溫室氣體造成發生在上次冰河期的冰河後退現象

原文網址：www.sciencedaily.com/releases/2015/08/150821082727.htm

Greenhouse gases caused glacial retreat during last Ice Age

溫室氣體造成發生在上次冰河期的冰河後退現象

A recalculation of the dates at which boulders were uncovered by melting glaciers at the end of the last Ice Age has conclusively shown that the glacial retreat was due to rising levels of carbon dioxide and other greenhouse gases, as opposed to other types of forces.

重新計算上次冰河期末時因為冰河融化而露出來的礫石年代，確認了冰河後退的主因為二氧化碳以及其他溫室氣體的濃度上升，而非其他作用力。

Carbon dioxide levels are now significantly higher than they were at that time, as a result of the Industrial Revolution and other human activities since then. Because of that, the study confirms predictions of future glacial retreat, and that most of the world's glaciers may disappear in the next few centuries.

工業革命以及之後的其他人類活動，造成現今的二氧化碳濃度遠比上次冰河期末高上許多。這使得此篇研究也證實了未來冰河將會繼續後退，而世界上大多數的冰河也許在不久之後的數個世紀內就會融化殆盡。

The findings were published today in Nature Communications by researchers from Oregon State University, Boston College and other institutions. They erase some of the uncertainties about glacial melting that had been due to a misinterpretation of data from some of these boulders, which were exposed to the atmosphere more than 11,500 years ago.

此篇刊登在今日《自然通訊》(Nature Communications )的研究的作者來自於奧勒岡州立大學、波士頓學院以及其他機構。之前利用這些暴露在空氣中的時間已超過11,500年的礫石，來預估冰河融化的時間時，有可能會因為判讀錯誤而產生誤差。而這群科學家在這篇論文中成功降低了這些誤差。

"This shows that at the end of the last Ice Age, it was only the increase in carbon dioxide and other greenhouse gases that could have caused the loss of glaciers around the world at the same time," said Peter Clark, a professor in the OSU College of Earth, Ocean and Atmospheric Sciences, and co-author on the study.

「在上次冰河期末時，唯有二氧化碳以及其他溫室氣體的濃度上升，才能造成世界各地的冰河在同一時間開始融化。」本研究的共同作者，奧勒岡州立大學地球、海洋與大氣科學系的教授Peter Clark說。

"This study validates predictions that future glacial loss will occur due to the ongoing increase in greenhouse gas levels from human activities," Clark said. "We could lose 80-90 percent of the world's glaciers in the next several centuries if greenhouse gases continue to rise at the current rate."

「此研究證實了未來冰河將會因為人類活動造成的溫室氣體濃度持續上升而消失。」Clark說。「若溫室氣體的濃度繼續以現在的速率攀升，在未來的數世紀內我們可能就會失去世界上百分之80至90的冰河。」

Glacial loss in the future will contribute to rising sea levels and, in some cases, have impacts on local water supplies.

冰河的消失在未來將會造成全球海平面上升，而在某些地區當地的水源供應可能也會受到相當大的影響。

As the last Ice Age ended during a period of about 7,000 years, starting around 19,000 years ago, the levels of carbon dioxide in the atmosphere increased from 180 parts per million to 280 parts per million. But just in the past 150 years, they have surged from 280 to about 400 parts per million, far higher than what was required to put an end to the last Ice Age.

從19,000年前起，上次冰河期末的7,000年間，大氣中二氧化碳的濃度從百萬分之180(180 p.p.m.)升高至280 p.p.m.。但僅僅在過去的150年間，二氧化碳已從280 p.p.m.飆升至400 p.p.m.，遠比終結上次冰河期所需的濃度還要高上許多。

The new findings, Clark said, were based on a recalculation of the ages at which more than 1,100 glacial boulders from 159 glacial moraines around the world were exposed to the atmosphere after being buried for thousands of years under ice.

Clark說這項新發現建立於重新測量159層世界各地冰磧(glacial moraine)中的1100顆冰河礫石的年代。這些冰磧曾被深埋在冰層底下數千年，直到冰河融化後才重見天日。

The exposure of the boulders to cosmic rays produced cosmogenic nuclides, which had been previously measured and used to date the event. But advances have been made in how to calibrate ages based on that data. Based on the new calculations, the rise in carbon dioxide levels -- determined from ancient ice cores -matches up nicely with the time at which glacial retreat took place.

冰河融化後露出的礫石會暴露在宇宙射線的照射之下，而產生宇生核種(cosmogenic nuclide)，在先前的研究中可以測量其濃度來定年事件發生的年代。本研究改良之處在於如何以測量到的數據來換算成更精確的年代。根據他們新的計算方式而得出的冰河後退年代，與顯示在古老冰芯中的二氧化碳濃度上升時刻，兩者之間相當符合。

"There had been a long-standing mystery about why these boulders were uncovered at the time they were, because it didn't properly match the increase in greenhouse gases," said Jeremy Shakun, a professor at Boston College and lead author on the study. "We found that the previous ages assigned to this event were inaccurate. The data now show that as soon as the greenhouse gas levels began to rise, the glaciers began to melt and retreat."

「長久以來的疑惑在於為何這些礫石會在這個時間點開始暴露在地表，因為這與溫室氣體開始升高的時刻並不太符合。」本研究的第一作者，波士頓學院的Jeremy Shakun教授說。「我們發現之前對這起事件的年代的推估並不準確。現在的數據顯示溫室氣體的濃度一開始上升，冰河便會開始融化並後退。」

There are other forces that can also cause glacial melting on a local or regional scale, the researchers noted, such as changes in the Earth's orbit around the sun, or shifts in ocean heat distribution. These factors probably did have localized effects. But the scientists determined that only the change in greenhouse gas levels could have explained the broader global retreat of glaciers all at the same time.

研究人員注意到尚有其他因素會造成局部或區域性的冰河融化，像是地球繞日軌道的變化，或者海洋熱能分佈的改變。這些因素或多或少會造成區域性效應，然而科學家斷定唯有溫室氣體濃度的改變，才能在同一時間造成範圍廣至全球的冰河後退。

In the study of climate change, glaciers have always been of considerable interest, because their long-term behavior is a more reliable barometer that helps sort out the ups-and-downs caused by year-to-year weather variability, including short-term shifts in temperature and precipitation.

在氣候變遷的研究當中，冰河總是佔有一席之地，這是由於它們的長期變化並不會被年際氣候變化影響，包括溫度以及降雨的短週期變化，使得它們可以做為較可靠的長時間尺度氣壓計。

Other collaborators on this research were from the University of Wisconsin, Purdue University, and the National Center for Atmospheric Research. The work was supported by the National Oceanic and Atmospheric Administration and the National Science Foundation.

其他的協同研究人員來自威斯康辛大學、普渡大學以及美國國家大氣研究中心。本研究由美國國家海洋和大氣管理局及美國國家科學基金會所資助。

引用自：Oregon State University. "Greenhouse gases caused glacial retreat during last Ice Age." ScienceDaily. ScienceDaily, 21 August 2015. 

沒有人類，整個世界也許看起來就像塞倫蓋蒂(Serengeti)般的生機盎然

原網址：www.sciencedaily.com/releases/2015/08/150820212652.htm

Without humans, the whole world could look like Serengeti

沒有人類，整個世界也許看起來就像塞倫蓋蒂(Serengeti)般的生機盎然

New study shows what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts

新的研究顯示出若沒有過去與現在的人類影響，自然世界中哺乳類的多樣性應該如何分佈

The fact that the greatest diversity of large mammals is found in Africa reflects past human activities -- and not climatic or other environmental constraints. This is determined in a new study, which presents what the world map of mammals would look like if modern man (Homo sapiens) had never existed.

在這篇新研究中，研究人員呈現出若現代人(Homo sapiens)從未出現，哺乳類在這個世界上應是如何分佈。他們的結果顯示非洲擁有最高的大型哺乳類多樣性，反映出來的是過往人類活動的影響，而非氣候或其他環境限制導致。

In a world without humans, most of northern Europe would probably now be home to not only wolves, Eurasian elk (moose) and bears, but also animals such as elephants and rhinoceroses.

在沒有人類的世界，現今北歐大部分的地區可能不只是狼、歐亞駝鹿(麋鹿)與熊的家園，也會有其它動物生活於此，像是大象與犀牛。

This is demonstrated in a new study conducted by researchers from Aarhus University, Denmark. In a previous analysis, they have shown that the mass extinction of large mammals during the Last Ice Age and in subsequent millennia (the late-Quaternary megafauna extinction) is largely explainable from the expansion of modern man (Homo sapiens) across the world. In this follow-up study, they investigate what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts, based on estimates of the natural distribution of each species according to its ecology, biogeography and the current natural environmental template. They provide the first estimate of how the mammal diversity world map would have appeared without the impact of modern man.

此幅景象呈現於丹麥奧胡斯大學(Aarhus University)的研究人員新進行的研究結果之中。在先前的分析當中，他們已經顯示在上次冰河期以及之後數千年間，發生的大型哺乳類滅絕事件(晚第四紀巨型動物群滅絕事件，the late-Quaternary megafauna extinction)絕大部分要歸咎於現代人(Homo sapiens)往世界各地遷徙。在這篇後續研究當中，他們根據不同種哺乳類各自的生態、生物地理分佈以及在自然條件下，各地環境應有的樣貌為何，來預測牠們的自然分佈模式，並總和所有結果得出若沒有過去及現今的人類影響，在自然情形下哺乳類多樣性在全世界的分佈模式。他們的結果呈現了首幅在沒有現代人的影響下，哺乳類多樣性會如何分佈的世界地圖。

"Northern Europe is far from the only place in which humans have reduced the diversity of mammals -- it's a worldwide phenomenon. And, in most places, there's a very large deficit in mammal diversity relative to what it would naturally have been," says Professor Jens-Christian Svenning, Department of Bioscience, Aarhus University, who is one of the researchers behind the study.

「北歐絕不是唯一人類導致哺乳類多樣性下降的地區─這是一個在全世界都相當普及的現象。而且在多數地區，哺乳類多樣性跟在自然背景下應有的相比，都下降了非常多。」此篇研究的作者之一，奧胡斯大學生命科學系的教授Jens-Christian Svenning說。

Africa is the last refuge

非洲─最後的淨土

The current world map of mammal diversity shows that Africa is virtually the only place with a high diversity of large mammals. However, the world map constructed by the researchers of the natural diversity of large mammals shows far greater distribution of high large-mammal diversity across most of the world, with particularly high levels in North and South America, areas that are currently relatively poor in large mammals.

現今的哺乳類多樣性世界地圖顯示出非洲為僅存大型哺乳類仍具有高度多樣性的地區。然而，由研究人員建立的世界地圖卻顯示在自然情況下，具有高度大型哺乳類多樣性的地區廣泛分佈於世界各地。其中又以南北美洲為特別高的地區，儘管目前這些地方的大型哺乳類相對來說相當罕見。

"Most safaris today take place in Africa, but under natural circumstances, as many or even more large animals would no doubt have existed in other places, e.g., notably parts of the New World such as Texas and neighboring areas and the region around northern Argentina-Southern Brazil. The reason that many safaris target Africa is not because the continent is naturally abnormally rich in species of mammals. Instead it reflects that it's one of the only places where human activities have not yet wiped out most of the large animals," says Postdoctoral Fellow Soren Faurby, Department of Bioscience, Aarhus University, who is the lead author on the study.

「現今的遊獵(safari，原本意指以狩獵大型動物為主的遠行活動，現在多已轉變成觀光性質)多半僅見於非洲，但在自然條件下，毫無疑問地會有同樣多數量，甚至更大批的大型動物生存在其他地區，譬如說目前新世界的都會區，如德州與其鄰近區域，以及阿根廷部北部至巴西南部地區。許多遊獵選在非洲並非因為當地本來就擁有特別多種的哺乳類，而是反應出非洲為人類活動尚未殲滅大部分大型哺乳類的僅存地區之一。」本篇研究的第一作者，奧胡斯大學生命科學系的博士後研究員Soren Faurby說。

The existence of Africa's many species of mammals is thus not due to an optimal climate and environment, but rather because it is the only place where they have not yet been eradicated by humans. The underlying reason includes evolutionary adaptation of large mammals to humans as well as greater pest pressure on human populations in long-inhabited Africa in the past.

因此非洲擁有許多種哺乳類的原因並非是其擁有特別宜人的氣候以及環境，而是因為它是尚未遭人類染指的最後淨土。這背後的原因包括了當地的大型哺乳類演化出對人類有較高的適應能力，以及長久以來非洲的住人地區因為寄生蟲肆虐，而大幅限制了人口增長。

Better understanding helps nature preservation

瞭解更多有助於生態保育

The study's openly accessible data set of natural range maps for all late-Quatenary mammals provides researchers with the first opportunity to analyse the natural patterns in the species diversity and composition of mammals worldwide. Hereby, it can be used to provide a better understanding of the natural factors that determine the biodiversity in a specific area.

此篇研究提供了所有晚第四紀以來的哺乳動物，在自然條件下應會如何分佈的公開地圖資料，有了這些資料，研究人員首度有機會分析世界各地的哺乳動物多樣性及組成，在僅考慮自然條件下的分佈模式。而這可以讓我們對特定地區的自然因子如何影響當地的生物多樣性有更深入的瞭解。

Today, there is a particularly large number of mammal species in mountainous areas. This is often interpreted as a consequence of environmental variation, where different species have evolved in deep valleys and high mountains. According to the new study, however, this trend is much weaker when the natural patterns are considered.

現今的山區環境有特別多樣的哺乳類。這通常被視作山區能提供各式各樣的環境而造成的結果。生物在高山與深谷中會往不同的方向演化，因而創造出特別高的多樣性。然而根據此篇新研究，在僅考慮自然因素的生物多樣性分佈模式中，這種趨勢並不特別明顯。

"The current high level of biodiversity in mountainous areas is partly due to the fact that the mountains have acted as a refuge for species in relation to hunting and habitat destruction, rather than being a purely natural pattern. An example in Europe is the brown bear, which now virtually only live in mountainous regions because it has been exterminated from the more accessible and most often more densely populated lowland areas," explains Soren Faurby.

「現今的山區擁有相當高的生物多樣性，部分原因來自於高山對生物來說，是躲避人類狩獵以及棲地破壞的避難所，而非純粹由自然因素造成。在歐洲一個很好的例子便是棕熊。棕熊現在僅生存於深山地區，這是因為牠們已難以生活在對人類而言易於抵達且人口密集的平地。」

Hereby, this new study can provide an important base-line for nature restoration and conservation.

此新研究能夠提供未來自然保育與復育的研究上重要的基準點。

The study has been published in the scientific journal Diversity and Distributions.

本研究刊登於科學期刊《生物多樣性與分佈》(Diversity and Distributions)。

The natural diversity of large mammals is shown as it would appear without the impact of modern man (Homo sapiens). The figure shows the variation in the number of large mammals (45 kg or larger) that would have occurred per 100 x 100 kilometer grid cell. The numbers on the scale indicate the number of species.

上圖為在沒有現代人類(Homo sapiens)的影響下，大型哺乳類多樣性的自然分佈模式。將地圖分成100 x 100 公里的網格後，計算每一格當中有多少種大型哺乳類(45公斤以上)而得到此圖。右方刻度代表物種數目。

Credit: Illustration: Soren Faurby

引用自：Aarhus University. "Without humans, the whole world could look like Serengeti: New study shows what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts." ScienceDaily. ScienceDaily, 20 August 2015.

古植物學家發現了可能是傳說中的「第一朵花」

原文網址：www.sciencedaily.com/releases/2015/08/150817160613.htm

Paleobotanist identifies what could be the mythical 'first flower'

古植物學家發現了可能是傳說中的「第一朵花」

New analysis represents major change in the presumed nature of the planet's earliest angiosperms

新的分析展現了推測為地球上最早的被子植物在本質上發生的重大改變

Indiana University paleobotanist David Dilcher and colleagues in Europe have identified a 125 million- to 130 million-year-old freshwater plant as one of earliest flowering plants on Earth.

印第安納大學的古植物學家David Dilcher以及歐洲的科學家發現生活在1億2500萬至1億3000萬年前的一種淡水水生植物，可能是地球上最早的開花植物。

The finding, reported Aug. 17 in the Proceedings of the National Academy of Sciences, represents a major change in the presumed form of one of the planet's earliest flowers, known as angiosperms.

發表在8月17日的《美國國家科學院院刊》( Proceedings of the National Academy of Sciences)的發現顯示出推測為地球上最早的花朵(又稱為被子植物，angiosperm)，在型態上發生的重大變化。

"This discovery raises significant questions about the early evolutionary history of flowering plants, as well as the role of these plants in the evolution of other plant and animal life," said Dilcher, an emeritus professor in the IU Bloomington College of Arts and Sciences' Department of Geological Sciences.

「這項發現引發了更重要的問題：開花植物的早期演化史究竟為何，以及它們在其他動植物的演化中占據了何種地位。」Dilcher說，他是印第安納大學文理學院地質科學系的榮譽教授。

The aquatic plant, Montsechia vidalii, once grew abundantly in freshwater lakes in what are now mountainous regions in Spain. Fossils of the plant were first discovered more than 100 years ago in the limestone deposits of the Iberian Range in central Spain and in the Montsec Range of the Pyrenees, near the country's border with France.

雖然現為西班牙的山區，但在過去淡水湖遍佈時，名稱為Montsechia vidalii的水生植物曾一度在這些湖泊當中繁榮生長。早在一百多年前這種植物的化石就已經首度在鄰近法國邊界，西班牙中部的伊比利山脈以及庇里牛斯山蒙特塞克山脈中的石灰岩層中發現。

Also previously proposed as one of the earliest flowers is Archaefructus sinensis, an aquatic plant found in China.

在這之前另一種被認為可能是最早的花朵─中國古果(Archaefructus sinensis)，則是一種發現於中國的水生植物。

"A 'first flower' is technically a myth, like the 'first human,'" said Dilcher, an internationally recognized expert on angiosperm anatomy and morphology who has studied the rise and spread of flowering plants for decades. "But based on this new analysis, we know now that Montsechia is contemporaneous, if not more ancient, than Archaefructus."

「專業上來講，「第一朵花」其實是種迷思，就跟「第一位人類」一樣。」Dilcher說，他是享譽國際的被子植物解剖學及演化專家，鑽研開花植物的出現與散佈已長達數十年之久。「但根據最新的分析結果，我們現在確知Montsechia 就算不比中華古果還要古老，至少也會跟它生存在同一時代。」

He also asserted that the fossils used in the study were "poorly understood and even misinterpreted" during previous analyses.

他也主張他們研究的這些化石在之前的分析中，「根本沒有被仔細解析，甚至判釋錯誤」。

"The reinterpretation of these fossils provides a fascinating new perspective on a major mystery in plant biology," said Donald H. Les, a professor of ecology and evolutionary biology at the University of Connecticut, who is the author of a commentary on the discovery in the journal PNAS. "David's work is truly an important contribution to the continued quest to unravel the evolutionary and ecological events that accompanied the rise of flowering plants to global prominence."

「重新解析這些化石讓我們對這個植物學上的重大謎題有了引人注目的全新想法」。在PNAS期刊上對此論文撰寫評論的作者，康乃狄克大學生態學與演化生態學系的Donald H. Les教授說。「科學界一直致力於闡明開花植物崛起並成稱霸全球的過程中，曾伴隨哪些演化與生態事件。David的研究成果毫無疑問地對此議題有重大的實質貢獻。」

The conclusions are based upon careful analyses of more than 1,000 fossilized remains of Montsechia, whose stems and leaf structures were coaxed from stone by applying hydrochloric acid on a drop-by-drop basis. The plant's cuticles -- the protective film covering the leaves that reveals their shape -- were also carefully bleached using a mixture of nitric acid and potassium chlorate.

經由細心分析超過一千個用以下方法處理的樣品後，他們才做出這些結論。他們將鹽酸一滴一滴地慢慢滴在岩石上，以逐漸分離出嵌在其中的Montsechia化石的莖部以及葉片構造。葉片表面薄薄一層用來保護用的角質層，也利用硝酸與氯酸鉀的混合液來仔細脫除。

Examination of the specimens was conducted under a stereomicroscope, light microscope and scanning electron microscope.

這些經過處理後的樣品分別利用解剖顯微鏡、光學顯微鏡與掃描式電子顯微鏡來詳盡檢視。

The age of the plant at 125 million to 130 million years is based upon comparisons to other fossils in the same area, notably the freshwater algae charophytes, which places Montsechia in the Barremian age of the early Cretaceous period, making this flowering plant a contemporary of dinosaurs such as the brachiosaurus and iguanodon.

藉由比對同一地區出土的其它化石，其中又以輪藻(charophytes)這種淡水藻類最為重要，可以知道Montsechia的生存年代約在1億2500萬年至1億3000萬年前之間，白堊紀早期的巴姆雷期(Barremian age)。同時間與此開花植物共享棲地的恐龍包括了腕龍與禽龍。

The precise, painstaking analysis of fossilized structures remains crucial to paleobotany, in contrast to other biological fields, due to the current inability to know the molecular characters of ancient plants from millions of years ago, Dilcher said.

Dilcher說，由於目前的技術仍無法取得數百萬年以前的古代植物的分子特徵，因此相對於生物學的其他領域，分析化石結構這種需要高精確度且耗費心力的工作，對古植物學家而言仍然相對重要。

This careful examination was particularly important to Montsechia since most modern observers might not even recognize the fossil as a flowering plant.

對於Montsechia這種時下大部分的科學家甚至不認為它是開花植物的化石來說，細心的觀察更是至關重要。

"Montsechia possesses no obvious 'flower parts,' such as petals or nectar-producing structures for attracting insects, and lives out its entire life cycle under water," he said. "The fruit contains a single seed" -- the defining characteristic of an angiosperm -- "which is borne upside down."

「Montsechia 外觀上並沒有明顯與花相似的部分，像是用來吸引昆蟲的花瓣或是可以製造花蜜的構造，而且它們畢生都生活在水面以下。」他說。「它們的果實之中含有一顆種子，」─這是被子植物的決定性特徵─「以上下顛倒的方式生長。」

In terms of appearance, Dilcher said, Montsechia resembles its most modern descendent, identified in the study as Ceratophyllum. Also known as coontails or hornworts, Ceratophyllum is a dark green aquatic plant whose coarse, tufty leaves make it a popular decoration in modern aquariums and koi ponds.

Dilcher說就外觀上而言，Montsechia與金魚藻相當類似。這是他們在此研究中判斷出來，Montsechia生存於現代的後裔。金魚藻又稱為松藻，是一種深綠色的水生植物，其粗長且叢生的葉片使得它們成為現代水族箱與景觀池中的熱門造景用水草。

Next up, Dilcher and colleagues want to understand more about the species connecting Montsechia and Ceratophyllum, as well as delve deeper into when precisely other species of angiosperms branched off from their ancient forefathers.

接下來Dilcher與其同僚想要更了解連結Montsechia與金魚藻之間的物種為何，並且更深入探究其他被子植物與它們的老祖宗分家的準確時間點。

"There's still much to be discovered about how a few early species of seed-bearing plants eventually gave rise to the enormous, and beautiful, variety of flowers that now populate nearly every environment on Earth," he said.

「關於這些僅帶有種子的少數遠古物種，是如何演化出幾乎在現今地球上任何環境都能見到，為數眾多、繽紛且千變萬化的花兒，仍有許多事物有待我們去發現。」他說。

引用自：Indiana University. "Paleobotanist identifies what could be the mythical 'first flower': New analysis represents major change in the presumed nature of the planet's earliest angiosperms." ScienceDaily. ScienceDaily, 17 August 2015. 

人類為古代巨型哺乳類滅絕的元凶

原文網址：www.sciencedaily.com/releases/2015/08/150813104305.htm

Humans responsible for demise of gigantic ancient mammals

人類為古代巨型哺乳類滅絕的元凶

Early humans were the dominant cause of the extinction of a variety of species of giant beasts

早期人類為許多種巨型野獸滅絕的主因

Early humans were the dominant cause of the extinction of a variety of species of giant beasts, new research has revealed.

新的研究顯示早期人類為許多種巨型野獸滅絕的主因

Scientists at the universities of Exeter and Cambridge claim their research settles a prolonged debate over whether humankind or climate change was the dominant cause of the demise of massive creatures in the time of the sabretooth tiger, the woolly mammoth, the woolly rhino and the giant armadillo.

劍齒虎、真猛瑪象、披毛犀(woolly rhino)、巨犰狳以及其他同時代的巨型生物滅絕的主因究竟是人類或者氣候變遷？艾克斯特大學與劍橋大學的科學家主張他們的研究能解決這起歷時已久的爭議。

Known collectively as megafauna, most of the largest mammals ever to roam the earth were wiped out over the last 80,000 years, and were all extinct by 10,000 years ago.

曾漫步在地球上，這些合稱為巨型動物群(megafauna)的哺乳類巨獸在過去的8萬年間逐漸消失，並在1萬年前完全滅絕。

Lewis Bartlett, of the University of Exeter, led the research, which also involved the universities of Reading and Bristol and is published in the journal Ecography. He said cutting-edge statistical analysis had helped solve the mystery almost beyond dispute, concluding that man was the dominant force in wiping out the creatures, although climate change could also have played a lesser role.

此篇刊登在期刊《描述生態學》(Ecography.)上的研究由艾克斯特大學的Lewis Bartlett領導，包含了來自雷丁大學與布里斯托爾大學的學者。他說最尖端的統計分析技術近乎完全解開了這道謎題。結論是，人類就是這些生物消亡的主要推手，雖然氣候變遷可能在其中扮演了次要角色。

The researchers ran thousands of scenarios which mapped the windows of time in which each species is known to have become extinct, and humans are known to have arrived on different continents or islands. This was compared against climate reconstructions for the last 90,000 years.

研究人員統計分析了數千筆個別物種滅絕的時段，以及人類到達不同的大陸或島嶼的時間，並將結果與過去9萬年來的氣候重建結果互相比對。

Examining different regions of the world across these scenarios, they found coincidences of human spread and species extinction which illustrate that man was the main agent causing the demise, with climate change exacerbating the number of extinctions. However, in certain regions of the world -- mainly in Asia -- they found patterns which patterns were broadly unaccounted for by either of these two drivers, and called for renewed focus on these neglected areas for further study.

在檢視了世界各地不同區域的情況之後，他們發現人類擴張與物種滅絕的時間相當雷同，顯示人類為物種滅絕的主因，而氣候變遷則導致了滅亡物種的數目增加。然而，在世界上的某些地區，主要位於亞洲，他們發現大部分物種滅亡的模式並不能以這兩種趨動因子的變化模式來解釋，因此他們認為之後的研究需要進一步聚焦在這些之前未受重視的區域。

Lewis Bartlett, a researcher from the University of Exeter's Centre for Ecology and Conservation, said: "As far as we are concerned, this research is the nail in the coffin of this 50-year debate -- humans were the dominant cause of the extinction of megafauna. What we don't know is what it was about these early settlers that caused this demise. Were they killing them for food, was it early use of fire or were they driven out of their habitats? Our analysis doesn't differentiate, but we can say that it was caused by human activity more than by climate change. It debunks the myth of early humans living in harmony with nature."

艾克斯特大學生態與保育中心的研究員Lewis Bartlett說：「就我們來看，這篇研究終於將這件長達50年的爭議蓋棺論定-人類就是巨型動物群滅亡的主因。但我們所不知道的是這些早期的移民者究竟是如何造成牠們的滅亡。他們是為了食物而獵殺牠們嗎？還是因為早期人類開始用火的影響？或者他們將這些巨獸驅離出牠們原本的棲地？我們的研究無法辨認孰是孰非，但我們可以很肯定地說人類活動的影響比氣候變遷要大得多。而這也破除了早期人類與大自然和諧共處的迷思。」

Dr Andrea Manica, of Cambridge University, was lead supervisor on the paper. He said: "Whilst our models explain very well the timing and extent of extinctions for most of the world, mainland Asia remains a mystery. According to the fossil record, that region suffered very low rates of extinctions. Understanding why megafauna in mainland Asia is so resilient is the next big question."

劍橋大學的Andrea Manica是這篇論文的主要指導教授。他說：「雖然我們的模型能夠成功地解釋世界上大部分地區的滅絕事件的發生時間以及規模大小，但對亞洲本土卻起不了作用。亞洲本土的巨型動物群為何有如此強韌的適應能力將會是下一個重要的問題。」

引用自：University of Exeter. "Humans responsible for demise of gigantic ancient mammals: Early humans were the dominant cause of the extinction of a variety of species of giant beasts." ScienceDaily. ScienceDaily, 13 August 2015.