2021年经济学人 史前动物猛犸象有望复活(1)

Palaeontology

古生物学

Very, very long in the tooth

牙齿很长很长

Million-year-old mammoth¹ genomes push the limits of a revolutionary technique

百万年前的猛犸象基因组突破了一项革命性技术的极限

In the 1966 science-fiction movie "One Million Years B.C.", Raquel Welch and John Richardson traverse a primitive² landscape inhabited by dinosaurs³ and early humans. The film was low on science and high on fiction: by then dinosaurs were long dead and humans—at least, ones resembling Ms Welch and Mr Richardson— were hundreds of millennia⁴ away.

在1966年的科幻电影《公元前一百万年》中，拉克尔·韦尔奇和约翰·理查森穿越了恐龙和早期人类居住的原始景观。这部电影的科学含量低，但科幻含量高：那时恐龙早已灭绝，而人类——至少像韦尔奇和理查森这样的人——数十万年后才能出现。

A more accurate picture of Earth's inhabitants at the time is now being revealed. In research published in Nature, a team of scientists led by Anders Gotherstrom, at the University of Stockholm, and Love Dalen at the Centre for Palaeogenetics, also in Sweden, describe sequencing DNA⁵ samples from mammoths that lived and died in north-eastern Siberia around a million years ago.

一幅更精准的地球居民图正徐徐展开。在《自然》杂志上发表的一项研究中，斯德哥尔摩大学的安德斯·哥斯特伦和同样在瑞典的古遗传学中心的洛夫·戴伦领导的一个科学家团队描述了大约100万年前在西伯利亚东北部生活和灭绝的猛犸象的测序DNA样本。

The team's work represents a new record, for their mammoth DNA is, by some half a million years, the oldest ever successfully reconstituted. Extracted from horses, bears and even Neanderthals and Denisovans, two close cousins of modern humans, such ancient DNA has proved an invaluable⁶ tool for investigating the past. Although fossils preserve the gross physical features of extinct animals, they are silent about many crucial details that even an incomplete genome can help to fill in.

这个团队的这一工作创造了新的纪录，因为他们的猛犸象DNA是迄今为止成功重组的最古老的DNA，距今大约50万年。这种古老的DNA从马、熊，甚至是现代人的近亲尼安德特人和丹尼索瓦人身上所提取，并被证明是研究过去的宝贵工具。化石尽管保存了灭绝动物的大体物理特征，但它们无法查证许多关键的细节，而就算是一个不完整的基因组也能帮助填补这些细节。

The trouble with DNA is that it breaks down post mortem. The more brokendown it is, the harder it is to sequence. Scientists think that, after about 6m years, all that would be left would be individual base pairs, the equivalent of trying to reconstruct a book from a heap of its constituent⁷ letters. Under the right conditions, however, such as the extreme cold of Arctic permafrost, this decay can be slowed.

DNA的问题在于死后会分解。越分解就越难排序。科学家们认为大约600万年之后只会剩下单个的碱基对，这就相当于从一堆组成字母中重建一本书。然而，在适当的条件下，比如极寒的北极永久冻土层，分解的速度可以减缓。

Dr Dalen and his colleagues were interested in three mammoth molars extracted in the 1970s from Siberian geological layers that suggested great age. Samples from each were sent to Dr Dalen's laboratory in 2017. Having checked they had not been unduly⁸ contaminated by bacteria or the shaking hands of awe-struck palaeontologists, strands⁹ of DNA were extracted, sequenced, and dated. Whereas DNA samples from a living animal can run to several hundreds of thousands of letters, the timeworn mammoth samples yielded strands mere¹⁰ dozens of letters long. This is close to the limit of what is scientifically usable, says Ludovic Orlando, a biologist at the Centre for Anthropobiology and Genomics of Toulouse.

戴伦博士和他的同事们对三颗猛犸象的臼齿感兴趣，这三颗臼齿是20世纪70年代从年代久远的西伯利亚地质层中提取出来的。2017年，所有的样本都被送到了戴伦博士的实验室。经过检查，它们没有被细菌和充满敬畏的古生物学家们的握手过度污染，DNA链被提取出来，测序，并确定了年代。活体动物的DNA样本可以有几十万个字母，而年代久远的猛犸象样本中的DNA样本只有几十个字母长。图卢兹人类生物学和基因组学中心的生物学家卢多维克·奥兰多说，这接近科学可用的极限。

1 mammoth   

n.长毛象；adj.长毛象似的，巨大的

参考例句：

• You can only undertake mammoth changes if the finances are there.资金到位的情况下方可进行重大变革。
• Building the new railroad will be a mammoth job.修建那条新铁路将是一项巨大工程。

2 primitive   

adj.原始的；简单的；n.原(始)人，原始事物

参考例句：

• It is a primitive instinct to flee a place of danger.逃离危险的地方是一种原始本能。
• His book describes the march of the civilization of a primitive society.他的著作描述了一个原始社会的开化过程。

3 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

4 millennia   

n.一千年，千禧年

参考例句：

• For two millennia, exogamy was a major transgression for Jews. 两千年来，异族通婚一直是犹太人的一大禁忌。
• In the course of millennia, the dinosaurs died out. 在几千年的时间里，恐龙逐渐死绝了。

5 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。

6 invaluable   

adj.无价的，非常宝贵的，极为贵重的

参考例句：

• A computer would have been invaluable for this job.一台计算机对这个工作的作用会是无法估计的。
• This information was invaluable to him.这个消息对他来说是非常宝贵的。

7 constituent   

n.选民；成分，组分；adj.组成的，构成的

参考例句：

• Sugar is the main constituent of candy.食糖是糖果的主要成分。
• Fibre is a natural constituent of a healthy diet.纤维是健康饮食的天然组成部分。

8 unduly   

adv.过度地，不适当地

参考例句：

• He did not sound unduly worried at the prospect.他的口气听上去对前景并不十分担忧。
• He argued that the law was unduly restrictive.他辩称法律的约束性有些过分了。

9 strands   

n.（线、绳、金属线、毛发等的）股( strand的名词复数 )；缕；海洋、湖或河的)岸；（观点、计划、故事等的）部份v.使滞留，使搁浅( strand的第三人称单数 )

参考例句：

• Twist a length of rope from strands of hemp. 用几股麻搓成了一段绳子。 来自《简明英汉词典》
• She laced strands into a braid. 她把几股线编织成一根穗带。 来自《简明英汉词典》

10 mere   

adj.纯粹的；仅仅，只不过

参考例句：

• That is a mere repetition of what you said before.那不过是重复了你以前讲的话。
• It's a mere waste of time waiting any longer.再等下去纯粹是浪费时间。