I know it because people come up to me, like colleagues, and say,

我的職業很奇怪。

"Chris, you have a strange career."

這麼講是因為常有人這樣告訴我，例如我的同事

(Laughter)

都會說:「克里斯，你的職業很奇怪耶。」

And I can see their point,

(觀眾笑聲)

because I started my career as a theoretical nuclear physicist.

其實我理解他們的意思,

And I was thinking about quarks and gluons and heavy ion collisions,

因為我一開始當過

and I was only 14 years old --

理論核子物理學家。

No, no, I wasn't 14 years old.

那時我成天想的都是夸克和膠子,

But after that,

還有重離子的撞擊,

I actually had my own lab

那時我才14歲而已。

in the Computational Neuroscience department,

不，不對，不是14歲那年的事。

and I wasn't doing any neuroscience.

不過在那之後

Later, I would work on evolutionary genetics,

我有了一間專屬的實驗室,

and I would work on systems biology.

就在計算神經科學系那邊,

But I'm going to tell you about something else today.

但是我完全都沒有做神經科學的研究。

I'm going to tell you about how I learned something about life.

後來我開始研究演化基因,

And I was actually a rocket scientist.

接著便是系統生物學。

I wasn't really a rocket scientist,

不過以上這些跟我今天要講的主題一點關係也沒有。

but I was working at the Jet Propulsion Laboratory

我要講的是

in sunny California, where it's warm;

我如何探悉到生命的一些東西。

whereas now I am in the mid-West, and it's cold.

我以前當過火箭專家。

But it was an exciting experience.

但嚴格上來說我不算是真正的火箭專家,

One day, a NASA manager comes into my office,

只不過我曾經在

sits down and says,

位於陽光普照的加州的太空總署的

"Can you please tell us, how do we look for life outside Earth?"

噴射推進實驗室工作過;

And that came as a surprise to me,

而我現在在中西部,

because I was actually hired to work on quantum computation.

氣候很寒冷。

Yet, I had a very good answer.

不過這是一個很有趣的經驗。

I said, "I have no idea."

有一天NASA主管走進我的辦公室,

(Laughter)

坐下後說:

And he told me, "Biosignatures, we need to look for a biosignature."

「請你告訴我們，

And I said, "What is that?"

如何能尋找到外太空的生命?」

And he said, "It's any measurable phenomenon

我當時很驚訝,

that allows us to indicate the presence of life."

因為我當初是被請來

And I said, "Really?

進行量子計算研究的。

Because isn't that easy?

然而我回答得很漂亮。

I mean, we have life.

我答:「我一點也不知道。」

Can't you apply a definition,

接著他對我說:「生命跡象,

for example, a Supreme Court-like definition of life?"

我們必須找出生命跡象。」

And then I thought about it a little bit, and I said,

我問他:「那是什麼?」

"Well, is it really that easy?

他說:「生命跡象就是能讓我們能

Because, yes, if you see something like this,

辨識出任何可量化

then all right, fine, I'm going to call it life --

生命的存在的現象。」

no doubt about it.

我說:「真的嗎?

But here's something."

真的有這麼簡單嗎?

And he goes, "Right, that's life too. I know that."

我是說，我們有生命。

Except, if you think that life is also defined by things that die,

但你能為生命下一個

you're not in luck with this thing,

類似最高法院般的終極定義嗎?」

because that's actually a very strange organism.

我再想了想, 然後說,

It grows up into the adult stage like that

「就只有這樣而已嗎?

and then goes through a Benjamin Button phase,

沒錯，如果你看到這個,

and actually goes backwards and backwards until it's like a little embryo again,

毫無疑問，我會稱它為生命--

and then actually grows back up, and back down and back up --

這是無庸置疑的。

sort of yo-yo -- and it never dies.

但如果換成這個。」

So it's actually life,

他說:「沒錯，這個也是生命。我很確定。」

but it's actually not as we thought life would be.

可是倘若你認為得生命

And then you see something like that.

是由會死亡的物體來定義,

And he was like, "My God, what kind of a life form is that?"

那你就無法解釋這個東西,

Anyone know?

因為這是一個相當奇怪的有機體。

It's actually not life, it's a crystal.

當它進入成年期的時候就像這樣,

So once you start looking and looking at smaller and smaller things --

然後就像班傑明的奇幻旅程一樣

so this particular person wrote a whole article and said,

不斷退化,

"Hey, these are bacteria."

直到胚胎為止,

Except, if you look a little bit closer,

接著又長回來，再長大 -- 像溜溜球一樣過程循環 --

you see, in fact, that this thing is way too small to be anything like that.

而永生不死。

So he was convinced, but, in fact, most people aren't.

這也算是生命的一種,

And then, of course, NASA also had a big announcement,

只不過它不是

and President Clinton gave a press conference,

我們一般所認知的型態。

about this amazing discovery of life in a Martian meteorite.

再來你如果看到這個。

Except that nowadays, it's heavily disputed.

他問:「天啊，這到底是什麼樣的生命形態呢?」

If you take the lesson of all these pictures,

有人知道嗎?

then you realize, well, actually, maybe it's not that easy.

其實這不算是生命，這是一種結晶體。

Maybe I do need a definition of life

所以當你觀察的東西

in order to make that kind of distinction.

越來越小時--

So can life be defined?

有位老兄

Well how would you go about it?

花了整篇文章的篇幅 只為傳達一件事:「嗨, 這是細菌。」

Well of course, you'd go to Encyclopedia Britannica and open at L.

但如果你靠近一點觀察

No, of course you don't do that; you put it somewhere in Google.

你會發現，事實上這個物體 已經比細菌還要小。

And then you might get something.

於是他被說服了,

(Laughter)

可是大部分的人還是不相信。

And what you might get --

當然,

and anything that actually refers to things that we are used to,

NASA做了一個重大的宣布,

you throw away.

此外前總統柯林頓也召開記者會,

And then you might come up with something like this.

宣布在火星的隕石裡

And it says something complicated with lots and lots of concepts.

發現有生命的存在。

Who on Earth would write something as convoluted and complex and inane?

但是現今這個說法受到嚴重的質疑。

Oh, it's actually a really, really, important set of concepts.

如果你仔細地研究這些照片,

So I'm highlighting just a few words

就會發覺區別生命並沒有那麼簡單。

and saying definitions like that rely on things

也許我需要

that are not based on amino acids or leaves or anything that we are used to,

一個生命的定義

but in fact on processes only.

才能夠來做區別。

And if you take a look at that,

生命能被定義嗎?

this was actually in a book that I wrote that deals with artificial life.

你會如何著手?

And that explains why that NASA manager was actually in my office to begin with.

當然

Because the idea was that, with concepts like that,

你會從大英百科的L開始查起。

maybe we can actually manufacture a form of life.

不，你當然不會那樣做; 你會用Google搜尋。

And so if you go and ask yourself, "What on Earth is artificial life?",

然後你或會得到一些資料。

let me give you a whirlwind tour of how all this stuff came about.

接著把你搜尋到的 --

And it started out quite a while ago,

所有我們習以為常的觀念

when someone wrote one of the first successful computer viruses.

拋諸腦後。

And for those of you who aren't old enough,

然後你可能會得到這段

you have no idea how this infection was working --

複雜的解釋,

namely, through these floppy disks.

裡頭包括許許多多的概念。

But the interesting thing about these computer virus infections

到底有誰會寫出

was that, if you look at the rate at which the infection worked,

這麼人費解,複雜

they show this spiky behavior that you're used to from a flu virus.

又空洞的東西?

And it is in fact due to this arms race

但是這段定義確實涵蓋了 一堆非常重要的概念。

between hackers and operating system designers

我標出了幾個關鍵字眼,

that things go back and forth.

這類的定義

And the result is kind of a tree of life of these viruses,

不是基於

a phylogeny that looks very much like the type of life

胺基酸或葉子

that we're used to, at least on the viral level.

或者我們熟悉的東西,

So is that life?

而是只基於過程。

Not as far as I'm concerned.

如果你仔細看這段話的出處,

Why? Because these things don't evolve by themselves.

就知道是從我寫的一本 有關人造生命的書而來。

In fact, they have hackers writing them.

這說明了

But the idea was taken very quickly a little bit further,

那位NASA主管來辦公室找我的原因。

when a scientist working at the Santa Fe Institute decided,

因為用這樣的想法與概念,

"Why don't we try to package these little viruses

我們也許能創造

in artificial worlds inside of the computer

一個生命的形式。

and let them evolve?"

如果你反問自己

And this was Steen Rasmussen.

「到底什麼是人工生命?」

And he designed this system, but it really didn't work,

就讓我快速地帶你認識

because his viruses were constantly destroying each other.

人工生命的由來。

But there was another scientist who had been watching this, an ecologist.

這是好幾年前發生的,

And he went home and says, "I know how to fix this."

有人寫了早期史上

And he wrote the Tierra system,

上最具破壞力的電腦病毒。

and, in my book,

對年紀較輕的觀眾來說,

is in fact one of the first truly artificial living systems --

你們可能不清楚這種病毒是從哪裡散播開來的...

except for the fact that these programs didn't really grow in complexity.

就是從這種磁碟片傳染的。

So having seen this work, worked a little bit on this,

不過這種電腦中毒有趣的地方

this is where I came in.

可以從電腦的

And I decided to create a system that has all the properties

感染速率來看,

that are necessary to see, in fact, the evolution of complexity,

這張圖表反映出的上下波動

more and more complex problems constantly evolving.

跟一般的流感病毒沒有兩樣。

And of course, since I really don't know how to write code, I had help in this.

事實上因為駭客

I had two undergraduate students

和作業系統開發人員之間發生的爭奪戰,

at California Institute of Technology that worked with me.

而使結果反反復複。

That's Charles Ofria on the left, Titus Brown on the right.

這張電腦病毒的關係圖

They are now, actually, respectable professors

便成樹狀展開,

at Michigan State University,

一個看似我們熟悉的生命發展史,

but I can assure you, back in the day, we were not a respectable team.

至少從病毒的層面來看是如此。

And I'm really happy that no photo survives

病毒能算是生命嗎? 我可不這麼認為。

of the three of us anywhere close together.

怎麼說呢? 因為它們無法自行演化。

But what is this system like?

事實上，電腦病毒是駭客寫出來的。

Well I can't really go into the details,

但是這個想法不久就有了一點進展,

but what you see here is some of the entrails.

有一個在新墨西哥州的科學家決定,

But what I wanted to focus on is this type of population structure.

「我們為何不把這些電腦病毒

There's about 10,000 programs sitting here.

放進電腦的虛擬世界,

And all different strains are colored in different colors.

讓它們自行演化?」

And as you see here, there are groups that are growing on top of each other,

這位科學家就是斯蒂恩•拉斯穆森。

because they are spreading.

他設計了這套系統，不過沒效,

Any time there is a program that's better at surviving in this world,

因為他的病毒會不斷自相殘殺。

due to whatever mutation it has acquired,

但當時還有一位科學家對這件事情很關心，是一名生態學者。

it is going to spread over the others and drive the others to extinction.

他回了家說:「我知道怎麼解決。」

So I'm going to show you a movie

他寫出Tierra系統,

where you're going to see that kind of dynamic.

根據我書裡寫的，Tierra正是最早出現的

And these kinds of experiments are started with programs that we wrote ourselves.

人造生命系統之一--

We write our own stuff, replicate it, and are very proud of ourselves.

只不過這些程式沒有真正複雜性的成長。

And we put them in, and what you see immediately

看過這個成果之後，我自己也做了一點研究,

is that there are waves and waves of innovation.

而我的研究就從此展開。

By the way, this is highly accelerated,

我決定創造一個系統,

so it's like a 1000 generations a second.

該系統必須滿足

But immediately, the system goes like, "What kind of dumb piece of code was this?

複雜演化的所有必要條件,

This can be improved upon in so many ways, so quickly."

有越來越多複雜的問題持續在演變。

So you see waves of new types taking over the other types.

當然，由於我不會編碼，所以我找了槍手。

And this type of activity goes on for quite a while,

我請到了兩位

until the main easy things have been acquired by these programs.

在加州理工學院與我共事的大學生。

And then, you see sort of like a stasis coming on

左邊的是查爾斯•奧佛瑞亞，右邊這位是提多•布朗。

where the system essentially waits

他們如今都是在密西根州立大學

for a new type of innovation, like this one,

備受尊崇的教授了,

which is going to spread over all the other innovations that were before

但我可以向你保證, 在當時

and is erasing the genes that it had before,

我們並不是可受尊敬的團隊。

until a new type of higher level of complexity has been achieved.

我很慶幸我們三人形影不離的合照,

And this process goes on and on and on.

一張都沒有留下。

So what we see here

這個系統是什麼樣子?

is a system that lives in very much the way we're used to how life goes.

我不方便探討細節,

But what the NASA people had asked me really was,

不過我可以給你們看一點內部的構造。

"Do these guys have a biosignature?

我著重的是

Can we measure this type of life?

這種族群結構圖。

Because if we can,

這裡大約有一萬個程式。

maybe we have a chance of actually discovering life somewhere else

每個種類都用不同顏色來分類。

without being biased by things like amino acids."

你會發現族群間會相互掩蓋,

So I said, "Well, perhaps we should construct a biosignature

因為它們散播開來了。

based on life as a universal process.

不論何時都有一個程式

In fact, it should perhaps make use of the concepts that I developed

較能夠在虛擬世界中存活下來,

just in order to sort of capture what a simple living system might be."

因為經過突變的過程,

And the thing I came up with --

這個程式將會蓋過其它群體甚至把它們趕盡殺絕。

I have to first give you an introduction about the idea,

在我接下來要放的影片裡你們可以觀察到這樣的變化。

and maybe that would be a meaning detector,

這個實驗是從我們

rather than a life detector.

自行開發的程式進行的。

And the way we would do that --

我們寫了程式, 然後進行複製,

I would like to find out how I can distinguish text

我們對此感到非常驕傲。

that was written by a million monkeys, as opposed to text that is in our books.

我們把程式放到系統裡,

And I would like to do it in such a way

就成了你現在看到不斷變動的波形。

that I don't actually have to be able to read the language,

順便提一下，這段影片是加快播放,

because I'm sure I won't be able to.

所以變化的速度大約是一秒衍生一千次。

As long as I know that there's some sort of alphabet.

很快系統就有了改變,

So here would be a frequency plot

「這究竟是什麼蠢代碼呢?

of how often you find each of the 26 letters of the alphabet

這可以藉由很多種方法

in a text written by random monkeys.

快速獲得改善。」

And obviously, each of these letters comes off about roughly equally frequent.

你可以看到新種類

But if you now look at the same distribution in English texts,

取代其它種類的過程。

it looks like that.

這樣子的過程會持續一段時間,

And I'm telling you, this is very robust across English texts.

直到這些程式把大多數單純的結構納入為止。

And if I look at French texts, it looks a little bit different,

接下來系統會面臨停滯期,

or Italian or German.

系統在等待一個

They all have their own type of frequency distribution,

全新的轉變，就像這樣。

but it's robust.

它將會覆蓋

It doesn't matter whether it writes about politics or about science.

先前所有的變化

It doesn't matter whether it's a poem or whether it's a mathematical text.

並且消滅之前所有的基因,

It's a robust signature,

直到系統演化到更具複雜性的層面。

and it's very stable.

這個過程會不斷重複上演。

As long as our books are written in English --

所以我們在這看到的

because people are rewriting them and recopying them --

就是一個與我們熟悉的

it's going to be there.

生命形式雷同的系統。

So that inspired me to think about, well, what if I try to use this idea

但NASA官員問我的是

in order, not to detect random texts from texts with meaning,

「這些玩意兒

but rather detect the fact that there is meaning

有生命跡象嗎?」

in the biomolecules that make up life.

我們可不可以衡量這樣的生命形式?

But first I have to ask:

因為如果我們可以,

what are these building blocks,

也許我們就能以客觀角度

like the alphabet, elements that I showed you?

證實其它星球有生命存在,

Well it turns out, we have many different alternatives