2021年经济学人 莫桑比克的无象牙大象是如何进化的

Science and technology

科技版块

Evolution in action

行为影响的进化论

Spoils of war

“战利品”

How tuskless elephants evolved in Mozambique

莫桑比克的无象牙大象是如何进化的

EVOLUTION ENSURES that animals are well-adapted to their circumstances.

进化可以确保动物能很好地适应它们的环境。

Sometimes, as with predators¹ and prey², those circumstances include the behaviour of other creatures.

有时，就像捕食者和猎物一样，这些情况也包括其他生物的行为。

And, as a paper just published in Science describes, that includes the behaviour of human beings, which can force drastic changes on a species in an evolutionary³ eyeblink.

正如刚刚发表在《科学》杂志上的一篇论文所描述的那样，人类的行为可以迫使一个物种在进化的瞬间发生巨大变化。

Shane Campbell-Staton, a biologist at Princeton University, studies how animals adapt to human creations like cities and pollution.

普林斯顿大学的生物学家坎贝尔-斯塔顿研究动物如何适应人类的创造，如城市和污染。

His interest was piqued⁴ by a film about the tuskless female elephants of Gorongosa National Park, in Mozambique.

引起他兴趣的是一部关于莫桑比克戈龙戈萨国家公园里无象牙母象的电影。

Their lack of tusks⁵ was thought to be a consequence of another human creation—the Mozambican civil war, which lasted from 1977 to 1992 and was partly paid for by the killing⁶ of elephants for their ivory.

他们缺乏象牙被认为是另一个人类创造的结果——莫桑比克内战，这场内战从1977年持续到1992年，部分费用来自于猎杀大象获得象牙。

Around 90% of the pachyderms living in Gorongosa are thought to have been killed.

大约90%生活在戈龙戈萨的厚皮动物被认为已经被杀死。

Biologists therefore wondered if rising tusklessness might be an adaptation to make elephants less attractive to human hunters.

因此，生物学家想知道，是不是越来越多的无牙是一种适应，因为可以降低大象对人类猎人的吸引力。

It was a plausible⁷ theory, says Dr Campbell-Staton, but no one had actually tested it.

坎贝尔-斯塔顿博士说，这是一个貌似合理的理论，但没有人真正验证过它。

Through a mix of old video footage and surveys, he and his colleagues concluded that around 18% of the female elephants in Gorongosa lacked tusks before the war.

通过老视频和相关调查，他和他的同事们得出结论，内战前大约18%的戈龙戈萨母象缺少象牙。

Three decades later, after it was over, that number had risen to 50%.

三十年后，内战结束，无象牙母象的数量上升到了50%。

Computer simulations suggested that the likelihood of such a rapid change happening by chance, even in a diminished population, was tiny.

计算机模拟表明，即使在人口减少的情况下，如此迅速的变化偶然发生的可能性很小。

Besides confirming the change, the researchers managed to unravel⁸ its genetic⁹ roots.

除了证实这一变化外，研究人员还设法揭开了它的基因根源。

Tusklessness is caused by a mutation¹¹ in a gene¹⁰ on the elephantine X chromosome¹².

无牙是由大象X染色体上的一个基因突变引起的。

(As with humans, two X chromosomes¹³ make a female, while an X and a Y make a male.)

（和人类一样，两条X染色体构成雌性，而X和Y染色体构成雄性。）

Unfortunately for males, the mutation is a package deal, coming with changes to nearby genes¹⁴ that interfere¹⁵ with embryonic¹⁶ development.

不幸的是，对于雄性来说，这种突变是一揽子交易，伴随而来的是干扰胚胎发育的邻近基因的变化。

Males who inherit the mutant gene die before birth.

继承突变基因的雄性在出生前就会死亡。

Females can avoid the lethal¹⁷ side-effects if one of their two X chromosomes contains a non-mutated gene—but they will still grow up without tusks.

如果雌性的两条X染色体中有一条含有未突变的基因，则可以避免致命的副作用——但她们长大后仍然没有象牙。

Fortunately for the females, the specifics of how the mutant gene is inherited make it impossible for them to inherit two copies.

幸运的是，对于雌性来说，突变基因遗传的具体方式使她们不可能继承两个副本。

Since mutant males die before being born, those which survive to reproductive age carry only non-mutated versions of the X chromosome, ensuring that their daughters will have at least one copy too.

由于突变的雄性在出生前死亡，那些活到育龄的雄性只携带非突变版本的X染色体，这确保了他们的女儿也会至少有一个副本。

At the moment, the continual reintroduction of non-mutant X chromosomes from males puts a limit on how far tusklessness can spread through the female population.

目前，来自雄性的非突变X染色体的不断重新引入限制了无牙现象在雌性群体中传播的程度。

But, given time and genetic recombination, says Dr Campbell-Staton, evolution might disentangle the mutation for tusklessness from the maladaptive mutations in its neighbouring genes, opening the door for males to shed their tusks, too.

但是，坎贝尔-斯塔顿博士说，经过一定的时间和基因重组，进化可能会将无牙突变从邻近基因的不适应突变中解脱出来，也为雄性打开无牙的大门。

There are occasional rumours¹⁸, he says, of tuskless male elephants in the wild, but—so far at least—no firm evidence.

他说，偶尔会有传言说野外有无牙公象，但至少到目前为止还没有确凿的证据。

Finding one now seems unlikely.

现在看来似乎不太可能找到。

With the war over, the evolutionary pressure from poaching has eased.

随着战争的结束，偷猎带来的进化压力有所缓解。

Tusks have gone back to being useful tools, helping¹⁹ their owners strip bark from trees and dig for water.

象牙已经重新成为有用的工具，帮助它们的主人剥树皮和挖洞取水。

In recent years the prevalence of tuskless females has fallen, to around 33%.

近年来，无牙母象的流行率已经下降到33%左右。

But the speed of the change is a reminder²⁰ that wars can alter evolutionary history as well as the human sort.

但变化的速度提醒人们，战争不仅可以改变人类，也可以改变进化史。

1 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

2 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。

3 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

4 piqued   

v.伤害…的自尊心( pique的过去式和过去分词 )；激起（好奇心）

参考例句：

• Their curiosity piqued, they stopped writing. 他们的好奇心被挑起，停下了手中的笔。 来自辞典例句
• This phenomenon piqued Dr Morris' interest. 这一现象激起了莫里斯医生的兴趣。 来自辞典例句

5 tusks   

n.（象等动物的）长牙( tusk的名词复数 )；獠牙；尖形物；尖头

参考例句：

• The elephants are poached for their tusks. 为获取象牙而偷猎大象。
• Elephant tusks, monkey tails and salt were used in some parts of Africa. 非洲的一些地区则使用象牙、猴尾和盐。 来自英语晨读30分（高一）

6 killing   

n.巨额利润；突然赚大钱，发大财

参考例句：

• Investors are set to make a killing from the sell-off.投资者准备清仓以便大赚一笔。
• Last week my brother made a killing on Wall Street.上个周我兄弟在华尔街赚了一大笔。

7 plausible   

adj.似真实的，似乎有理的，似乎可信的

参考例句：

• His story sounded plausible.他说的那番话似乎是真实的。
• Her story sounded perfectly plausible.她的说辞听起来言之有理。

8 unravel   

v.弄清楚（秘密）；拆开，解开，松开

参考例句：

• He was good with his hands and could unravel a knot or untangle yarn that others wouldn't even attempt.他的手很灵巧，其他人甚至都不敢尝试的一些难解的绳结或缠在一起的纱线，他都能解开。
• This is the attitude that led him to unravel a mystery that long puzzled Chinese historians.正是这种态度使他解决了长期以来使中国历史学家们大惑不解的谜。

9 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。

10 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

11 mutation   

n.变化，变异，转变

参考例句：

• People who have this mutation need less sleep than others.有这种突变的人需要的睡眠比其他人少。
• So far the discussion has centered entirely around mutation in the strict sense.到目前为止，严格来讲，讨论完全集中于围绕突变问题上。

12 chromosome   

n.染色体

参考例句：

• Chromosome material with exhibits of such behaviour is called heterochromatin.表现这种现象的染色体物质叫做异染色质。
• A segment of the chromosome may become lost,resulting in a deletion.染色体的一个片段可能会丢失，结果产生染色体的缺失。

13 chromosomes   

n.染色体( chromosome的名词复数 )

参考例句：

• Chromosomes also determine the sex of animals. 染色体也决定动物的性别。 来自《简明英汉词典》
• Each of four chromosomes divide longitudinally. 四种染色体的每一种都沿着纵向分裂。 来自《现代汉英综合大词典》

14 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

15 interfere   

v.(in)干涉，干预；(with)妨碍，打扰

参考例句：

• If we interfere, it may do more harm than good.如果我们干预的话，可能弊多利少。
• When others interfere in the affair,it always makes troubles. 别人一卷入这一事件，棘手的事情就来了。

16 embryonic   

adj.胚胎的

参考例句：

• It is still in an embryonic stage.它还处于萌芽阶段。
• The plan,as yet,only exists in embryonic form.这个计划迄今为止还只是在酝酿之中。

17 lethal   

adj.致死的；毁灭性的

参考例句：

• A hammer can be a lethal weapon.铁锤可以是致命的武器。
• She took a lethal amount of poison and died.她服了致命剂量的毒药死了。

18 rumours   

n.传闻( rumour的名词复数 )；风闻；谣言；谣传

参考例句：

• The rumours were completely baseless. 那些谣传毫无根据。
• Rumours of job losses were later confirmed. 裁员的传言后来得到了证实。

19 helping   

n.食物的一份&adj.帮助人的，辅助的

参考例句：

• The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
• By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。

20 reminder   

n.提醒物，纪念品；暗示，提示

参考例句：

• I have had another reminder from the library.我又收到图书馆的催还单。
• It always took a final reminder to get her to pay her share of the rent.总是得发给她一份最后催缴通知，她才付应该交的房租。