but we don't normally think of cancer

每個人都熟悉癌症，

as being a contagious disease.

但是一般我們並不認為癌症

The Tasmanian devil has shown us

是一種傳染性疾病。

that, not only can cancer be a contagious disease,

然而塔司馬尼亞惡魔告訴我們

but it can also threaten

癌症不僅是一種傳染性疾病

an entire species with extinction.

而且它會威脅到

So first of all, what is a Tasmanian devil?

整個物種的存亡。

Many of you might be familiar with Taz, the cartoon character,

所以，首先，什麼是塔司馬尼亞惡魔呢？

the one that spins around and around and around.

許多人或許很熟悉塔司，

But not many people know

那個總是不斷旋轉的卡通動物。

that there actually is a real animal called the Tasmanian devil,

但是，並不是很多人知道

and it's the world's largest carnivorous marsupial.

實際上真的有一種動物叫做塔司馬尼亞惡魔，

A marsupial is a mammal with a pouch

而且牠是世界上最大的肉食性有袋類動物。

like a kangaroo.

有袋類動物是一種有一個口袋的哺乳類動物

The Tasmanian devil got its name

比如袋鼠。

from the terrifying nocturnal scream that it makes.

塔司馬尼亞惡魔得名于

(Screaming)

牠在夜間發出的可怕尖叫聲。

(Laughter)

（尖叫）

The Tasmanian devil is predominantly a scavenger,

（笑）

and it uses its powerful jaws

塔司馬尼亞惡魔主要以食腐為生。

and its sharp teeth

牠用有力的下顎

to chomp on the bones of rotting dead animals.

和尖銳的牙齒

[The] Tasmanian devil is found only on the island of Tasmania,

啃食腐爛的動物屍體。

which is that small island

唯有塔司馬尼亞島上才有這種動物。

just to the south of the mainland of Australia.

這個小島

And despite their ferocious appearance,

就在澳洲大陸南方

Tasmanian devils are actually

盡管長相兇惡，

quite adorable little animals.

塔司馬尼亞惡魔實際上

In fact, growing up in Tasmania,

是一種很可愛的動物。

it always was incredibly exciting

實際上，牠在塔司馬尼亞成長，

when we got a chance to see

當我們有機會

a Tasmanian devil in the wild.

在野外親眼看見塔司馬尼亞惡魔時

But the Tasmanian devil population

總是會感到非常興奮。

has been undergoing a really extremely fast decline.

但是塔司馬尼亞惡魔的數量

And in fact, there's concern

卻在急速減少中。

that the species could go extinct in the wild

實際上，有人擔心

within 20 to 30 years.

這種動物可能會在20至30年間

And the reason for that

滅絕

is the emergence of a new disease,

原因是

a contagious cancer.

一種新疾病的出現，

The story begins in 1996

一種具傳染性的癌症。

when a wildlife photographer took this photograph here

事情起自於1996年

of a Tasmanian devil

一個野生攝影師拍下這張

with a large tumor on its face.

塔司馬尼亞惡魔的照片。

At the time, this was thought to be a one-off.

牠的臉上有一個巨大的腫瘤。

Animals, just like humans,

當時，人們認為這是偶發狀況。

sometimes get strange tumors.

因為動物，就像人一樣，

However, we now believe

有時也會長奇怪的腫瘤。

that this is the first sighting of a new disease,

然而，我們現在相信，

which is now an epidemic spreading through Tasmania.

這是某種目前正在塔司馬尼亞蔓延

The disease was first sighted

的傳染性疾病，最早被目擊的案例。

in the northeast of Tasmania in 1996

這種疾病最早

and has spread across Tasmania like a huge wave.

是在1996年塔司馬尼亞州的東北部被發現的，

Now there's only a small part of the population,

其後就如大浪般席捲了整個塔司馬尼亞。

which remains unaffected.

現在僅有一小部分

This disease appears first as tumors,

未受傳染。

usually on the face or inside the mouth

通常，在臉上或嘴裡

of affected Tasmanian devils.

長出腫瘤

These tumors inevitably grow into larger tumors,

是塔司馬尼亞惡魔被感染後的第一病徴。

such as these ones here.

之後腫瘤就越長越大，勢不可擋，

And the next image I'm going to show

就像這些一樣。

is quite gruesome.

我要讓各位看的下一張圖片

But inevitably, these tumors progress

十分可怕。

towards being enormous, ulcerating tumors like this one here.

但是，無可奈何是，這些腫瘤會

This one in particular sticks in my mind,

越長越大，就像這個巨大的潰瘍性腫瘤。

because this is the first case of this disease

這一個我特別難忘，

that I saw myself.

因為這是在此種疾病中

And I remember the horror of seeing this little female devil

我所見到的第一個案例。

with this huge ulcerating, foul-smelling tumor

我還記得我見到這隻母塔司時的恐懼感覺。

inside her mouth

她的嘴裏長着一個非常大的潰瘍性腫瘤

that had actually cracked off her entire lower jaw.

散發出難聞的氣味。

She hadn't eaten for days.

腫瘤使她的整個下顎崩塌，

Her guts were swimming with parasitic worms.

她好幾天沒吃東西。

Her body was riddled with secondary tumors.

她的肚子裏有許多寄生蟲，

And yet, she was feeding three little baby Tasmanian devils

她的身上長滿了繼發性腫瘤，

in her pouch.

但是，她還在餵她口袋裏的

Of course, they died along with the mother.

三個小寶貝。

They were too young to survive without their mother.

當然，在母親去世後，牠們也跟着去了。

In fact, in the area where she comes from,

因為牠們還太小，無法離開母親。

more than 90 percent of the Tasmanian devil population

實際上在她生活的地區

has already died of this disease.

已有百分之九十以上的塔司馬尼亞惡魔死於

Scientists around the world

這種疾病。

were intrigued by this cancer,

全世界的科學傢

this infectious cancer,

都對這種癌症很感興趣，

that was spreading through the Tasmanian devil population.

這種傳染性的癌症

And our minds immediately turned to cervical cancer in women,

在塔司馬尼亞惡魔中傳播，

which is spread by a virus,

讓我們不由立即想起子宮頸癌

and to the AIDS epidemic,

也是由病毒傳播的，

which is associated with a number of different types of cancer.

還有愛滋病的傳播

All the evidence suggested that this devil cancer

和好幾種不同類型的癌症有關。

was spread by a virus.

所有的證據都表明塔司馬尼亞惡魔所得的癌症

However, we now know -- and I'll tell you right now --

是由病毒傳染的。

that we know that this cancer is not spread by a virus.

但是，我們現在知道－我現在就告訴各位：

In fact, the infectious agent of disease in this cancer

這種癌症並非由病毒傳染。

is something altogether more sinister,

實際上，這種癌症的傳染性病原體

and something that we hadn't really thought of before.

非常兇險，

But in order for me to explain what that is,

而且是我們以前甚至不曾想到的。

I need to spend just a couple of minutes

但是為了向各位解釋它究竟是什么，

talking more about cancer itself.

我需要花一兩分鐘的時間，

Cancer is a disease

談談癌症本身。

that affects millions of people around the world every year.

癌症這種疾病

One in three people in this room

每年感染全球數百萬人

will develop cancer at some stage in their lives.

在座的三分之一

I myself had a tumor removed from my large intestine

將會在今後人生的不同階段患上癌症

when I was only 14.

我自己就曾動過大腸腫瘤切除手術，

Cancer occurs

當時我年僅14歲。

when a single cell in your body

癌症的發生

acquires a set of random mutations in important genes

是由於體內某個細胞中

that cause that cell to start to produce

的重要基因發生了一系列突變，

more and more and more copies of itself.

導致該細胞開始

Paradoxically, once established,

不斷自我複製。

natural selection actually favors

矛盾的是，一旦出現這種情況，

the continued growth of cancer.

‘自然選擇’實際上更傾向於

Natural selection is survival of the fittest.

不斷增長的癌症。

And when you have a population of fast-dividing cancer cells,

因為‘自然選擇’就是適者生存。

if one of them acquires new mutations,

當你有相當數目的快速分裂的癌細胞時，

which allow them to grow more quickly,

如果其中之一發生新的突變

acquire nutrients more successfully,

而增長更為迅速

invade the body,

更成功的獲得營養

they'll be selected for by evolution.

侵入身體，

That's why cancer is such a difficult disease to treat.

它就會成為演變的選擇。

It evolves.

這就是癌症如此難以治療的原因。

Throw a drug at it,

因為它會進化。

and resistant cells will grow back.

對它用藥，

An amazing fact is that,

抗性細胞會重新生長。

given the right environment and the right nutrients,

驚人的事實是，

a cancer cell has the potential

如果有合適的環境和營養，

to go on growing forever.

一個癌細胞就有可能

However cancer is constrained

永遠生長下去。

by living inside our bodies,

可是癌症

and its continued growth,

受到生活在我們體內的限制，

its spreading through our bodies

如果它繼續生長，

and eating away at our tissues,

就會遍佈我們的身體

leads to the death of the cancer patient

啃噬我們的組織，

and also to the death of the cancer itself.

導致癌症病人死亡

So cancer could be thought of

最後自己也被消滅。

as a strange, short-lived, self-destructive life form --

所以癌症是一種

an evolutionary dead end.

奇怪的，短命的，自我毀滅的生命形式－－

But that is where the Tasmanian devil cancer

一種演化的死亡終結。

has acquired an absolutely amazing

但是塔司馬尼亞惡魔所得的癌症

evolutionary adaptation.

卻獲得了一種絕對神奇的

And the answer came from studying

進化適應。

the Tasmanian devil cancer's DNA.

這個結論是來自

This was work from many people,

對塔司馬尼亞惡魔的癌症DNA研究。

but I'm going to explain it through a confirmatory experiment

這項研究工作有許多人參與，

that I did a few years ago.

但是我想通過一個驗證實驗來向大家解釋。

The next slide is going to be gruesome.

這個試驗是在好幾年前做的。

This is Jonas.

下一張幻燈片會很可怕。

He's a Tasmanian devil that we found

這是喬納斯。

with a large tumor on his face.

我們發現這隻塔司馬尼亞惡魔

And being a geneticist,

的臉上長着巨大的腫瘤。

I'm always interested to look at DNA and mutations.

我是基因學家，

So I took this opportunity

對于DNA 和突變總是很感興趣。

to collect some samples from Jonas' tumor

所以我抓住這個機會，

and also some samples from other parts of his body.

從喬納斯的腫瘤當中取樣，

I took these back to the lab.

同時也從它身體的其它部分取樣。

I extracted DNA from them.

我把這些樣本帶回實驗室

And when I looked at the sequence of the DNA,

從中提取DNA。

and compared the sequence of Jonas' tumor

我研究喬納斯的DNA序列，

to that of the rest of his body,

把它的腫瘤DNA的序列

I discovered that they had a completely different genetic profile.

和它身體其它部分作比較。

In fact, Jonas and his tumor

我發現它們的基因圖譜完全不同。

were as different from each other

實際上，喬納斯和它身上的腫瘤的基因

as you and the person sitting next to you.

就好像妳和妳的鄰座的一樣

What this told us was that Jonas' tumor

完全不同。

did not arise from cells of his own body.

這說明喬納斯的腫瘤

In fact, more genetic profiling

不是來自於它自身的細胞

told us that this tumor in Jonas

實際上，更多的基因圖譜

actually probably first arose

告訴我們喬納斯的這個腫瘤

from the cells of a female Tasmanian devil --

最早可能是來自於

and Jonas was clearly a male.

一隻母惡魔的細胞，

So how come

而喬納斯是公的。

a tumor that arose from the cells of another individual

那麼，為什么

is growing on Jonas' face?

一個來自別人細胞的腫瘤

Well the next breakthrough

會長在喬納斯的臉上呢？

came from studying hundreds of Tasmanian devil cancers

下一個突破

from all around Tasmania.

來自于對于整個塔司馬尼亞地區數百隻

We found that all of these cancers

塔司馬尼亞惡魔的研究。

shared the same DNA.

我們發現所有的癌症

Think about that for a minute.

有同樣的DNA。

That means that all of these cancers

想一想吧。

actually are the same cancer

這說明這些癌症

that arose once from one individual devil,

實際上是來源於

that have broken free of that first devil's body

一隻塔司馬尼亞惡魔，

and spread through the entire Tasmanian devil population.

癌細胞突破了這隻惡魔的身體

But how can a cancer spread in a population?

傳染到整個種群。

Well the final piece of the puzzle came

可是癌症是怎樣在整個族群裡傳播的呢？

when we remember how devils behave when they meet each other in the wild.

最後一個謎團終於解開。

They tend to bite each other,

我們想起它們在野外見面時的表現。

often quite ferociously and usually on the face.

它們喜歡啃咬對方

We think that cancer cells

常常很兇猛，而且通常是咬對方的臉。

actually come off the tumor, get into the saliva.

我們認為癌細胞

When the devil bites another devil,

是從腫瘤脫落，進入唾液的。

it actually physically implants living cancer cells into the next devil,

當一隻惡魔咬了另一隻的時候，

so the tumor continues to grow.

實際上它把活的癌細胞移植到另一隻的體內，

So this Tasmanian devil cancer

由此腫瘤就繼續生長。

is perhaps the ultimate cancer.

所以這隻塔司馬尼亞惡魔感染的

It's not constrained by living within the body that gave rise to it.

可能就是已發展的癌症。

It spreads through the population,

從而使得這種癌症不受限於在體內生長，

has mutations that allow it to evade the immune system,

而可以在整個族群中傳播。

and it's the only cancer that we know of

它的突變體使其得以避開免疫系統。

that's threatening an entire species with extinction.

它是我們所知道的唯一一種

But if this can happen in Tasmanian devils,

威脅到整個種群生存的癌症。

why hasn't it happened in other animals

但是，既然塔司馬尼亞惡魔會患上這種癌症，

or even humans?

為什麼其他動物，

Well the answer is, it has.

或者說人類就不會感染呢？

This is Kimbo.

實際上已經有了。

He's a dog that belongs to a family in Mombasa in Kenya.

這是金波，

Last year, his owner noticed some blood

是一個住在肯亞盟巴撒島的家庭所養的一隻小狗。

trickling from his genital region.

去年，牠的主人發現

She took him to the vet

牠的生殖器部位淌血。

and the vet discovered something quite disgusting.

她帶牠去看獸醫。

And if you're squeamish, please look away now.

而獸醫發現情況頗為糟糕。

He discovered this,

如果你覺得噁心，請不要看下面的畫面。

a huge bleeding tumor

他發現了這個，

at the base of Kimbo's penis.

巨大的出血性腫瘤

The vet diagnosed this as transmissible venereal tumor,

長在金波的隂莖底部。

a sexually transmitted cancer

根據獸醫的診斷，這是傳染性花柳腫瘤

that affects dogs.

是一種犬類會經過性行為感染的

And just as the Tasmanian devil cancer is contagious

傳染性癌症。

through the spread of living cancer cells,

正如塔司馬尼亞惡魔所患的癌症，

so is this dog cancer.

是通過感染癌症活細胞而傳播的，

But this dog cancer is quite remarkable,

這隻狗也是同樣情況。

because it spread all around the world.

但是牠的癌症更驚人

And in fact, these same cells

因為這種癌症傳播到全世界。

that are affecting Kimbo here

實際上，同樣的細胞

are also found affecting dogs

在此感染到金波，

in New York City,

也一樣感染到

in mountain villages in the Himalayas

紐約市、

and in Outback Australia.

喜馬拉雅山村、

We also believe this cancer might be very old.

和澳洲內地的狗。

In fact, genetic profiling tells

我們還認為這種癌症的來歷可能非常久遠。

that it may be tens of thousands of years old,

事實上，根據基因圖譜，

which means that this cancer

這種癌症可能已有超過萬年以上的歷史。

may have first arisen

這意味著這種癌症

from the cells of a wolf

最早可能是

that lived alongside the Neanderthals.

來自那些住在

This cancer is remarkable.

尼安德塔人聚落附近的狼群。

It's the oldest mammalian-derived life form that we know of.

這個癌症很驚人，

It's a living relic

因為這是我們迄今所知最古老的哺乳類生命，

of the distant past.

是遠古時代的

So we've seen that this can happen in animals.

活化石。

Could cancers be contagious between people?

我們已經看到這在動物身上發生，

Well this is a question

那麼癌症是否也會在人們之間傳染呢？

which fascinated Chester Southam,

這個問題

a cancer doctor in the 1950s.

吸引了50年代的

Ad he decided to put this to the test

一位癌症專傢－－切斯特.索思姆。

by actually deliberately inoculating people

他決定做一個試驗，

with cancer from somebody else.

將癌症病人的細胞

And this is a photograph of Dr. Southam in 1957

注射到其他人體內。

injecting cancer into a volunteer,

這張照片是1957年索思姆醫生

who in this case was an inmate

將癌細胞注射到在監獄服刑

in Ohio State Penitentiary.

的志願囚犯身體的照片。

Most of the people that Dr. Southam injected