[考博英語]2017考博英語閱讀題源經濟學人文章每日精析（八十八）_考博_旭晨教育

2017 考博英語 閱讀題源經濟學人文章每日精析（八十八）

考博英語閱讀大部分博士研究生招生院校都使用《經濟學人》雜志文章作為題源，旭晨教育考博頻道為考博生們將其中的文章進行深度分析，希望能提高大家的考博英語閱讀水平，讀懂長難句。

導讀

貓和小熊貓屬于食肉目不同的科：大熊貓屬于熊科，而小熊貓屬于鼬超科中的小熊貓科，二者分歧已有4000多萬年。盡管其系統發育關系較遠，它們卻演化出相同的食竹食性;更為有趣的是，這兩種熊貓的前掌還演化出一個特殊的結構——偽拇指，以幫助抓握竹子，是適應性演化和趨同演化的經典案例。

Panda genetics

熊貓遺傳學

Two strange mammals illuminate the process of natural selection

兩種不同的哺乳動物闡明自然選擇的過程

Hey dude. Give me six!

嘿，伙計。用六指擊個掌吧!

Jan 21st 2017

2017年1月21日

CONVERGENT evolution—the arrival, independently, by different species at the same answer to a question posed by nature—is a topic of great interest to biologists. One aspect of the phenomenon which has not yet been much looked at, however, is its underlying genetics. In particular, an issue not previously addressed is how often such changes arise from similar mutations in the two convergent lines, and how often they have different genetic causes that happen to have similar effects on the organisms’ forms and functions. That has now been rectified by an examination of two creatures which, though only distantly related, share an unusual feeding habit, an unusual anatomical feature and an unusual name: panda.

趨同進化是生物學家們有著極大興趣的話題，它是指在自然作用下，不同物種獨立的共同進程。然而該現象在潛在基因方面尚未得到許多的關注。尤其是在兩條趨勢線中來自相似基因突變引起趨同變化的頻率，以及不同基因對生物的形態功能起到相似作用的概率的方面，尚未得到解決。如今通過對兩種生物的檢驗已得到糾正，雖然這兩種動物是遠親，但他們都具有與眾不同的飲食習性、解剖特性以及一個不尋常的名字：熊貓。

mutation [mju?'te??(?)n] n.突變

anatomical [?n?'t?m?k(?)l] adj.解剖的

注：convergent evolution——趨同進化：不同的物種在進化過程中，由于適應相似的環境而呈現出表型上的相似性。也指不同起源的蛋白質或核酸分子出現相似的結構和功能。

The giant panda is a black and white bear. The red panda is related to weasels, raccoons and skunks. Their habitats—mountainous areas of southern China and its neighbours—overlap, but their last common ancestor lived 43m years ago. They do, though, share a limited kinship, for both are members (along with dogs, cats, hyenas, mongooses, seals and so on) of the mammalian order Carnivora. Which is curious, because both are vegetarian.

大熊貓是一種黑白相間的熊。小熊貓與鼬鼠，浣熊和臭鼬具有親屬關系。他們的棲息地在華南山區且近親重疊，在4300萬年前，他們有著共同祖先。盡管如此，由于它們都是食肉目哺乳動物類(像狗，貓，鬣狗，貓鼬，海豹等)，所以確實有一些相同的血緣關系。令人好奇的是它們都是食草動物。

weasel ['wi?z(?)l] n.鼬鼠

skunk [sk??k] n.臭鼬

hyena [ha?'i?n?] n.鬣狗

mongoose ['m??gu?s] n.貓鼬

carnivora [kɑr'n?v?r?] n.食肉類; 食肉目

More intriguing still, both subsist almost entirely on bamboo (some etymologists think their mutual name is derived from the Nepali phrase nigalyaponya, meaning “bamboo-eater”). And most curiously of all, both have a sixth digit on their forepaws—a kind of ancillary thumb derived from one of the bones of the wrist that helps them hold bamboo stalks for consumption.These common features led Hu Yibo of the Institute of Zoology, in Beijing, and his colleagues, to wonder if the two vegetarian carnivores also shared genetic modifications that might explain those features. And, as Dr Hu observes in a paper just published in the Proceedings of the National Academy of Sciences, they do.

更有趣的是，它們幾乎完全以竹子為食(一些詞源學家認為它們的共同名字源于尼泊爾語nigalyaponya，指“食竹者”)。最令人驚奇的是，它們的前爪上都長有第六指，是從腕骨長出用來幫助它們在進食時拿住竹莖的輔助拇指。基于這些共同特征，北京動物研究所的胡一波和他的同事們設想，這兩種食肉目食草動物是否共有一種能解釋這些特征的修飾基因。正如胡博士剛剛在《美國國家科學院院報》發表的論文中所說的，它們確實共有。

Intriguing ['?ntri?g??] 有趣的

Ancillary [?n's?l?r?] 輔助的

To search for such genetic commonalities, Dr Hu and his colleagues compared the DNA of the two pandas with that of four other members of the Carnivora: polar bears (close relatives of giant pandas),ferrets (close relatives of red pandas), and tigers and dogs (close relatives of neither). If pandas share features of their DNA with each other, but not with the four comparison species, he reasoned, then it is likely that those features encode recent adaptations common to the two of them.

為了找到這樣的遺傳共性，胡博士團隊將兩只熊貓的DNA與另外4種食肉目動物(北極熊(大熊貓的近親)，白鼬(小熊貓的近親)，老虎和狗(非兩者近親))的DNA進行比較。如果熊貓們有相同的DNA特征，而四種對照物種沒有熊貓所共有的DNA特征，他則推理很有可能這些DNA特征編碼了它們兩者間近代的共同特性。

Ferret ['fer?t] 雪貂

Altogether, the team identified 70 genes (out of the 20,000 or so that mammals have) which sport bits of DNA that seemed to be shared. They also found ten genes which have been disabled by crippling mutations in both of the pandas, but not in the other four species. Not all of the shared genetic features obviously tied in with the shared peculiarities of pandas, but some did. These fell into three categories: genes affecting anatomy, genes affecting appetite and genes affecting the digestion and metabolism of nutrients.

研究小組從哺乳動物約20000個基因中，確定了可以共有的70個DNA片段。他們也在兩種熊貓中找到了十個因嚴重突變而喪失功能的基因，而其他四個物種中并未發現。盡管哺乳動物共有遺傳特征并不都與熊貓的特性一致，但有些確實具有一定的關系。這分為三類：影響動物體結構的基因，影響食欲的基因和影響營養物質消化和新陳代謝的基因。

peculiarity [p?,kju?l?'?r?t?] n.古怪; 怪癖; 特色; 奇形怪狀;

metabolism [m?'t?b?l?z(?)m] n.[生理]新陳代謝