Jack Horner: Shape-shifting dinosaurs

翻译人员: Candice Liu 校对人员: Xiaoqiao Xie

现在我想就年龄问题

Shall I ask for a show of hands or a clapping

请大家举个手

或是鼓个掌

of people in different generations?

I'm interested in how many are three to 12 years old.

我想知道

在座有多少人的年龄介于3至12岁之间？

(Laughter)

（笑声）

没有是吧？

None, huh?

(Laughter)

我知道了

All right.

今天我要来讲一讲恐龙

I'm going to talk about dinosaurs.

Do you remember dinosaurs when you were that age?

你还记得你小时候有多喜欢恐龙吗？

(Applause)

（鼓掌）

Dinosaurs are kind of funny, you know.

恐龙是种很有趣的东西

(Laughter)

（笑声）

We're going to kind of go in a different direction right now.

不过今天

我们要从另一个角度来看待它们

I hope you all realize that.

So I'll just give you my message up front:

从恐龙身上我学到了一些东西

那就是尽量别让自己灭绝了

Try not to go extinct.

（笑声）

(Laughter)

That's it.

就这么简单

(Laughter)

（笑声）

人们常常问我

People ask me a lot --

事实上，我被问得最多的问题就是

in fact, one of the most asked questions I get

is, why do children like dinosaurs so much?

为什么小孩子都那么喜欢恐龙？

What's the fascination?

恐龙到底有哪里特别吸引人？

And I usually just say,

这时候我一般会这么回答

"Well, dinosaurs were big,

因为恐龙很大，很与众不同

而且它们灭绝了

different and gone."

是的，所有恐龙都灭绝了

They're all gone.

Well that's not true,

虽然我也不能百分百肯定

but we'll get to the goose in a minute.

不过我们马上就要讲到重点了

所以恐龙总体来说就是

So that's sort of the theme:

big, different and gone.

很大，很与众不同，而且已经灭亡

The title of my talk:

我今天演讲的主题是：

Shape-shifting Dinosaurs:

会“变形”的恐龙

The cause of a premature extinction.

及它们过早灭亡的原因

我们印象中的恐龙

Now I assume that we remember dinosaurs.

有大有小，形态各异

And there's lots of different shapes.

有许多不同的种类

Lots of different kinds.

A long time ago,

很久以前

back in the early 1900s, museums were out looking for dinosaurs.

大概是二十世纪初的时候

各大博物馆都对恐龙很感兴趣

他们四处搜集恐龙化石

They went out and gathered them up.

And this is an interesting story.

这个过程非常有趣

因为每个博物馆都想要比别人更大更好的

Every museum wanted a little bigger or better one than anybody else had.

恐龙化石

So if the museum in Toronto went out and collected a Tyrannosaur, a big one,

所以如果多伦多的博物馆

找到一个大家伙——霸王龙

那么渥太华的博物馆就一定要找到一个更大、更好的

then the museum in Ottawa wanted a bigger one, and a better one.

才肯罢休

当时几乎所有博物馆都是这样

And that happened for all museums.

So everyone was out looking for all these bigger and better dinosaurs.

所以所有人都在四处寻找

大型的恐龙化石

这是在上世纪初的时候

And this was in the early 1900s.

By about 1970,

到了1970年

有些科学家就开始思考

some scientists were sitting around and they thought, "What in the world --

怎么回事

Look at these dinosaurs, they're all big.

看看我们找到的这些恐龙化石

全都这么大

那小恐龙去哪了？

Where are all the little ones?"

(Laughter)

And they thought about it and they even wrote papers about it:

科学家们就开始思考这个问题

针对这个问题做研究、写论文

"Where are the little dinosaurs?"

“小恐龙到哪里去了？”

(Laughter)

（笑声）

你要是去博物馆就能发现

Well, go to a museum, you'll see,

see how many baby dinosaurs there are.

那里根本就没有几个小恐龙

People assumed -- and this was actually a problem --

人们假设——这也正是问题所在

people assumed that if they had little dinosaurs,

人们假设

如果小恐龙、或者说幼年时期的恐龙

真的存在的话

if they had juvenile dinosaurs, they'd be easy to identify.

应该很容易被辨别出来

You'd have a big dinosaur and a littler dinosaur.

既然有大恐龙

就应该有小恐龙

(Laughter)

但是我们现在看到的全是些大家伙

But all they had were big dinosaurs.

这就让我们发现了几个问题

And it comes down to a couple of things.

First off, scientists have egos,

首先，科学家都是很自负的

他们都很喜欢给恐龙起名字

and scientists like to name dinosaurs.

They like to name anything.

他们喜欢给任何东西起名字

Everybody likes to have their own animal that they named.

所有人都想要一个自己亲自给起名的新动物

（笑声）

(Laughter)

所以每当他们发现一个新物种看起来有一点点不一样

And so every time they found something that looked a little different,

他们就给它起一个新名字

they named it something different.

And what happened, of course,

这样一来

is we ended up with a whole bunch of different dinosaurs.

我们就有了一大堆不同名字的恐龙

In 1975,

1975年

有个人脑子里突然灵光一现

a light went on in somebody's head.

这个人就是宾夕法尼亚大学的

Dr. Peter Dodson at the University of Pennsylvania

彼得·道森博士

他意识到

actually realized that dinosaurs grew kind of like birds do,

恐龙的发育过程

其实和鸟类很相似

which is different than the way reptiles grow.

而与爬行类动物

却不怎么一样

And in fact,

然后

he used the cassowary as an example.

他拿食火鸡举了个例子

And it's kind of cool -- if you look at the cassowary,

食火鸡这种鸟很酷——事实上

or any of the birds that have crests on their heads,

所有头上有冠的鸟都很酷

they grow to about 80 percent adult size before the crest starts to grow.

因为它们直到

发育到成年个体的百分之八十的时候

头上的冠才会开始生长

现在我们仔细想想

Now think about that.

They're basically retaining their juvenile characteristics

它们实际上一直保持着幼年时期的特征

very late in what we call ontogeny.

直到发育过程的后期

So allometric cranial ontogeny is relative skull growth.

这种颅骨发育

非常的迅速

So you can see that if you actually found one that was 80 percent grown

所以

如果你看到一只

发育到百分之八十的小食火鸡

and you didn't know that it was going to grow up to a cassowary,

你也认不出来它是一只食火鸡

你会觉得这是两种不同的动物

you would think they were two different animals.

So this was a problem,

这就是问题所在

and Peter Dodson pointed this out using some duck-billed dinosaurs

彼得·道森认识到了这一点

于是他拿鸭嘴恐龙

来举例说明

then called Hypacrosaurus.

And he showed that if you were to take a baby and an adult

他把幼年鸭嘴龙

和成年鸭嘴龙放在一起比较

and make an average of what it should look like,

如果它的生长

是呈线性发展的

if it grew in sort of a linear fashion,

那么幼年鸭嘴龙应该有一个

it would have a crest about half the size of the adult.

差不多成年鸭嘴龙一半大小的顶冠

But the actual subadult at 65 percent had no crest at all.

但事实上

百分之六十五即将成年的小鸭嘴龙

都没有顶冠

So this was interesting.

这就很有意思了

So this is where people went astray again.

看来这就是使人们的思维

走入误区的地方

I mean, if they'd have just taken that,

我的意思是

如果人们能接受并发展彼得·道森的发现

taken Peter Dodson's work, and gone on with that,

我们现在所拥有的恐龙种类

then we would have a lot less dinosaurs than we have.

就会少得多

But scientists have egos; they like to name things.

但是别忘了，科学家都是很自负的

而且特别喜欢给东西起名字

And so they went on naming dinosaurs because they were different.

所以当他们发现了与原先不一样的恐龙

还是会不断地给它们取新名字

Now we have a way of actually testing

现在我们有了一种方法

可以测定一只恐龙，或是任何一种动物

to see whether a dinosaur, or any animal, is a young one or an older one.

是幼年的还是成年的

And that's by actually cutting into their bones.

那就是切开它们的骨头进行分析

但是你也能够想象

But cutting into the bones of a dinosaur is hard to do, as you can imagine,

要去切一只恐龙的骨头还是挺困难的

because in museums, bones are precious.

因为在博物馆里

这些骨头相当珍贵

他们把每一块骨头

You go into a museum, and they take really good care of them.

They put them in foam, little containers.

都包着泡沫放进小罐子里

保存得好好的

They're very well taken care of.

如果你拿着锯子走进去说要切开这些骨头看看

They don't like it if you come in and want to saw them open and look inside.

恐怕不会受到太多欢迎

（笑声）

(Laughter)

So they don't normally let you do that.

所以一般情况下我们没这个机会

(Laughter)

但是我也有一个博物馆

But I have a museum and I collect dinosaurs

我也搜集恐龙化石

而且我一点也不介意把这些骨头切开

and I can saw mine open.

所以我就把它切开了

So that's what I do.

（掌声）

(Applause)

如果你切开小恐龙的骨头

So if you cut open a little dinosaur,

it's very spongy inside, like A.

会发现里面空隙很大呈海绵状，如图A

如果你切开老恐龙的骨头

And if you cut into an older dinosaur, it's very massive.

则会发现里面的骨质排列很紧密

You can tell it's mature bone.

所以你知道这是一根已经发育成熟了的骨头

这就很容易分清楚了

So it's real easy to tell them apart.

So what I want to do is show you these.

现在

我们来看看这个

In North America in the northern plains of the United States

在北美洲，美国的北部平原

and the southern plains of Alberta and Saskatchewan,

和加拿大的阿尔伯塔及萨斯喀彻温省南部平原

there's this unit of rock called the Hell Creek Formation

有一种叫做“地狱溪地层”的岩石群

在那里发现了最晚生活在地球上的恐龙化石

that produces the last dinosaurs that lived on Earth.

一共有12个

And there are 12 of them that everyone recognizes --

我们可以看到

I mean the 12 primary dinosaurs that went extinct.

这是12个已经灭绝了的

恐龙化石

And so we will evaluate them.

我们现在就是要

研究这些化石

And that's sort of what I've been doing.

我的学生，还有其他工作人员

So my students, my staff, we've been cutting them open.

我们一起把这些骨头切开

你也知道

Now as you can imagine, cutting open a leg bone is one thing,

切开一条恐龙的腿骨也就算了

but when you go to a museum

但是你要是去博物馆

问他们：“你介不介意我把你们的

and say, "You don't mind if I cut open your dinosaur's skull, do you?"

恐龙头骨切开？”

they say, "Go away."

他们一定会说：“给我滚。”

(Laughter)

（笑声）

所以，在这12个恐龙化石里

So here are 12 dinosaurs.

And we want to look at these three first.

我们先看看这三个

这三个都属于厚头龙类

So these are dinosaurs that are called Pachycephalosaurus.

大家都看得出来

And everybody knows that these three animals are related.

它们之间是有亲缘关系的

人们普遍假设

And the assumption is that they're related like cousins or whatever.

它们是堂兄弟

或者这之类的关系

But no one ever considered that they might be more closely related.

但从来没有人想过

它们的关系可能比这还要近得多

换句话说

In other words,

people looked at them and they saw the differences.

人们看到的是它们之间的差异

And you all know that if you are going to determine

但是

如果你想判断

whether you're related to your brother or your sister,

两个人之间是否有亲缘关系

你肯定不会去看他们有多不同

you can't do it by looking at differences.

You can only determine relatedness by looking for similarities.

而是寻找他们的

相同之处

So people were looking at these

现在人们只注意到了

and they were talking about how different they are.

这三种恐龙不同的地方

Pachycephalosaurus has a big, thick dome on its head,

厚头龙的颅顶大而厚

脑后有一些小的突起

and it's got some little bumps on the back of its head,

鼻端也有不少瘤状物

and it's got a bunch of gnarly things on the end of its nose.

第二种恐龙——冥河龙

And then Stygimoloch, another dinosaur from the same age, lived at the same time,

和厚头龙生活在同一时期

has spikes sticking out the back of its head.

它的脑后有数根钉状尖刺

颅顶很小

It's got a little, tiny dome,

鼻子上也有瘤状物

and it's got a bunch of gnarly stuff on its nose.

And then there's this thing called Dracorex hogwartsia.

第三种恐龙叫做龙王龙

它还有一个名字叫做“霍格沃茨”

因为它和小说中描写的“龙”

Guess where that came from?

Dragon.

非常相似

So here's a dinosaur that has spikes sticking out of its head,

它脑后也有钉状的尖刺，鼻子上有瘤状物

no dome and gnarly stuff on its nose.

但没有颅顶

Nobody noticed the gnarly stuff sort of looked alike.

没有人注意到这三种恐龙鼻子上的瘤状物非常相似

他们一下子就下了结论：

But they did look at these three

and they said, "These are three different dinosaurs,

“这是三种不同的恐龙

龙王龙应该是最原始的一种

and Dracorex is probably the most primitive of them.

这种又应该比那种原始”

And the other one is more primitive than the other."

我就不明白了

It's unclear to me how they actually sorted these three of them out.

他们是怎么看出来的呢？

But if you line them up,

如果光从头骨来看的话

if you just take those three skulls and just line them up,

把它们以大小顺序排成一列

they line up like this.

就成了这样

Dracorex is the littlest one,

龙王龙是最小的

Stygimoloch is the middle-size one,

其次是冥河龙

厚头龙最大

Pachycephalosaurus is the largest one.

And one would think, that should give me a clue.

这是不是应该

给我们一点启示了？

(Laughter)

（笑声）

But it didn't give them a clue.

但可惜他们都没发现

(Laughter)

Because, well we know why.

我们也知道是为什么了

Scientists like to name things.

因为科学家们最爱给东西起名字

那么，如果我们把这些头骨切开的话

So if we cut open Dracorex --

龙王龙——

I cut open our Dracorex --

我把我的龙王龙给切了——

and look, it was spongy inside, really spongy inside.

看！里面是海绵状的

非常疏松

I mean, it is a juvenile and it's growing really fast.

这说明这是一只幼年的恐龙

而且它长得很快

会越长越大

So it is going to get bigger.

如果你切开冥河龙的骨头

If you cut open Stygimoloch, it is doing the same thing.

会发现也是一样

The dome, that little dome, is growing really fast.

它的颅顶虽小

却发育得

It's inflating very fast.

非常迅速

What's interesting is the spike on the back of the Dracorex

最有意思的还是龙王龙脑袋后面的尖刺

它也长得非常快

was growing very fast as well.

而冥河龙脑后的刺

The spikes on the back of the Stygimoloch are actually resorbing,

却是在退化的

which means they're getting smaller as that dome is getting bigger.

也就是说它在颅顶变大的同时

尖刺会越来越小

And if we look at Pachycephalosaurus,

我们再看厚头龙

Pachycephalosaurus has a solid dome

它的颅顶非常坚实

and its little bumps on the back of its head were also resorbing.

而它脑后的突起

也是在退化的

So just with these three dinosaurs,

所以，就光从这三种恐龙来看

作为一个科学家

as a scientist, we can easily hypothesize

我们很容易就能做出这样的假设：

that it is just a growth series of the same animal.

这是同一种动物的

生长序列

这样一来

Which of course means

冥河龙和龙王龙

that Stygimoloch and Dracorex are extinct.

就不得不“灭绝”了

(Laughter)

（笑声）

OK.

好了

(Laughter)

现在我们还剩下

Which of course means we have 10 primary dinosaurs to deal with.

10种恐龙要研究

So a colleague of mine at Berkeley -- he and I were looking at Triceratops.

我和一个在伯克利的同事

一起研究了三角龙

And before the year 2000 --

我们发现在2000年前——

now remember, Triceratops was first found in the 1800s --

我想想

三角龙是在19世纪发现的

before 2000, no one had ever seen a juvenile Triceratops.

但是在2000年之前

从来没有人见过幼年的三角龙

There's a Triceratops in every museum in the world,

世界上几乎所有博物馆都有三角龙的化石

就是没有一个小三角龙

but no one had ever collected a juvenile.

我们都知道为什么，是吧？

And we know why, right?

因为大家都想要大的

Because everybody wants to have a big one.

所以每家博物馆都有一个大的

So everyone had a big one.

我和我的同事在外面搜索了一圈

So we went out and collected a whole bunch of stuff

结果发现了许多小三角龙

and we found a whole bunch of little ones.

它们到处都是

They're everywhere, they're all over the place.

So we have a whole bunch of them at our museum.

所以现在我们的博物馆里收藏了一大堆小三角龙

（笑声）

(Laughter)

And everybody says it's because I have a little museum.

大家都说这是因为我有一个小博物馆

小博物馆里自然是小恐龙

When you have a little museum, you have little dinosaurs.

（笑声）

(Laughter)

仔细观察一下三角龙

If you look at the Triceratops,

you can see it's changing, it's shape-shifting.

你能看到它在变化、在“变形”

在小三角龙长大的过程中

As the juveniles are growing up, their horns actually curve backwards.

它们的角是向后弯曲的

但当它们长大之后

And then as they get older, the horns grow forward.

角却变成了向前弯曲

这是不是很酷？

And that's pretty cool.

If you look along the edge of the frill,

我们再看看它头盾的边褶

they have these little triangular bones that actually grow big as triangles

有很多小小的三角形骨突

这些骨突会逐渐长大

使头盾的边缘逐渐平滑

and then they flatten against the frill

pretty much like the spikes do on the Pachycephalosaurs.

这和厚头龙脑后的尖刺

是类似的

And then, because the juveniles are in my collection,

因为我的博物馆里有幼年的三角龙化石

I cut them open ...

我就把它切开

(Laughter)

来看看

and look inside.

And the little one is really spongy.

结果发现小的三角龙骨头内部果然是海绵状的

And the middle-size one is really spongy.

中等大小的骨头内部也是海绵状的

But what was interesting was the adult Triceratops was also spongy.

但最有意思的是

成年三角龙的骨头内部居然也是海绵状的

And this is a skull that is two meters long.

它的头骨都达到两米长了

非常的大

It's a big skull.

不过在这个地层内出土的化石里面

But there's another dinosaur that is found in this formation

还有另一种恐龙

that looks like a Triceratops, except it's bigger,

与三角龙非常相似，只不过还要更大些

叫做牛角龙

and it's called Torosaurus.

当我们切开牛角龙骨头化石的时候

And Torosaurus, when we cut into it, has mature bone.

发现骨质发育非常成熟

But it's got these big holes in its shield.

但是牛角龙的头盾上有这种很大的孔洞

And everybody says,

所有人都说：

"A Triceratops and a Torosaurus can't possibly be the same animal

三角龙和牛角龙不可能是同一种动物

because one of them's bigger than the other one."

因为这种比那种大太多了

（笑声）

(Laughter)

"And it has holes in its frill."

而且头上还有洞

我就问他们：“你们见过小牛角龙吗？”

And I said, "Well do we have any juvenile Torosauruses?"

他们回答：“这个还没有，

And they said, "Well, no, but it has holes in its frill."

但是它头上有洞啊”

So one of my graduate students, John Scannella,

所以，我的学生约翰·斯堪那拉

对我们所有馆藏的化石进行了研究

looked through our whole collection

and he actually discovered that the hole starting to form in Triceratops

他终于发现

在三角龙身上

这些洞就开始形成了

当然，到了牛角龙时期才完全打开

and, of course it's open, in Torosaurus --

约翰发现了一个处于

so he found the transitional ones between Triceratops and Torosaurus,

三角龙向牛角龙转型时期的化石

非常的神奇

which was pretty cool.

So now we know that Torosaurus is actually a grown-up Triceratops.

所以，我们现在知道

牛角龙其实是

长大了的三角龙

当我们给恐龙起名字

Now when we name dinosaurs,

或者说给任何东西起名字的时候

when we name anything, the original name gets to stick

都倾向于保留原有的那一个

and the second name is thrown out.

而放弃新取的那一个

所以牛角龙就这么“灭绝”了

So Torosaurus is extinct.

至于三角龙，如果你看新闻的话

Triceratops, if you've heard the news, a lot of the newscasters got it all wrong.

就会发现好多新闻主播都搞错了

They thought Torosaurus should be kept and Triceratops thrown out,

他们认为应该保留“牛角龙”这个名字，而放弃“三角龙”

但这是不会发生的

but that's not going to happen.

(Laughter)

（笑声）

All right, so we can do this with a bunch of dinosaurs.

好，所以我们可以把这种方法用在许多种恐龙身上

I mean, here's Edmontosaurus

比如说，埃德蒙顿龙

and Anatotitan.

和大鸭龙

Anatotitan: giant duck.

顾名思义

It's a giant duck-bill dinosaur.

大鸭龙就是很大的鸭嘴恐龙

它们也是一对这样的组合

Here's another one.

So we look at the bone histology.

同样，我们还是从它们的骨组织入手

骨质分析告诉我们

The bone histology tells us that Edmontosaurus is a juvenile,

埃德蒙顿龙是幼年恐龙

或者顶多是青少年恐龙

or at least a subadult,

and the other one is an adult, and we have an ontogeny.

而大鸭龙则是成年恐龙

根据个体发生学

“大鸭龙”也灭绝了

And we get rid of Anatotitan.

所以我们就可以一直不断地这么做

So we can just keep doing this.

And the last one is T. Rex.

最后我要讲的

是雷克斯暴龙（即霸王龙）

So there's these two dinosaurs, T. Rex and Nanotyrannus.

现在我们有两种恐龙

暴龙和矮暴龙

(Laughter)

（笑声）

现在我们自然而然产生怀疑了

Again, it makes you wonder.

(Laughter)

（笑声）

但是他们的理由也很充分

But they had a good question.

他们仔细检查后说：

They were looking at them and they said, "One's got 17 teeth,

小的那个有17颗牙，大的才12颗牙

and the biggest one's got 12 teeth.

这怎么可能是同一种呢？

And that doesn't make any sense at all,

我们还不知道哪种恐龙

because we don't know of any dinosaurs that gain teeth as they get older.

是越长大牙越少的

So it must be true --

所以它们肯定

是两种不同的恐龙

they must be different."

So we cut into them.

所以我把它们都切开了

果然和我想的一样

And sure enough, Nanotyrannus has juvenile bone

矮暴龙是幼年的恐龙

and the bigger one has more mature bone.

暴龙的骨头则成熟得多

而且看起来还会继续长大

It looks like it could still get bigger.

在我工作的洛基博物馆里

And at the Museum of the Rockies where we work,

有四具暴龙化石

I have four T. rexes, so I can cut a whole bunch of them.

所以我有机会把它们都切开来

但是我发现我根本用不着这么做

But I didn't have to cut any of them really,

because I just lined up their jaws

因为我只是简单地将它们的下颌骨按顺序排列起来

and it turned out the biggest one had 12 teeth

就发现最大的一个有12颗牙

and the next smallest one had 13

第二大的有13颗牙

and the next smallest had 14.

第三大的有14颗牙

当然了，矮暴龙有17颗牙

And of course, Nano has 17.

然后我们就跑去其他博物馆里看别人收藏的暴龙

And we just went out and looked at other people's collections

发现了一只有15颗牙的

and we found one that has sort of 15 teeth.

So again, real easy to say

这下事情又简单了

that Tyrannosaurus ontogeny included Nanotyrannus,

暴龙（即霸王龙）的个体发生序列中

是包括矮暴龙的

and therefore we can take out another dinosaur.

这下我们又能从恐龙名单里划掉一个名字了

(Laughter)

（笑声）

所以

So when it comes down to our end Cretaceous,

到了白垩纪末期

we have seven left.

我们还剩七种恐龙

这个数字

And that's a good number.

That's a good number to go extinct, I think.

听起来就合理多了吧

Now as you can imagine,

你也知道

this is not very popular with fourth-graders.

我这次演讲的主题对刚上四年级的小男生可能没什么吸引力

(Laughter)

他们喜欢他们的恐龙

Fourth-graders love their dinosaurs, they memorize them.

他们印象中的恐龙

可不是这个样子的

And they're not happy with this.

（笑声）

(Laughter)

谢谢大家！

Thank you very much.

(Applause)

（鼓掌）