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万物简史(MP3+中英字幕) 第490期:多灾多难的生命进程(10)

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Dinosaurs, whales, birds, humans, even fish— all are tetrapods, which clearly suggests they come from a single common ancestor. The clue to this ancestor, it was assumed, would be found in the Devonian era, from about 400 million years ago. Before that time nothing walked on land. After that time lots of things did. Luckily the team found just such a creature, a three-foot-long animal called an Ichthyostega. The analysis of the fossil fell to Jarvik, who began his study in 1948 and kept at it for the next forty-eight years. Unfortunately, Jarvik refused to let anyone study his tetrapod. The world's paleontologists had to be content with two sketchy interim papers in which Jarvik noted that the creature had five fingers in each of four limbs, confirming its ancestral importance.

恐龙、鲸、鸟、人甚至鱼——都是四足动物。这显然表明,它们出自一个共同的祖先。据认为,这个祖先的线索要在大约4亿年以前的泥盆纪寻找。在此之前,陆地上没有行走的动物。在此之后,许多动物在陆地上行走。很走运,那个小组恰好发现一个这样的动物。一个1米长的名叫鱼甲龙的动物。分析那个化石的任务落在贾维克身上。他于l948年开始研究,这项研究持续了48年。不幸的是,贾维克不让别人插手他的研究工作。世界上的古生物学家不得不满足于两篇简短的临时性论文。贾维克在论文中指出,那种动物有4肢,每肢有5个指头,确认了它的祖先地位。
鱼甲龙

Jarvik died in 1998. After his death, other paleontologists eagerly examined the specimen and found that Jarvik had severely miscounted the fingers and toes—there were actually eight on each limb—and failed to observe that the fish could not possibly have walked. The structure of the fin was such that it would have collapsed under its own weight. Needless to say, this did not do a great deal to advance our understanding of the first land animals. Today three early tetrapods are known and none has five digits. In short, we don't know quite where we came from.

贾维克于l998年去世。他死了以后,别的古生物学家连忙对那件标本做了仔细研究,发现贾维克把指头或脚趾的数目大大地数错了——每肢其实有8个——而且没有注意到那种鱼很可能不会走路。从鳍的结构看来,它支撑不起自身的重量。不用说,这对增进我们对第一批陆地动物的了解没有作出多大贡献。今天,已经知道早期有三种四足动物,但没有一种跟数字5有关系。总之,我们不大清楚我们是从哪儿来的。

重点单词   查看全部解释    
analysis [ə'næləsis]

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n. 分析,解析

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assumed [ə'sju:md]

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adj. 假装的;假定的

 
limb [lim]

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n. 枝干,树枝,肢体
vt. 切断(树枝,手

 
interim ['intərim]

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adj. 中间的,暂时的,临时的
n. 中间时

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ancestor ['ænsistə]

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n. 祖宗,祖先,原种

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fin [fin]

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n. 鳍,鱼翅,鳍状物,散热片,五元纸币 vt. 装上鳍

 
sketchy ['sketʃi]

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adj. 概略的,不完全的,略图的,不确定的

 
fell [fel]

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动词fall的过去式
n. 兽皮
v

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needless ['ni:dlis]

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adj. 不需要的,无用的

 
observe [əb'zə:v]

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v. 观察,遵守,注意到
v. 评论,庆

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