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The Cradle of Humankind (Cradle) in South Africa preserves a rich collection of fossil hominins representing Australopithecus, Paranthropus and Homo.sup.1. The ages of these fossils are contentious.sup.2-4 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 chronology.sup.5. Flowstones are ubiquitous cave features and provide a palaeoclimatic context, because they grow only during phases of increased effective precipitation.sup.6,7, 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., Author(s): Robyn Pickering [sup.1] [sup.2] , Andy I. R. Herries [sup.3] [sup.4] , Jon D. Woodhead [sup.5] , John C. Hellstrom [sup.5] , Helen E. Green [sup.5] , Bence Paul [...]

Author(s): Robyn Pickering [sup.1] [sup.2] , Andy I. R. Herries [sup.3] [sup.4] , Jon D. Woodhead [sup.5] , John C. Hellstrom [sup.5] , Helen E. Green [sup.5] , Bence Paul [...]

Explaining the Late Pleistocene demise of many of the world's larger terrestrial vertebrates is arguably the most enduring and debated topic in Quaternary science. Australia lost >90% of its larger species by around 40 thousand years (ka) ago, but the relative importance of human impacts and increased aridity remains unclear. Resolving the debate has been hampered by a lack of sites spanning the last glacial cycle. Here we report on an exceptional faunal succession from Tight Entrance Cave, southwestern Australia, which shows persistence of a diverse mammal community for at least 100 ka leading up to the earliest regional evidence of humans at 49 ka. Within 10 millennia, all larger mammals except the gray kangaroo and thylacine are lost from the regional record. Stable-isotope, charcoal, and small-mammal records reveal evidence of environmental change from 70 ka, but the extinctions occurred well in advance of the most extreme climatic phase. We conclude that the arrival of humans was probably decisive in the southwestern Australian extinctions, but that changes in climate and fire activity may have played facilitating roles. One-factor explanations for the Pleistocene extinctions in Australia are likely oversimplistic. climate change | human hunting | megafauna | fire history | paleoecology doi/ 10.1073/pnas.1011073107

Author(s): Gavin J. Prideaux (corresponding author) [1]; John A. Long [1, 2]; Linda K. Ayliffe [3, 4]; John C. Hellstrom [5]; Brad Pillans [4]; Walter E. Boles [6]; Mark N. [...]

Evidence of millennial-scale cold events following the last interglacial are well preserved in North Atlantic marine cores, Greenland ice, and pollen records from Europe. However, their timing was previously undetermined by radiometric dating. We report the first precise radiometric ages for two such events, C23 (105.1 [+ or -] 0.9 ka to 102.6 [+ or -] 0.8 ka) and C24 (112.0 [+ or -] 0.8 ka and 108.8 [+ or -] 1.0 ka), based on stable carbon and oxygen isotope measurements on a stalagmite from Italy (CC28). In addition to providing new information on the duration of these events in southern Europe, the age data provide invaluable tuning points for the Melisey I (C24) and Montaigu (C23) pollen zones identified in western Europe. The former event is of particular significance because it represents the end of the Eemian interglacial forest phase in western Europe. The new age data will also allow fine tuning of the timing and duration of Greenland stadial 24 (equivalent to C23) in the North Greenland Ice Core Project ice core and, via a common gas-age chronology, tuning of the Vostok and EPICA (European Project for Ice Coring in Antarctica) ice cores. Keywords: speleothems, U-series dating, ice-rafted debris, last interglacial, paleoclimate.

Resolving faunal responses to Pleistocene climate change is vital for differentiating human impacts from other drivers of ecological change. While 90 % of Australia's large mammals were extinct by ca. 45 ka, their responses to glacial-interglacial cycling have remained unknown, due to a lack of rigorous biostratigraphic studies and the rarity of terrestrial climatic records that can be related directly to faunal records. We present an analysis of faunal data from the Naracoorte Caves in southeastern Australia, which are unique not only because of the species richness and time-depth of the assemblages that they contain, but also because this faunal record is directly comparable with a 500 k.y. speleothem-based record of local effective moisture. Our data reveal that, despite significant population fluctuations driven by glacial-interglacial cycling, the species composition of the mammal fauna was essentially stable for 500 k.y. before the late Pleistocene extinctions. Larger species declined during a drier interval between 270 and 220 ka, likely reflecting range contractions away from Naracoorte, but they then recovered locally, persisting well into the late Pleistocene. Because the speleothem record and prior faunal response imply that local conditions should have been favorable for megafauna until at least 30 ka, climate change is unlikely to have been the principal cause of the extinctions. Keywords: mammals, megafauna, extinction, climate change, Pleistocene, Australia.

230Th/234U dating of speleothems from southeastern Australia documents changes in effective precipitation over the past 500 k.y. at a temporal resolution not previously achieved. Results show that the highest effective precipitation for the southeastern interior of Australia occurred during stadials and cool interstadials of the past four glacial cycles. Interglacials and warm interstadials, as well as glacial maxima, are comparatively arid. We suggest that lower regional temperatures over the continent and changes in atmospheric circulation (stronger Walker circulation) produced the observed periods of increased effective precipitation.