2015年经济学人 性选择与进化 美丽的雌性

 

Sexual selection and evolution

性选择与进化

My pretty maid

美丽的雌性

A glamorous¹ raiment sometimes helps a female bird as much as it helps a male

华丽的外表有时给雌性的益处和雄性一样多

HOW the peacock got his tail is one of natural history's “Just So” stories that biologists like to think they have cracked. His tail is for showing off to the ladies just how fit he and his genes² are. A less-than-perfect tail means no offspring. Genes for spectacular male tails are thus preserved and promoted over the generations in a process that is called sexual selection.

孔雀是如何得到它的尾巴，生物学家乐意认为这是他们已经破解的自然界奥秘故事之一。它的尾巴是向雌性炫耀它和它的基因是多么优秀。稍有瑕疵的尾巴意味着没有后代。受世代性选择的过程的影响，雄性华丽的尾巴的基因因此得到保留并进化。

There is, though, a problem with this story. Peahens, though not as showy as cocks, are by no means dowdy³. Their heads have fetching crests⁴, and their necks are a beautiful, iridescent⁵ blue. Such flummery is costly⁶ to grow and likely to attract predators⁷. If you do not have to strut⁸ your stuff to get a mate, why do you need it?

然而，这个故事有一个疑问。雌孔雀虽不如雄性那样艳丽，但也绝不俗气。它们头上有迷人的羽冠，以及光泽艳丽的蓝色脖子。这种装饰物会威胁生存，可能招致天敌。如果你不是为了求偶炫耀，那你为什么需要它？

Even more confusingly, in many species both sexes are equally showy—the Gouldian finches overleaf, for example (the female is on the right). So, though no one thinks the theory is incorrect, as far as it goes, it clearly does not go far enough. To understand things better James Dale of Massey University, in Auckland, New Zealand, and his colleagues have therefore examined the plumage of both sexes of all 5,983 species of passerine bird (peafowl, not being passerines, are not among them), and compared them in exquisite⁹ detail.

更不解的是，许多物种雄性和雌性都绚丽——例如上图的彩虹鸟（右为雌性）。虽然没人认为这个理论是错的，但就现状而言，显然不够正确。为了了解更多，新西兰奥克兰区梅西大学的詹姆斯戴尔，和同事调查了总共5,983种雀形目鸟类雌雄的羽毛，并比较了他们的细微细节（孔雀不是雀形目，不在调查之中）。

First, the team had to devise a way to deal with the 11,966 types of plumage they had set out to examine. Using the “Handbook of the Birds of the World”, regarded by ornithologists as the definitive¹⁰ work in the field, they picked six points on a bird's body (nape, crown, forehead, throat, upper breast and lower breast) and performed a spectral¹¹ analysis of each to measure how red, green and blue it was. The average let them plot each plumage as a dot on a graph with three axes—red, green and blue.

首先，团队设计了处理将要调查的11,966种羽毛的方法。用《全世界鸟类手册》——被鸟类学家视为该领域最为完整可靠的资料，他们在鸟身上挑了6处（颈部,羽冠,前额,喉咙,前胸和下胸），然后用光谱分析来测量红色，绿色和蓝色。在红绿蓝三维坐标系上用小点绘制了平均羽毛颜色的散点图。

To translate this into a “showiness” score, the researchers started from the fact that, despite the exceptions, showiness is still more a male than a female phenomenon. They therefore calculated, as a proxy¹² for showiness, a “maleness” score for each dot, regardless of which sex it represented, by counting the sexes of its nearest 120 neighbours in the graph (ie, the nearest 1% of dots). They then ran these scores against characteristics, such as the size of a species, its habitat and its pattern of family life.

为了转化成“绚丽”分数，研究者从事实发现：除了个别例外，炫耀现象雄性多余雌性。因此他们计算出每一“雄性”点得分：无论雌性还是雄性有绚丽的装饰物，通过计算它附近120个两性点（将近1%的点）。然后将这些分数对比特征，比如物种的大小，栖息地以及生活习性。

Their first observation, as they report this week in Nature, was that in species where a few males monopolise all the females, with a consequent lack of male involvement in parental¹³ care, males were more colourful than females. This is what the theory of sexual selection would predict. What it would not predict in its simple form, though, was a second finding—that females in co-operatively breeding species (those in which, for lack of other opportunities, several females collaborate¹⁴ to raise the young of only one of them) are more ornamented¹⁵ than those in which all adult females have a chance of breeding. In this case it is females who are competing for the right to reproduce, thus putting themselves in a more male-like position.

他们第一次观察报告结果出版在本周《自然》上：在少量雄性配对所有雌性的物种，在亲代抚育中缺少雄性角色的缘故，雄性比雌性更艳丽。这是性选择理论做出的预测。然而，这个简单形式的理论不能预测的是第二个发现：在合作哺育的物种（缺少雄性情况下，几个雌性合作只能抚养其中一个后代），雌性比有机会和雄性一起繁殖后代的雌性更花哨。这个例子中正是雌性完成了繁殖的任务，因此他们扮演了雄性的角色。

Another widespread belief Dr Dale and his colleagues confirmed is that tropical species are more colourful than those from temperate¹⁶ climes. But again, there was a twist—the effect was much more marked in females than in males. Something about the tropics favours colourful females. It may be that tropical birds, which face more intense competition for food and nesting sites than temperate ones do because the tropics have more species, form more stable and collaborative pair-bonds than do temperate birds. In these circumstances males also need to be choosy, and females competitive. Selection for gaudy¹⁷ plumage therefore works in both directions.

戴尔博士和同事证实的另一个普遍的观点是，热带气候里的物种比温带的更鲜艳。但有一点不同——这种效果雌性比雄性表现得更明显。热带环境偏爱外表鲜艳的雌性。这可能是热带鸟类形成了更稳定更协作的一夫一妻制，因为热带有更多物种，热带鸟类比温带鸟类存在更激烈的食物竞争和巢穴竞争。这种环境下雄性挑选配偶，而雌性去竞争。因此绚丽羽毛在自然选择上往两个方向发展。

The final effect the researchers found was that big species are more colourful than small ones. That is true of both sexes, and probably reflects the fact that bigger birds are more difficult prey¹⁸ and thus have less need to hide. When released from the threat of predation, then, females tend to be gaudier¹⁹. That suggests gaudiness²⁰ is always good when it can be got away with (for even in a promiscuous²¹ species, pretty females are likely to be at an advantage to ugly ones)—and probably explains the decorated necks and heads of peahens, which are among the biggest of birds.

研究人员发现的最后一个结果是，体型大的物种比体型小的更鲜艳。雌性和雄性都符合这点，也反映了大型鸟不容易被捕杀故而不必隐藏的事实。一旦没有天敌的威胁，雌性就变得更花哨。这表明在没有天敌威胁下，华丽点总是好的（即使在一个滥交的物种，漂亮的雌性比丑的可能更有优势），也解释了为何雌孔雀拥有艳丽的脖子和头部，因为它是体型最大的鸟类。

Putting these results together, then, suggests that what is happening in the arena²² of sexual selection is as much to do with females as with males. Just as females are half the world, so the conventional explanation of the peacock's tail, though not wrong, is only half the story.

这些结果一起暗示了性选择过程中雌性和雄性变化一样多。就像雌性占世界的一半，孔雀尾巴的传言虽然不是错的，但只是故事的一半。

1 glamorous   

adj.富有魅力的；美丽动人的；令人向往的

参考例句：

• The south coast is less glamorous but full of clean and attractive hotels.南海岸魅力稍逊，但却有很多干净漂亮的宾馆。
• It is hard work and not a glamorous job as portrayed by the media.这是份苦差，并非像媒体描绘的那般令人向往。

2 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

3 dowdy   

adj.不整洁的；过旧的

参考例句：

• She was in a dowdy blue frock.她穿了件不大洁净的蓝上衣。
• She looked very plain and dowdy.她长得非常普通，衣也过时。

4 crests   

v.到达山顶（或浪峰）( crest的第三人称单数 )；到达洪峰，达到顶点

参考例句：

• The surfers were riding in towards the beach on the crests of the waves. 冲浪者们顺着浪头冲向岸边。 来自《简明英汉词典》
• The correspondent aroused, heard the crash of the toppled crests. 记者醒了，他听见了浪头倒塌下来的轰隆轰隆声。 来自辞典例句

5 iridescent   

adj.彩虹色的，闪色的

参考例句：

• The iridescent bubbles were beautiful.这些闪着彩虹般颜色的大气泡很美。
• Male peacocks display their iridescent feathers for prospective female mates.雄性孔雀为了吸引雌性伴侣而展现了他们彩虹色的羽毛。

6 costly   

adj.昂贵的，价值高的，豪华的

参考例句：

• It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
• This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。

7 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》

8 strut   

v.肿胀，鼓起；大摇大摆地走；炫耀；支撑；撑开；n.高视阔步；支柱，撑杆

参考例句：

• The circulation economy development needs the green science and technology innovation as the strut.循环经济的发展需要绿色科技创新生态化作为支撑。
• Now we'll strut arm and arm.这会儿咱们可以手挽着手儿，高视阔步地走了。

9 exquisite   

adj.精美的；敏锐的；剧烈的，感觉强烈的

参考例句：

• I was admiring the exquisite workmanship in the mosaic.我当时正在欣赏镶嵌画的精致做工。
• I still remember the exquisite pleasure I experienced in Bali.我依然记得在巴厘岛所经历的那种剧烈的快感。

10 definitive   

adj.确切的，权威性的；最后的，决定性的

参考例句：

• This book is the definitive guide to world cuisine.这本书是世界美食的权威指南。
• No one has come up with a definitive answer as to why this should be so.至于为什么该这样，还没有人给出明确的答复。

11 spectral   

adj.幽灵的，鬼魂的

参考例句：

• At times he seems rather ordinary.At other times ethereal,perhaps even spectral.有时他好像很正常，有时又难以捉摸，甚至像个幽灵。
• She is compelling,spectral fascinating,an unforgettably unique performer.她极具吸引力，清幽如鬼魅，令人着迷，令人难忘，是个独具特色的演员。

12 proxy   

n.代理权，代表权；（对代理人的）委托书；代理人

参考例句：

• You may appoint a proxy to vote for you.你可以委托他人代你投票。
• We enclose a form of proxy for use at the Annual General Meeting.我们附上委任年度大会代表的表格。

13 parental   

adj.父母的；父的；母的

参考例句：

• He encourages parental involvement in the running of school.他鼓励学生家长参与学校的管理。
• Children always revolt against parental disciplines.孩子们总是反抗父母的管束。

14 collaborate   

vi.协作，合作；协调

参考例句：

• The work gets done more quickly when we collaborate.我们一旦合作，工作做起来就更快了。
• I would ask you to collaborate with us in this work.我们愿意请你们在这项工作中和我们合作。

15 ornamented   

adj.花式字体的v.装饰，点缀，美化( ornament的过去式和过去分词 )

参考例句：

• The desk was ornamented with many carvings. 这桌子装饰有很多雕刻物。 来自《简明英汉词典》
• She ornamented her dress with lace. 她用花边装饰衣服。 来自《简明英汉词典》

16 temperate   

adj.温和的，温带的，自我克制的，不过分的

参考例句：

• Asia extends across the frigid,temperate and tropical zones.亚洲地跨寒、温、热三带。
• Great Britain has a temperate climate.英国气候温和。

17 gaudy   

adj.华而不实的；俗丽的

参考例句：

• She was tricked out in gaudy dress.她穿得华丽而俗气。
• The gaudy butterfly is sure that the flowers owe thanks to him.浮华的蝴蝶却相信花是应该向它道谢的。

18 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。

19 gaudier   

adj.花哨的，俗气的( gaudy的比较级 )

参考例句：

• But no, there was something gaudier even than this. He would be a pirate! 这不还不够劲，还有比这更神气的事情，他要去当海盗！ 来自互联网

20 gaudiness   

n.华美，俗丽的美

参考例句：

• July, yearses~now, at Kun mountain gaudiness plastic hardware product limited company work. 2006年7月~现在，在昆山华美塑胶五金制品有限公司工作。 来自互联网
• The European antique furniture are gaudiness. 欧洲的古典家具一向以华美著称。 来自互联网

21 promiscuous   

adj.杂乱的，随便的

参考例句：

• They were taking a promiscuous stroll when it began to rain.他们正在那漫无目的地散步，突然下起雨来。
• Alec know that she was promiscuous and superficial.亚历克知道她是乱七八糟和浅薄的。

22 arena   

n.竞技场，运动场所；竞争场所，舞台

参考例句：

• She entered the political arena at the age of 25. 她25岁进入政界。
• He had not an adequate arena for the exercise of his talents.他没有充分发挥其才能的场所。