经济学人112:进化并不总是意味着改变

 　　Science and Technology Palaeontology Splay-footed, not flat-footed

　　科技 古生物学 八字足，而非平足

　　A new fossil shows that evolution does not always mean change

　　一个新的化石表明：进化并不总是意味着改变

　　WHEN a coelacanth, a type of lobe-finned fish once considered the missing link between fish and amphibians¹, was found off the coast of South Africa in 1938, it came as a shock to palaeontologists. Until then, the most recent traces of such a creature had been in rocks dating from the last days of the dinosaurs², 65m years ago. It was, in its way, as surprising as if a live Tyrannosaurus had been found hiding in an obscure part of Montana. Now the same experience is hitting palaeontologists again—but this time in reverse. Instead of finding a "living fossil" identical to an ancient beast, they have found a real fossil identical to a modern one.

　　以前人们一度认为一种叫做腔棘鱼的鳍鱼是鱼类和两栖类之间缺少的环节，1938年当腔棘鱼在南非海岸沿海被发现时，古生物学家对它的出现大感震惊。在此之前，这种动物最近的遗迹出现在6500万年前恐龙时代后期的岩层中。而它这次的出现方式，就好像一个活生生的霸王龙属被发现藏身在蒙大拿州的模糊地带一样令人惊讶。现在，同样的经历再次让古生物学家碰上了，不过这次相反。他们不是找到了一个与古兽相同的"活化石"，而是找到了一个跟现代兽类相同的真正化石。

　　The fossil in question, a 100m-year-old specimen³ from north-east Brazil, belongs to the genus Schizodactylus. These are large, carnivorous, cricket-like insects whose feet splay out wildly in different directions. Modern Schizodactylus use their feet like snowshoes, to help them remain stable as they travel over sandy terrain⁴ in search of prey⁵.

　　所讨论的的化石采自巴西东北部，是一亿年前的标本，属于节肢动物类。这类节肢动物是大型类似板球的食肉昆虫，其足向不同方向伸展开来。现代节肢动物在沙地爬行寻找猎物时用它们雪鞋般的脚来帮助身体保持稳定。

　　If the new fossil—whose discovery has just been published in ZooKeys by Sam Heads of the Illinois Natural History Survey and Léa Leuzinger of the University of Fribourg, in Switzerland—were merely similar to modern splay-footed insects, the find would not be particularly surprising: it simply demonstrates a phenomenon called evolutionary⁶ stasis, in which a specific type of body form hangs around for a long time. What is surprising is just how static Schizodactylus has been.

　　如果新化石（其发现刚由伊利诺斯州自然史调查的负责人山姆和瑞士弗里堡大学的李?劳伊辛格发表在《动物图谱》上）仅是类似现代的八字足昆虫，那么这个发现不会特别令人惊讶：它只是证明了一种被称为进化停滞的现象，在这种现象中特定类型的体型存留很长一段时间了。令人惊讶的是节肢动物停止进化竟有这么久了。

　　Evolutionary stasis is fairly common at the higher levels of the Linnaean system of biological classification (class, order and family). Natural selection hits on a good design. That design is then adopted in slightly different forms by species after species. The shelled bodies of turtles, for example, evolved between 250m and 200m years ago, while the body plans of scorpions⁸ have been around for more than 400m years. That does not mean, however, that a zoologist⁹ would mistake a 200m-year-old turtle or a 400m-year-old scorpion⁷ for any species now alive.

　　在林耐生物分类（类，属和门）系统的高等类别中进化停滞现象是相当普遍的。自然选择的图案都是最好的。然后，这种图案就被一个接一个的物种以略有不同的形式所采纳。例如，海龟的壳体是在2.5～2.0亿年前进化的，而蝎子的体型方案已超过4亿年的历史。然而这并不意味着一个动物学家会弄错2亿岁的海龟或是4亿岁的蝎子属于现在存活的何种物种。

　　What is remarkable¹⁰ about the new find is that it is so similar to modern animals that it can be assigned to an existing genus—the lowest level of Linnaean classification above a species—rather than just to some higher taxonomic group. That is rare indeed. Even the modern coelacanth, on closer examination, had to be put in a different genus from any known fossil.

　　新发现引人注目的是它与现代动物如此相似，以致它可以被列入现有生物分类种类（林奈物种以上分类的最低等），而不是只被列入某一更高等的分类组。这的确罕见。经过仔细观察，甚至就连现代腔棘鱼都必须得归类于不同于任何已知化石的种类。

　　Clearly the body plan of Schizodactylus is not merely good, but optimal¹¹, at least for the environment the animal lives in. Alas¹² for Schizodactylus, the sandy deserts it prefers have retreated from north-eastern Brazil and its optimality¹³ there has vanished. But its discovery shows better what this part of the world was like 100m years ago—and also illustrates¹⁴ an important point about evolution that is often forgotten in biologists' understandable focus on the development of novelty. The first rule of natural selection is: "If it ain't broke, don't fix it."

　　显然，节肢动物的体型方案不仅是最好的，也是最佳的，至少对这种动物生活的环境而言是如此。唉，对节肢动物来说，它所喜爱的沙质沙漠已经从巴西东北部退却，它在那里的最佳体态已经消失。但它的发现恰好说明这部分的大千世界跟1亿年前的样子很象，也说明了进化论的一个重点，而这点在生物学家关注理解新颖性的发展时往往被遗忘了。自然选择的第一条规则是："如果没坏，就不要修理它。"

1 amphibians   

两栖动物( amphibian的名词复数 )； 水陆两用车； 水旱两生植物； 水陆两用飞行器

参考例句：

• The skin of amphibians is permeable to water. 两栖动物的皮肤是透水的。
• Two amphibians ferry them out over the sands. 两辆水陆两用车把他们渡过沙滩。

2 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

3 specimen   

n.样本，标本

参考例句：

• You'll need tweezers to hold up the specimen.你要用镊子来夹这标本。
• This specimen is richly variegated in colour.这件标本上有很多颜色。

4 terrain   

n.地面，地形，地图

参考例句：

• He had made a detailed study of the terrain.他对地形作了缜密的研究。
• He knows the terrain of this locality like the back of his hand.他对这一带的地形了如指掌。

5 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。

6 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

7 scorpion   

n.蝎子，心黑的人，蝎子鞭

参考例句：

• The scorpion has a sting that can be deadly.蝎子有可以致命的螫针。
• The scorpion has a sting that can be deadly.蝎子有可以致命的螫针。

8 scorpions   

n.蝎子( scorpion的名词复数 )

参考例句：

• You promise me that Black Scorpions will never come back to Lanzhou. 你保证黑蝎子永远不再踏上兰州的土地。 来自电影对白
• You Scorpions are rather secretive about your likes and dislikes. 天蝎：蝎子是如此的神秘，你的喜好很难被别人洞悉。 来自互联网

9 zoologist   

n.动物学家

参考例句：

• Charles darwin was a famous zoologist.查尔斯达尔文是一位著名的动物学家。
• The zoologist had spent a long time living with monkeys.这位动物学家与猴子一起生活了很长时间。

10 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。

11 optimal   

adj.最适宜的；最理想的；最令人满意的

参考例句：

• What is the optimal mix of private and public property rights in natural resources?私人和国家的自然资源产权的最适宜的组合是什么？
• Optimal path planning is a key link for the sailing contest.帆船最优行驶路径规划是帆船比赛取胜的关键环节。

12 alas   

int.唉(表示悲伤、忧愁、恐惧等)

参考例句：

• Alas!The window is broken!哎呀！窗子破了！
• Alas,the truth is less romantic.然而，真理很少带有浪漫色彩。

13 optimality   

n.最优性；最佳性

参考例句：

• The optimality method are introduced on slope cutting project in the paper. 将优化理论引入到削坡方案的选择上。 来自互联网
• The necessary conditions for optimality were derived calculus of variations. 利用变分法原理，推导出满足优化问题的必要条件。 来自互联网

14 illustrates   

给…加插图( illustrate的第三人称单数 )； 说明； 表明； （用示例、图画等）说明

参考例句：

• This historical novel illustrates the breaking up of feudal society in microcosm. 这部历史小说是走向崩溃的封建社会的缩影。
• Alfred Adler, a famous doctor, had an experience which illustrates this. 阿尔弗莱德 - 阿德勒是一位著名的医生，他有过可以说明这点的经历。 来自中级百科部分