Evolution and Wheels

 In the past, evolutionary biologists contemplating the absence of wheels in

 nature agreed that the explanation was      not undesirability: wheels would be

 good for animals, just as they are for us. Animals were prevented from

 evolving wheels, the biologists reasoned, by the following dilemma: living

cells in an animal's body are connected to the    heart by blood vessels, and

 to the brain by nerves. Because a rotating joint is essential to a wheel, a

 wheel made         of living cells would twist

 its artery vein and nerve connections at the first revolution, making

 living          impracticable. However, there is a flaw in the argument that the

evolution of wheeled animals was thwarted

 by the insoluble joint    problem. The theory fails to explain why animals

 have not evolved wheels of  dead  tissue  with  no  need  for  arteries   

 and  nerves.  Countless  animals,  including  us,  bear external structures

 without blood supply or nerves - for        example, our hair and fingernails, or

 the scales, claws, and ho rns of other animals. Why have rats not evolved     

 bony wheels, similar to roller skates?Paws  might be more useful than

wheels in some situations, but  cats' claws are retractable: why not

 retractable wheels?We thus arrive at the serious biological paradox

flippantly termed the RRR     dilemma: nature's failure to produce rats with

retractable roller skates.

進化與輪子 

 從前，研究自然界沒有輪子的進化論生物學家都同意不能用無此需要來解釋 這種現象：輪子對于動物會像對于我們人類一樣有好處。

 生物學家們推論，動物沒有進化 出輪子是由下述困難所致：動物身上的活細胞通過血管與心臟相連，通過神經與大腦相連。

 因為一個旋轉的接頭對輪子來說是至關重要的，由活的細胞構成的輪子在第一次轉動時便會 扭傷其上的動脈和神經的連結，因而不現實。

 不過，動物未能進化出輪子是受阻于無法解決接頭問題的說法有一個缺陷。  這種理論 無法解釋為何動物沒有進化出由死組織構成的而無需動脈和神經的輪子。

 包括人在內的無 數動物都有一些沒有血液供應和神經的體外構造，例如，我們的頭發和指甲，或者鱗片、爪 子和其它一些動物的角。

 為什么老鼠沒有進化出類似于滑輪溜冰鞋的骨質的輪子呢?在某些 情況下，爪子可能比輪子更有用，但貓的爪子是可以伸縮的：  為什么不能有可以伸縮的輪

 子呢?這樣，我們便得出了一個被戲稱為 RRR 的嚴肅的生物學悖論：大自然未能產生出有可 伸縮的滑輪溜冰鞋的老鼠。

譯路通武漢江漢區翻譯公司整理

2012.6.19