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The timing and effect of the earliest human arrivals in North America 期刊论文
NATURE, 2020
作者:  Lorena Becerra-Valdivia;  Thomas Higham
收藏  |  浏览/下载:27/0  |  提交时间:2020/08/09

The peopling of the Americas marks a major expansion of humans across the planet. However, questions regarding the timing and mechanisms of this dispersal remain, and the previously accepted model (termed '  Clovis-first'  )-suggesting that the first inhabitants of the Americas were linked with the Clovis tradition, a complex marked by distinctive fluted lithic points(1)-has been effectively refuted. Here we analyse chronometric data from 42 North American and Beringian archaeological sites using a Bayesian age modelling approach, and use the resulting chronological framework to elucidate spatiotemporal patterns of human dispersal. We then integrate these patterns with the available genetic and climatic evidence. The data obtained show that humans were probably present before, during and immediately after the Last Glacial Maximum (about 26.5-19 thousand years ago)(2,3)but that more widespread occupation began during a period of abrupt warming, Greenland Interstadial 1 (about 14.7-12.9 thousand years beforead 2000)(4). We also identify the near-synchronous commencement of Beringian, Clovis and Western Stemmed cultural traditions, and an overlap of each with the last dates for the appearance of 18 now-extinct faunal genera. Our analysis suggests that the widespread expansion of humans through North America was a key factor in the extinction of large terrestrial mammals.


A Bayesian age model suggests that human dispersal to the Americas probably began before the Last Glacial Maximum, overlapping with the last dates of appearance for several faunal genera.


  
Millennial-scale hydroclimate control of tropical soil carbon storage 期刊论文
NATURE, 2020, 581 (7806) : 63-+
作者:  Lam, Tommy Tsan-Yuk;  Jia, Na;  Zhang, Ya-Wei;  Shum, Marcus Ho-Hin;  Jiang, Jia-Fu;  Zhu, Hua-Chen;  Tong, Yi-Gang;  Shi, Yong-Xia;  Ni, Xue-Bing;  Liao, Yun-Shi;  Li, Wen-Juan;  Jiang, Bao-Gui;  Wei, Wei;  Yuan, Ting-Ting;  Zheng, Kui;  Cui, Xiao-Ming;  Li, Jie;  Pei, Guang-Qian
收藏  |  浏览/下载:25/0  |  提交时间:2020/05/13

Over the past 18,000 years, the residence time and amount of soil carbon stored in the Ganges-Brahmaputra basin have been controlled by the intensity of Indian Summer Monsoon rainfall, with greater carbon destabilization during wetter, warmer conditions.


The storage of organic carbon in the terrestrial biosphere directly affects atmospheric concentrations of carbon dioxide over a wide range of timescales. Within the terrestrial biosphere, the magnitude of carbon storage can vary in response to environmental perturbations such as changing temperature or hydroclimate(1), potentially generating feedback on the atmospheric inventory of carbon dioxide. Although temperature controls the storage of soil organic carbon at mid and high latitudes(2,3), hydroclimate may be the dominant driver of soil carbon persistence in the tropics(4,5)  however, the sensitivity of tropical soil carbon turnover to large-scale hydroclimate variability remains poorly understood. Here we show that changes in Indian Summer Monsoon rainfall have controlled the residence time of soil carbon in the Ganges-Brahmaputra basin over the past 18,000 years. Comparison of radiocarbon ages of bulk organic carbon and terrestrial higher-plant biomarkers with co-located palaeohydrological records(6) reveals a negative relationship between monsoon rainfall and soil organic carbon stocks on a millennial timescale. Across the deglaciation period, a depletion of basin-wide soil carbon stocks was triggered by increasing rainfall and associated enhanced soil respiration rates. Our results suggest that future hydroclimate changes in tropical regions are likely to accelerate soil carbon destabilization, further increasing atmospheric carbon dioxide concentrations.


  
Monumental architecture at Aguada Fenix and the rise of Maya civilization 期刊论文
NATURE, 2020
作者:  Bedding, Timothy R.;  Murphy, Simon J.;  Hey, Daniel R.;  Huber, Daniel;  Li, Tanda;  Smalley, Barry;  Stello, Dennis;  White, Timothy R.;  Ball, Warrick H.;  Chaplin, William J.;  Colman, Isabel L.;  Fuller, Jim;  Gaidos, Eric;  Harbeck, Daniel R.;  Hermes, J. J.;  Holdsworth, Daniel L.;  Li, Gang;  Li, Yaguang;  Mann, Andrew W.;  Reese, Daniel R.;  Sekaran, Sanjay;  Yu, Jie;  Antoci, Victoria;  Bergmann, Christoph;  Brown, Timothy M.;  Howard, Andrew W.;  Ireland, Michael J.;  Isaacson, Howard;  Jenkins, Jon M.;  Kjeldsen, Hans;  McCully, Curtis;  Rabus, Markus;  Rains, Adam D.;  Ricker, George R.;  Tinney, Christopher G.;  Vanderspek, Roland K.
收藏  |  浏览/下载:30/0  |  提交时间:2020/07/03

Archaeologists have traditionally thought that the development of Maya civilization was gradual, assuming that small villages began to emerge during the Middle Preclassic period (1000-350 bc  dates are calibrated throughout) along with the use of ceramics and the adoption of sedentism(1). Recent finds of early ceremonial complexes are beginning to challenge this model. Here we describe an airborne lidar survey and excavations of the previously unknown site of Aguada Fenix (Tabasco, Mexico) with an artificial plateau, which measures 1,400 m in length and 10 to 15 m in height and has 9 causeways radiating out from it. We dated this construction to between 1000 and 800 bc using a Bayesian analysis of radiocarbon dates. To our knowledge, this is the oldest monumental construction ever found in the Maya area and the largest in the entire pre-Hispanic history of the region. Although the site exhibits some similarities to the earlier Olmec centre of San Lorenzo, the community of Aguada Fenix probably did not have marked social inequality comparable to that of San Lorenzo. Aguada Fenix and other ceremonial complexes of the same period suggest the importance of communal work in the initial development of Maya civilization.


Lidar survey of the Maya lowlands uncovers the monumental site of Aguada Fenix, which dates to around 1000-800 bc and points to the role of communal construction in the development of Maya civilization.


  
The spatiotemporal spread of human migrations during the European Holocene 期刊论文
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2020, 117 (16) : 8989-9000
作者:  Racimo, Fernando;  Woodbridge, Jessie;  Fyfe, Ralph M.;  Sikora, Martin;  Sjogren, Karl-Goran;  Kristiansen, Kristian;  Vander Linden, Marc
收藏  |  浏览/下载:11/0  |  提交时间:2020/05/13
migrations  ancient DNA  Neolithic  Bronze Age  land cover  
Sediment controls dynamic behavior of a Cordilleran Ice Stream at the Last Glacial Maximum 期刊论文
NATURE COMMUNICATIONS, 2020, 11 (1)
作者:  Cowan, Ellen A.;  Zellers, Sarah D.;  Mueller, Juliane;  Walczak, Maureen H.;  Worthington, Lindsay L.;  Caissie, Beth E.;  Clary, Wesley A.;  Jaeger, John M.;  Gulick, Sean P. S.;  Pratt, Jacob W.;  Mix, Alan C.;  Fallon, Stewart J.
收藏  |  浏览/下载:10/0  |  提交时间:2020/05/13
Accurate compound-specific C-14 dating of archaeological pottery vessels 期刊论文
NATURE, 2020, 580 (7804) : 506-+
作者:  Yin, Yafei;  Lu, J. Yuyang;  Zhang, Xuechun;  Shao, Wen;  Xu, Yanhui;  Li, Pan;  Hong, Yantao;  Cui, Li;  Shan, Ge;  Tian, Bin;  Zhang, Qiangfeng Cliff;  Shen, Xiaohua
收藏  |  浏览/下载:20/0  |  提交时间:2020/05/13

Pottery is one of the most commonly recovered artefacts from archaeological sites. Despite more than a century of relative dating based on typology and seriation(1), accurate dating of pottery using the radiocarbon dating method has proven extremely challenging owing to the limited survival of organic temper and unreliability of visible residues(2-4). Here we report a method to directly date archaeological pottery based on accelerator mass spectrometry analysis of C-14 in absorbed food residues using palmitic (C-16:0) and stearic (C-18:0) fatty acids purified by preparative gas chromatography(5-8). We present accurate compound-specific radiocarbon determinations of lipids extracted from pottery vessels, which were rigorously evaluated by comparison with dendrochronological dates(9,10) and inclusion in site and regional chronologies that contained previously determined radiocarbon dates on other materials(11-15). Notably, the compound-specific dates from each of the C-16:0 and C-18:0 fatty acids in pottery vessels provide an internal quality control of the results(6) and are entirely compatible with dates for other commonly dated materials. Accurate radiocarbon dating of pottery vessels can reveal: (1) the period of use of pottery  (2) the antiquity of organic residues, including when specific foodstuffs were exploited  (3) the chronology of sites in the absence of traditionally datable materials  and (4) direct verification of pottery typochronologies. Here we used the method to date the exploitation of dairy and carcass products in Neolithic vessels from Britain, Anatolia, central and western Europe, and Saharan Africa.


Using lipid residues absorbed in potsherds, the ages of pottery from various archaeological sites are determined and validated using sites for which the dates are well known from other methods.


  
East Siberian Arctic inland waters emit mostly contemporary carbon 期刊论文
NATURE COMMUNICATIONS, 2020, 11 (1)
作者:  Dean, Joshua F.;  Meisel, Ove H.;  Rosco, Melanie Martyn;  Marchesini, Luca Belelli;  Garnett, Mark H.;  Lenderink, Henk;  van Logtestijn, Richard;  Borges, Alberto, V;  Bouillon, Steven;  Lambert, Thibault;  Rockmann, Thomas;  Maximov, Trofim;  Petrov, Roman;  Karsanaev, Sergei;  Aerts, Rien;  van Huissteden, Jacobus;  Vonk, Jorien E.;  Dolman, A. Johannes
收藏  |  浏览/下载:14/0  |  提交时间:2020/05/13
C-14-Dating Model for Groundwater Affected by CO2 Inputs From Deep Underground Formations 期刊论文
WATER RESOURCES RESEARCH, 2020, 56 (3)
作者:  Wang, Tao;  Chen, Jiansheng;  Zhang, Chenming;  Zhan, Lucheng;  Li, Ling
收藏  |  浏览/下载:9/0  |  提交时间:2020/07/02
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:25/0  |  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.


  
Offshore transport of particulate organic carbon in the California Current System by mesoscale eddies 期刊论文
NATURE COMMUNICATIONS, 2019, 10
作者:  Amos, Caitlin M.;  Castelao, Renato M.;  Medeiros, Patricia M.
收藏  |  浏览/下载:4/0  |  提交时间:2019/11/27