演講MP3+雙語文稿:巖石與生命起源的真相

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聽力課堂TED音頻欄目主要包括TED演講的音頻MP3及中英雙語文稿，供各位英語愛好者學(xué)習(xí)使用。本文主要內(nèi)容為演講MP3+雙語文稿:巖石與生命起源的真相，希望你會喜歡！

【演講者及介紹】Tara Djokic

Tara Djokic，天體生物學(xué)家，發(fā)現(xiàn)直接證據(jù)證明地球上一些最古老的生命曾經(jīng)在陸地上的溫泉中繁衍。

【演講主題】這塊古老的巖石正在改變我們關(guān)于生命起源的理論

【中英文字幕】

Translated by Yan Gao. Reviewed by Yolanda Zhang

00:17

The Earth is 4.6 billion years old, but ahuman lifetime often lasts for less than 100 years. So why care about thehistory of our planet when the distant past seems so inconsequential toeveryday life? You see, as far as we can tell, Earth is the only planet in oursolar system known to have sparked life, and the only system able to providelife support for human beings.

地球的壽命有46億年，但人類的壽命還不到100年。那我們?yōu)槭裁匆P(guān)心地球歷史呢，它那么遙遠(yuǎn)，好像與我們的生活完全無關(guān)。就我們所知，在太陽系里，只有地球擁有燦爛的生命，也只有地球能提供讓人類存活的環(huán)境。

00:50

So why Earth? We know Earth is unique forhaving plate tectonics, liquid water on its surface and an oxygen-richatmosphere. But this has not always been the case, and we know this becauseancient rocks have recorded the pivotal moments in Earth's planetary evolution.And one of the best places to observe those ancient rocks is in the Pilbara ofWestern Australia. The rocks here are 3.5 billion years old, and they containsome of the oldest evidence for life on the planet.

為什么偏偏是地球？我們知道地球是獨(dú)一無二的，它有板塊構(gòu)造、表面有液體水、 還有富含氧氣的大氣層。但并不是一直這樣，因?yàn)楣艓r石記錄了地球演化過程中的每個(gè)關(guān)鍵時(shí)刻。觀察古巖石的最佳去處之一，是澳大利亞西部的皮爾布拉。這里的巖石存在了 35 億年之久，其中藏著地球上最早期生命的證據(jù)。

01:29

Now, often when we think of early life, wemight imagine a stegosaurus or maybe a fish crawling onto land. But the earlylife that I'm talking about is simple microscopic life, like bacteria. Andtheir fossils are often preserved as layered rock structures, calledstromatolites. This simple form of life is almost all we see in the fossilrecord for the first three billion years of life on Earth. Our species can onlybe traced back in the fossil record to a few hundred thousand years ago. Weknow from the fossil record, bacteria life had grabbed a strong foothold byabout 3.5 to four billion years ago. The rocks older than this have been eitherdestroyed or highly deformed through plate tectonics. So what remains a missingpiece of the puzzle is exactly when and how life on Earth began. Here again isthat ancient volcanic landscape in the Pilbara. Little did I know that ourresearch here would provide another clue to that origin-of-life puzzle.

通常，說起古生命時(shí)，我們想到的是劍龍，或者一種魚爬到了陸地上。但我說的古生命，是簡單微生物，比如細(xì)菌。它們的化石通常是層疊的巖石結(jié)構(gòu)，稱為疊層石。地球出現(xiàn)生命的前 30 億年里，化石記錄中幾乎只能見到這種簡單的生命形式。在化石記錄中尋找人類的蹤跡，只能追蹤到幾萬年前。從化石記錄中我們了解到，細(xì)菌生命開始得很早，大約 35 至 40 億年前就存在了。而比這個(gè)時(shí)間更久的巖石，要么被破壞了，要么隨板塊運(yùn)動過度變形。所以遺留下來一個(gè)待解決的難題就是，地球上的生命到底是什么時(shí)間開始的。回到皮爾布拉的古火山地貌。我當(dāng)時(shí)完全不知道，我們在這里的研究會給生命起源之謎提供另一個(gè)線索。

02:46

It was on my first field trip here, towardthe end of a full, long week mapping project, that I came across somethingrather special. Now, what probably looks like a bunch of wrinkly old rocks areactually stromatolites. And at the center of this mound was a small, peculiarrock about the size of a child's hand. It took six months before we inspectedthis rock under a microscope, when one of my mentors at the time, MalcolmWalter, suggested the rock resembled geyserite. Geyserite is a rock type thatonly forms in and around the edges of hot spring pools.

那是我第一次到這里實(shí)地考察，在整整一周的地圖繪制項(xiàng)目快要結(jié)束時(shí)，我發(fā)現(xiàn)了一件不尋常的東西。這一堆紋路橫生的石頭，其實(shí)是疊層石。在這一堆的中間，是一塊小小的罕見的巖石，像小孩的手那么大。我們花了六個(gè)月才得以在顯微鏡下觀察它，當(dāng)時(shí)我的一位老師，馬爾科姆·沃爾特，提出這石頭像硅華。硅華是一種巖石類型，它的形成地只在熱泉池里面和邊緣周圍。

03:30

Now, in order for you to understand thesignificance of geyserite, I need to take you back a couple of centuries. In1871, in a letter to his friend Joseph Hooker, Charles Darwin suggested:"What if life started in some warm little pond with all sort of chemicalsstill ready to undergo more complex changes?"

為了讓各位理解硅華的重要，我要帶大家回到十九世紀(jì)。1871年，查爾斯·達(dá)爾文在信中對他的朋友約瑟夫·虎克說：“如果生命是在一些溫暖的小池塘里誕生呢——池塘里有各種化學(xué)物質(zhì)，已準(zhǔn)備好進(jìn)行更復(fù)雜的進(jìn)化呢？”

03:56

Well, we know of warm little ponds. We callthem "hot springs." In these environments, you have hot waterdissolving minerals from the underlying rocks. This solution mixes with organiccompounds and results in a kind of chemical factory, which researchers haveshown can manufacture simple cellular structures that are the first stepstoward life.

我們知道這些溫暖的小池塘指的是“溫泉”。在這類環(huán)境中，有熱水，從底下的巖石里溶解出礦物質(zhì)。這種液體與有機(jī)化合物混合，形成了某種化學(xué)環(huán)境，而研究人員已證明這種化學(xué)環(huán)境可以產(chǎn)生簡單的細(xì)胞結(jié)構(gòu)，這種細(xì)胞結(jié)構(gòu)就是邁向生命起源的第一步。

04:23

But 100 years after Darwin's letter,deep-sea hydrothermal vents, or hot vents, were discovered in the ocean. Andthese are also chemical factories. The black smoke that you see billowing outof these chimneylike structures is also mineral-rich fluid, which is being fedoff by bacteria. And since the discovery of these deep-sea vents, the favoredscenario for an origin of life has been in the ocean. And this is for goodreason: deep-sea vents are well-known in the ancient rock record, and it'sthought that the early Earth had a global ocean and very little land surface.So the probability that deep-sea vents were abundant on the very early Earthfits well with an origin of life in the ocean.

但達(dá)爾文寫出這封信之后的一百年，海洋里發(fā)現(xiàn)了深海熱液噴口，即熱泉。這些也是化學(xué)環(huán)境。從這些煙囪一樣的結(jié)構(gòu)里飄出的“黑煙”，也是富含礦物質(zhì)的液體，是細(xì)菌的食物來源。自從發(fā)現(xiàn)了這些深海熱泉，生命起源地的說法就聚焦在海洋。這是很合理的：深海熱泉在古巖石記錄中很常見，通常認(rèn)為地球早期整體被海洋覆蓋，陸地表面極少。所以，地球最初擁有大量深海熱泉，與之非常符合的情況是生命在海洋里起源。

05:20

However ... our research in the Pilbaraprovides and supports an alternative perspective. After three years, finally,we were able to show that, in fact, our little rock was geyserite. So thisconclusion suggested not only did hot springs exist in our 3.5 billion-year-oldvolcano in the Pilbara, but it pushed back evidence for life living on land inhot springs in the geological record of Earth by three billion years. And so,from a geological perspective, Darwin's warm little pond is a reasonableorigin-of-life candidate.

但是——我們在皮爾巴拉的研究給出了另一種視角和證據(jù)。三年后，我們終于能證明，實(shí)際上，這塊小石頭就是硅華。這個(gè)結(jié)論說明，不僅皮爾巴拉有 35 億年歷史的火山里有溫泉，而且意味著，在地球的地質(zhì)記錄中，生命在陸地的熱泉中存活的證據(jù)，向前推了 30 億年。所以，從地質(zhì)角度來看，達(dá)爾文說的小池塘是合理的生命起源地。

06:13

Of course, it's still debatable how lifebegan on Earth, and it probably always will be. But it is clear that it'sflourished; it has diversified, and it has become ever more complex.Eventually, it reached the age of the human, a species that has begun toquestion its own existence and the existence of life elsewhere: Is there acosmic community waiting to connect with us, or are we all there is?

當(dāng)然，地球生命起源的方式仍有待探討，也許可以永遠(yuǎn)爭論下去。但有一點(diǎn)很清楚，生命已經(jīng)蓬勃發(fā)展起來；它變得多樣了，還越來越復(fù)雜。最終，到達(dá)了人類的時(shí)代，人類這個(gè)物種開始質(zhì)疑自身的存在，也質(zhì)疑外星球生命的存在：有宇宙聯(lián)盟要與我們聯(lián)系嗎，還是宇宙只有人類孤單存在？

06:42

A clue to this puzzle again comes from theancient rock record. At about 2.5 billion years ago, there is evidence thatbacteria had begun to produce oxygen, kind of like plants do today. Geologistsrefer to the period that followed as the Great Oxidation Event. It is impliedfrom rocks called banded iron formations, many of which can be observed ashundreds-of-meter-thick packages of rock which are exposed in gorges that carvetheir way through the Karijini National Park in Western Australia. The arrivalof free oxygen allowed two major changes to occur on our planet.

關(guān)于這個(gè)問題的線索再次出現(xiàn)在古巖石記錄中。大約 25 億年前，有證據(jù)表明，細(xì)菌已經(jīng)開始產(chǎn)生氧氣，有點(diǎn)像現(xiàn)在的植物產(chǎn)生氧氣。地質(zhì)學(xué)家把隨后的那段時(shí)期稱為“大氧化事件”。這一推測是從稱為帶狀鐵形成區(qū)的巖石里得出的，這種層層堆疊的巖石大多幾百米厚，位于澳大利亞西部，在橫穿卡瑞吉尼國家公園的峽谷里可以看到。游離氧的到來讓我們的星球發(fā)生了兩個(gè)重大變化。

07:25

First, it allowed complex life to evolve.You see, life needs oxygen to get big and complex. And it produced the ozonelayer, which protects modern life from the harmful effects of the sun's UVBradiation. So in an ironic twist, microbial life made way for complex life, andin essence, relinquished its three-billion-year reign over the planet. Today,we humans dig up fossilized complex life and burn it for fuel. This practicepumps vast amounts of carbon dioxide into the atmosphere, and like ourmicrobial predecessors, we have begun to make substantial changes to ourplanet. And the effects of those are encompassed by global warming.

首先，氧氣讓復(fù)雜生命得以進(jìn)化。生命需要氧氣來變大、變復(fù)雜。氧氣還制造了臭氧層，它保護(hù)現(xiàn)代生命不受陽光中波紫外線輻射的傷害。諷刺的是，微生物艱難進(jìn)化成復(fù)雜生命，在這顆星球上耗費(fèi)了 30 億年的時(shí)光。今天，我們?nèi)祟惏炎兂苫膹?fù)雜生命挖出來，把它們當(dāng)燃料燒掉。這種行為會釋放出大量二氧化碳到大氣，就像我們的微生物祖先一樣，我們已經(jīng)開始讓這顆星球發(fā)生了重大變化。這些改變的結(jié)果包括全球變暖。

08:14

Unfortunately, the ironic twist here couldsee the demise of humanity. And so maybe the reason we aren't connecting withlife elsewhere, intelligent life elsewhere, is that once it evolves, itextinguishes itself quickly.

不幸的是，這個(gè)諷刺會指向人類的終結(jié)。也許我們聯(lián)系不到外星生物、聯(lián)系不到外星智慧生物的原因，是一旦智慧生物進(jìn)化了，就會很快自取滅亡。

08:32

If the rocks could talk, I suspect theymight say this: life on Earth is precious. It is the product of four or sobillion years of a delicate and complex co-evolution between life and Earth, ofwhich humans only represent the very last speck of time. You can use thisinformation as a guide or a forecast -- or an explanation as to why it seems solonely in this part of the galaxy. But use it to gain some perspective aboutthe legacy that you want to leave behind on the planet that you call home.

如果巖石能說話，我感覺它們會說：地球上的生命是寶貴的。它的誕生用了大約 40 億年，經(jīng)歷了生命與地球之間精細(xì)復(fù)雜的共同進(jìn)化，而人類只在這 40 億年的最后一瞬間存在過。這些信息可以為你提供指引或預(yù)測——或者說是解釋，為什么銀河系的地球如此孤單。但是，通過這些信息多想想吧，在這個(gè)我們稱為家園的星球上，人類要留下些什么。

09:28

Thank you.

謝謝。

09:29

(Applause)

（掌聲）