Robyn Pickering

Timing and climatic impact of Greenland interstadials recorded in stalagmites from northern Turkey.

A 50 kyr-long exceptionally well-dated and highly resolved stalagmite oxygen (δ 18O) and carbon (δ 13C) isotope record from Sofular Cave in northwestern Turkey helps to further improve the dating of Greenland Interstadials (GI) 1, and 3–12. Timing of most GI in the Sofular record is consistent within ±10 to 300 years with the “iconic” Hulu Cave record. Larger divergences (>500 years) between Sofular and Hulu are only observed for GI 4 and 7. The Sofular record differs from the most recent NGRIP chronology by up to several centuries, whereas age offsets do not increase systematically with depth. The Sofular record also reveals a rapid and sensitive climate and ecosystem response in the eastern Mediterranean to GI, whereas a phase lag of ∼100 years between climate and full ecosystem response is evident. Finally, results of spectral analyses of the Sofular isotope records do not support a 1,470-year pacing of GI.

Australopithecus sediba at 1.977 Ma and Implications for the Origins of the Genus Homo

Further U-series dating and the magnetic stratigraphy of the hosting cave deposits show that Australopithecus sediba lived just under 2 million years ago, near or just before the emergence of Homo. Newly exposed cave sediments at the Malapa site include a flowstone layer capping the sedimentary unit containing the Australopithecus sediba fossils. Uranium-lead dating of the flowstone, combined with paleomagnetic and stratigraphic analysis of the flowstone and underlying sediments, provides a tightly constrained date of 1.977 ± 0.002 million years ago (Ma) for these fossils. This refined dating suggests that Au. sediba from Malapa predates the earliest uncontested evidence for Homo in Africa.

Geological Setting and Age of Australopithecus sediba from Southern Africa

From Australopithecus to Homo Our genus Homo is thought to have evolved a little more than 2 million years ago from the earlier hominid Australopithecus. But there are few fossils that provide detailed information on this transition. Berger et al. (p. 195; see the cover) now describe two partial skeletons, including most of the skull, pelvis, and ankle, of a new species of Australopithecus that are informative. The skeletons were found in a cave in South Africa encased in sediments dated by Dirks et al. (p. 205) to about 1.8 to 1.9 million years ago. The fossils share many derived features with the earliest Homo species, including in its pelvis and smaller teeth, and imply that the transition to Homo was in stages. A new species of Australopithecus, about 1.9 million years old, shows many derived features with Homo, helping to reveal its evolution. We describe the geological, geochronological, geomorphological, and faunal context of the Malapa site and the fossils of Australopithecus sediba. The hominins occur with a macrofauna assemblage that existed in Africa between 2.36 and 1.50 million years ago (Ma). The fossils are encased in water-laid, clastic sediments that were deposited along the lower parts of what is now a deeply eroded cave system, immediately above a flowstone layer with a U-Pb date of 2.026 ± 0.021 Ma. The flowstone has a reversed paleomagnetic signature and the overlying hominin-bearing sediments are of normal polarity, indicating deposition during the 1.95- to 1.78-Ma Olduvai Subchron. The two hominin specimens were buried together in a single debris flow that lithified soon after deposition in a phreatic environment inaccessible to scavengers.

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 approximately 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.

New Australopithecus robustus fossils and associated U-Pb dates from Cooper's Cave (Gauteng, South Africa).

Australopithecus robustus is one of the best represented hominin taxa in Africa, with hundreds of specimens recovered from six fossil localities in the Bloubank Valley area of Gauteng Province, South Africa. However, precise geochronological ages are presently lacking for these fossil cave infills. In this paper, we provide a detailed geological background to a series of hominin fossils retrieved from the newly investigated deposit of Coopers D (located partway between Sterkfontein and Kromdraai in the Bloubank Valley), including uranium-lead (U-Pb) ages for speleothem material associated with A. robustus. U-Pb dating of a basal speleothem underlying the entire deposit results in a maximum age of 1.526 (+/-0.088) Ma for Coopers D. A second U-Pb date of ca. 1.4 Ma is produced from a flowstone layer above this basal speleothem; since this upper flowstone is not a capping flowstone, and fossiliferous sediments are preserved above this layer, some of the hominins might be slightly younger than the calculated age. As a result, we can broadly constrain the age of the hominins from Coopers D to between 1.5 and approximately 1.4 Ma. Extinct fauna recorded in this comparatively young deposit raise the possibility that the Bloubank Valley region of South Africa represented a more stable environmental refugium for taxa relative to tectonically more active East Africa. The sediments of the deposit likely infilled rapidly during periods when arid conditions prevailed in the paleoenvironment, although it is unclear whether sediment deposition and bone deposition were necessarily contemporaneous occurrences. We reconstruct the paleoenvironment of Coopers D as predominantly grassland, with nearby woodlands and a permanent water source. The hominin teeth recovered from Coopers D are all from juveniles and can be confidently assigned to A. robustus. In addition, two juvenile mandibular fragments and an adult thoracic vertebra are tentatively attributed to A. robustus.

A Multi-Disciplinary Perspective on the Age of Australopithecus in Southern Africa

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 <2.4 Ma. The new 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.

Newly discovered fossil- and artifact-bearing deposits, uranium-series ages, and Plio-Pleistocene hominids at Swartkrans cave, South Africa.

We report on new research at Swartkrans Cave, South Africa, that provides evidence of two previously unrealized artifact- and fossil-bearing deposits. These deposits underlie a speleothem dated by the uranium-thorium disequilibrium technique to 110,000+/-1,980 years old, the first tightly constrained, geochronological date available for the site. Recovered fauna from the two underlying deposits-including, prominently, the dental remains of Paranthropus (Australopithecus) robustus from the uppermost layer (Talus Cone Deposit)-indicate a significantly older, late Pliocene or early Pleistocene age for these units. The lowest unit (LB East Extension) is inferred to be an eastward extension of the well-known Lower Bank of Member 1, the earliest surviving infill represented at the site. The date acquired from the speleothem also sets the maximum age of a rich Middle Stone Age lithic assemblage.

1.32 ± 0.11 Ma age for underwater remains constrain antiquity and longevity of the Dominican primate Antillothrix bernensis

Endemic New World monkeys are an important element of the extinct mammal faunas of the Caribbeans Greater Antilles. Here we report the first geochronometric evidence that the primate Antillothrix bernensis existed in the Dominican Republic during the Pleistocene, based on the uranium-series age of carbonate speleothem that encased a tibia when it was collected in a flooded cave. Three-dimensional geometric morphometrics of laser-scanned living and extinct samples provide evidence to support the hypothesis that this specimen and other Dominican primate tibial remains belong to that same species. U-Th dating of the host cave carbonate returns ages consistently at the 600 ka upper limit of the technique. However, U-Pb, capable of resolving ages of greater antiquity, is more robust in this context, returning a secure age of 1.32 ± 0.11 Ma, which is the oldest chronometric age recorded for a Hispaniolan mammal. While its origins and manner and time of arrival are obscure, the morphometric studies are consistent with phylogenetic analyses that place A. bernensis within the pitheciid clade of the platyrrhines. The species apparently endured for over 1 million years during the climatic perturbations of the Pleistocene, as a frugivorous climbing quadruped, one of two known primate species occupying the hazard prone island of Hispaniola.

Appendix: Dating Methods Applied to Azokh Cave Sites

Dating is basic for archaeological and paleontological investigations and results of different dating methods used in Azokh caves are described in this chapter. Fossils from Azokh were not dated by any method previously. Lithic technology and taxonomy suggested a middle Pleistocene age for Unit V (from where Acheulian industries and a human mandible fragment were recovered) while Units III and II yielded Mousterian industries indicating middle Paleolithic ages. Dates from Azokh by Electron Spin Resonance (ESR) previously published elsewhere were given before final calculations and they slightly differ from those given in this Appendix, which are the definitive dating results.