[考博英語]2017考博英語閱讀題源經濟學人文章每日精析（六十一）_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（六十一）

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

從生物的形成到進化的歷程中，我幾乎都能找到相對應的化石來證明，但是在3億6千萬至3億4千萬年前我們卻很難找到這一時期的化石來證明節肢動物和脊椎動物的進化歷程，這一時期就被稱為柔默空缺。有學者指出是因為石化問題，地層不適合形成化石，也有學者指出是考古挖掘人員沒有找對地方。

New fossils illuminate the route that led ultimately to human beings

最新發掘的化石照亮了人類進化之路

A 25m-year dark age known as Romer’s gap is dark no longer

柔默空缺這段2500萬年的黑暗時代終于揭開神秘面紗

ONE of the most important steps on the journey to Homo sapiens was that made by the first fish to crawl onto dry land. It was both a metaphorical and a literal step, but knowing exactly when it happened is tricky. It depends, for one thing, on the definition of “dry land”. Scrambling over the mud from one pool to another, assisted by fins that had evolved to walk along the seabed in the way modern coelacanths do, was probably going on by 385m years ago.

魚類首次爬上陸地無疑是生物向“智人”進化階段中的眾多重要步驟中的一步。這是既有字面又有隱喻意義的一步，但是要想弄清楚具體發生時間卻很難。這取決于“陸地”一次的定義。可能在大約3億8千5百萬年前，魚類就可以借助魚鰭從一個泥潭爬到另一個泥潭了。就像現代腔棘魚那樣，它們的魚鰭已經進化到可以在海床上行走了。

By 375m years ago, the descendants of these first-footers had evolved four limbs clearly recognisable as legs. They were no longer fish, but “tetrapods”. Their legs, though, could have as many as eight digits each, and do not look capable of supporting an animal properly when it was out of the water. Some might thus argue that even by this stage, the step onto dry land had not been truly made.

大約3億7千5百萬年前，第一批魚類“登陸者”的后代進化出了四肢(可以清晰的看出來是腿)。它們已經不再屬于魚類，而是“四足動物”。盡管它們每個腿的腳趾最多可以達到八個，但是看起來并不能夠支撐它們在陸地行走。因此有人認為甚至直到這一時期，魚類還沒有真正地從海洋爬上陸地。

All of these events occurred during a period called the Devonian when, though the oceans teamed with organisms no less varied than today’s, life on the continents was just getting going. Vascular plants (those bigger than mosses and liverworts) had evolved only recently. Insects were evolving fast, too. But there were no large land animals. Occupying the new habitat thus looked like an evolutionary open goal for the tetrapods. But then, 359m years ago, in a mass extinction as big as that which did for the dinosaurs, the Devonian came crashing to an end. (讀者試譯) For 25m years after this the tetrapods more or less disappear from the fossil record. When they re-emerge, in what is called the Lower Carboniferous period, they do, indeed, live up to their potential. They are now proper terrestrial animals, possessing five-digit limbs powerful enough to support them without the assistance of water’s buoyancy. But how they got there has been a mystery.

這一切都發生在泥盆紀時期，雖然當時的海洋生物多種多樣，種類一點也不比現在少，但陸地上的生命才剛剛開始。在這一時期，維管植物(比苔蘚和苔類要大)才剛剛出現。昆蟲類生物也在快速進化。但尚未有大型陸地生物。2千5百萬年后，四足動物差不多已從化石記錄里消失了。當它們再次出現時，已經到了始石炭紀時期。它們確實充分發揮了自身的潛力。現在它們已經是標準的陸生生物了，四肢都有五趾，無需借助海水的浮力即可支撐身體。但是四足動物如何進化成今天的樣子仍是個迷。

Buoyancy: n. 浮力

注：石炭紀：石炭紀(Carboniferous)約處于地質年代兩億八千六百萬至三億六千萬年前，它可以區分為兩個時期:始石炭紀(又叫密西西比紀，三億兩千至三億六千萬年前)、和后石炭紀(又叫賓夕法尼亞紀，兩億八千六百至三億兩千萬年前)。 石炭紀(Carboniferous period)是古生代的第5個紀，開始于距今約3.55億年至2.95億年，延續了6500萬年。石炭紀時陸地面積不斷增加，陸生生物空前發展。當時氣候溫暖、濕潤，沼澤遍布。大陸上出現了大規模的森林，給煤的形成創造了有利條件。