo-land surface. The deposit extends 100 s of meters laterally beyond the Dart and Hrdlička Pinnacles where it is interbedded with the Thabaseek Tufa, indicating multiple episodes of calcrete development and tufa growth. The presence of in situ rhizoconcretions and insect trace fossils (Celliforma sp. and Coprinisphaera sp.) and the distinctive carbonate microfabric confirm that the pink deposit is a pedogenic calcrete, not a calcified cave sediment. Paleomagnetic and stratigraphic evidence indicates that a second, reversed polarity, fossil-bearing deposit (YRSS) is a younger fissure-fill formed within a solutional cavity of the normal polarity tufa and pink calcrete (PCS). These observations have implications for the dating, environment, and taphonomy of the site, and increase the likelihood of future fossil discoveries within the Buxton-Norlim Limeworks.

Morphometric variation in the papionin muzzle and the biochronology of the South African Plio-Pleistocene karst cave deposits

Papionin monkeys are widespread, relatively common members of Plio-Pleistocene faunal assemblages across Africa. For these reasons, papionin taxa have been used as biochronological indicators by which to infer the ages of the South African karst cave deposits. A recent morphometric study of South African fossil papionin muzzle shape concluded that its variation attests to a substantial and greater time depth for these sites than is generally estimated. This inference is significant, because accurate dating of the South African cave sites is critical to our knowledge of hominin evolution and mammalian biogeographic history. We here report the results of a comparative analysis of extant papionin monkeys by which variability of the South African fossil papionins may be assessed. The muzzles of 106 specimens representing six extant papionin genera were digitized and interlandmark distances were calculated. Results demonstrate that the overall amount of morphological variation present within the fossil assemblage fits comfortably within the range exhibited by the extant sample. We also performed a statistical experiment to assess the limitations imposed by small sample sizes, such as typically encountered in the fossil record. Results suggest that 15 specimens are sufficient to accurately represent the population mean for a given phenotype, but small sample sizes are insufficient to permit the accurate estimation of the population standard deviation, variance, and range. The suggestion that the muzzle morphology of fossil papionins attests to a considerable and previously unrecognized temporal depth of the South African karst cave sites is unwarranted.