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Science and technology
科學技術
The Cambrian explosion
寒武紀大爆發
Kingdom come
動物王國出現
Chinese palaeontologists hope to explain the rise of the animals
中國古生物學家希望解釋動物的起源
AMONG the mysteries of evolution, one of the most profound is what exactly happened at the beginning of the Cambrian period.
在眾多進化之謎中，其中意義最深遠的就是在寒武紀開始時期到底發生了什么。
Before that period, which started 541m years ago and ran on for 56m years, life was a modest thing.
在寒武紀之前，從5.41億年前開始持續5600萬年的時代里，生命是適度存在的。
Bacteria had been around for about 3 billion years, but for most of this time they had had the Earth to themselves.
細菌已經存在了大約30億年，但是在多數時間里，它們主宰著地球。
Seaweeds, jellyfish-like creatures, sponges and the odd worm do start to put in an appearance a few million years before the Cambrian begins.
海藻、類似水母的生物、海綿生物和奇怪的蟲子確實在寒武紀開始的前幾百萬年已經出現。
But red in tooth and claw the Precambrian was not—for neither teeth nor claws existed.
但是前寒武紀時期卻不是腥牙血爪，因為那個時候牙齒和爪子都沒有出現。
Then, in the 20m-year blink of a geological eye, animals arrived in force.
然后，在地質學看來一眨眼的2000萬年中，動物大規模的出現了。
Most of the main groups of the animal kingdom—arthropods, brachiopods, coelenterates, echinoderms, molluscs and even chordates, the branch from which vertebrates went on to develop—are found in the fossil beds of the Cambrian.
人們在寒武紀群落里發現了動物王國的主要動物集群，包括腕足、腔腸、棘皮、軟體和脊索。
The sudden evolution of this megafauna is known as the Cambrian explosion.
寒武紀因威爾士的群山而得名，
But two centuries after it was noticed, in the mountains of Wales after which the Cambrian period is named, nobody knows what detonated it.
在寒武紀被注意到的兩個多世紀里，沒人知道到底為什么會發生大爆炸。
A group of Chinese scientists, led by Zhu Maoyan of the Nanjing Institute of Geology and Palaeontology, plan to change that with a project called “From the Snowball Earth to the Cambrian explosion: the evolution of life and environment 600m years ago”.
由南京地質古生物研究所的朱茂炎領導的中國科學家小組計劃通過一個名為“從雪球事件到寒武紀大爆發：距今6億年前后的生物與環境演變”的項目改變這種情況。
The “Snowball Earth” refers to a series of ice ages that happened between 725m and 541m years ago.
雪球事件指的是7.25億-5.41年前一系列的冰川時代。
These were, at their maxima, among the most extensive glaciations in the Earth’s history.
在頂峰時期，它們是地球史上最大規模的冰川時期。
They alternated, though, with periods that make the modern tropics seem chilly: the planet’s average temperature was sometimes as high as 50C.
不過他們是交替發生的，在某些時候，使得現在的熱帶地區變的寒冷，有時候全球的平均溫度卻高達50度。
Add the fact that a supercontinent was breaking up at this time, and you have a picture of a world in chaos.
從而導致了一個超大陸分裂，從此我們就有了一個混亂的地球，
Just the sort of thing that might drive evolution.
就是這些事情可能導致進化的發生。
Dr Zhu and his colleagues hope to find out exactly how these environmental changes correspond to changes in the fossil record.
朱博士和他的同事希望從化石記錄的變化中發現這個時期環境是如何確切變化的。
The animals’ carnival
動物狂歡節
Fortunately, China’s fossil record for this period is rich.
幸運的是，中國在這個時期的化石資料是非常豐富的。
Until recently, the only known fossils of Precambrian animals were what is called the Ediacaran fauna—a handful of strange creatures found in Australia, Canada and the English Midlands that lived in the Ediacaran period, between 635m and 541m years ago, and which bear little resemblance to what came afterwards.
直到目前，唯一知道的前寒武紀一少部分化石是埃迪卡拉動物群。它們生活與生活在距今6.35億年到5.42億年之間埃迪卡拉紀，在澳大利亞、加拿大、英格蘭中部等地區被發現，但是他們和寒武紀的生物相似性很少。
In 1998, however, a team led by Chen Junyuan, also of the Nanjing Institute, and another led by Xiao Shuhai of the Virginia Polytechnic Institute, in America, discovered a 580m-year-old Lagersttte—a place where fossils are particularly well preserved—in a geological formation called the Doushantuo, which spreads out across southern China.
然而，1998年，一個由同樣來自南京所的陳俊元和美國弗吉尼亞理工大學的肖書海共同領導的小組在中國南部一個廣泛存在的陡山沱地質構造中發現了一個距今5.8億年且保存出奇的好的生物群。
Portents of the modern world
現代世界的前兆
This Lagersttte has yielded many previously unknown species, including microscopic sponges, small tubular organisms of unknown nature, things that look like jellyfish but might not be and a range of what appear to be embryos that show bilateral symmetry.
這個生物群落發現了許多之前不知道的物種，包括微型海綿生物，不知名物種的小管器官，一些似是而非的軟體動物，以及一些有對稱結構的像是胚胎的生物。
What these embryos would have grown into is unclear. But some might be the ancestors of the Cambrian megafauna.
這些胚胎將會長成什么不得而知，但是他們中的一些可能就是寒武紀大型動物的祖先。
To try to link the evolution of these species with changes in the environment, Chu Xuelei of the Institute of Geology and Geophysics in Beijing and his colleagues have been looking at carbon isotopes in the Doushantuo rocks.
為了把這些物種的進化和環境變化聯系起來，北京地質與地球物理研究所的儲雪雷和他的同事用碳同位素方法測試陡山沱石塊。
They have found that the proportion of 12C—a light isotope of carbon that is more easily incorporated by living organisms into organic matter than its heavy cousin, 13C—increased on at least three occasions during the Ediacaran period.
他們發現在埃迪卡拉紀有至少三次12C的增加，而較輕的碳同位素12C相比于它的同胞13C更容易被生物體吸收轉化為有機物。
They suggest these increases mark moments when the amount of oxygen in seawater went up, because more oxygen would mean more oxidisation of buried organic matter. That would liberate its 12C, for incorporation into rocks.
他們推測這些增長標志當時海水中的氧含量在增長，因為更多的氧氣意味著更多的埋藏的有機物的氧化。他們在變成化石的過程中就將釋放12C。
Each of Dr Chu’s oxidation events corresponds with an increase in the size, complexity and diversity of life, both plant and animal.
褚博士的每個氧化事項都與動植物在其體積，復雜性、多樣性上的增加有關。
What triggered what, however, is unclear.
然而，哪一個引發哪一個卻不得而知。
There may have been an increase in photosynthesis because there were more algae around.
這有可能因為出現了更多的藻類，光合作用增強，
Or eroded material from newly formed mountains may have buried organic matter that would otherwise have reacted with oxygen, leading to a build-up of the gas.
或者是新形成的山脈上的腐蝕物質埋藏本該和氧氣反應的有機物，導致氣體的增加。
The last—and most dramatic—rise in oxygen took place towards the end of the Ediacaran.
最戲劇性的，也是氧氣含量最后的增長發生在埃迪卡拉紀末期。
Follow-up work by Dr Zhu, in nine other sections of the Doushantuo formation, suggests this surge started just after the final Precambrian glacial period about 560m years ago, and went on for 9m years.
后續的工作由朱博士完成，有九個其他的陡山沱構造說明這個激增僅僅是在最后一次前寒武紀冰川之后，大約5.6億年前，并且持續了900萬年。
These dates overlap with those of signs of oxidation found in rocks in other parts of the world, confirming that whatever was going on affected the entire planet.
這些數據和全球其他地方發現的化石中的氧化物一起確定了到底是什么將影響整個星球。
Dr Zhu suspects this global environmental shift propelled the evolution of complex animals.
朱博士認為是全球環境的變化促進了復雜動物的進化。
Dr Zhu also plans to push back before the Ediacaran period.
朱博士還計劃回推到埃迪卡拉紀之前。
Other researchers have found fossils of algae and wormlike creatures in rocks in northern China that pre-date the end of the Marinoan glaciation, 635m years ago, which marks the boundary between the Ediacaran and the Cryogenian period that precedes it.
其他研究者已經在中國北部的石塊中發現了藻類和類似蟲子的生物的化石，其年代在6.35億年之前的圣馬力諾冰期末端之前，圣馬力諾冰期確定了其之前埃迪卡拉紀和成冰紀之間的邊界。
Such fossils are hard to study, so Dr Zhu will use new imaging technologies that can look at them without having to clean away the surrounding rock, and are also able to detect traces of fossil organic matter invisible to the eye.
這些化石很難去研究，所以朱博士利用可以清晰成像而不用去清除周邊石塊的新成像技術，并且可以探測不被肉眼可見的化石有機物的蹤跡。
Besides digging back before the Ediacaran, the new project’s researchers also intend to analyse the unfolding of the Cambrian explosion itself by taking advantage of other Lagersttten—for China has several that date from the Cambrian.
除了研究埃迪卡拉紀之前以外，新項目的研究者還利用其他生物群去分析未解開的寒武紀大爆炸，因為中國有好幾個這樣寒武紀的群落。
Dr Chen, indeed, first made his name in 1984, when he excavated one at Chengjiang in Yunnan province.
陳博士因為1984年發掘了云南澄江生物群而出名，
It dates from 525m years ago, which make it 20m years older than the most famous CambrianLagersttte in the West, the Burgess shale of British Columbia, in Canada.
澄江生物群大概在5.25億年以前，這就使得他比西方著名的加拿大不列顛哥倫比亞的波基斯頁巖寒武紀群落早了2000萬年。
The project’s researchers plan to see how, evolutionarily speaking, the various Lagerst?tten relate to one another, to try to determine exactly when different groups of organisms emerged.
這個項目的研究者計劃從進化學上解釋，不同的群落是怎么和其他的群落發生聯系，并且試圖解決到底什么時候出現了不同的生物分類。
They will also look at the chemistry of elements other than carbon and oxygen—particularly nitrogen and phosphorous, which are essential to life, and sulphur, which often indicates the absence of oxygen and is thus antithetical to much animal life.
他們不單單只是觀察氧和碳元素，尤其是生命必須的氮和磷，以及經常指示缺少氧且和大部分動物生命對立的硫。
Dr Zhu hopes to map changes in the distribution of these chemicals across time and space.
朱博士希望繪制這些元素隨著時間和空間分布變化圖，確認這些變化的關聯性，
He will assess how these changes correlate, whether they are related to weathering, mountain building and the ebb and flow of glaciers, how they could have affected the evolution of life, and how plants and animals might themselves have altered the chemistry of air and sea.
它們是否和天氣，造山，冰川的起伏有關，他們怎樣影響生命的進化，以及動植物他們自己是如何改變空氣和海洋中的化學組成。
Most ambitiously, Dr Zhu, Dr Xiao and their colleagues hope to drill right through several fossiliferous sites in southern China where Ediacaran rocks turn seamlessly into Cambrian ones.
朱博士，肖博士以及他們的團隊很有雄心的希望在中國南部那些無縫連接埃迪卡拉紀和寒武紀的幾個含有化石的地方穿鑿而過。
Such places are valuable because in most parts of the world there is a gap, known as an unconformity, between the Ediacaran and the Cambrian.
這些地方都很有價值，世界的大部分地區，埃迪卡拉和寒武紀之間都有空白，這種空白被稱為不整合面。
Unconformities are places where rocks have been eroded before new ones are deposited, and the widespread Ediacaran-Cambrian unconformity has been a big obstacle to understanding the Cambrian explosion.
不整合面地方的石塊在新的沉積之前已經被侵蝕，埃迪卡拉紀-寒武紀之間廣泛的不整合面是了解寒武紀大爆發的一個重大障礙。
With luck, then, a mystery first noticed in the Welsh mountains in the early 19th century will be solved in the Chinese ones in the early 21st.
幸運的是，在19世紀早期威爾士群山中發現的神奇事件將被21世紀中國發現的群落所解決。
If it is, the origin of the animal kingdom will have become clear, and an important gap in the history of humanity itself will have been filled.
如果是的話，那動物王國的起源將會變得更清晰，人類歷史中一個重要的空白將被填補。
