达尔文和生命之树（2009）

它们会露出一只虾或一条鱼
they reveal a shrimp or a fish.
你几乎无法抗拒这样的诱惑：
It’s almost impossible to resist the temptation
把你看到的每一块石头都拉下来
of pulling down almost every boulder you see,
然后将它象一本书一样打开，查看尚未打开的每一页
and then opening it like a book,
to look at each unopened page
看看它是否还包含另一个化石
to see whether maybe it contains yet another fossil.
而这一块化石是前所未有的
But this fossil was something unprecedented.
它现在仍然是自然历史博物馆中最宝贵的藏品之一
It is still one of the greatest of the treasures that are stored
in the Natural History Museum.
这就是它 – 叫作始祖鸟
And this is it – it’s called archaeopteryx.
它的翅膀上有明显的羽毛
It has unmistakable feathers on its wings
尾巴上也有
and down its tail.
所以欧文毫不犹豫地称它为鸟
So Owen had no hesitation in calling it a bird.
但它与人们所知道的任何其他鸟类都不一样
But it was unlike any other bird that anyone knew of,
因为它的翅膀前面有爪子
because it had claws on the front of its wings,
而且，正如后来发现的那样，它没有喙，只有带牙齿的下颚
and, as was later discovered, it didn’t have a beak,
but jaws with teeth in it.
还有一排支撑尾巴的骨头
And a line of bones supporting its tail.
因此它有一部分是爬行动物，一部分是鸟类
So it was part reptile, part bird.
这正是两个大物种群之间的联♥系♥
Here was a link between those two great groups
不再缺失了
that was no longer missing.
天哪，你真的能看到那里的羽毛纤维
Gosh, you really can see the filaments there.
同一生物的其他样本更清楚地显现出它的羽毛
Other examples of the same creature
show its feathers even more clearly.
我们从始祖鸟的骨质知道，充其量它只是一只勉强的飞行者
We know from the bones of archaeopteryx that it was,
at best, a very poor flyer.
因此，它最终被更现代、更高效的鸟类所取代
So it’s not surprising that eventually it was superseded
也就不足为奇了
by more modern, more efficient birds.
这些过渡物种的命运就是如此
And that’s the fate of these links between great groups.
最终他们灭绝了
Eventually they become extinct,
我们只有从它们的化石遗迹中才能知道它们曾经存在
and the only way we know they existed is from
their fossilised remains.
尽管如此，今天仍有一种活着的鸟类
Even so, there is a bird alive today
可以说明现代鸟类和爬行动物之间的联♥系♥
that illustrates the link between modern birds and reptiles.
麝雉在南美洲的热带沼泽里筑巢
The hoatzin nests in the swamps of tropical South America.
水下有鳄鱼，随时准备吃掉任何可能从它的巢里掉下的雏鸟
There are cayman in the water beneath,
ready to snap up any chick that might fall from its nest,
所以紧紧抓住的能力是很有用的
so an ability to hold on tight is very valuable.
雏鸟有一种很有趣的方式来抓紧
And the nestlings have a very interesting way of doing that.
幼鸟的翅膀前部还有爪子，就像始祖鸟一样
The young still have claws on the front of their wings,
as archaeopteryx did.
这是生动的证据，表明鸟类的翅膀是经过进化的前肢
Here is vivid evidence that the wings
of birds are modified forelegs
一度曾是长有脚趾的爪子
and once had toes with claws on them.
另一种现存的生物代表了这一大的动物物种之间的联♥系♥
There’s another creature alive today that represents
a link between the great animal groups,
这是一组爬行动物的后代，它们经历了不同的进化过程
a descendant of a group of reptiles that took
a different evolutionary course
进化出来的不是羽毛而是毛皮 –
and evolved not feathers, but fur –
鸭嘴兽
the platypus.
当这种生物的标本在18世纪末第一次
When specimens of this creature first reached
Europe from Australia
从澳大利亚到达欧洲时
at the very end of the 18th century,
人们拒绝相信自己的眼睛
people refused to believe their eyes.
他们说这是一场骗局 –
They said it was a hoax –
几种不同的动物碎片被粗糙地拼凑起来的
bits and pieces of different creatures rather
crudely sewn together.
在某种程度上，这些早期的怀疑论者是对的
And yet in a way those early sceptics were right.
鸭嘴兽是最特别的不同动物的混合体
The platypus is the most extraordinary mixture
of different animals.
它是半哺乳半爬行动物
It’s part mammal and part reptile.
这可以让我们了解最早的哺乳动物是如何进化的
And so it can give us some idea
of how the first mammals developed.
在繁殖方面，它的行为有别于其他所有哺乳动物，只有一种除外
When it comes to breed, it does something that separates
it from all other mammals except one.
它在洞穴深处的巢穴里产卵
In its nest, deep in a burrow, it lays eggs.
正是这一点把鸭嘴兽和爬行动物联♥系♥在了一起
It’s this that links the platypus with the reptiles,
这也使得鸭嘴兽被认为是
and this that entitles it to be regarded
现存的最原始的哺乳动物
as the most primitive living mammal.
因此，大的动物物种之间的联♥系♥
So the links between the great animal groups
实际上并没有消失
are not, in fact, missing,
而是以化石和现存动物的形式存在着
but exist both as fossils and as living animals.
虽然化石记录提供了线索缺失问题的
Although the fossil record provides
an answer to the problem
答案，它也提出了一个重大问题
of missing links, it also posed a major problem.
它开始得很突然
It started very abruptly.
达尔文时代已知的最早化石
The earliest known fossils in Darwin’s time
来自一个叫寒武纪的岩层
came from a formation called the Cambrian,
有二个主要的类型
and there were two main kinds –
这些看起来像线锯片的，叫做笔石
these, which look like fretsaw blades and are called graptolite,
而这些，像巨大的木虱的叫做三叶虫
and these, like giant woodlice, which are called trilobites.
地球上的生命真的起源于
Could it really be that life on Earth started
象这样复杂的生物吗？
with creatures as complex as these?
小时候，我是一个热情的化石收集者
As a boy, I was a passionate collector of fossils.
我在莱斯特市长大
I grew up in the city of Leicester,
我知道在离这座城市不远的查恩伍德森林
and I knew that in this area, not far from the city,
called Charnwood Forest,
有世界上最古老的岩石，甚至比寒武纪还要古老
there were the oldest rocks in the world,
older even than the Cambrian.
因此，根据定义，它们不会有化石
So therefore, by definition, they would be without fossils.
我没有理由在这些远古的岩石中寻找化石
There was no point in me looking
for fossils in these ancient rocks.
确实，非常罕见
There were, it’s true, very rarely,
在这些岩石中有些很奇怪的形状
some rather odd shapes in these rocks,
比如这一块
like this one here.
它们被认为是某种机械失常而不予理睬
But they were dismissed as being some kind
of mechanical aberration.
我的意思是，毕竟
I mean, after all,
在这些极其古老的岩石中，怎么可能有什么生物？
how could there be anything living in these extremely
ancient rocks?
然后在1957年
And then in 1957,
一个比我更有耐心和洞察力的学生
a schoolboy with rather more patience
and perspicacity than I had
发现了一些非常了不起的东西 –
found something really remarkable –
不可否认的，是一个生物的遗骸
and undeniably, the remains of a living creature.
它在这里的莱斯特博物馆
And here it is in Leicester Museum,
被带到这里妥善保管
where it’s been brought for safekeeping.
它叫做加尼亚虫
It’s called Charnia.
谁能怀疑这是一个活的生物体的印象呢？
Who could doubt that this is the impression
of a living organism?
它有一个中心的茎，两边都有分枝
It has a central stem, and branches on either side.
事实上，它看起来就像今天生长在
In fact, it seems to have been something like the sea pens
珊瑚暗礁上的海鳃
that today grow on coral reefs.
自从它被发现以来，在这种极其古老的岩石中
Since its discovery, a whole range of organisms
have been found
整个系列的生物体都找到了
in rocks of this extreme age,
不仅在这里的查恩伍德森林，而且在世界上许多不同的地方
not only here in the Charnwood Forest,
but in many other different parts of the world.
在澳大利亚埃迪卡拉山寻找化石的人
Fossil hunters searching these rocks
in the Ediacra Hills of Australia
还发现了其他奇怪的形状
had also been discovering other strange shapes.
起初，许多科学家拒绝相信
At first, many scientists refused to believe
这些模糊的痕迹是水母的残骸
that these faint impressions were the remains of jellyfish.
到目前为止，已经发现了足够的标本，足以确定它们
But by now, enough specimens had been discovered
to make quite sure
确实是这样的
that that indeed is what they are.
现在我们知道生命并不是突然从那些复杂的寒武纪动物开始的
So now we know that life did not begin suddenly with
those complex animals of the Cambrian.
它开始的时间要早得多
It started much, much earlier,
最初是简单的微观形态，逐渐逐渐变大
first with simple microscopic forms which eventually
became bigger,
但它们仍然很软很精致，很少在岩石上留下任何痕迹
but which were still so soft and delicate that they only
very rarely left any mark in the rocks.
地球的年龄疑问给达尔文的理论造成了另一个问题
The question of the age of the Earth posed another
problem for Darwin’s theory.
在17世纪，一个爱尔兰的主教根据圣经里记录的系谱
In the 17th century, an Irish bishop
had used the genealogies recorded in the Bible
追溯到亚当，并计算出创世纪的那一周
that lead back to Adam to work out that the week of Creation
一定发生在公元前4004年
must have taken place in the year 4004 BC.
在我们看来，这可能是一种非常幼稚的做事方式
That may seem to us to be a very naive way of doing things,
但还有什么其他的方法呢？
but what other method was there anyway?
维多利亚时代的地质学家已经得出结论，
认为地球一定有数百万年的历史了
The Victorian geologists had already concluded that
the Earth must be millions of years old.
但到底是几百万年，没有人说得清
But how many millions, no-one could say.
然后，在《物种起源》出版之后不到50年
Then, less than 50 years after the publication of The Origin,
人们发现了一个看似完全不相关的科学分支
a discovery was made in what seemed a totally
disconnected branch of science