PBS高端访谈:DNA革命帮助揭开远古人类之谜

JUDY WOODRUFF: Now: who we are and how we got here. Jeffrey Brown takes a time traveling look at how modern researchers are using the latest DNA¹ sequencing technology to understand the movements and interactions of very ancient humans. It is the latest in our weekly science series, the Leading Edge.

JEFFREY BROWN: It's a trip into the deep human past in a lab at the Harvard Medical School, disposable Tyvek suits, gloves, headgear, all required to avoid contamination of the ancient bones being studied here.

DAVID REICH, Harvard Medical School: The bones that we're looking at right now are about 5,000- or 6,000-year-old samples from Italy. And we're trying to understand population transformations² in Italy over time.

JEFFREY BROWN: David Reich, who heads this lab, is at the forefront of a revolution in DNA studies, now providing new insight into human history as old as 40,000 years.

DAVID REICH: We can open up an ancient skeleton from 10,000 years ago, sequence its genome, have as much information from that ancient individual as we would have from a person living today.

JEFFREY BROWN: And tell a story about them and their movement, and their relations to others?

DAVID REICH: Exactly. And the power of this information is evident from the fact that the stories are always so surprising.

JEFFREY BROWN: Finding our roots is all the rage these days. There's a deep human interest in where we come from. Reich and his colleagues go deeper, much deeper into the past, powered by enormous advances in sequencing technology in the last decade. He's using it to answer very big questions. The title of his new book, "Who We Are and How We Got Here."

DAVID REICH: We're looking at the history of humans and how we got to all the different places we are in the world today, and it's not something that's been possible to look at before this technology. And, really, what the ancient DNA has done, and the ability to look with high resolution at human variation has done, is, it's opened up a whole Pandora's box of archaic³ humans, and ancient mixtures, that we didn't know about before, but that we already can see some of them.

JEFFREY BROWN: Reich and his team work on bones collected around the world, brought to them by archaeologists and museums.

WOMAN: I think that might be an ossicle.

JEFFREY BROWN: In the so-called clean lab, we watched as an ancient skull⁴ fragment was sandblasted to isolate⁵ the cochlea, or inner ear. The petrous bone surrounding this area can retain traces of DNA for thousands of years. In another room, we met Harold the robot.

WOMAN: He prepares all of our libraries for us and our DNA so we can sequence it.

JEFFREY BROWN: Reich was part of a group of scientists which confirmed that ancient humans and Neanderthals mixed and mated until some 40,000 years ago, and that some living humans today still carry traces of Neanderthal DNA. A cave in Siberia produced another surprise, a species later dubbed⁶ Denisovans.

DAVID REICH: My colleagues obtained DNA from a finger bone from Siberia that they thought was a modern human. But when they sequenced its DNA, it was from a population that was neither Neanderthal nor modern human. So this was an incredible revelation to all of us.

JEFFREY BROWN: That suggests and that's what I wanted to ask you that there are still yet to be found, other kinds of archaic humans?

DAVID REICH: That's right. You know, I think we're alone on the planet now, but 50,000 years ago, it would have been much like the scene in Star Wars, with many, many different humans, all similar to each other and comprehensible to each other in some ways, many of them as big-brained as us, but much more different from each other than people who live today.

JEFFREY BROWN: Perhaps the biggest surprise in the ancient DNA research, though, is in more recent human history. We may think mass migration⁷ and mixing of cultures is a modern phenomenon, but it turns out to be the story of our species. We have always moved and always mixed.

DAVID REICH: The idea that human populations today might correspond to age-old separations, tens of thousands of years old, that have existed from time immemorial, has now been profoundly undermined by genetics. What the genetic⁸ data shows is that groups that we see today, and that we recognize, in fact are the results of profound mixtures, and that none of these groups are pure in any sense at all.

JEFFREY BROWN: Original populations in most regions of the world have been replaced, sometimes several times over. Europe, for example, saw what Reich calls a collision of three very different populations over the last 9,000 years, the last of them part of a great migration that began far to the east, in what we now call the Russian Steppes. To make this more concrete, Reich points to the iconic site of Stonehenge, which reached its final form around 4,500 years ago, constructed by people who descended⁹ by Europe's first farmers.

DAVID REICH: But within 100 years or 200 years, Stonehenge was taken over by these new people who were not the same people genetically¹⁰.

JEFFREY BROWN: So if you're living in Britain today and you're thinking, my ancestors built Stonehenge, you're wrong?

DAVID REICH: You're basically wrong, or maybe only 10 percent of your ancestors or fewer did. And so I think that this is sort of an example of this point, which is that people today are almost never directly descended from the people who first lived in those places. There's waves and waves of population replacement¹¹, and that we're all interconnected.

JEFFREY BROWN: That, of course, blows up concepts of pure races and national identity, ideas of genetics misused¹² by the Nazis¹³ and many others into our own time. Differences? Yes. But more connections and mixing than we'd known. It's hardly the end of the story. Reich says the ancient DNA revolution is just beginning. And there's plenty the DNA doesn't tell us, just why people migrated at a given time, for example, what, in fact, where they thinking? New secrets, he says, will continue to be unlocked.

DAVID REICH: It's gonna really profoundly change the way we do archaeology¹⁴, history, linguistics¹⁵, sociology, even demography¹⁶, and even sort of economic history, because we will be able to learn things about, for example, how population sizes have changed over time.

JEFFREY BROWN: It's all there in the ancient bones. For the "PBS NewsHour," I'm Jeffrey Brown at the Harvard Medical School in Cambridge, Massachusetts.

朱蒂·伍德拉夫：现在：我们是谁，又如何来到这里。杰弗里·布朗耗时游历，看现代研究人员如何利用最新的DNA测序技术来了解远古人类的迁徙及相互作用。这是我们每周系列科学节目《前沿》的最新一期。

杰弗里·布朗：我深入哈佛大学医学院实验室，开启了一场深入人类过去的旅行，身着一次性特卫强套装，手套，头罩，以保证正在这里接受研究的远古人类骸骨免遭污染。

戴维·瑞奇，哈佛大学医学院：现在我们看到的骨骼来自意大利，距今大约已有5000到6000年的历史。我们正试图了解长久以来意大利人口的变化情况。

杰弗里·布朗：这一实验室的负责人是戴维·瑞奇，这里的研究正处于DNA研究的革命前沿，现在这些研究成果为人类长达40,000年的历史提供新的洞察力。

戴维·瑞奇：我们可以开启距今10,000年之久的古老人类遗骨，对它的基因组进行测序，从中所得到的信息堪比在现存人类身上所获得的信息。

杰弗里·布朗：我们可以了解他们的故事，他们的迁徙情况以及他们与他人之间关系？

戴维·瑞奇：没错。而这些故事总是令人惊讶万分，这种信息的力量因此显而易见。

杰弗里·布朗：寻根研究在当下非常流行。我们来自何方，人类对此总充满浓厚的兴趣。瑞奇和他的同事经过了十年的深入研究，在测序技术方面取得了巨大进展。他用测序技术来回答非常大的问题。他新书的标题是《我们是谁，又如何来到这里》。

戴维·瑞奇：我们正在研究人类的历史，探寻我们如何到达今天世界上各个不同的地方，而在这项技术应用以前，这些我们无从而知。而且，真的，古老的DNA，以及研究人类变异时的高分辨能力，打开了古人类的潘多拉魔盒，揭开了古代人类相互融合的谜团，这些我们以前从未知晓，但现在已经可以了解到其中的一些。

杰弗里·布朗：瑞奇和他的团队从世界各地收集人类骸骨，将它们呈递给考古学家和博物馆。

女人：我想这可能是一块听小骨。

杰弗里·布朗：在所谓的无菌实验室里，我们看到了一块古人类颅骨碎片被喷砂以及进行耳蜗或内耳隔离的过程。这一区域四周的岩骨可将DNA痕迹保存数千年之久。在另一个房间里，我们遇见了机器人哈罗德。

女人：他为我们和我们的DNA提供了各种图书馆资源，以便我们可以对其进行排序。

杰弗里·布朗：瑞奇是科学家团队的一员。这个团队证实了古代人类曾在约40,000年前与尼安德特人混合交配，现存人类中，仍有一些携带尼安德特人DNA痕迹。西伯利亚的一个洞穴又为我们带来了一个惊喜，这一人种后来被称为丹尼索瓦人。

戴维·瑞奇：我的同事从西伯利亚的一根手指骨中获取了DNA，他们以为这属于现代人类。但当他们对DNA进行测序时，发现它来自一个既不是尼安德特人也不是现代人类的群体。所以这给了我们所有人一个不可思议的启迪。

杰弗里·布朗：这就表明了，也是我想问你的，是否还存在我们尚未发现的远古人类？

戴维·瑞奇：没错。你知道，现在我们认为在这个星球上的人类只此一种，但50,000年前，也许就像星球大战中的场景一样，有许许多多不同的人类物种，它们彼此相似，在某种程度上互相理解，它们中的许多与我们的脑容量相当。但与现在的人有很大的不同。

杰弗里·布朗：但也许在古代DNA研究中，最大的惊喜仍存在于近代人类历史的研究上。我们可能认为大规模迁移和文化融合是一种现代现象，但事实证明这些现象在很早以前就已经发生了。我们的迁徙与融合从未停止。

戴维·瑞奇：人们此前曾认为，现代人口可能与由来已久的隔离相契合，这些隔离，早在远古时代就已经存在，但这种想法现在已被遗传学大大地打破了。遗传数据显示，我们今天看到和认识到的人类群体，事实上，已经经过了深度混合，绝无纯粹血统可言。

杰弗里·布朗：世界上大部分地区的原始种群已经被取代，有时还会被多次取代。例如，欧洲在过去9,000年里，三个截然不同的人口种群，发生了瑞奇所谓的碰撞，他们中的最后一个，进行了一次从远东开始的大迁移，那个地区我们现称之为俄罗斯草原。为了使这更加具体，瑞奇指出了标志性地点巨石阵，4,500年前后，这里形成了如今的样式，它们由欧洲最早一批农民的后裔建造。

戴维·瑞奇：但在距今100年或200年内，巨石阵被一些新人接管了，从基因上来讲，他们不是同一人种。

杰弗里·布朗：所以，如果今天你住在英国，你在想，我的祖先建造了巨石阵，你错了吗？

戴维·瑞奇：你基本上错了，或者也许这些建造者只有10%或更少是你的祖先。所以我认为这是这个观点的一个例子，这就是今天的人类几乎都不是曾经原住民的直接后裔。人口更迭接连不断，我们所有人都相互关联。

杰弗里·布朗：当然，这与纯粹种族和民族身份的概念形成了对立，遗传学思想遭到了纳粹以及当今很多现代人的滥用。差异？是的。但更多的是联系与融合，这些超乎我们所知。还有后文。瑞奇说古代DNA革命才刚刚开始。还有很多东西，DNA并没有告诉我们，例如，人们为什么在特定时间进行迁移，他们在想什么，事实上，在哪里？他说，我们还将揭开更多新的秘密。

戴维·瑞奇：这将深刻地改变我们考古学、历史、语言学、社会学，甚至人口统计学，乃至经济史的研究方式，因为我们将能够了解一些关于，比如，人口规模随时间推移而变化的内容。

杰弗里·布朗：一切尽在远古遗骸身上。PBS新闻一小时，我是杰弗里·布朗，曼彻斯特剑桥哈佛大学医学院为您报道。

1 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

2 transformations   

n.变化( transformation的名词复数 )；转换；转换；变换

参考例句：

• Energy transformations go on constantly, all about us. 在我们周围，能量始终在不停地转换着。 来自辞典例句
• On the average, such transformations balance out. 平均起来，这种转化可以互相抵消。 来自辞典例句

3 archaic   

adj.(语言、词汇等)古代的，已不通用的

参考例句：

• The company does some things in archaic ways,such as not using computers for bookkeeping.这个公司有些做法陈旧，如记账不使用电脑。
• Shaanxi is one of the Chinese archaic civilized origins which has a long history.陕西省是中国古代文明发祥之一，有悠久的历史。

4 skull   

n.头骨；颅骨

参考例句：

• The skull bones fuse between the ages of fifteen and twenty-five.头骨在15至25岁之间长合。
• He fell out of the window and cracked his skull.他从窗子摔了出去，跌裂了颅骨。

5 isolate   

vt.使孤立，隔离

参考例句：

• Do not isolate yourself from others.不要把自己孤立起来。
• We should never isolate ourselves from the masses.我们永远不能脱离群众。

6 dubbed   

v.给…起绰号( dub的过去式和过去分词 )；把…称为；配音；复制

参考例句：

• Mathematics was once dubbed the handmaiden of the sciences. 数学曾一度被视为各门科学的基础。
• Is the movie dubbed or does it have subtitles? 这部电影是配音的还是打字幕的？ 来自《简明英汉词典》

7 migration   

n.迁移，移居，（鸟类等的）迁徙

参考例句：

• Swallows begin their migration south in autumn.燕子在秋季开始向南方迁移。
• He described the vernal migration of birds in detail.他详细地描述了鸟的春季移居。

8 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

9 descended   

a.为...后裔的，出身于...的

参考例句：

• A mood of melancholy descended on us. 一种悲伤的情绪袭上我们的心头。
• The path descended the hill in a series of zigzags. 小路呈连续的之字形顺着山坡蜿蜒而下。

10 genetically   

adv.遗传上

参考例句：

• All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
• Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物

11 replacement   

n.取代，替换，交换；替代品，代用品

参考例句：

• We are hard put to find a replacement for our assistant.我们很难找到一个人来代替我们的助手。
• They put all the students through the replacement examination.他们让所有的学生参加分班考试。

12 misused   

v.使用…不当( misuse的过去式和过去分词 )；把…派作不正当的用途；虐待；滥用

参考例句：

• He misused his dog shamefully. 他可耻地虐待自己的狗。 来自《简明英汉词典》
• He had grossly misused his power. 他严重滥用职权。 来自《简明英汉词典》

13 Nazis   

n.（德国的）纳粹党员( Nazi的名词复数 )；纳粹主义

参考例句：

• The Nazis worked them over with gun butts. 纳粹分子用枪托毒打他们。 来自《简明英汉词典》
• The Nazis were responsible for the mass murder of Jews during World War Ⅱ. 纳粹必须为第二次世界大战中对犹太人的大屠杀负责。 来自《简明英汉词典》

14 archaeology   

n.考古学

参考例句：

• She teaches archaeology at the university.她在大学里教考古学。
• He displayed interest in archaeology.他对考古学有兴趣。

15 linguistics   

n.语言学

参考例句：

• She plans to take a course in applied linguistics.她打算学习应用语言学课程。
• Linguistics is a scientific study of the property of language.语言学是指对语言的性质所作的系统研究。

16 demography   

n.人口统计，人口学

参考例句：

• Demography is the analysis of population variables.人口学是对人口变量的分析。
• It was once a rule of demography that people have fewer children as their countries get richer.按人口统计学的一贯规律，一个国家里的人民越富有，他们所拥有的孩子就越少。