《参考译文 kingdom come》由会员分享，可在线阅读，更多相关《参考译文 kingdom come（9页珍藏版）》请在金锄头文库上搜索。
1、The Cambrian explosion寒武纪大爆发Kingdom come 动物王国出现Chinese palaeontologists hope to explain the rise of the animals中国古生物学家希望解释动物的起源Mar 23rd 2013 | Nanjing |From the print editionAMONG the mysteries of evolution, one of the most profound is what exactly happened at the beginning of the Cambrian period. B
2、efore that period, which started 541m years ago and ran on for 56m years, life was a modest thing. Bacteria had been around for about 3 billion years, but for most of this time they had had the Earth to themselves. Seaweeds, jellyfish-like creatures, sponges and the odd worm do start to put in an ap
3、pearance a few million years before the Cambrian begins. But red in tooth and claw the Precambrian was notfor neither teeth nor claws existed.在众多进化之谜中，其中意义最深远的就是在寒武纪开始时期到底发生了什么。在寒武纪之前，从 5.41 亿年前开始持续 5600 万年的时代里，生命是适度存在的。细菌已经存在了大约 30 亿年，但是在多数时间里，它们主宰着地球。海藻、类似水母的生物、海绵生物和奇怪的虫子确实在寒武纪开始的前几百万年已经出现。但是前寒武纪时
4、期却不是腥牙血爪，因为那个时候牙齿和爪子都没有出现。Then, in the 20m-year blink of a geological eye, animals arrived in force. Most of the main groups of the animal kingdomarthropods, brachiopods, coelenterates, echinoderms, molluscs and even chordates, the branch from which vertebrates went on to developare found in the fos
5、sil beds of the Cambrian. The sudden evolution of this megafauna is known as the Cambrian explosion. But two centuries after it was noticed, in the mountains of Wales after which the Cambrian period is named, nobody knows what detonated it.然后，在地质学看来一眨眼的 2000 万年中，动物大规模的出现了。人们在寒武纪群落里发现了动物王国的主要动物集群，包括腕
6、足、腔肠、棘皮、软体和脊索（脊椎动物进化的分支） 。寒武纪因威尔士的群山而得名，在寒武纪被注意到的两个多世纪里，没人知道到底为什么会发生大爆炸。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 envi
7、ronment 600m years ago”. The “Snowball Earth” refers to a series of ice ages that happened between 725m and 541m years ago. These were, at their maxima, among the most extensive glaciations in the Earths history. They alternated, though, with periods that make the modern tropics seem chilly: the pla
8、nets average temperature was sometimes as high as 50C. Add the fact that a supercontinent (illustrated above, viewed from the Earths south pole) was breaking up at this time, and you have a picture of a world in chaos. Just the sort of thing that might drive evolution. Dr Zhu and his colleagues hope
9、 to find out exactly how these environmental changes correspond to changes in the fossil record.由南京地质古生物研究所的朱茂炎领导的中国科学家小组计划通过一个名为“从雪球事件到寒武纪大爆发：距今 6 亿年前后的生物与环境演变”的项目改变这种情况。雪球事件指的是7.25 亿-5.41 年前一系列的冰川时代。在顶峰时期，它们是地球史上最大规模的冰川时期。不过他们是交替发生的，在某些时候，使得现在的热带地区变的寒冷，有时候全球的平均温度却高达 50。从而导致了一个超大陆（见上图，从南极角度观察）分裂，从此
10、我们就有了一个混乱的地球，就是这些事情可能导致进化的发生。朱博士和他的同事希望从化石记录的变化中发现这个时期环境是如何确切变化的。The animals carnival动物狂欢节Fortunately, Chinas fossil record for this period is rich. Until recently, the only known fossils of Precambrian animals were what is called the Ediacaran faunaa handful of strange creatures found in Australia,
11、 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. In 1998, however, a team led by Chen Junyuan, also of the Nanjing Institute, and another led by Xiao Shuhai of the Virginia Polytechnic Ins
12、titute, in America, discovered a 580m-year-old Lagerstttea place where fossils are particularly well preservedin a geological formation called the Doushantuo, which spreads out across southern China.幸运的是，中国在这个时期的化石资料是非常丰富的。直到目前，唯一知道的前寒武纪一少部分化石是埃迪卡拉动物群。它们生活与生活在距今 6.35 亿年到 5.42 亿年之间埃迪卡拉纪，在澳大利亚、加拿大、英格兰
13、中部等地区被发现，但是他们和寒武纪的生物相似性很少。然而，1998 年，一个由同样来自南京所的陈俊元(音译) 和美国弗吉尼亚理工大学的肖书海（音译）共同领导的小组在中国南部一个广泛存在的陡山沱地质构造中发现了一个距今 5.8 亿年且保存出奇的好的生物群。Portents of the modern world 现代世界的前兆This Lagersttte has yielded many previously unknown species, including microscopic sponges, small tubular organisms of unknown nature, th
14、ings that look like jellyfish but might not be and a range of what appear to be embryos that show bilateral symmetry (pictured right). What these embryos would have grown into is unclear. But some might be the ancestors of the Cambrian megafauna.这个生物群落发现了许多之前不知道的物种，包括微型海绵生物，不知名物种的小管器官，一些似是而非的软体动物，以及
15、一些有对称结构（右图）的像是胚胎的生物。这些胚胎将会长成什么不得而知，但是他们中的一些可能就是寒武纪大型动物的祖先。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. They have found t
16、hat the proportion of Ca light isotope of carbon that is more easily incorporated by living organisms into organic matter than its heavy cousin, Cincreased on at least three occasions during the Ediacaran period. 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 C, for incorporation into rocks.为了把这些物种的进化和环境变化联系起来，北京地质与地球物理研究所的储雪
