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I'm on a fantastic journey to look for the origins of life.
我踏上了生命溯源的奇妙旅程，

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I shall be travelling，not only around the world，but back in time，
我即将游历的不仅是世界各的景观，而且让时光倒流，

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to try and build a picture
试着完成一幅

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of what life was like in that very early period.
最初生命的画面。

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Last time I saw how，600 million years ago，
上一次我看见了在6亿年前，

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simple cells evolved into the first multi-cellular animals.
单细胞演化为最原始的多细胞动物。

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In this programme，I investigate what happened next.
在这一次旅行中，我将探索接下来发生的事。

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I will look for evidence in both
我将会用现代生物的证据

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fossils and living creatures of what happened in that
或是古老的化石证据

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far, distant past,
来证明

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when the fundamental features of modern animals
现代动物的基本特征

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were being established for the first time.
早在最初的阶段已经建立了。

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One group，the arthropods，were the great pioneers。
节肢动物是最主要的先驱物种。

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They were the first big predators.
它们是最早的大型食肉动物。

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They had eyes
它们具有眼睛

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Legs
附肢

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And hard external skeletons。
并且具有坚硬的外骨骼。

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They were the first to crawl out of water
它们也是最先爬出水面的动物

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to conquer the land and the air.
征服了陆地与天空。

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600 million years ago，the world was very different
早在6亿年前，

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from the planet we know today。
当时的世界与我们现在所熟知的地球非常不同。

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The land was entirely without animals or plants.
陆地上毫无动物和植物的踪迹。

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But the oceans were teeming with life.
但是在海洋中，却充满了生命。

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The first proto-animals were immobile organisms
最初的动物是固生的。

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that lived on the sea floor and extracted their nourishment
它们生活在海床上，

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from the water flowing around them.
从它们周围的水流中吸取所需的营养物质

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But once animals developed mouths
但是一旦这些动物发育出了口，

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and the ability move，evolution took off.
并且具有移动的能力，演化的飞跃开始了。

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Canada's Rocky Mountains.
在加拿大的落基山脉

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Here we can find evidence of a sudden explosion of life
被称为寒武纪的地史时期，

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when animals started to evolve with astonishing rapidity.
我们发现动物的演化以惊人的速度启动了，

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It happened during a period called the Cambrian.
即爆发式的演化的证据。

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And it began 542 million years ago.
距今5.42亿年前，

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During the next 10-20 million years,
在随后的1-2千万年间，

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animals increased in numbers，diversity and size as never before.
动物的多样性及大小发生了前所未有的增加。

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And as they got bigger，so they became more complex.
由于它们变得更大，因此它们变得更加复杂。

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And they're preserved to an extraordinary degree of perfection
在我下面的岩石中，

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in the rocks right below me.
它们以异乎寻常的完美保存下来了,

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The Burgess Shales，where a rich seam of fossils
在布尔吉斯页岩中，有丰富的化石层

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documents this Cambrian explosion in astonishing detail.
记载了寒武纪大爆发中让人惊叹的细节。

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All this area was once the floor of a shallow sea，teeming with life.
曾经这些地区是浅海海床，生命繁衍生息之处。

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As sediment settled down onto the floor，so it became compressed
由于沉积物的沉降使得它们压得扁平

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and turned into mudstones and shales that you can see around me here.
并且变为现在我周围的泥岩和页岩。

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About a century ago,
大约一个世纪以前，

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an American geologist from the Smithsonian Institution
美国Smithsonian研究所的地质学家

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was making a survey of this part of the Rockies.
当时他正在考察落基山脉的这个地区。

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And he came walking along this particular path.
并且他沿着这条特别的路走着。

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And when he got to precisely this spot,
刚好走到这个地方，

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he noticed a tiny fossil of a kind he had never seen before.
他发现了一块从未见过的小化石。

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He bent down and picked it up and it looked like this.
他就像这样弯着腰捡起来

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What sort of a creature could this be?
这是一种什么样的生物呢？

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It was only the first of the enigmatic creatures
这仅仅是第一个在布尔吉斯页岩

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to come from the Burgess Shales.
现身的神秘生物。

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Since then over 65,000 different specimens of now extinct
从那以后，在这个小小的采石场

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Cambrian animals have been from this one small quarry.
发现了超过65 000种已灭绝动物的化石。

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Many species have never been found elsewhere.
许多种类以前从未被发现。

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It seems that the Burgess Shales were deposited in a place
布尔吉斯页岩具有得天独厚的沉积环境

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where conditions for fossilisation were uniquely perfect.
这种环境能够让生物体极其完美地保存下来

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As a consequence, even bodies of animals that were soft
因此，即使没有硬的组织，

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and lacking any hard parts were, nonetheless, preserved.
软体组织也依然能够保存下来。

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They survive as thin, almost imperceptible layers,
它们残留为难以察觉的薄层，

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that you only see if you get the light just right.
因此你得通过特殊角度的光线去观察。

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It's these fossils that have transformed our understanding
正是这些化石

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of how animals we know today have come to be the way they are.
改变了我们对现生生物是如何演化的理解。

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In some of these specimens we can glimpse shapes and forms
在有些标本中我们能看到它们的形状和构造。

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that look faintly familiar.
看起来似曾相识

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But many of these bizarre creatures seem like nothing we know of today.
但其中大部分的奇异生物我们似乎从未见过。

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This is one of the more mysterious animals from the Shales.
这是布尔吉斯页岩中较神秘的成员之一。

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There are two clues as to how this creature might have lived.
这有两条线索可以推测这种生物是如何生活的。

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It has flaps along the side of its body,
在它身体的两侧有一排翼状物，

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but no legs，and also a broad, flat tail.
但是它却没有附肢，只有扁平宽阔的尾扇。

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So it's reasonable to assume that they helped it swim
因此有理由推测尾扇和翼状物是用来游泳的。

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and that it lived not crawling along the floor,
它并不是在海底爬行的动物，

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but up higher in the water.
而是可以游到较高的海面。

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But the really, truly mysterious thing about it is that here
但是非常诡异的是

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on its head it had five eyes,
它的头部长着五只眼睛，

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each of them like a kind of little mushroom.
每一个眼睛就像是一个小蘑菇。

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And beneath that it had a long proboscis
在眼睛的下方还有一个长长的吻

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with which it grabbed things.
长吻可以用来捕捉猎物。

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It's a truly primitive animal
虽然它是十分原始的动物。

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and one that, still, we don't fully understand.
但是，我们并不完全了解它。

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It's been named opabinia.
它被命名为“欧巴宾”

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And it seems to have been a kind of evolutionary experiment.
似乎它曾经是演化的一种尝试。

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It's almost as if an assortment of different body parts
身体的组成就像个大杂烩

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had been put together in something of a hurry.
被胡乱组合在一起。

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What other animal has five eyes?
还有什么动物具有五个眼睛呢？

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And opabinia wasn't the only oddball.
欧巴宾不是唯一的怪物。

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Wiwaxia was once thought to be an ancestor of earthworms,
威瓦亚虫曾经被认为是蚯蚓的祖先

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but now is considered to be an early snail.
但是现在被列为早期的蜗牛。

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Most of the Burgess Shale creatures
布尔吉斯页岩中的大部分生物

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are unlike anything ever discovered before.
非常不用于以前的发现。

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There were countless bizarre creatures
在寒武纪海洋中，

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living in the Cambrian Seas,
生活着有无数的奇异的生物

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This unprecedented surge of diversity was something
这种多样性的空前激增

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that had never happened before and would never happen again.
是整个地史时期独一无二的。

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For many years, scientists excavated and scrutinised the Shales
为了寻找寒武纪爆发的原因

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looking for the causes of the Cambrian explosion.
科学家进行了多年来的挖掘与研究。

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Their first task was to try and reconstruct
它们的首要任务是

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what these strange animals must have looked like when they were alive
试图复原这些奇异生物生活面貌

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and that was not at all easy.
这可不是容易的。

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This is one of the oddest of the fossils from Burgess Shales.
这是布尔吉斯页岩中最古老的化石。

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It seems to have five legs along the bottom,
沿着它的底部好像有五条腿，

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and curious kind of lobes along the top,
上部部有奇怪的圆柱状突出物，

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which presumably were some devices, which help it to feed.
这大概是有助于进食的设备。

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But what kind of animal is that with five walking legs
但是这种五条腿、背部具有进食设备的的动物

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and feeding lobes along the top of its back?
究竟是什么种类呢？

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It was such an extraordinary thought that the scientist
对于科学家来说这简直是奇幻的生物

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who described it thought it was a kind of hallucination,
描述他的人认为它是个荒诞的幻觉

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and he called it "hallucigenia".
因此命名为“怪诞虫”。

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But since then, more specimens have shown that in fact,
但是，之后更多的化石显示，

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this is probably the wrong way up and that it was really like that.
曾经背腹颠倒了，实际是这样的。

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The projections at the bottom are, in fact, legs.
底部的实际上是腿

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And those along the top are tipped with sharp spines
背部有一系列尖锐的刺

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that were presumably, defensive.
这些可能是防御装备。

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Perhaps these animals evolved these strange shapes
难道这些动物为了保护自己

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because they needed to protect themselves?
因而演化为如此怪异的外形吗？

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But if so, from what?
但是，它们要防卫什么呢？

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Where were the predators?
天敌在哪里？

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No-one could find a likely candidate.
嫌疑犯尚未找到。

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And then the answer came from a couple of fossil species
然而，答案就在这两块化石里面。

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that they had known almost from the very beginning.
几乎从一开始他们就知道这个答案了。

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One of the strangest fossils found here is this.
这是这里找到最奇特的标本之一。

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It's also one of the commonest.
也是这最常见的一种。

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But what is it?
但是，这是什么呢？

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Well, it has what looks like legs, so you might think
可能你觉得它看起来像条腿

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it was some kind of caterpillar, or shrimp maybe.
也许是一种毛虫或是虾类？

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But the most mysterious thing about it was that
但是最令人费解的是

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they never found one with a head.
从未发现过一个带有头部的标本

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Then there was another mystery,
之后又有了另一个神秘事件。

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not as common as the headlessshrimp,
虽然不如无头虾化石那么普遍

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but one that looked like a sort of jellyfish,
有一类具有辐射线的水母状的化石，

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with radiating lines out, and this strange hole in the middle.
中间有个奇特的洞。

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And about twenty years ago,
大约20年前，古生物学家发现

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it was discovered that actually, there is a link between
事实上这两类标本

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this and this.
有惊人的联系

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This bit is not a separate shrimp, it's actually a claw.
这块不是无头的虾，事实上是个螯肢

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And this bit is not a jellyfish, it's a mouth.
并且这块也不是水母，而是个口器。

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And in the mouth you can see something
这个口器中，

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that looks very significant.
你能看见些至关重要的东西。

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Could these be teeth?
这有可能是牙齿吗？

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And were these not legs but spikes, used to stab and grab prey?
这些不是腿，而是，用来抓取、刺穿猎物的尖刺。

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The two were, in fact, connected.
这两块，实际上是有联系的。

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But now we have a most perfect fossil,
但是现在我们有了近乎完整的标本，

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which really demonstrates that that is indeed the case.
因此证实了前面两者的联系。

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This, you might say, is the Mona Lisa of the Burgess Shales.
你会说，这位是布尔吉斯页中的蒙娜丽莎。

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This specimen, at last, gave scientists a picture
这个标本为科学家展现了

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of the complete animal.
这个完整的生物。

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It had plates along its back, and a tail at the rear end.
它背部具有一系列的片状物，且身体后端具有尾扇。

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It was a swimmer. And between those two spiked claws
它是个游泳者，并且在身体前部、两个带刺的螯肢之间，

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at the front there was a mouth...
有一个口...

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with teeth.
具有齿的口

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This was the hunter they had been looking for.
这就是科学家们苦苦寻找的捕食者。


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The scientist who discovered the claws called them anomalocaris,
发现它的爪的科学家把它命名为“奇虾”

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meaning strange shrimp.
意思是奇怪的虾。

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That name is now used for the whole animal.
那个名字现在用来命名这类完整的动物。

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With its large tail and flexible plates along its flanks,
奇虾具有宽大的尾扇，沿着侧面柔韧的桨状物

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anomalocaris could propel itself through the water at speed.
奇虾可以在水中可以游得飞快

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Other specimens show that it could grow to a length of nearly a metre,
其他的标本显示，它几乎可以长到一米。

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two feet or so.
或两英尺。

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00:12:42,240 --> 00:12:46,720
It was, as far as we know, the first big predator on Earth.
这是据我们所知最早的大型捕食性动物。

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We can get clues as to what it was like
我们可以得到这样的线索

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from an animal that is alive today.
有一种和它很类似的现生的生物。

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It's much smaller than anomalocaris, though remarkably similar.
虽然比起奇虾，它显得很小，但是它们非常相似。

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And it lives in Australia, here on the Great Barrier Reef.
它们栖息于澳大利亚的大堡礁中。

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Professor Justin Marshall has been studying these ferocious
Justin Marshall教授致力于

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and powerful hunters for over 20 years.
研究那些生猛的肉食动物长达20多年。

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You have to very cautious about the way you handle them.
当你抓起它时你必须特别小心。

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If you pick them up they can knock the ends off your fingers.
否则它们会切断你的手指。

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Fishermen call them thumb splitters because
鱼民称它们是手指刀片

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as they handle them they get thumbs and fingers split open.
因为鱼民抓着它们时，手指就被割裂了。

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The other, slightly more technical name for them is mantis shrimp.
专业的术语的命名为“螳螂虾”。

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They have a very ancient ancestry.
它们有古老的祖先。

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Fossils of almost identical creatures have been found
已发现几乎与它们相同的化石

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that date back 400 million years.
可追溯到4亿年前。

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This animal is almost as ancient as anomalocaris itself.
这种动物几乎与奇虾一样古老。

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It lurks in burrows, waiting for its victims
它潜伏在洞穴中等待着它的猎物

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to swim within range of its claws.
在它螯肢可以活动的范围内游泳。

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Looking at the fossils of anomalocaris
看看奇虾的化石

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and comparing them to mantis shrimps,
与螳螂虾对比

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one could imagine that these animals are similar.
人们可以想象到它们十分相似。

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They both have big raptorial appendages
它们都具有巨大的捕食附肢

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that are shot out at the front to grasp prey.
用来对猎物的突然袭击。

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You could imagine them lurking behind a rock
你可以想象它们潜伏在石头后面

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waiting for unwitting prey to come past.
等待毫无防备的猎物经过。

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And bang! Suddenly that's dinner.
啪！速来的美味。

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The mantis shrimp illustrates the essential characteristics
螳螂虾具有

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of this brand new predator class of animals.
肉食性动物的基本的特征

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Superb vision, great speed and superior size.
极佳的视力，游速快以及较大的体格。

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Like anomalocaris, it's considerably larger than its victims.
像奇虾一样，它比猎物大很多。

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It also has extremely acute vision,
它具有敏锐的视力，

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with 12 different types of colour receptors in its eyes.
在它的眼中具有十二种原色接收器。

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We have just three.
而我们人类却只能看见三种原色。

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And it's one of the fastest animals alive,
它是现存游得最快的动物。

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some species striking with the speed of a pellet from a gun.
有些种类具有子弹的速度。

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It's unlikely anomalocaris was as fast, or that it saw its prey
奇虾的运动不会比它的猎物更慢，

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so clearly, but nonetheless, it was a formidable predator,
显然，它是个强大的猎食者，

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just as the mantis shrimp is today.
正如现生的螳螂虾一样凶猛。

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Even a glimpse of a finger through glass is enough
即使瞥见隔着玻璃的手指，

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to make this animal strike,
足以激起这个动物的攻击。

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and with alarming force.
它具有惊人的攻击性。

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So why did the mantis shrimp evolve in this way?
那么，为何螳螂虾演化为这种形式？

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Well, obviously...
显然，

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in order that it could
它为了能够抓住猎物

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outfox and outmanoeuvre, and eventually catch its prey.
从而采取以智取胜的策略。

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It's become very fast, very powerful,
它变得很快，非常强大，

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and capable of great patience.
并且具有极大的耐心。

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And those are characteristics of predators everywhere.
这些都是肉食动物的基本特征。

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So the fossilised remains of anomalocaris
因此，奇虾化石的证据证明

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are evidence that hunting had begun in the Cambrian.
在寒武纪初期，就有了猎食行为。

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And as predators became bigger, faster and stronger,
作为肉食者，它们变得更大，更加凶猛。

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so their prey had to develop increasingly elaborate defences.
因此，不想成为它们的猎物就必须开发出一系列的防御措施。

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Opabinia's five eyes helped it spot trouble.
欧巴宾的五只眼睛，帮助他尽快发现危险。

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And Hallucigenia protected itself with those spines along its back.
怪诞虫用背部的刺来保护自己。

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One of the world's leading experts on the Burgess Shales,
作为世界领先的布尔吉斯页岩的研究专家，

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Dr Jean-Bernard Caron, believes that it was the arrival
Jean-Bernard Caron先生认为，

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of predators like anomalocaris that stimulated the great
像奇虾这样的猎食者的出现，

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Cambrian explosion of diversity.
激发了寒武纪爆发的多样性。

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It is during the Cambrian
在寒武纪时期

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that we can start seeing animals with legs, eyes, swimming.
我们可以看到动物具有附肢、眼睛并且它们可以四处游动。

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This didn't exist before and this evolved very, very quickly
在寒武纪早期，

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at the beginning of the Cambrian.
这些前所未有生物就以惊人的速度演化了。

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But once you have a big predator,
presumably the rest of life,
但是一旦你的天敌出现了，那么你的余生

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which it was feeding on,
很有可能成为它们的食物，

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had to evolve quite fast to develop some sort of defences.
那么就必须发展某种防御措施。

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Would that be true?
那是真的吗？

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Well, we think that this evolution occurred relatively quickly because,
我们认为演化事件发生得迅速

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in a place like the Burgess Shale you find organisms
因为，在布尔吉斯页岩发现的众多生物中

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that may have had some kind of defensive mechanism,
它们都有各种防御装备。

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which is thought to be a response to higher predatory levels.
这些可以认为是对高等的天敌的反应。

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Arms race, if you want, between predators and prey.
捕食者与猎物之间展开了一场军备竞赛。

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One result of this duel between predators and prey
竞赛的结果是

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was the development of armour.
它们都发展了盔甲。

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Animals everywhere were absorbing calcium carbonate
动物无时不刻地吸收着

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and other inorganic substances from the seawater
海水中碳酸钙及各种无机物质

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and mineralising their bodies.
从而加固着它们的身体。

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00:18:54,560 --> 00:18:58,840
Many of them, like wiwaxia, that early mollusc,
它们中间，像威瓦亚虫早期的软体动物

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and ancestors of the squid, ammonites,
以及章鱼、菊石的祖先，

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developed protective shells.
都发展出具保护作用的外壳。

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But one group, the arthropods, which had jointed legs,
像具有关节的附肢的节肢动物，

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encased their entire bodies with hard armour plating.
它们的身体包裹在坚硬的盔甲内。

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And what began as defensive armour, necessary for survival,
“防御装甲是生存的必需品 ”的时代开始了。

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brought with it another great advantage.
此外，带来了意想不到的好处。

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Hard parts can be used not only to give protection,
坚硬的部分不仅仅用来防御，

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but to provide support for a body.
而是用来支撑身体。

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00:19:36,800 --> 00:19:38,320
Ha-ha!
哈哈！

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This spider crab is a crustacean.
这是个甲壳纲的蜘蛛蟹。

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And it secretes chitin from its body,
它的身体的外骨骼

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which it then strengthens with calcium carbonate.
由几丁质与碳酸钙结合起来形成的。

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And a whole range of creatures
有一系列的生物

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00:19:52,640 --> 00:19:55,680
have skeletons like this, based on chitin.
有像这样几丁质骨骼

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Arthropods today include shrimps, lobsters and crabs,
包括现生的节肢动物包括小虾、龙虾、蟹，

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as well as land-living creatures,
当然还有陆生的生物，

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such as millipedes, scorpions and insects.
比如蜈蚣、蝎子和昆虫。

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But the ancestors of all of them first appeared in the Cambrian Seas.
但是它们的祖先最早出现在寒武纪的海洋中。

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Over 50% of fossils in the Burgess Shales
在布尔吉斯页岩中，

256
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are arthropods of one kind or another.
节肢动物的化石的种类占所有种类的50%。

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But one family was particularly abundant and varied.
一个科的的多样性就十分丰富。

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Just across the valley from the quarry,
对面山谷的采石场

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near the summit of Mount Stephen,
在斯提芬山脉的顶端的附近

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almost every rock you turn over contains their remains.
几乎随便翻开一块石头都能找到化石。

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Here, they are found all over the place.
这里遍地都是这种化石。

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They're called trilobites.
它们被称为三叶虫，

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Trilobites because their bodies were in three sections.
之所以叫它们三叶虫是因为它们的身体分为三个部分。

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Here on this slab there are several of them.
在这块标本上有好几个三叶虫。

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That's the head.
这是头甲。

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There's the middle bit. And there's the tail.
这是胸甲这是尾甲。

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One, two, three trilobites.
一、二、三个三叶虫。

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Trilobites, at this particular time,
三叶虫，在这个特别的时期，

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right at the beginning of the Cambrian,
就在寒武纪之初

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began to proliferate into all sorts of forms.
开始辐射为各种形态。

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These creatures, for the next 250 million years,
在接下来的2.5亿年，

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were probably the most advanced forms of life on this planet.
三叶虫很可能以最先进的形式生活在这个星球上。

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To see how advanced the trilobites eventually became,
三叶虫的巅峰时期是怎样的情形呢？

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I'm going to North Africa.
我即将到非洲北部。

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In Morocco, on the southern flanks of the Atlas Mountains,
在摩洛哥Atlas山脉南翼，

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the hills contain an amazing variety of them.
山上保存着成千上万的三叶虫。

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They were only discovered a few years ago,
它们仅在几年前刚被发现

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but now the demand for them is so great
但现在的需求量是如此之大

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that digging them out has become a major industry.
以至于挖掘化石成了这里的主要产业。

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These rocks, which were laid down about 150 million years after
这些岩石，比布尔吉斯页岩年轻1.5亿年

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00:22:02,040 --> 00:22:06,120
the Burgess Shale, also contain trilobites.
也含有三叶虫

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The trouble is, the rock is very hard
岩石非常坚硬

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and the trilobites are quite rare.
三叶虫是十分罕见的。

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But when these people find them,
但是当人们发现它们，

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00:22:13,480 --> 00:22:17,360
their specimens are absolutely extraordinary.
它们的种类绝对特别。

286
00:22:25,240 --> 00:22:29,240
Some species have features that are so delicate
一些种类具有非常脆弱的特征

287
00:22:29,240 --> 00:22:32,760
that it can take days, sometimes weeks,
需要几天，甚至几个星期

288
00:22:32,760 --> 00:22:35,280
to fully prepare a specimen.
来完成化石修理的准备工作。

289
00:22:35,280 --> 00:22:38,320
Skilled technicians use dentists' drills
训练有素的人员用牙科钻头去修理

290
00:22:38,320 --> 00:22:40,320
to get down to the finest detail.
以完成最细致入微的作品。

291
00:22:44,240 --> 00:22:47,440
Every particle of rock must be carefully removed,
要非常小心地移除每一个岩屑

292
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with enormous patience and absolute precision.
这需要巨大的耐心和缜密的精确性。

293
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The end results reveal that trilobites
最后，三叶虫展现出来了

294
00:22:59,040 --> 00:23:01,760 
moulded their external skeletons
它们外骨骼的构型

295
00:23:01,760 --> 00:23:05,240
into an almost unbelievable variety of shapes.
显示出难以置信的多样性。

296
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And that enabled them to colonise a great variety of habitats,
这使得它们能够占领各种栖息地。

297
00:23:27,280 --> 00:23:30,520
just as modern arthropods still do today.
正如现生的节肢动物一样。

298
00:23:36,280 --> 00:23:41,400
There were about 50,000 different trilobite species that we know of,
据我们所知，这里的三叶虫具有50000个种

299
00:23:41,400 --> 00:23:44,760
and doubtless there are still many more to be discovered.
毫无疑问，还有很多种类还没有被发现 

300
00:23:51,600 --> 00:23:53,120
Their hard exoskeletons
坚硬的外骨骼   

301
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not only ensured their abundance in the fossil record,
不仅保证了丰富的化石记录

302
00:23:56,600 --> 00:24:00,760
they also tell us a lot about their owners' lives.
也告诉我们许多它们的生活

303
00:24:03,240 --> 00:24:07,440
Many of the trilobites that are found in these cliffs
这个悬崖上发现很多三叶虫，

304
00:24:07,440 --> 00:24:10,320
are curled up like this one.
像这个一样卷曲着，

305
00:24:10,320 --> 00:24:12,680
Sometimes even more tightly than this is,
有些甚至卷曲得比它更加紧

306
00:24:12,680 --> 00:24:16,120
with their tail tucked underneath their heads.
它们头尾蜷缩在一起。

307
00:24:16,120 --> 00:24:19,320
And it's clear that this was some kind of protective posture,
这显然是一种防御姿势。

308
00:24:19,320 --> 00:24:22,240
just as it is for some kinds of woodlice
这种行为与如今我们花园里

309
00:24:22,240 --> 00:24:24,920
that you find in the garden today.
潮虫科的窃虫（俗称西瓜虫）非常类似。

310
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That protected them against their enemies.
这种行为保护它们免受天敌的攻击。

311
00:24:28,280 --> 00:24:31,880
But there are so many that are curled in these deposits,
但是这里保存了如此多蜷曲一团的的三叶虫

312
00:24:31,880 --> 00:24:35,240
together with others that have their backs arched upwards
它们的背部都向上拱起，

313
00:24:35,240 --> 00:24:37,400
and others in other strange postures,
也有些其他的奇特姿势。

314
00:24:37,400 --> 00:24:42,920
that it seems that they are the victim of some kind of catastrophe.
这些似乎看来它们是一次大灾难的遇难者。

315
00:24:42,920 --> 00:24:46,400
The sea floor, it seems, was quite steep.
海底看来很陡峭，

316
00:24:46,400 --> 00:24:48,400
And the mud that accumulated on
在上部的泥质不断地积累，

317
00:24:48,400 --> 00:24:51,480
the bottom slipped down
时不时地滑下来

318
00:24:51,480 --> 00:24:53,320
in a submarine avalanche,
类似发生在在海底的泥石流，

319
00:24:53,320 --> 00:24:56,600
carrying the animals that lived in it and on it,
泥质带着那些动物，

320
00:24:56,600 --> 00:25:00,320
higgledy-piggeldy, and burying them alive.
滚得乱七八糟，就这样把它们活埋了。

321
00:25:09,640 --> 00:25:13,680
Moroccan trilobites are big business these days.
摩洛哥的三叶虫成为当今的一大产业，

322
00:25:13,680 --> 00:25:18,800
Particularly rare species sell for thousands of pounds.
尤其是某些稀有的品种，以数千英镑的价值销售。

323
00:25:21,640 --> 00:25:24,760
The world's leading trilobite experts,
世界三叶虫研究的首席专家，

324
00:25:24,760 --> 00:25:26,960
such as Professor Richard Fortey,
比如说，Richard Fortey教授，

325
00:25:26,960 --> 00:25:30,160
come here to study these extraordinary animals.
来到这里致力于这些奇特生物的研究。

326
00:25:34,200 --> 00:25:36,840
He believes that their external skeleton
他认为三叶虫的外骨骼

327
00:25:36,840 --> 00:25:39,880
was the key to their success.
是它们成功的关键。

328
00:25:39,880 --> 00:25:42,200
The trilobites did almost everything
所有的三叶虫都有外骨骼

329
00:25:42,200 --> 00:25:46,200
you possibly can do with an exoskeleton.
所以研究它的外骨骼可能会有收获。

330
00:25:46,200 --> 00:25:50,640
I think that skeleton was what gave them an advantage.
我认为外骨骼为它们提供了极大的好处。

331
00:25:50,640 --> 00:25:54,960
They were protected. They could do all kinds of interesting things.
为它们提供保护并能做各种有趣的事情。

332
00:25:54,960 --> 00:25:57,040
They could grow spines.
它们可以长出刺。

333
00:25:57,040 --> 00:26:00,080
They could get flat, like pancakes.
它们可以变得扁平，像个烙饼。

334
00:26:00,080 --> 00:26:02,960
They could protect themselves by getting thick exoskeleton
它们通过较厚的外骨骼保护自己

335
00:26:02,960 --> 00:26:04,200
with pobbles all over it.
具有各种袖珍的突起。

336
00:26:04,200 --> 00:26:08,040
It was a great advantage to them, just as it is to crabs and lobsters
对于它们是很大的进步，

337
00:26:08,040 --> 00:26:10,680
living today, which of course weren't around
正如现生的龙虾与螃蟹一般，

338
00:26:10,680 --> 00:26:12,400
at the time of the trilobites.
虾蟹们在三叶虫时代并不存在的。

339
00:26:12,400 --> 00:26:17,080
So they utilised the virtues of having a tough exoskeleton,
因此三叶虫利用它们有坚硬的外骨骼的优势

340
00:26:17,080 --> 00:26:20,400
to radiate into all kinds of ecological niches.
占领了所有不同的生态位。

341
00:26:25,160 --> 00:26:28,760
You can see one of the most comprehensive collections
你看这个最复杂的

342
00:26:28,760 --> 00:26:30,320
of trilobite fossils
三叶虫化石

343
00:26:30,320 --> 00:26:34,880
just a few miles from where they're quarried, at Erfoud Museum.
它采集于离采石场几英里的地方，现在的伊尔福德博物馆。

344
00:26:38,920 --> 00:26:41,840
The collection here reveals just how varied
这里的收藏品展示了它们

345
00:26:41,840 --> 00:26:44,400
the trilobite skeleton could be.
形态各异的外骨骼。

346
00:26:47,760 --> 00:26:50,600
There is no question that an exoskeleton
毫无疑问，

347
00:26:50,600 --> 00:26:53,000
gave the trilobites protection.
外骨骼为三叶虫提供了保护。

348
00:26:53,000 --> 00:26:57,200
But it also gave them something else of great value.
但也给它们带来了意想不到的好处。

349
00:26:59,120 --> 00:27:02,760
There must have been many reasons why trilobites were so successful.
三叶虫的成功因素是多方面的。

350
00:27:02,760 --> 00:27:07,560
But one of them, unquestionably, was their power of sight.
其中之一是它们视力极佳。

351
00:27:07,560 --> 00:27:08,720
They had eyes.
它们具有眼睛。

352
00:27:08,720 --> 00:27:11,360
not just eyespots that could tell the difference
眼点不仅能够分别明暗

353
00:27:11,360 --> 00:27:13,000
between light and dark,
复眼的形成，

354
00:27:13,000 --> 00:27:16,560
but complex eyes that could form detailed pictures
完成了生命史上

355
00:27:16,560 --> 00:27:20,560
of their surroundings, for the first time in the history of life.
最先对周围环境的细节的感知。

356
00:27:20,560 --> 00:27:23,920
Eyes like these.
即这样的眼睛。

357
00:27:23,920 --> 00:27:29,640
Most animals on Earth today have eyes of one kind of another.
然而，现生的大部分动物拥有另一种眼睛。

358
00:27:29,640 --> 00:27:33,480
Most are made of soft tissue, as ours our.
和我们的眼睛一样，大部分由软组织形成。

359
00:27:33,480 --> 00:27:36,320
But trilobite eyes are unique.
但是三叶虫的眼睛十分独特。

360
00:27:36,320 --> 00:27:41,400
Their lenses are derived from their mineralised external skeleton.
它们的镜头（小眼）是矿化的外骨骼的衍生而来的。

361
00:27:41,400 --> 00:27:42,920
They're made of rock.
它们是由岩石制成的。

362
00:27:45,120 --> 00:27:48,280
Each one of these little dots is a lens.
每一个这样的小眼是一个镜头。

363
00:27:48,280 --> 00:27:50,520
And each is made from calcite,
每个镜头是由

364
00:27:50,520 --> 00:27:53,600
a crystalline form of chalk.
柱状的方解石晶体形成的。

365
00:27:53,600 --> 00:27:56,120
Trilobites were the only organisms
三叶虫是唯一利用这种材料

366
00:27:56,120 --> 00:28:02,200
ever really to use this stuff as their lens material.
作为它们的视觉镜头的生物。

367
00:28:02,200 --> 00:28:06,680
And in doing so they evolved very sophisticated vision indeed.
它们一定以这种方式演化出精密的视觉。

368
00:28:06,680 --> 00:28:12,760
For example, these sorts of trilobites had very large lenses.
比如说这种三叶虫有非常大的视觉镜头。

369
00:28:12,760 --> 00:28:16,480
And each lens is readily visible with the naked eye
并且我们可以用肉眼看见每个镜片（小眼）

370
00:28:16,480 --> 00:28:18,800
and each one is biconvex.
每个都是是双凸的镜片。

371
00:28:18,800 --> 00:28:23,720
And it's been proven that individual lenses have little bowls inside them
并且单独的镜片内部有一个小的碗状物，

372
00:28:23,720 --> 00:28:26,120
to help them focus more precisely.
可以帮助它们更好的聚焦。

373
00:28:26,120 --> 00:28:28,680
These creatures were among the first,
这些生物是首批能够聚焦

374
00:28:28,680 --> 00:28:31,680
certainly, to actually focus a picture, weren't they?
真正的聚焦成像，不是吗？

375
00:28:31,680 --> 00:28:34,760
It wasn't just a question of telling light from dark,
这不仅仅分辨明暗，

376
00:28:34,760 --> 00:28:36,400
they could do better than that?
或是比分别明暗稍好点？

377
00:28:36,400 --> 00:28:39,280
On no, these, these had really sophisticated vision.
哦，不！这些可是十分精密的视觉系统。

378
00:28:40,800 --> 00:28:44,480
The kind of trilobites that have these eyes were probably hunters.
具有这种眼的三叶虫很可能是捕食者。

379
00:28:44,480 --> 00:28:48,960
Some people have claimed that they could form stereoscopic images,
也有人认为这种眼睛可以辨认出立体形状。

380
00:28:48,960 --> 00:28:52,480
using both eyes, so they could really home in on the prey.
用两只眼睛，因此它们可以轻而易举地捕食。

381
00:28:55,160 --> 00:28:58,760
May predators today, including ourselves,
包括我们在内的肉食性动物，

382
00:28:58,760 --> 00:29:02,200
have 3D, or stereoscopic vision.
具有三维或者立体视觉。

383
00:29:02,200 --> 00:29:06,080
It makes it possible for a hunter to accurately judge the distance
这种视觉有助于猎食者准确判断

384
00:29:06,080 --> 00:29:08,720
between itself and its prey.
自己和猎物之间的距离。

385
00:29:17,760 --> 00:29:21,400
But not all trilobites were predators.
但是并不是所有的三叶虫都是猎食者。

386
00:29:21,400 --> 00:29:24,800
Some were inoffensive creatures that lived by munching mud.
许多长得相貌平平的家伙以嚼泥为生。

387
00:29:24,800 --> 00:29:27,400
But sight must have been valuable
但是视力也是很必要的，对它们来说，

388
00:29:27,400 --> 00:29:31,320
for them too, enabling them to spot enemies in time to escape.
视力让它们及时地逃跑。

389
00:29:31,320 --> 00:29:33,960
There are trilobite eyes with more than 5,000 lenses.
这只三叶虫具有5000只小眼。

390
00:29:33,960 --> 00:29:37,000
5,000? More than 5,000 lenses.
5000？也许更多。

391
00:29:37,000 --> 00:29:39,400
Now each of those, does it have an image?
那么，每一个小眼都能成像吗？

392
00:29:39,400 --> 00:29:42,720
Each doesn't have an image, but if they go for lots of tiny lenses,
单个小眼并不能成像，但是许多小眼可以成像

393
00:29:42,720 --> 00:29:44,880
they're particularly sensitive to movement,
它们对运动特别敏感。

394
00:29:44,880 --> 00:29:48,960
i.e. something changing between one lens and the next.
例如，一有动静，小眼就会接二连三地察觉到。

395
00:29:50,680 --> 00:29:54,920
This trilobite's eyes are so big they extend right round its head
这只三叶虫的眼睛十分大，围绕着头部

396
00:29:54,920 --> 00:29:57,000
and meet in the middle.
在中间连接起来。

397
00:29:57,000 --> 00:30:01,120
And that suggests that the animal swam high above the sea floor
这说明这种动物生活距在海底较高的水域

398
00:30:01,120 --> 00:30:05,400
and had a 360-degree view of the scene below.
对下面的景象视角达到360°。

399
00:30:06,920 --> 00:30:10,160
With each lens capable of detecting movement
每个小眼能够察觉移动。

400
00:30:10,160 --> 00:30:14,400
its owner must have been able to see an enemy coming from any direction.
物主能够从任何角度察觉到敌人行动方向。

401
00:30:16,880 --> 00:30:20,520
But the shape of a trilobite's eyes can reveal more than the
但是三叶虫的眼睛的形态展现了

402
00:30:20,520 --> 00:30:22,520
kind of image they produced.
比视觉识别更重要的东西。

403
00:30:24,640 --> 00:30:30,840
Eyes can tell us a surprising amount about how and where an animal lived.
眼睛可以告诉我们生物生活的大量的信息，比如它在什么地方、怎样生活。

404
00:30:30,840 --> 00:30:36,960
This one with its eyes on turrets probably lived in the sea where it
这只具有塔楼式的复眼，很可能它生活在

405
00:30:36,960 --> 00:30:41,240
was gloomy, but nonetheless there was enough light for the animal to
昏暗的光线下，尽管如此，

406
00:30:41,240 --> 00:30:44,520
be able to see on either side of it.
这里对于三叶虫来说可以看见任何一方。

407
00:30:44,520 --> 00:30:49,680
This one, on the other hand, has eyes also on turrets, but at the top
这只三叶虫，也可以认为是塔楼式的眼睛，

408
00:30:49,680 --> 00:30:52,720
it has flanges, like sun shades.
但是它眼睛顶部有一个凸檐用来档住阳光。

409
00:30:52,720 --> 00:30:56,880
So it's, er, likely that it lived in the shallow, sunlit sea
因此，这只似乎生活在充满阳光的浅水区。

410
00:30:56,880 --> 00:31:01,520
and valued shades above its eyes so it didn't get dazzled.
这种形式的眼，功能在于不会受到炫目的阳光的影响。

411
00:31:01,520 --> 00:31:06,440
This one, however, has very reduced eyes, and it may well be
这只，却有非常少的小眼，

412
00:31:06,440 --> 00:31:09,160
that it skated along the mud along the bottom, 
这样它可以沿着底部的泥前进

413
00:31:09,160 --> 00:31:12,440
where it was gloomy anyway and there wasn't much to see,
反正生活在阴暗的地方，视觉并没有多大用处

414
00:31:12,440 --> 00:31:16,960
so like an animal living in a cave, it slowly lost the use of its eyes.
所以像生活在洞穴中的动物一样，它的视觉慢慢地退化了，

415
00:31:16,960 --> 00:31:20,200
And finally there's this creature,
最后就成了这个样子了。

416
00:31:20,200 --> 00:31:23,800
and this is the one I think is particularly delightful.
我认为这个让我觉得十分新奇。

417
00:31:23,800 --> 00:31:27,680
This one has its eyes on stalks.
这只三叶虫具有带柄的眼睛。

418
00:31:27,680 --> 00:31:30,600
And probably lived under the mud,
它很可能生活在泥质底之下

419
00:31:30,600 --> 00:31:33,840
gobbling up food there with its, just its eyes
它在埋头大吃时，伸出两只长长的眼睛

420
00:31:33,840 --> 00:31:37,920
peeking out of the top, to see whether there was danger around.
去窥探上方是否有危险。

421
00:31:39,800 --> 00:31:44,680
So trilobites were the first animals to see clearly.
所以三叶虫是最早能看清的动物了。

422
00:31:44,680 --> 00:31:47,880
But they had other senses as well, perhaps some
但是它们具有其他的感官，

423
00:31:47,880 --> 00:31:50,120
we don't even know about.
可能并不为我们所知。

424
00:31:50,120 --> 00:31:55,520
Take this species with this bizarre trident structure on its nose.
就这个种类的头部具有奇特的三叉戟。


425
00:31:55,520 --> 00:31:58,920
What was it for? Some kind of motion sensor?
这是用来做什么的？某种动力传感器？

426
00:31:58,920 --> 00:32:02,080
Prehistoric radar, perhaps?
或许是史前的雷达？

427
00:32:03,600 --> 00:32:05,960
Trilobites were, without question,
毫无疑问，

428
00:32:05,960 --> 00:32:09,160
the most successful animals of their time.
在那段时间，三叶虫是最成功的类群。

429
00:32:09,160 --> 00:32:12,320
They flourished in all parts of the ocean.
它们在整个海洋中相当繁盛。

430
00:32:12,320 --> 00:32:14,800
Indeed, they could be counted as one
事实上，它们可以算是整个生命史上

431
00:32:14,800 --> 00:32:18,960
of the most successful kinds of animals in the entire history of life.
最成功的类群。

432
00:32:20,880 --> 00:32:25,640
Most trilobites are quite small, rather like beetles are today.
大部分的三叶虫相当小，和现在的甲虫差不多。

433
00:32:25,640 --> 00:32:30,880
But the biggest living beetle is about that big, the goliath beetle.
但是现生最大的歌利亚甲虫有这么大，

434
00:32:30,880 --> 00:32:36,040
Trilobites, on the other hand, grew very big indeed. Like this one.
三叶虫能够长到很大，就像这个。

435
00:32:36,040 --> 00:32:37,880
And this is by no means the biggest.
这绝不是最大的三叶虫了。

436
00:32:37,880 --> 00:32:41,920
The biggest known is nearly a metre, nearly three feet long.
已知最大的将近一米长，几乎三英尺。

437
00:32:41,920 --> 00:32:45,720
And it's thought that these really big ones grew to this size
这么大的算比较大的了，

438
00:32:45,720 --> 00:32:50,560
because they lived in cold waters, and that's a tendency of animals
因为它们生活在冷水域，

439
00:32:50,560 --> 00:32:52,320
in cold, to grow large.
这是个冷水动物的生长趋势。

440
00:32:52,320 --> 00:32:56,560
And at the time that these rocks were laid down, Africa,
这些岩石发现于现在在非洲，

441
00:32:56,560 --> 00:32:59,320
where we are now, and where these are found,
在当时还没有沉积下来，

442
00:32:59,320 --> 00:33:01,040
was down by the South Pole.
当时这里却在南极地区。

443
00:33:04,360 --> 00:33:06,840
Spectacular though these are,
虽然这些非常壮观，

444
00:33:06,840 --> 00:33:11,520
they were by no means the largest arthropods in the ocean at the time.
它们在当时海洋中绝不是最大的节肢动物。

445
00:33:11,520 --> 00:33:16,840
The trilobites had remote cousins, also arthropods, that had grown
三叶虫有同样也是节肢动物门的远亲，

446
00:33:16,840 --> 00:33:19,400
into monsters.
它能够长成个巨型怪物。

447
00:33:19,400 --> 00:33:22,520
Their remains are much rarer, and often fragmentary,
它们的化石非常罕见，并且很不完整。

448
00:33:22,520 --> 00:33:26,600
but some of the most complete have been found in Scotland.
但是最完整的化石在苏格兰发现了。

449
00:33:33,360 --> 00:33:35,480
ALARM SOUNDS
警报声

450
00:33:39,520 --> 00:33:41,760
One of the best is held in the vaults
它被存放在最好的储藏室

451
00:33:41,760 --> 00:33:43,960
of Edinburgh's National Museum.
即爱丁堡国家博物馆。

452
00:34:03,400 --> 00:34:05,720
Gosh!
天哪！

453
00:34:05,720 --> 00:34:13,080
Well, this is a magnificent example of just how big an animal can grow
那么，如果它具有外骨骼的话

454
00:34:13,080 --> 00:34:15,880
if it has an external skeleton.
这是一个绝佳的证据证明这种动物能长到多大。

455
00:34:15,880 --> 00:34:20,160
This is a creature called the Eurypterid, or a sea scorpion.
这种生物被称为“广翅鲎”或海蝎。

456
00:34:20,160 --> 00:34:22,400
And it was a hunter.
它也是肉食类。

457
00:34:22,400 --> 00:34:27,200
It had a pair of powerful pincers at the top, just behind its head.
它头部后面与身体前部之间具有一对强壮的钳状螯枝，

458
00:34:27,200 --> 00:34:31,640
It was obviously a monster, a terror of the seas.
它是神秘海洋中的一个巨怪

459
00:34:31,640 --> 00:34:36,640
And this is by no means the biggest of the eurypterids.
这绝不是板足鲎类中最大的

460
00:34:39,440 --> 00:34:43,920
Sea scorpions were the top predators of their day.
在当时，海蝎是肉食动物

461
00:34:43,920 --> 00:34:46,960
As far as we know, they were the biggest arthropod
据我们所知，它们是最大的节肢动物

462
00:34:46,960 --> 00:34:48,760
that has ever existed.
它们前所未有的。

463
00:34:50,520 --> 00:34:54,600
The discovery of a large fossilised claw suggests
它的最大的前螯肢化石表明

464
00:34:54,600 --> 00:34:58,600
that they could grow up to two and a half metres, eight feet in length.
它们可以长到将近2.5m，长达八英尺。

465
00:35:07,320 --> 00:35:09,920
So arthropods of one kind or another
所以，各式各样的节肢动物

466
00:35:09,920 --> 00:35:15,200
were certainly dominant 420 million years ago.
它们曾经主宰着4.2亿年前的海洋世界。

467
00:35:15,200 --> 00:35:18,080
The seas were full of life.
海洋孕育着各类生物。

468
00:35:18,080 --> 00:35:21,560
From huge complex animals like this sea scorpion
从巨大且复杂的海蝎

469
00:35:21,560 --> 00:35:23,040
creeping along the bottom,
到在爬行于海底的小生物

470
00:35:23,040 --> 00:35:27,280
to simple creatures, like jellyfish, floating on the surface waters.
到漂浮在海面上的水母。

471
00:35:27,280 --> 00:35:33,160
But the land was barren and without animals of any kind.
但是当时的陆地是贫瘠的，没有任何动物的踪迹。

472
00:35:34,680 --> 00:35:39,880
But there was food up there, simple plants,
但是，在那里有食物--低等植物，

473
00:35:39,880 --> 00:35:45,760
and that tempted some animals to venture out of the water.
这些美味诱惑着动物们离开水面。

474
00:35:45,760 --> 00:35:49,760
Surviving on land, however, was a problem for them.
对它们来说到陆地上生活，却存在一个问题。

475
00:35:49,760 --> 00:35:51,920
Coming from the sea, they had to evolve ways
从海洋里出来后，

476
00:35:51,920 --> 00:35:54,920
of preventing their bodies from drying out.
它们必须防止身体脱水。

477
00:35:54,920 --> 00:36:01,120
And even more difficult, they had to develop a method of breathing air.
而更加困难是，它们得设法呼吸空气。

478
00:36:01,120 --> 00:36:03,680
The very first animals had simply absorbed
最初的动物

479
00:36:03,680 --> 00:36:05,840
dissolved oxygen from the water
可以直接吸收水中的游离氧。

480
00:36:05,840 --> 00:36:09,000
through the skins of their soft bodies.
这是通过皮肤软组织的渗透来完成的。

481
00:36:09,000 --> 00:36:12,200
As they began to move and grow bigger, they needed more energy,
一旦它们开始运动、生长，

482
00:36:12,200 --> 00:36:15,200
more quickly.
它们需要更快地补充能量。

483
00:36:15,200 --> 00:36:17,000
And that meant
这就意味着

484
00:36:17,000 --> 00:36:20,960
they had to improve their method of collecting dissolved oxygen.
它们得改进方法收集到更多的溶解氧。

485
00:36:25,360 --> 00:36:29,320
Bigger, more complex animals,
对于更大、更复杂的动物，

486
00:36:29,320 --> 00:36:32,080
like for example, this lobster,
比如说龙虾。

487
00:36:32,080 --> 00:36:35,680
have to have specialised devices,
必须有专门的设备获取氧

488
00:36:35,680 --> 00:36:40,400
Here in the lobster they are these flaps underneath its abdomen,
在这只龙虾的腹部有很多桨状物。

489
00:36:40,400 --> 00:36:42,160
which is flaps forwards
当它们来回划动时，

490
00:36:42,160 --> 00:36:47,160
and backwards to increase the flow of oxygenated water over them.
增加了含氧水的流量

491
00:36:47,160 --> 00:36:51,840
But the trouble with gills is that they only work when they're wet.
然而，问题是腮只能在潮湿的环境下工作。

492
00:36:51,840 --> 00:36:55,680
In the dry, they do not absorb oxygen.
在干燥的地方，它们不能够吸收氧气。

493
00:36:55,680 --> 00:36:58,480
So if animals are to live on land,
因此，如果动物想要生活在陆地上，

494
00:36:58,480 --> 00:37:03,360
they had have to have a new way of breathing.
它们必须具有全新的呼吸方式。

495
00:37:08,480 --> 00:37:10,040
The Burgess Shales,
在布尔吉斯页岩中，

496
00:37:10,040 --> 00:37:14,200
that astonishingly rich treasury of Cambrian fossils,
保存了异常丰富的寒武纪生物。

497
00:37:14,200 --> 00:37:16,440
contain the remains of just one
有一类十分稀有的化石，

498
00:37:16,440 --> 00:37:21,120
particularly rare species that may well have been the very first animal
这种生物被认为是最先

499
00:37:21,120 --> 00:37:23,920
to make that move onto land.
移居到陆地上的生物。

500
00:37:23,920 --> 00:37:27,640
It was not, as you might think, an amphibian, it was not even
你可别以为是两栖动物，

501
00:37:27,640 --> 00:37:31,200
a true arthropod, but one of their far distant cousins.
也不是真正的节肢动物，而是与节肢动物门较远的姐妹类群。

502
00:37:36,600 --> 00:37:38,920
This little creature,
这个小家伙，被称为“埃谢栉蚕”

503
00:37:38,920 --> 00:37:44,640
from the Burgess Shale seas, is thought to be the ancestor
在布尔吉斯页岩中发现的海洋生物，

504
00:37:44,640 --> 00:37:50,520
of the very first creature that went on to land. It's called Aysheaia.
被认为是最早登陆物种的祖先。

505
00:37:50,520 --> 00:37:54,120
And we don't have to imagine what it was like in life,
我们没必要联想有什么和它相似的现生生物，

506
00:37:54,120 --> 00:37:59,160
because there's a creature, that seems to be almost identical,
因为现生有和它长得几乎完全相同的生物

507
00:37:59,160 --> 00:38:00,840
that is alive today.
它们还活着。

508
00:38:03,280 --> 00:38:08,080
It lives in many parts of the tropics, including the rainforest,
热带地区很常见，尤其是雨林中。

509
00:38:08,080 --> 00:38:11,000
here in Queensland, Australia.
这里是澳大利亚的昆士兰州。

510
00:38:17,520 --> 00:38:20,800
It's nocturnal and seldom seen.
这是一种罕见的夜行动物。

511
00:38:25,120 --> 00:38:30,800
It spends most of its time hidden away inside rotten logs.
它爱在腐木中度过大半的时光。

512
00:38:32,480 --> 00:38:35,160
Ah, it's nice and wet!
哈，这里很好，很湿！

513
00:38:35,160 --> 00:38:38,200
Certainly, er, perfect for what we're looking for.
当然，呃，这里是找到它的绝佳之地。

514
00:38:38,200 --> 00:38:42,040
You need local expertise to find one.
你需要个当地专家帮忙才能找到它。

515
00:38:44,040 --> 00:38:46,840
I generally find that it's just from the outside
我通常在枯树干中

516
00:38:46,840 --> 00:38:48,520
of the, er, core of the tree.
能发现它。

517
00:38:50,680 --> 00:38:54,520
All nice and... Oh! What is that? Ooh, look at that.
非常漂亮 啊！那是什么？呵，看那个。

518
00:38:54,800 --> 00:38:59,240
And this enchanting little creature
这个讨人喜欢的小家伙

519
00:38:59,240 --> 00:39:01,120
is what we were looking for.
就是我们一直在寻找的。

520
00:39:06,040 --> 00:39:10,040
Sometimes called a velvet worm,
俗名：天鹅绒虫，

521
00:39:10,040 --> 00:39:13,680
or to give it its scientific name, Peripatus.
学名：栉蚕

522
00:39:15,560 --> 00:39:19,840
If there is such a thing as a living fossil,
如果要找活化石的话，

523
00:39:19,840 --> 00:39:22,600
this surely must be one of them.
它显然是其中之一。

524
00:39:22,600 --> 00:39:26,400
Because it seems to be almost identical
因为它与布尔吉斯的埃谢栉蚕相比

525
00:39:26,400 --> 00:39:32,920
with that fossil, Aysheaia, which we saw in the Burgess Shales.
几乎完全相同。

526
00:39:32,920 --> 00:39:38,280
It looks at first sight like a worm.
猛地一瞅很像个蠕虫，

527
00:39:38,280 --> 00:39:43,280
But of course no worm has legs. In fact,
但是，世上没有带腿的蠕虫。

528
00:39:43,280 --> 00:39:46,640
it seems to be halfway
它似乎是

529
00:39:46,640 --> 00:39:49,320
between a worm
处于节肢动物与蠕形动物之间的

530
00:39:49,320 --> 00:39:51,240
and an insect.
过渡类群。

531
00:39:52,760 --> 00:39:57,040
Aysheaia, of course, lived in the sea.
当然，埃谢栉蚕生活在海洋中，

532
00:39:57,040 --> 00:40:00,920
But this little creature lives on land.
然而，这只小家伙生活在陆地上。

533
00:40:00,920 --> 00:40:03,680
And it has one further attribute,
并且它具有更加先进的功能

534
00:40:03,680 --> 00:40:08,680
which Aysheaia could not have had.
而埃谢栉蚕却没有的

535
00:40:08,680 --> 00:40:12,400
It has tiny little holes all along its flanks,
那就是，沿着它的侧面具有一系列的小孔，

536
00:40:12,400 --> 00:40:15,200
which enable it to breathe air.
它们是用来呼吸空气的。

537
00:40:15,200 --> 00:40:20,320
So this is one of the first creatures
因此，

538
00:40:20,320 --> 00:40:22,480
that moved on to land,
这是5.4亿年前，

539
00:40:22,480 --> 00:40:26,320
540 million years ago.
最初登陆的成员之一。

540
00:40:44,400 --> 00:40:48,360
Velvet worms may have been the first animals to set foot on land,
天鹅绒虫曾经很可能是最早踏上陆地的生物。

541
00:40:48,360 --> 00:40:53,280
but they have hardly changed during the following half-billion years.
然而几亿年来它们几乎没有什么变化。

542
00:40:54,800 --> 00:40:57,240
Why?
为什么？

543
00:40:57,240 --> 00:40:59,840
Well, unlike true arthropods, their bodies are covered,
然而，不同于真节肢动物，它们没有外骨骼

544
00:40:59,840 --> 00:41:06,200
not by an exoskeleton, but by soft, permeable skin.
而是覆盖着一层柔软、可渗透的皮肤。

545
00:41:06,200 --> 00:41:11,000
That lack of an external skeleton means that their bodies,
外骨骼的缺乏，意味着它们的身体是由水来支撑的，

546
00:41:11,000 --> 00:41:13,160
unsupported by water, can't grow any bigger.
没有水的支撑，长不了多大大。

547
00:41:13,160 --> 00:41:18,800
It also means that in order to prevent themselves from drying out,
因此，为了不让它们自己晒伤，

548
00:41:18,800 --> 00:41:23,280
they have to stay in damp environments.
它们不得不呆在潮湿的环境中。

549
00:41:23,280 --> 00:41:25,080
True arthropods, like this scorpion,
对于巨型海蝎的后代-蝎子这类真节肢动物来说

550
00:41:25,080 --> 00:41:30,200
a descendent of those giant sea scorpions, were not so restricted.
可没有那么多的生存限制。

551
00:41:30,200 --> 00:41:32,520
They had external skeletons.
它们具有外骨骼，

552
00:41:34,040 --> 00:41:38,720
That meant that not only were their bodies protected from drying out,
这意味着，不仅能够防止身体脱水，

553
00:41:38,720 --> 00:41:42,120
but they were strong and rigid enough to allow them to grow bigger
并且它们很强壮可以把自己养得更大

554
00:41:42,120 --> 00:41:45,320
and get around without the support of water.
它们并不需要水支持身体形状。

555
00:41:53,680 --> 00:41:57,400
So how and when did true arthropods with exoskeletons
那么，这些具有外骨骼的真节肢动物

556
00:41:57,400 --> 00:41:59,480
draw their first breath of air?
是何时、怎样第一次呼吸的？

557
00:42:05,080 --> 00:42:07,880
The answer can be found in this.
这里可以找到答案。

558
00:42:07,880 --> 00:42:12,880
It is perhaps the smallest and most fragmentary fossil I've seen so far,
这是我见过的最小的化石碎片，

559
00:42:12,880 --> 00:42:16,040
but don't be fooled by appearances.
可别被它的外表骗了。

560
00:42:16,040 --> 00:42:19,680
It's almost certainly one of the most significant.
它的意义极其重大。

561
00:42:25,800 --> 00:42:33,400
This specimen was collected in Cowie Harbour, here in Scotland, in 2004.
这块标本于2004年发现于苏根兰的考伊港口。

562
00:42:33,400 --> 00:42:38,440
Even though it's so small, under the microscope you can see
虽然很小，但是我们可以在显微镜下

563
00:42:38,440 --> 00:42:40,760
extraordinary detail.
观察到非凡的的细节。

564
00:42:40,760 --> 00:42:46,880
This is the main body of the animal with its segments.
这是它的身体和体节，

565
00:42:46,880 --> 00:42:50,720
And here are its legs.
这是它的腿。

566
00:42:50,720 --> 00:42:55,560
But above each there is a tiny hole.
但是在每个腿的上部有一个极小的洞。

567
00:42:57,440 --> 00:43:02,760
That is a spiracle, through which the animal was able to breathe air
这是个气孔，这个生物通过过这个气孔呼吸

568
00:43:02,760 --> 00:43:05,800
just as insects do today.
就像现生的许多昆虫一样。

569
00:43:05,800 --> 00:43:09,880
And since it breathed air, if it had gone into the water
那么，既然它可以呼吸空气，

570
00:43:09,880 --> 00:43:11,440
it would have drowned.
如果把它放在水里，会淹死的。

571
00:43:11,440 --> 00:43:16,880
So this is a truly land-living animal and what is more,
所以，这是一个真正的陆生动物，

572
00:43:16,880 --> 00:43:19,680
it's the first and oldest that we know.
这是我们所知道最早的登陆者，

573
00:43:19,680 --> 00:43:24,040
It's 428 million years old.
距今4.28亿年。

574
00:43:27,680 --> 00:43:32,720
But what kind of creatures were these early land-dwelling arthropods?
但是最早的陆生节肢动物是什么种类呢？

575
00:43:38,680 --> 00:43:42,680
Animals very like them are still quite common
在世界的很多地方，

576
00:43:42,680 --> 00:43:44,200
in many parts of the world.
像这样的动物随处可见。

577
00:43:44,200 --> 00:43:48,160
There are certainly plenty of them in those Australian rainforests.
在澳大利亚的热带雨林中有很多这样的动物。

578
00:43:51,080 --> 00:43:53,680
One sort are millipedes,
其中一类是马陆。

579
00:43:53,680 --> 00:43:59,120
which today grow as long as that and live on vegetation
它们生存与植被丰盛且含有枯枝烂叶的环境中。

580
00:43:59,120 --> 00:44:01,800
and rotting wood, harmless vegetarians.
它们是温柔的的草食动物。

581
00:44:01,800 --> 00:44:07,200
But there's also another multi-leg creature, which is a much more
但是，这还有个多腿的

582
00:44:07,200 --> 00:44:08,880
difficult customer.
但却不好惹的家伙。

583
00:44:11,080 --> 00:44:13,040
This is one of them.
这是条蜈蚣

584
00:44:13,040 --> 00:44:18,840
A centipede. A very formidable hunter, with a powerful bite,
它是个强悍的肉食动物，具有有力的大颚

585
00:44:18,840 --> 00:44:23,360
and some centipedes have bites that are lethal to human beings.
有些种类的蜈蚣甚至会伤人致命的。

586
00:44:23,360 --> 00:44:26,640
What kind of a bite this one has,
被这个家伙咬一口会是怎样，

587
00:44:26,640 --> 00:44:28,920
I don't know.
我不知道。

588
00:44:28,920 --> 00:44:30,840
But when I let him out I shall do so
但是放他出去的时候我得非常小心。

589
00:44:30,840 --> 00:44:36,240
very carefully, because I don't propose to find out.
我可不打算知道答案。

590
00:44:36,240 --> 00:44:38,200
Come on.
去吧。

591
00:44:45,520 --> 00:44:50,480
So multi-legged arthropods invaded the land and became
多足类节肢动物侵占陆地后，

592
00:44:50,480 --> 00:44:52,280
more successful than ever.
它们变得更加成功。

593
00:44:59,360 --> 00:45:00,920
Back in Scotland,
让我们回到苏格兰，

594
00:45:00,920 --> 00:45:06,120
there is impressive evidence of just how successful they became.
我们来看看究竟它们变得有多成功。

595
00:45:08,240 --> 00:45:11,280
This is a small fishing village
这是个小渔村，

596
00:45:11,280 --> 00:45:14,920
on the East Coast of Scotland called Crail.
苏格兰南部海岸线的克雷尔。

597
00:45:14,920 --> 00:45:18,480
Nothing particularly strange about it, you might think...
你可能认为这里没什么特别的

598
00:45:18,480 --> 00:45:22,280
until, that is, you go down to the shore.
直到你来到这个岸边

599
00:45:22,280 --> 00:45:26,640
And then you can see something that is really extraordinary.
那么你会发现些非常奇特的东西。

600
00:45:31,520 --> 00:45:34,560
Standing here and there on the beach are fossils,
在海岸保存的化石中，

601
00:45:34,560 --> 00:45:37,920
not of animals, but of plants.
保存的不是动物而是植物。

602
00:45:40,200 --> 00:45:46,360
This huge circular stump looks just like the base of a tree.
这个大的圆柱形很像个树桩。

603
00:45:46,360 --> 00:45:49,560
And indeed that is what it is, or rather,
更确切地说

604
00:45:49,560 --> 00:45:54,000
what it was, 335 million years ago.
但是它并不是我们现在意义上的树。

605
00:45:54,000 --> 00:45:57,120
But it wasn't a tree like trees we know today.
远在3.3亿年前，

606
00:45:57,120 --> 00:45:58,880
It was related
它们与现生的一种小型植物

607
00:45:58,880 --> 00:46:02,280
to the small plants that are alive today called horsetails.
木贼类有关，

608
00:46:02,280 --> 00:46:06,880
But this tree grew to 90 feet.
但是这棵树长到90英尺高。

609
00:46:06,880 --> 00:46:08,560
It was immense.
如此硕大，

610
00:46:11,720 --> 00:46:15,440
When they were alive, during a period called the Carboniferous,
它们生活在"石炭纪"

611
00:46:15,440 --> 00:46:17,360
long after the Cambrian,
在寒武纪之后的很长一段时期，

612
00:46:17,360 --> 00:46:19,320
this whole area was very different
当时的那片地区

613
00:46:19,320 --> 00:46:21,960
from the windswept coastline of today.
不同于今天这个疾风拍岸的景象，

614
00:46:24,480 --> 00:46:28,680
This was a time when the continents of the world were grouped together
当时形成了联合大陆，

615
00:46:28,680 --> 00:46:30,960
and forests were widespread.
有广袤的森林。

616
00:46:34,280 --> 00:46:37,240
So much plant life was pumping out oxygen
由于植物制造了大量的氧气。

617
00:46:37,240 --> 00:46:41,240
that the composition of the atmosphere began to change.
因此大气的成分开始发生变化。

618
00:46:45,400 --> 00:46:49,480
This had a profound effect on animal life.
从而对动物的生活产生深远的影响。

619
00:46:54,480 --> 00:46:58,160
In the forest that was growing near Crail, the ancient trees。
这棵古树生长在克雷尔附近。

620
00:46:58,160 --> 00:47:01,040
were rooted in a sandy swamp. 
它2根植于一个沙地沼泽。

621
00:47:01,040 --> 00:47:05,880
And on the expanses of sand that stretched between those huge trees,
这些沙子使这些巨树能够固定住。

622
00:47:05,880 --> 00:47:09,240
sand that's now turned to this sandstone,
现在那些沙子成了现在的砂岩。

623
00:47:09,240 --> 00:47:10,960
there are tracks.
这些是爬痕

624
00:47:10,960 --> 00:47:15,320
Tracks that come in pairs, there's one pair that goes up there.
爬痕是成对的附肢留下的，一处在那儿。

625
00:47:15,320 --> 00:47:18,920
There's another pair that goes up here.
这是另一处爬痕

626
00:47:18,920 --> 00:47:21,680
And when you look at them in detail, you can see,
当你观察细节时，你能发现，

627
00:47:21,680 --> 00:47:26,680
particularly on this pair, that each track has a number of dimples in it.
特别是这个，爬痕有许多凹坑。

628
00:47:29,160 --> 00:47:34,080
And those are the imprints of individual feet.
这是每一个附肢留下的足迹。

629
00:47:34,080 --> 00:47:36,880
So this animal had a lot of feet.
因此，这种动物有很多的附肢。

630
00:47:36,880 --> 00:47:41,080
It's thought to have been a giant millipede.
被认为是巨大的百足虫留下的。

631
00:47:41,080 --> 00:47:43,320
It was about...
它大约有...

632
00:47:43,320 --> 00:47:46,320
four and a half feet long, one and a half metres.
0.5-1米

633
00:47:46,320 --> 00:47:50,000
And it had 26 or 28 segments.
并且大约有26-28个体节。

634
00:47:50,000 --> 00:47:52,840
A magnificent beast.
一个巨型怪物

635
00:48:09,960 --> 00:48:11,480
Arthropleura.
节胸属的

636
00:48:13,880 --> 00:48:15,920
A giant millipede,
巨大的百足虫，

637
00:48:15,920 --> 00:48:21,360
probably the biggest terrestrial arthropod that has ever existed.
它们可能是史上最大的陆生节肢动物。

638
00:48:21,360 --> 00:48:26,160
The largest specimen discovered so far was nearly as long as a car...
最大的标本有将近一辆卡车那么大...

639
00:48:26,160 --> 00:48:27,840
two and a half metres.
长达2.5米

640
00:48:29,960 --> 00:48:34,440
The Carboniferous was the golden age for the arthropods,
石炭纪是节肢动物的鼎盛时期,

641
00:48:34,440 --> 00:48:38,240
for the air was now particularly rich in oxygen.
因当时空气中的氧气异常地高。

642
00:48:38,240 --> 00:48:43,080
Today the atmosphere contains around 21% oxygen.
我们现在的空气中含氧量仅为21%。

643
00:48:43,080 --> 00:48:44,920
Back in the Carboniferous,
然而，追溯到石炭纪，

644
00:48:44,920 --> 00:48:50,560
it was around 35% and that enabled animals to grow very big indeed.
高达35%的含氧量使得动物长得如此硕大。

645
00:48:53,240 --> 00:48:57,560
But growing large was not their only success.
但是它们的成功之处不仅在于长得大，

646
00:48:57,560 --> 00:49:01,600
Some other arthropods in these carboniferous rainforests
在石炭纪雨林中的许多其他节肢动物

647
00:49:01,600 --> 00:49:03,800
were evolving in a different way.
以截然不同的方式演化。

648
00:49:03,800 --> 00:49:07,080
Instead of becoming huge and ponderous,
它们并不是变得巨大而笨重，

649
00:49:07,080 --> 00:49:09,200
they became agile and speedy.
而是灵活而敏捷。

650
00:49:09,200 --> 00:49:13,640
To do that it's better to be short rather than long, and some
因此它们通过减少体节来使身体变短

651
00:49:13,640 --> 00:49:17,600
reduced their segments and ran
around on just three pairs of legs,
并且只有三对腿，

652
00:49:17,600 --> 00:49:20,480
as silverfish and bristletails do today.
正如今天的蠹虫无翼昆虫。

653
00:49:25,240 --> 00:49:29,440
These early insects then made another dramatic move...
这些早期昆虫的又一戏剧性事件是...

654
00:49:29,440 --> 00:49:35,360
they developed wings and became the first animals of any kind to fly.
它们演化出了翅，成为最早飞翔在天空的动物。

655
00:49:40,720 --> 00:49:44,400
Truly the invertebrates had colonised
真正的无脊椎动物不仅占领了陆地，

656
00:49:44,400 --> 00:49:46,120
not only the land, but the air.
还称霸了天空。

657
00:49:47,920 --> 00:49:51,120
And in an atmosphere so rich in oxygen,
大气中丰富的氧含量使得

658
00:49:51,120 --> 00:49:54,240
they did so in a truly dramatic way.
它们形成了如此生动多样的生存方式。

659
00:49:56,000 --> 00:49:58,200
This giant dragonfly,
这个巨大的蜻蜓，

660
00:49:58,200 --> 00:50:03,680
the biggest flying insect that has ever existed, is called Meganeura.
是有史以来最大的类型，被命名为“古蜻蜓”。

661
00:50:12,280 --> 00:50:15,560
Its wings were nearly three feet across.
它的翅膀将近3英尺长，

662
00:50:21,200 --> 00:50:27,800
But the golden age of the giant arthropods was not to last.
但是巨型节肢动物的黄金时代并没有持续多长时间。

663
00:50:27,800 --> 00:50:32,880
The rainforest died back, and oxygen in the atmosphere dropped.
热带雨林衰退后，氧气含量下降。

664
00:50:35,040 --> 00:50:39,960
Giant insects are no longer alive today and that may be
巨大的昆虫现在已经不复存在，

665
00:50:39,960 --> 00:50:44,280
because the proportion of oxygen in the atmosphere is very much lower.
很可能是因为大气中的氧含量变得非常稀薄。

666
00:50:44,280 --> 00:50:47,880
But nonetheless, insects have managed to find a way
即使这样，昆虫总是有办法适应

667
00:50:47,880 --> 00:50:50,760
of overcoming the problems of size.
克服大小的问题

668
00:50:50,760 --> 00:50:52,960
They've become colonial.
它们组成社会性群体。

669
00:50:54,480 --> 00:50:57,880
Just as in the far distant, remote past,
正如很久很久以前，

670
00:50:57,880 --> 00:51:02,600
individual cells clubbed together to form a larger organism,
单个细胞聚集起来成为大型的有机体，

671
00:51:02,600 --> 00:51:03,880
such as a sponge,
例如海绵，

672
00:51:03,880 --> 00:51:08,480
so hundreds of thousands of individual insects, termites,
这些成千上万单独的昆虫，例如白蚁，

673
00:51:08,480 --> 00:51:11,520
have cooperated to build this nest.
它们合作建成这样的巢。

674
00:51:11,520 --> 00:51:14,840
And a colony like this can crop as much vegetation
蚁群能够联合起来形成羚羊群般的破坏力，

675
00:51:14,840 --> 00:51:19,880
from the surroundings as a bigger animal like an antelope.
它们割下周围环境中的植物。

676
00:51:33,520 --> 00:51:36,080
So by living in vast colonies like this,
通过这样巨大的群居生活，

677
00:51:36,080 --> 00:51:39,640
arthropods can still dominate their surroundings.
节肢动物仍然可以主宰它们周围的环境。

678
00:51:41,280 --> 00:51:43,840
They've become super-organisms...
它们变成超有机体（社会性动物的集合体）

679
00:51:43,840 --> 00:51:48,400
hundreds of thousands of individuals all descended from the same female,
数以千计的后代都出于同一个母亲，

680
00:51:48,400 --> 00:51:50,920
working and behaving as one.
它们具有万众一心的工作效率

681
00:51:58,000 --> 00:52:00,320
So arthropods remain
所以节肢动物仍然是

682
00:52:00,320 --> 00:52:03,320
one of the most successful
groups of animals on the planet.
这个星球动物中最成功的。

683
00:52:07,800 --> 00:52:11,440
They've spread to all its corners.
它们蔓延到世界的每个角落。

684
00:52:15,560 --> 00:52:21,720
Insects alone make up at least 80% of all animal species.
仅昆虫纲就占了所有动物种类的80%。

685
00:52:24,760 --> 00:52:29,120
But arthropods weren't the only ones to make this move on to land.
但是节肢动物不是唯一登上陆地的动物。

686
00:52:33,680 --> 00:52:35,600
The Burgess Shales -
在布尔吉斯页岩中-

687
00:52:35,600 --> 00:52:39,800
the place where the beginnings of all this proliferation of life
无比精细地展现了寒武纪时期的

688
00:52:39,800 --> 00:52:43,560
in the Cambrian period are recorded in unparalleled detail.
所有后生动物的起源。

689
00:52:47,280 --> 00:52:51,200
Among the ancestors of all the insects,
与昆虫的祖先在一起生活的生物还有：

690
00:52:51,200 --> 00:52:56,640
spiders, the scorpions, the shellfish, the crustaceans,
蜘蛛、蝎子、双壳类、甲壳类动物

691
00:52:56,640 --> 00:52:59,200
the shrimps, the sponges,
虾、海绵等。

692
00:52:59,200 --> 00:53:04,280
there's just one tiny little creature, very insignificant,
这是一个非常小的生物，但是意义重大

693
00:53:04,280 --> 00:53:10,360
which we human beings might think is perhaps the most important of all.
我们人类之所以认为它如此重要，

694
00:53:10,360 --> 00:53:11,640
Because this...
是因为...

695
00:53:11,640 --> 00:53:16,400
is the first creature to have the sign of a backbone,
这是最早具有脊索的生物，

696
00:53:16,400 --> 00:53:21,840
and thus, therefore, is probably the ancestor of us all.
因此，这很有可能是我们的祖先。

697
00:53:25,240 --> 00:53:29,360
It's a tiny, worm-like creature called Pikaia.
它很小，蠕虫般的形态，名叫皮卡虫。

698
00:53:32,080 --> 00:53:34,520
It was not a fearsome hunter.
他并不是凶猛的捕食者。

699
00:53:34,520 --> 00:53:41,160
It had no teeth for attack and no external skeleton for defence.
它既无爪牙以袭击，也无盔甲以御敌。

700
00:53:41,160 --> 00:53:44,200
But Pikaia did have something new.
但是皮卡虫具有它独特的之处。

701
00:53:46,720 --> 00:53:49,480
Instead of an external skeleton,
虽然没有外骨骼，

702
00:53:49,480 --> 00:53:53,000
it had an internal one, a thin gristly rod...
它的内部具有一个杆状的软骨。

703
00:53:53,000 --> 00:53:55,320
the beginnings of a backbone.
是脊锥的雏形

704
00:53:55,320 --> 00:53:59,560
It, or something very like it, was the ancestor of all vertebrates.
它看起来像是所有脊椎动物的祖先。

705
00:54:01,480 --> 00:54:05,880
From such a creature as this, the first fish evolved.
正如这样的生物，第一条鱼演化出来了。

706
00:54:05,880 --> 00:54:10,120
Some of them, living in swamps, started to gulp air and wriggled up
它们中的一些种类，生活在沼泽中，

707
00:54:10,120 --> 00:54:17,000
onto the land. They gave rise to moist-skinned amphibians.
开始大口吸气，并且它们在向陆地蠕动着，它们使那些皮肤湿润的两栖类崛起了。

708
00:54:17,000 --> 00:54:21,160
Some of them developed scaly, impermeable skins that enabled them
它们中的一些类群发展出了鳞片，

709
00:54:21,160 --> 00:54:22,960
to colonise the driest places...
防水的皮肤使它们可以向陆地进军了...

710
00:54:22,960 --> 00:54:24,720
they were the reptiles.
它们是爬行动物。

711
00:54:24,720 --> 00:54:27,720
And from them came the birds.
它们又变成了鸟类。

712
00:54:30,800 --> 00:54:32,440
And the mammals.
哺乳类，

713
00:54:35,400 --> 00:54:38,480
Today mammals, like this rhinoceros,
今天的哺乳类比如说犀牛

714
00:54:38,480 --> 00:54:41,360
are the biggest of all living animals.
已成为现生动物中最大的类群了。

715
00:54:43,640 --> 00:54:46,840
Hello, old boy. How are you?
嗨，你好，小伙子，你好吗？

716
00:54:46,840 --> 00:54:48,880
How are you?
你好吗？

717
00:54:48,880 --> 00:54:53,200
All mammals, including ourselves, extract oxygen from the air with
包括我们在内的所有哺乳动物，

718
00:54:53,200 --> 00:54:56,760
the end of internal lungs, and distribute it through our bodies
都用肺来吸收空气中的氧气

719
00:54:56,760 --> 00:54:57,880
in our blood.
并且通过血液循环至全身。

720
00:54:57,880 --> 00:55:00,720
There we are. There's a good lad.
我们在这儿，你是个好小伙。

721
00:55:00,720 --> 00:55:05,000
But we also owe our success, and our size,
但是我们也有我们的成就，

722
00:55:05,000 --> 00:55:07,400
to the nature of our skeletons.
我们的大小取决于我们骨骼的特质。

723
00:55:08,920 --> 00:55:14,040
Animals with an internal skeleton, like this rhinoceros,
这只犀牛具有内骨骼，

724
00:55:14,040 --> 00:55:20,840
have a huge advantage over animals whose skeleton is external.
这类动物比具有外骨骼的动物更加具有优势，

725
00:55:20,840 --> 00:55:24,200
A white rhinoceros, like this,
像这样的白犀牛，

726
00:55:24,200 --> 00:55:28,360
is one of the biggest land animals alive today.
是现生的陆生动物中较大的一类。

727
00:55:28,360 --> 00:55:31,000
Compare him
与它相比

728
00:55:31,000 --> 00:55:33,880
with him... a rhinoceros beetle.
一只独角仙

729
00:55:35,400 --> 00:55:38,680
Its skeleton is external.
它具有外部的骨骼。

730
00:55:38,680 --> 00:55:41,360
It's very powerful.
它非常强悍。

731
00:55:41,360 --> 00:55:44,560
It can carry 850 times its own weight.
它能够举起它体重的850倍的重物，

732
00:55:44,560 --> 00:55:49,160
But it can't grow much bigger. Because the only way it can grow is
但是它不能长得更大。因为它之所以长到现在这么大

733
00:55:49,160 --> 00:55:51,800
by shedding its skeleton and growing a new one.
是因为每一次蜕皮之后再长出新的外骨骼。

734
00:55:51,800 --> 00:55:57,720
And while its skeleton is not there, its body is unsupported.
当它的骨骼不存在时，它的身体就无法支撑。

735
00:55:57,720 --> 00:56:04,800
And after a certain size, the body will collapse under its own weight.
长到一定程度，外骨骼会因无法支撑体重的而崩溃。

736
00:56:04,800 --> 00:56:05,760
Here.
这儿。

737
00:56:08,400 --> 00:56:11,640
Here we are, come on boy. Come on boy.
我们在这儿，过来小伙子，过来小伙子。

738
00:56:11,640 --> 00:56:15,680
Despite these differences, it's no coincidence that
虽然有这么多差异，但是并非巧合使得

739
00:56:15,680 --> 00:56:21,320
backboned animals evolved many of the same features as the arthropods.
脊椎动物与节肢动物一样演化为许多共同的特征，

740
00:56:21,320 --> 00:56:23,400
Teeth.
牙齿

741
00:56:23,400 --> 00:56:26,000
Legs.
腿

742
00:56:26,000 --> 00:56:30,040
Shells. Eyes.
骨骼、眼睛

743
00:56:30,040 --> 00:56:31,240
And wings.
翅

744
00:56:31,240 --> 00:56:34,360
Any animal group needs such things if they are to colonise
因为对于任何要征服世界各种环境的动物类群来说

745
00:56:34,360 --> 00:56:37,880
all the Earth's varied habitats.
这些特殊的装备是很必要的。

746
00:56:44,880 --> 00:56:49,600
A journey that began for me near my boyhood home in Charnwood Forest
旅行的起点从童年故乡的Charnwood森林开始

747
00:56:49,600 --> 00:56:54,280
has taken me around the world and through 600 million years
之后，我环游世界，

748
00:56:54,280 --> 00:56:55,400
of evolutionary history.
并且追溯6亿年的生命演化史，

749
00:56:56,920 --> 00:57:02,680
I've seen evidence of how single-celled life dominated the planet for billions of years,
我见证了单细胞生物，曾主宰地球长达十亿年的证据。

750
751
00:57:02,680 --> 00:57:08,000
until a global ice age triggered the emergence of the first animals.
直到全球性的冰期启动时，最早的动物才诞生，

752
00:57:11,240 --> 00:57:14,320
Many animal groups lasted millions of years.
虽然许多动物类群历经了数百万年，

753
00:57:14,320 --> 00:57:18,200
But eventually their time ran out and they disappeared.
但是最终它们生命耗尽，永远地消失了。

754
00:57:29,040 --> 00:57:31,400
But others endured.
但是其他能够坚持下来的，

755
00:57:35,000 --> 00:57:37,400
And between them they evolved
其中一些类群

756
00:57:37,400 --> 00:57:42,360
into the wondrous variety of life that inhabits this planet today.
演化为现在生活在这个星球的纷繁多样的生物，

757
00:57:44,480 --> 00:57:47,840
Life originated in the oceans.
生命起源于海洋。

758
00:57:47,840 --> 00:57:53,560
After an immense period of time, some creatures managed to crawl up
经过非常漫长的一段时期，

759
00:57:53,560 --> 00:57:55,280
onto the land.
一些种类设法爬上了陆地。

760
00:57:55,280 --> 00:57:58,840
Those animals may seem to us to be very remote,
对我们来说，这些动物似乎离我们非常遥远，

761
00:57:58,840 --> 00:58:01,480
strange, even fantastic.
它们奇形怪状、荒诞离谱，

762
00:58:01,480 --> 00:58:07,240
But all of us alive today owe our very existence to them.
然而，今天我们能活着，归功于它们的存在。