2017考研英語(yǔ)閱讀沖刺精選：孔雀的性選擇與進(jìn)化
Sexual selection and evolution
性選擇與進(jìn)化
My pretty maid
美麗的雌性
A glamorous raiment sometimes helps a female birdas much as it helps a male
華麗的外表有時(shí)給雌性的益處和雄性一樣多
HOW the peacock got his tail is one of naturalhistory's “Just So” stories that biologists like to thinkthey have cracked. His tail is for showing off to the ladies just how fit he and his genes are. Aless-than-perfect tail means no offspring. Genes for spectacular male tails are thuspreserved and promoted over the generations in a process that is called sexual selection.
孔雀是如何得到它的尾巴，生物學(xué)家樂(lè)意認(rèn)為這是他們已經(jīng)破解的自然界奧秘故事之一。它的尾巴是向雌性炫耀它和它的基因是多么優(yōu)秀。稍有瑕疵的尾巴意味著沒(méi)有后代。受世代性選擇的過(guò)程的影響，雄性華麗的尾巴的基因因此得到保留并進(jìn)化。
There is, though, a problem with this story. Peahens, though not as showy as cocks, are by nomeans dowdy. Their heads have fetching crests, and their necks are a beautiful, iridescentblue. Such flummery is costly to grow and likely to attract predators. If you do not have tostrut your stuff to get a mate, why do you need it?
然而，這個(gè)故事有一個(gè)疑問(wèn)。雌孔雀雖不如雄性那樣艷麗，但也絕不俗氣。它們頭上有迷人的羽冠，以及光澤艷麗的藍(lán)色脖子。這種裝飾物會(huì)威脅生存，可能招致天敵。如果你不是為了求偶炫耀，那你為什么需要它?
Even more confusingly, in many species both sexes are equally showy—the Gouldian finchesoverleaf, for example (the female is on the right). So, though no one thinks the theory isincorrect, as far as it goes, it clearly does not go far enough. To understand things betterJames Dale of Massey University, in Auckland, New Zealand, and his colleagues have thereforeexamined the plumage of both sexes of all 5,983 species of passerine bird (peafowl, not beingpasserines, are not among them), and compared them in exquisite detail.
更不解的是，許多物種雄性和雌性都絢麗——例如上圖的彩虹鳥(niǎo)(右為雌性)。雖然沒(méi)人認(rèn)為這個(gè)理論是錯(cuò)的，但就現(xiàn)狀而言，顯然不夠正確。為了了解更多，新西蘭奧克蘭區(qū)梅西大學(xué)的詹姆斯戴爾，和同事調(diào)查了總共5,983種雀形目鳥(niǎo)類雌雄的羽毛，并比較了他們的細(xì)微細(xì)節(jié)(孔雀不是雀形目，不在調(diào)查之中)。
First, the team had to devise a way to deal with the 11,966 types of plumage they had set outto examine. Using the “Handbook of the Birds of the World”, regarded by ornithologists as thedefinitive 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 spectral analysis of each to measurehow red, green and blue it was. The average let them plot each plumage as a dot on a graphwith three axes—red, green and blue.
首先，團(tuán)隊(duì)設(shè)計(jì)了處理將要調(diào)查的`11,966種羽毛的方法。用《全世界鳥(niǎo)類手冊(cè)》——被鳥(niǎo)類學(xué)家視為該領(lǐng)域最為完整可靠的資料，他們?cè)邙B(niǎo)身上挑了6處(頸部,羽冠,前額,喉嚨,前胸和下胸)，然后用光譜分析來(lái)測(cè)量紅色，綠色和藍(lán)色。在紅綠藍(lán)三維坐標(biāo)系上用小點(diǎn)繪制了平均羽毛顏色的散點(diǎn)圖。
To translate this into a “showiness” score, the researchers started from the fact that, despitethe exceptions, showiness is still more a male than a female phenomenon. They thereforecalculated, as a proxy for showiness, a “maleness” score for each dot, regardless of which sexit represented, by counting the sexes of its nearest 120 neighbours in the graph (ie, thenearest 1% of dots). They then ran these scores against characteristics, such as the size of aspecies, its habitat and its pattern of family life.
為了轉(zhuǎn)化成“絢麗”分?jǐn)?shù)，研究者從事實(shí)發(fā)現(xiàn)：除了個(gè)別例外，炫耀現(xiàn)象雄性多余雌性。因此他們計(jì)算出每一“雄性”點(diǎn)得分：無(wú)論雌性還是雄性有絢麗的裝飾物，通過(guò)計(jì)算它附近120個(gè)兩性點(diǎn)(將近1%的點(diǎn))。然后將這些分?jǐn)?shù)對(duì)比特征，比如物種的大小，棲息地以及生活習(xí)性。
Their first observation, as they report this week in Nature, was that in species where a fewmales monopolise all the females, with a consequent lack of male involvement in parental care,males were more colourful than females. This is what the theory of sexual selection wouldpredict. What it would not predict in its simple form, though, was a second finding—thatfemales in co-operatively breeding species (those in which, for lack of other opportunities,several females collaborate to raise the young of only one of them) are more ornamented thanthose in which all adult females have a chance of breeding. In this case it is females who arecompeting for the right to reproduce, thus putting themselves in a more male-like position.
他們第一次觀察報(bào)告結(jié)果出版在本周《自然》上：在少量雄性配對(duì)所有雌性的物種，在親代撫育中缺少雄性角色的緣故，雄性比雌性更艷麗。這是性選擇理論做出的預(yù)測(cè)。然而，這個(gè)簡(jiǎn)單形式的理論不能預(yù)測(cè)的是第二個(gè)發(fā)現(xiàn)：在合作哺育的物種(缺少雄性情況下，幾個(gè)雌性合作只能撫養(yǎng)其中一個(gè)后代)，雌性比有機(jī)會(huì)和雄性一起繁殖后代的雌性更花哨。這個(gè)例子中正是雌性完成了繁殖的任務(wù)，因此他們扮演了雄性的角色。
Another widespread belief Dr Dale and his colleagues confirmed is that tropical species aremore colourful than those from temperate climes. But again, there was a twist—the effect wasmuch more marked in females than in males. Something about the tropics favours colourfulfemales. It may be that tropical birds, which face more intense competition for food andnesting sites than temperate ones do because the tropics have more species, form morestable and collaborative pair-bonds than do temperate birds. In these circumstances malesalso need to be choosy, and females competitive. Selection for gaudy plumage therefore worksin both directions.
戴爾博士和同事證實(shí)的另一個(gè)普遍的觀點(diǎn)是，熱帶氣候里的物種比溫帶的更鮮艷。但有一點(diǎn)不同——這種效果雌性比雄性表現(xiàn)得更明顯。熱帶環(huán)境偏愛(ài)外表鮮艷的雌性。這可能是熱帶鳥(niǎo)類形成了更穩(wěn)定更協(xié)作的一夫一妻制，因?yàn)闊釒в懈辔锓N，熱帶鳥(niǎo)類比溫帶鳥(niǎo)類存在更激烈的食物競(jìng)爭(zhēng)和巢穴競(jìng)爭(zhēng)。這種環(huán)境下雄性挑選配偶，而雌性去競(jìng)爭(zhēng)。因此絢麗羽毛在自然選擇上往兩個(gè)方向發(fā)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 difficultprey and thus have less need to hide. When released from the threat of predation, then,females tend to be gaudier. That suggests gaudiness is always good when it can be got awaywith (for even in a promiscuous species, pretty females are likely to be at an advantage tougly ones)—and probably explains the decorated necks and heads of peahens, which are amongthe biggest of birds.
研究人員發(fā)現(xiàn)的最后一個(gè)結(jié)果是，體型大的物種比體型小的更鮮艷。雌性和雄性都符合這點(diǎn)，也反映了大型鳥(niǎo)不容易被捕殺故而不必隱藏的事實(shí)。一旦沒(méi)有天敵的威脅，雌性就變得更花哨。這表明在沒(méi)有天敵威脅下，華麗點(diǎn)總是好的(即使在一個(gè)濫交的物種，漂亮的雌性比丑的可能更有優(yōu)勢(shì))，也解釋了為何雌孔雀擁有艷麗的脖子和頭部，因?yàn)樗求w型最大的鳥(niǎo)類。
Putting these results together, then, suggests that what is happening in the arena of sexualselection is as much to do with females as with males. Just as females are half the world, so theconventional explanation of the peacock's tail, though not wrong, is only half the story.
這些結(jié)果一起暗示了性選擇過(guò)程中雌性和雄性變化一樣多。就像雌性占世界的一半，孔雀尾巴的傳言雖然不是錯(cuò)的，但只是故事的一半。
1.show off 炫耀
例句:All right, there's no need to show off.
好了，沒(méi)必要炫耀。
2.by no means 決不
例句:This proposal is by no means a sure thing.
這個(gè)提議絕不會(huì)理所當(dāng)然地獲得通過(guò)。
3.likely to 可能
例句:This is likely to revive consumer spending and a whole raft of consumer industries.
這可能會(huì)帶動(dòng)消費(fèi)性支出和一大批消費(fèi)工業(yè)的復(fù)蘇。
4.for example 例如
例句:Aryl disulfides, for example, inhibit polyolefin oxidation.
例如芳基二硫化物可抑制聚烯烴的氧化。
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