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Ice retreat in Wilkes Basin of East Antarctica during a warm interglacial 期刊论文
NATURE, 2020, 583 (7817) : 554-+
作者:  T. Blackburn;  G. H. Edwards;  S. Tulaczyk;  M. Scudder;  G. Piccione;  B. Hallet;  N. McLean;  J. C. Zachos;  B. Cheney;  J. T. Babbe
收藏  |  浏览/下载:61/0  |  提交时间:2020/08/09

Uranium isotopes in subglacial precipitates from the Wilkes Basin of the East Antarctic Ice Sheet reveal ice retreat during a warm Pleistocene interglacial period about 400,000 years ago.


Efforts to improve sea level forecasting on a warming planet have focused on determining the temperature, sea level and extent of polar ice sheets during Earth'  s past interglacial warm periods(1-3). About 400,000 years ago, during the interglacial period known as Marine Isotopic Stage 11 (MIS11), the global temperature was 1 to 2 degrees Celsius greater(2)and sea level was 6 to 13 metres higher(1,3). Sea level estimates in excess of about 10 metres, however, have been discounted because these require a contribution from the East Antarctic Ice Sheet(3), which has been argued to have remained stable for millions of years before and includes MIS11(4,5). Here we show how the evolution of(234)U enrichment within the subglacial waters of East Antarctica recorded the ice sheet'  s response to MIS11 warming. Within the Wilkes Basin, subglacial chemical precipitates of opal and calcite record accumulation of(234)U (the product of rock-water contact within an isolated subglacial reservoir) up to 20 times higher than that found in marine waters. The timescales of(234)U enrichment place the inception of this reservoir at MIS11. Informed by the(234)U cycling observed in the Laurentide Ice Sheet, where(234)U accumulated during periods of ice stability(6)and was flushed to global oceans in response to deglaciation(7), we interpret our East Antarctic dataset to represent ice loss within the Wilkes Basin at MIS11. The(234)U accumulation within the Wilkes Basin is also observed in the McMurdo Dry Valleys brines(8-10), indicating(11)that the brine originated beneath the adjacent East Antarctic Ice Sheet. The marine origin of brine salts(10)and bacteria(12)implies that MIS11 ice loss was coupled with marine flooding. Collectively, these data indicate that during one of the warmest Pleistocene interglacials, the ice sheet margin at the Wilkes Basin retreated to near the precipitate location, about 700 kilometres inland from the current position of the ice margin, which-assuming current ice volumes-would have contributed about 3 to 4 metres(13)to global sea levels.


  
Methane, Monsoons, and Modulation of Millennial-Scale Climate 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2020, 47 (9)
作者:  Thirumalai, Kaustubh;  Clemens, Steven C.;  Partin, Judson W.
收藏  |  浏览/下载:19/0  |  提交时间:2020/07/02
methane  monsoon  modulation  orbital forcing  millennial-scale climate variability  late Pleistocene  
The dental proteome of Homo antecessor 期刊论文
NATURE, 2020, 580 (7802) : 235-+
作者:  Abram, Nerilie J.;  Wright, Nicky M.;  Ellis, Bethany;  Dixon, Bronwyn C.;  Wurtzel, Jennifer B.;  England, Matthew H.;  Ummenhofer, Caroline C.;  Philibosian, Belle;  Cahyarini, Sri Yudawati;  Yu, Tsai-Luen;  Shen, Chuan-Chou;  Cheng, Hai;  Edwards, R. Lawrence;  Heslop, David
收藏  |  浏览/下载:53/0  |  提交时间:2020/07/03

Analyses of the proteomes of dental enamel from Homo antecessor and Homo erectus demonstrate that the Early Pleistocene H. antecessor is a close sister lineage of later Homo sapiens, Neanderthal and Denisovan populations in Eurasia.


The phylogenetic relationships between hominins of the Early Pleistocene epoch in Eurasia, such as Homo antecessor, and hominins that appear later in the fossil record during the Middle Pleistocene epoch, such as Homo sapiens, are highly debated(1-5). For the oldest remains, the molecular study of these relationships is hindered by the degradation of ancient DNA. However, recent research has demonstrated that the analysis of ancient proteins can address this challenge(6-8). Here we present the dental enamel proteomes of H. antecessor from Atapuerca (Spain)(9,10) and Homo erectus from Dmanisi (Georgia)(1), two key fossil assemblages that have a central role in models of Pleistocene hominin morphology, dispersal and divergence. We provide evidence that H. antecessor is a close sister lineage to subsequent Middle and Late Pleistocene hominins, including modern humans, Neanderthals and Denisovans. This placement implies that the modern-like face of H. antecessor-that is, similar to that of modern humans-may have a considerably deep ancestry in the genus Homo, and that the cranial morphology of Neanderthals represents a derived form. By recovering AMELY-specific peptide sequences, we also conclude that the H. antecessor molar fragment from Atapuerca that we analysed belonged to a male individual. Finally, these H. antecessor and H. erectus fossils preserve evidence of enamel proteome phosphorylation and proteolytic digestion that occurred in vivo during tooth formation. Our results provide important insights into the evolutionary relationships between H. antecessor and other hominin groups, and pave the way for future studies using enamel proteomes to investigate hominin biology across the existence of the genus Homo.


  
Brain expansion in early hominins predicts carnivore extinctions in East Africa 期刊论文
ECOLOGY LETTERS, 2020, 23 (3) : 537-544
作者:  Faurby, Soren;  Silvestro, Daniele;  Werdelin, Lars;  Antonelli, Alexandre
收藏  |  浏览/下载:19/0  |  提交时间:2020/07/02
anthropogenic  bayesian  carnivora  humans  pleistocene  pliocene  PyRate  
Dating the skull from Broken Hill, Zambia, and its position in human evolution 期刊论文
NATURE, 2020, 580 (7803) : 372-+
作者:  Mergner, Julia;  Frejno, Martin;  List, Markus;  Papacek, Michael;  Chen, Xia;  Chaudhary, Ajeet;  Samaras, Patroklos;  Richter, Sandra;  Shikata, Hiromasa;  Messerer, Maxim;  Lang, Daniel;  Altmann, Stefan;  Cyprys, Philipp;  Zolg, Daniel P.;  Mathieson, Toby;  Bantscheff, Marcus
收藏  |  浏览/下载:19/0  |  提交时间:2020/07/03

The cranium from Broken Hill (Kabwe) was recovered from cave deposits in 1921, during metal ore mining in what is now Zambia(1). It is one of the best-preserved skulls of a fossil hominin, and was initially designated as the type specimen of Homo rhodesiensis, but recently it has often been included in the taxon Homo heidelbergensis(2-4). However, the original site has since been completely quarried away, and-although the cranium is often estimated to be around 500 thousand years old(5-7)-its unsystematic recovery impedes its accurate dating and placement in human evolution. Here we carried out analyses directly on the skull and found a best age estimate of 299 +/- 25 thousand years (mean +/- 2s). The result suggests that later Middle Pleistocene Africa contained multiple contemporaneous hominin lineages (that is, Homo sapiens(8,9), H. heidelbergensis/H. rhodesiensis and Homo naledi(10,11)), similar to Eurasia, where Homo neanderthalensis, the Denisovans, Homo floresiensis, Homo luzonensis and perhaps also Homo heidelbergensis and Homo erectus(12) were found contemporaneously. The age estimate also raises further questions about the mode of evolution of H. sapiens in Africa and whether H. heidelbergensis/H. rhodesiensis was a direct ancestor of our species(13,14).


  
Preindustrial (CH4)-C-14 indicates greater anthropogenic fossil CH4 emissions 期刊论文
NATURE, 2020, 578 (7795) : 409-+
作者:  Keener, Megan;  Hunt, Camden;  Carroll, Timothy G.;  Kampel, Vladimir;  Dobrovetsky, Roman;  Hayton, Trevor W.;  Menard, Gabriel
收藏  |  浏览/下载:56/0  |  提交时间:2020/05/13

Atmospheric methane (CH4) is a potent greenhouse gas, and its mole fraction has more than doubled since the preindustrial era(1). Fossil fuel extraction and use are among the largest anthropogenic sources of CH4 emissions, but the precise magnitude of these contributions is a subject of debate(2,3). Carbon-14 in CH4 ((CH4)-C-14) can be used to distinguish between fossil (C-14-free) CH4 emissions and contemporaneous biogenic sources  however, poorly constrained direct (CH4)-C-14 emissions from nuclear reactors have complicated this approach since the middle of the 20th century(4,5). Moreover, the partitioning of total fossil CH4 emissions (presently 172 to 195 teragrams CH4 per year)(2,3) between anthropogenic and natural geological sources (such as seeps and mud volcanoes) is under debate  emission inventories suggest that the latter account for about 40 to 60 teragrams CH4 per year(6,7). Geological emissions were less than 15.4 teragrams CH4 per year at the end of the Pleistocene, about 11,600 years ago(8), but that period is an imperfect analogue for present-day emissions owing to the large terrestrial ice sheet cover, lower sea level and extensive permafrost. Here we use preindustrial-era ice core (CH4)-C-14 measurements to show that natural geological CH4 emissions to the atmosphere were about 1.6 teragrams CH4 per year, with a maximum of 5.4 teragrams CH4 per year (95 per cent confidence limit)-an order of magnitude lower than the currently used estimates. This result indicates that anthropogenic fossil CH4 emissions are underestimated by about 38 to 58 teragrams CH4 per year, or about 25 to 40 per cent of recent estimates. Our record highlights the human impact on the atmosphere and climate, provides a firm target for inventories of the global CH4 budget, and will help to inform strategies for targeted emission reductions(9,10).


Isotopic evidence from ice cores indicates that preindustrial-era geological methane emissions were lower than previously thought, suggesting that present-day emissions of methane from fossil fuels are underestimated.


  
A low climate threshold for south Greenland Ice Sheet demise during the Late Pleistocene 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2020, 117 (1) : 190-195
作者:  Irvali, Nil;  Galaasen, Eirik V.;  Ninnemann, Ulysses S.;  Rosenthal, Yair;  Born, Andreas;  Kleiven, Helga (Kikki) F.
收藏  |  浏览/下载:17/0  |  提交时间:2020/05/13
Greenland Ice Sheet  Late Pleistocene interglacials  climate change  thresholds  
Classifying past climate change in the Chew Bahir basin, southern Ethiopia, using recurrence quantification analysis 期刊论文
CLIMATE DYNAMICS, 2019, 53: 2557-2572
作者:  Trauth, Martin H.;  Asrat, Asfawossen;  Duesing, Walter;  Foerster, Verena;  Kraemer, K. Hauke;  Marwan, Norbert;  Maslin, Mark A.;  Schaebitz, Frank
收藏  |  浏览/下载:26/0  |  提交时间:2019/11/27
Paleoclimate dynamics  Eastern Africa  Pleistocene  Holocene  Time-series analysis  Recurrence plot  
The middle Pleistocene transition by frequency locking and slow ramping of internal period 期刊论文
CLIMATE DYNAMICS, 2019, 53: 3023-3038
作者:  Nyman, Karl H. M.;  Ditlevsen, Peter D.
收藏  |  浏览/下载:13/0  |  提交时间:2019/11/27
Glacial cycles  Middle Pleistocene transition  Frequency locking  Internal period  Abrupt transition  
Late Quaternary climate legacies in contemporary plant functional composition 期刊论文
GLOBAL CHANGE BIOLOGY, 2018, 24 (10) : 4827-4840
作者:  Blonder, Benjamin;  Enquist, Brian J.;  Graae, Bente J.;  Kattge, Jens;  Maitner, Brian S.;  Morueta-Holme, Naia;  Ordonez, Alejandro;  Simova, Irena;  Singarayer, Joy;  Svenning, Jens-Christian;  Valdes, Paul J.;  Violle, Cyrille
收藏  |  浏览/下载:27/0  |  提交时间:2019/04/09
climate change  disequilibrium  exclusion  functional diversity  functional trait  Holocene  immigration  lag  legacy  Pleistocene