人类之外的生命体也许即将诞生

心灵

生命之源：试管中的伊甸园 为了更好的识别出不期而遇的地外生命，科学家们正致力于在实验室里创造简单的生 ...

生命之源：试管中的伊甸园 为了更好的识别出不期而遇的地外生命，科学家们正致力于在实验室里创造简单的生命。但就像记者所报道的一样，科学家们应当首先对生命的概念有一个认识。

---

SAN DIEGO — Here in a laboratory perched on the edge of the continent, researchers are trying to construct Life As We Don’t Know It in a thimbleful of liquid.

　　圣迭戈 — 坐落在这里一个大陆岬角上的一间实验室里，研究人员正在试图制造“我们所不了解的以一点儿液体形态存在的生命”*。

Generations of scientists, children and science fiction fans have grown up presuming that humanity’s first encounter with alien life will happen in a red sand dune on Mars, or in an enigmatic radio signal from some obscure star.

　　一代一代的科学家、少年儿童和科幻小说迷们都是这样长大成人的，他们设想着人类和外星人的首次接触会发生在火星红色的沙丘上或者在来自一些暗淡星球的神秘无线电信号中。

But it could soon happen right here on Earth, according to a handful of chemists and biologists who are using the tools of modern genetics to try to generate the Frankensteinian spark that will jump the gap separating the inanimate and the animate. The day is coming, they say, when chemicals in a test tube will come to life.

　　但是按照一些化学家和生物学家的说法，这些场景也许不久就会出现在地球上。他们正在利用现代遗传技术制造跨越无生命物质和有生命物质的“弗兰肯斯坦”火花（译注：弗兰肯斯坦，Frankensteinian，自己创造的东西却毁灭了自己的怪物）。这一天即将到来，如科学家所言，化学物质在试管里将会转化为生命。

By some measures, Gerald F. Joyce, a professor at the Scripps Research Institute here, has already crossed that line, although he would be the first to say he has not — yet.

　　尽管斯克里普斯研究所教授杰拉尔德·F·乔伊斯可能成为首位矢口否认的人，然而通过某些手段，他已经突破了上述界限。

Biologists do not agree on what the definition of life should be or whether it is even useful to have one. But most do agree that the ability to evolve and adapt is fundamental to life. And they also agree that having a second example of life could provide insight to how it began and how special life is or is not in the universe, as well as a clue for how to recognize life if and when we do stumble upon it out there among the stars.

　　生物学家并不赞成对生命妄加定义或者生命有了定义才会对科学研究有价值的说法，但是他们大部分人都同意进化和适应的能力是生命的基础。他们也赞同有了生命的第二实例可以为人类提供一种洞察力：生命是如何开始的？在宇宙中，生命有多么特殊或者多么的不特殊？同时还可以提供我们一个线索：如果我们（或者说当我们）在那些星球上偶然发现了它时，我们如何认出那就是生命？

“Everything we know about life is based on studies of life on Earth,” said Chris McKay, a researcher at NASA’s Ames Research Laboratory in Mountain View, Calif.

　　克里斯·麦凯是加州山景城NASA艾姆斯研究实验室的研究人员。他说，“我们知道的所有有关生命的内容都是基于地球生命的研究成果。”

Dr. Joyce said recently: “It drives me crazy when astronomers say, ‘Surely the universe is pregnant with life.’ If we have an Earthlike planet, what are the chances of life arising? Is it one in a million? Is it one in two? I don’t see how you can say.”

　　乔伊斯博士最近说：“听到宇航员说‘宇宙中确实孕育着生命。’真让我发疯。如果有一个和地球一样的星球，生命出现的几率有多大呢？百万分之一吗？还是二分之一？我知道你说不出来。”

He continued, “If you had a second example of life, even if it were synthetic, you might know better. I’m betting we’re just going to make it.”

　　他继续道，“如果你有了生命的第二实例，即使它是合成的，你对生命的了解也会更深一步。我愿意打赌，我们就要合成生命了。”

Four years ago Dr. Joyce and a graduate student, Tracey A. Lincoln, now a researcher at the University of Massachusetts Medical School, evolved a molecule in a test tube that could replicate and evolve all by itself, swapping little jerry-built genes in a test tube forever, as long as it was supplied with the right carefully engineered ingredients.

　　4年前乔伊斯博士和研究生特雷西·A·林肯（现为马萨诸塞大学医学院的研究人员）在试管中演化生成一个分子，它完全可以自行复制和进化。只要为它提供完全细致的设计好的辅料，它就会在试管中不断地交换生成少量不完整的基因。

An article in the Joyce Laboratory newsletter called it “The Immortal Molecule.” Dr. Joyce’s molecule is a form of RNA, or ribonucleic acid, which plays Robin to DNA’s Batman in Life As We Do Know It, assembling proteins in accordance with the blueprint encoded in DNA. Neither RNA nor DNA is alive by itself, any more than any other chemical, like bleach, or a protein. But in Dr. Joyce’s test tube, his specially engineered RNA molecule comes close, copying itself over and over, and evolving.

　　乔伊斯实验室的业务通讯上有一篇文章把它称之为“不朽的分子。”乔伊斯博士的分子是某种形式的RNA，也就是核糖核酸，它就是“我们知道的世界”里的罗宾**，而DNA就是蝙蝠侠。RNA负责按照DNA中已编码的设计图组装蛋白质。RNA和DNA自身都是没有生物活性的，与任何其它诸如漂白剂或者蛋白质之类的化学物质无异。但是在乔伊斯博士的试管里，他特殊设计的RNA分子终结了我们的常识，它自己反复地复制下去并进化了。

But, Dr. Joyce says, “We really would hope for more from our molecules than just replicating.”

　　但乔伊斯博士说，“我们想看到的不仅仅是复制，我们想从我们的分子里获取更多地秘密。”

Reproduction is the job of any life, he explained, but Earthly organisms have evolved a spectacular set of tricks to improve the odds of success — everything from peacock feathers to whale songs. Dr. Joyce’s molecules have not yet surprised him by striking out on their own to invent the molecular equivalent of writing a hit pop song.

　　他解释道，复制是任何生命的本职工作，但地球上的有机体已经进化了一套令人吃惊的技巧以提高成功（复制）的几率，从孔雀的羽毛到鲸鱼的叫声莫不如此。乔伊斯博士通过自主创新发明的这种分子并未使自己陶醉，他自认为与写一首流行热歌也差不多。

It is only a matter of time, he said, before they do.

　　他说，在他们着手这个项目之前，就知道一切只是时间问题。

“Our job is to give them the running room to do that,” Dr. Joyce said.

　　“我们的工作就是给它们展示的舞台，”乔伊斯说。

The deeper philosophical and intellectual ramifications of test tube life are as enormous as they are unknown. The achievement would probably not come with sci-fi drama, say scientists who are squeamish about such matters anyway, saying such speculation is beyond their pay grade. No microbe is going to leap out of the Petri dish and call home, or turn the graduate students into zombies. Indeed, given the human penchant for argument and scientists’ habit of understatement, it could be years before everybody agrees it has been done.

　　较之于试管生命实验的神秘性，实验面临的更深层次的哲学和学术方面的后果也是巨大的。科学家们说，这项科学成果可能不会伴随着科幻小说般的戏剧性，无论如何，面对这些结果他们是非常谨慎的，套用一句官话就是这不是他们需要考虑的内容。不会有细菌从培养皿里跳出来还把培养皿称之为“家”，研究生也不会变成了什么僵尸。确实，考虑到人类喜欢争论的嗜好和科学家们习惯性的遮遮掩掩，要让每个人都认可实验的结果怎么也要几年的时间。

“The ability to synthesize life will be an event of profound importance, like the invention of agriculture or the invention of metallurgy,” Freeman Dyson, a mathematician and physicist at the Institute for Advanced Study in Princeton, wrote in an e-mail. “Nobody can tell in advance what will come of it.”

　　弗里曼·戴森是普林斯顿高等研究院的数学家和物理学家，他在一封电子邮件中写到，“就像农业的发明或者冶金学的发明一样，生命能够合成会是一个具有深远意义的事件，”“没有人会提前知道下面会发生什么。”

On Earth, all life as we know it is based on DNA, the carbon-based molecule that contains the instructions for making and operating living cells in a four-letter alphabet along its double-helix spine.

　　在地球上，我们所知道的所有生命都以DNA为基础。DNA是以碳为基础的分子，它包含了制造和操作活细胞的指令，这些指令是以四字符字母表的形式沿着它的双螺旋脊柱结构表现出来的。

The possibilities of a second example of life are as deep as the imagination. It could be based on DNA that uses a different genetic code, with perhaps more or fewer than four letters; it could be based on some complex molecule other than DNA, or more than the 20 amino acids from which our own proteins are made, or even some kind of chemistry based on something other than carbon and the other elements that we take for granted, like phosphorous or iron. Others wonder whether chemistry is necessary at all. Could life manifest itself, for example, in the pattern of electrically charged dust grains in a giant interstellar cloud, as the British astronomer and author Fred Hoyle imagined in his novel “The Black Cloud”?

　　生命第二实例的可能性超乎想像。它可能是以使用不同遗传密码的DNA为基础，遗传密码可能多于或少于4字母密码表；它也可能是基于一些复杂的分子而非DNA，或者是超过20种的氨基酸，也就是我们人类蛋白质的原料，甚至也可能是一些化学物质，但不是我们想当然的以碳和其它磷或铁之类的元素为基础。（甚至还有）其他人在猜测生命的构成是否真的离不开化学物质。举个例子，就像英国宇航员弗雷德·霍伊尔在其小说《The Black Cloud》中想象的那样，生命会清楚地证明自己在一个巨大的星云里以带电荷的灰尘颗粒形态存在吗？

Dr. Joyce said that his RNA replicators would count as such a “second example, albeit one constructed as a homage to our ancient ancestors.”

　　乔伊斯博士说，尽管他的RNA复制因子是向我们远古先人表达敬意的礼物，但仍然可以算作这样一个“第二实例”。

So far, he said, his work with Dr. Lincoln has shown that manmade molecules can evolve over successive generations. “They can pass information from parent to progeny, they can mutate,” Dr. Joyce said. “They can win or die. The molecules are doing it all. We’re just keeping the lights on.”

　　他说，迄今为止他和林肯博士的工作已经表明人造的分子可以连续进化好多代。“她们可以从父代向子代传递信息，他们可以发生突变，”“他们或生或死，一切都是分子自己在做，我们仅仅提供了必要的生存条件。”

Dr. Joyce’s molecules may not be clever enough yet to qualify as life in his view, but all sorts of alternatives are being explored in other labs.

　　以乔伊斯博士自己的观点来看，他的分子还不是那么聪明、不足以称之为生命，但是在其它的实验室里各种“生命”创造方案都在探索之中。

Some researchers, like Steven Benner of the Foundation for Applied Molecular Evolution in Florida, are constructing and experimenting with forms of DNA that use coding alphabets of more than four letters. J. Craig Venter, who helped spearhead the decoding of the human genome and now works as president of the J. Craig Venter Institute, recently used store-bought chemicals to reconstruct the genome of a bacterial goat parasite and put it in another bacterium, where it took over, churning out copies of itself with Dr. Venter’s watermark inscribed in its gene code.

　　史蒂芬·本纳（佛罗里达应用分子进化基金会）和其它一些研究者，都在制造和试验使用超过4个字母的密码表的DNA分子。J·克莱格·温特曾经率先破译人类基因组，现在是J·克莱格·温特研究所的主席，他最近使用市售的化学药品重建了一种细菌性山羊寄生虫的基因组并把基因组植到另外的细菌体内。在被控制的细菌体内，新基因组大量制造遗传密码中带有温特博士水印的基因复制品。

In a related vein, George Church and Farren Isaacs of the Harvard Medical School recently reported that they had reprogrammed the genome of an E. Coli bacterium, opening up the possibility of incorporating new features into the ubiquitous little bug. Dr. Joyce called the work “really macho molecular biotechnology.”

　　与此有关的进展还有，哈佛医学院的乔治·丘奇和法伦·艾萨克最近报告说他们重组了一种大肠杆菌的基因组，打开了把新特征加入到无处不在的小虫子体内的可能性。乔伊斯博士称这项工作是“真有胆量的分子生物技术”。

Jack Szostak of Harvard Medical School and his collaborators have embarked on an ambitious project to build an artificial cell that can replicate and presumably evolve. Dr. Benner wrote in an e-mail, “In my view, a terran laboratory will make synthetic life before NASA or the E.S.A. finds it elsewhere,” referring to the European Space Agency. He added, “And a lot before, given the disassembling of NASA by the current administration.”

　　哈佛医学院的杰克·绍斯塔克及其合作者正在着手推进一个雄心勃勃的计划，制造一个可以复制并可能进化的人造细胞。本纳博士在一封邮件中写到，“在我看来，地球人的实验室会在NASA和ESA在其它星球找到生命之前造出合成生命”，这里的 ESA就是指欧洲空间局（European Space Agency）。他补充道，“考虑到NASA被当局拆分的可能性，（即便有地外生命，）NASA也是心有余而力不足了。”

According to modern science, life on Earth originated about 3.8 billion years ago, perhaps in a warm pond, as Darwin speculated, or perhaps in a boiling, bubbling mud bath or a scorching volcanic vent way under the sea. The first inhabitant of this Eden, chemists suspect, was RNA.

　　按照现代科学的解释，地球上的生命起源于大约38亿年前，根据达尔文的猜测，也许是在一个温暖的池塘里，也许是在一个咕嘟冒泡的、沸腾的泥坑里，或许在一个炽热的海底火山口里。化学家推测，这个小小伊甸园的最早居民就是RNA。

In today’s world RNA runs errands for DNA. Like DNA, RNA encodes genetic information. Unlike DNA, however, RNA can also catalyze chemical reactions between other molecules, chopping them up or binding them together, a task mostly performed by proteins in modern organisms.

　　在今天的世界里，RNA扮演的是DNA信使的角色。和DNA一样，RNA也会为遗传信息编码。与DNA不同的是，RNA还可以充当其它分子之间化学反应的催化剂，促使它们分裂或者把它们结合到一起。在现代有机体中，这是一项大部分由蛋白质完成的任务。

In 1962, the M.I.T. biologist Alexander Rich suggested that RNA could have played both roles — blueprint and machinery — at the beginning. Scientists cannot prove that this is how life arose on Earth, but they can do the next best thing. They can make their own RNA and see if they can then breathe life into it.

　　1962年，麻省理工学院的生物学家亚历山大·里奇暗示，RNA可能在一开始是扮演双重身份，即设计图和机器。科学家们不能证明地球的生命是如何出现的，但是他们可以把下面的工作做得很好。他们可以制造自己的RNA，看看他们是否可以为它注入生命。

Enter Dr. Joyce, who says he came to his vocation by reading “Gravity’s Rainbow,” Thomas Pynchon’s 1973 novel about rockets and death in World War II, while he was a student at the University of Chicago. The last section of that book, he pointed out, is called “The Counterforce,” about pockets of life and love carving order out of the rubble of wartime Europe. For biologists the counterforce creating order and life out of chaos is simply Darwinian evolution, Dr. Joyce explained. “I wanted to be a member of the counterforce.”

　　乔伊斯博士参加了这项研究。他说，当他还是芝加哥大学的学生时，他读到了托马斯·平琼1973年撰写的描写二战时火箭和死亡的小说《Gravity’s Rainbow》，由此触发他选择了目前的职业。他指出，该书的最后一节名为“反作用力”，讲的是通过零星的生命和爱在战时欧洲的废墟上建立秩序。对生物学家而言，可以在混沌中创造秩序和生命的反作用力很简单，就是达尔文的进化论。乔伊斯博士解释道，“我就想成为反作用力中的一员。”

At the center of the Joyce lab experiments is a T-shaped piece of RNA that has the ability to glue together other molecules of RNA. In 2002, Dr. Joyce and a postdoctoral fellow, Natasha Paul, configured it to recognize and glue together a pair of smaller molecules, essentially an L and a straight piece. When joined, those molecules would form a new copy of the original T-shaped molecule. It worked; the RNA was able to manufacture new versions of itself, but not fast enough to keep up with the original RNA’s natural tendency to fall apart. Essentially it was dying faster than it was reproducing. Dr. Joyce and Dr. Lincoln found a way to speed the process up, by having two complementary versions of the RNA manufacture each other.

　　乔伊斯博士实验的核心内容是一个T型RNA分子，这个RNA分子具有把其它RNA分子粘在一起的能力。2002年，乔伊斯博士和博士后娜塔莎·保罗把它设计成可以辨识出一对比较小的分子（必须是L型和直型）并能把它们粘在一起。这对分子结合到一起之后，会成为原始T型分子的新的复制品。结合过程是成功的；RNA分子可以制造自己的复制品，但是这个新的复制品跟不上原始T型分子分裂的自然趋势。从本质上说，它的死亡速度比复制速度要快。乔伊斯博士和林肯博士找到了一种方法来加速这个过程，就是让两个互补的RNA版本互相制造对方。

“There was a day that it all happened,” said Dr. Joyce, namely Oct. 1, 2007, when as he puts it, the replicators “went critical,” and their population began growing exponentially.

　　“终于有一天，事情完全按照预想发生了，”乔伊斯博士说，也就是在2007年10月1日，当他开始实验后，复制因子“进入临界状态”，它们的数量开始以指数方式增长。

The game, as he likes to say, was on. And it has never stopped. Dr. Joyce and his colleagues next proceeded to engineer a sort of March Madness for molecules. They synthesized 12 versions of the replicators, which could mutate and evolve to improve their ability to reproduce. The experimenters threw these into the pot, along with the appropriate “food” segments, to compete. “They just go at it,” Dr. Joyce explained.

　　就像他喜欢说的那样，游戏开始了，而且就没有停止。乔伊斯博士及其同事接下来便为分子着手设计一个类似“三月疯”***的计划。他们合成了12种版本的复制因子，这些复制因子会发生变异或者进化到可以提高其复制能力。然后，实验人员把复制因子扔进“锅”里，同时还加入适当的“食材”，共同参与竞争。“它们便开始了努力奋斗，”乔伊斯博士解释道。

By the end, the winning molecules were doubling their numbers every 15 minutes. Mistaken swaps had produced combinations, mutations, that had not been in the mix at the start. Most of the original versions almost completely disappeared. In short, the molecule evolved.

　　到最后，胜利的分子数量每隔15分钟便翻一番。一开始并没有卷入合并战斗的那些错误的交换也产生了合并和变异。大部分最初的复制因子几乎都消失了，总之，分子进化了。

“Evolution is not a theory for us chemists,” Dr. Joyce said. “It’s what molecules do when they have the property to replicate and transmit information from parents to progeny.”

　　乔伊斯博士说，“进化并不是为我们化学家准备的理论，”“进化是当分子们具有了从父代到子代复制和传输信息的特性时，自然而然产生的行动。”

In a separate experiment the molecules were redesigned so that they would replicate only when another chemical was present. “That’s the app that’s going to pay for this,” said Dr. Joyce, explaining that the replicating molecules could be fashioned into sensors to detect pollutants or dangerous toxins in the environment. Dr. Joyce and his collaborators are now starting to run the same tournament with 256 versions of the replication enzyme. “We are pipetting madly,” he reported recently.

　　在另外一个实验中，分子们被重新设计成只有当另外的化学物质存在时，它们才会复制。“会有一个应用程序来负责这种特殊操作，”乔伊斯博士解释道，复制的分子被培养成可以检测出环境中的污染物或者危险毒素的传感器。乔伊斯博士及其合作者正在利用256种复制酶进行同样（激烈）的锦标赛。“我们正在用移液管来进行疯狂的比赛，”他最近报告说。

That means that there will be about 65,000 possible gene combinations that can emerge and try out their wings, which means things are getting interesting. As Dr. Lincoln said, “We’re knocking on the door, but we’re not quite there yet.” Sidney Altman, a Yale professor who shared a Nobel prize for discovering some of the talents of RNA, said that true test tube life could still be years away. “Gerry Joyce’s replicators are very clever molecules,” he said, but added that they were not self-sufficient enough to be alive.

　　这意味着将有大约65000种可能的基因组合会出现或者尝试出现，也就是事情要变得有趣了。正像林肯博士所言，“我们正在敲门，但离真正地开门还有段距离。”西德尼·阿特曼，耶鲁大学教授，因发现一些RNA的特质和他人分享了诺贝尔奖，他说，真正的试管生命还要等几年，“格里·乔伊斯的复制因子是很聪明的分子，”他继续补充道，但它们还不能做到自给自足地存活下去。

Dr. Joyce said his team was working on having the replicating molecule invent a new ability, but he would not say what it was. Asked for an example of the kind of things he could teach his RNA to do, Dr. Joyce suggested it could take part in creating one of the ingredients for its own replication by adding together a pair of smaller molecules. “What would be cool,” he said, “would be if they could make their own food.” The key to more ability, he said, is complexity. His molecule has only two genes, compared with 25,000 in human beings, and experiments involved fiddling with four letters of these genes. The human genome has three billion letters.

　　乔伊斯博士说他的团队正在致力于为这种复制分子发明出一个新的功能，但他拒绝说出是什么功能。在我们希望他为教他的RNA分子去做的事举个例子时，乔伊斯博士暗示，通过添加一对小分子，他的“聪明”分子会根据自己复制过程的需要，参与创造某一种辅料。他说，“如果我的复制分子们可以自己制造食物的话，”“这真是太棒了，”他说，增加更多功能是很复杂的事情。他的分子只有2种基因，而人类有25000种基因，这些基因的4字母密码组合实验也是繁复异常的。人类的基因组有30亿个字母（30亿个DNA碱基对）。

“We have a little toy genome where we can have the complete book of life,” he said, “but the sentences only have two words.”

　　他说，“我们有一个玩具基因组，在这里我们有一本完整的生命之书，”“当然，这本书的句子就是两个单词。”

Dr. Joyce’s molecules will never catch up to the biosphere. But someday their genome may surprise their creator with a word — a trick or a new move in the game of almost life — that he has not anticipated. “If it would happen, it would do it for me, I would be happy,” Dr. Joyce said, adding, “I won’t say it out loud, but it’s alive.”

　　乔伊斯博士的分子永远也不会进入生物圈，但总有一天，它们的基因组会以一种在生命之间才会出现的出人意料的小把戏或者一个新的举动让它们的创造者大吃一惊的。“如果真有那么一天，我知道它们是为了让我惊喜，我会很幸福的，”乔伊斯博士说，并补充道，“我不会大声声张，但它确实是有生命的！”

---

*译注：此处原文“Life As We Do Know It”源自2010年12月6日华尔街日报记者Michio Kaku的一篇同标题的通讯，介绍了当时NASA发现异类生命的重磅消息。

**Batman 和 Robin 是《蝙蝠侠与罗宾》中的人物。罗宾擅长飞檐走壁。

***“三月疯”（March Madness）---是指每年三月举行举行的全美大学体育联盟NCAA第一级男篮锦标赛，是轰动全美的传统体育庆典，无数民众为之疯狂，由此才有“三月疯”之称