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1、新概念英语优美短文背诵： Evolution of Sleep Evolution of Sleep 睡眠的进化 Sleep is very ancient. In the electroencephalographic sense we share it with all the primates and almost all the other mammals and birds ： it may extend back as far as the reptiles. 睡眠自古就有。从脑电图上看，我们人类和所有灵长目动物以及几乎 所有的哺乳动物和鸟类都一样需要睡眠；甚至爬行类动物也有睡眠。
2、 There is some evidence that the two types of sleep, dreaming and dreamless, depend on the life-style of the animal, and that predators are statistically much more likely to dream than prey, which are in turn much more likely to experience dreamless sleep. In dream sleep, the animal is powerfully im
3、mobilized and remarkably unresponsive to external stimuli. Dreamless sleep is much shallower, and we have all witnessed cats or dogs cocking their ears to a sound when apparently fast asleep. 有证据显示，有梦睡眠和无梦睡眠这两种类型的睡眠取决于该动物的 生活方式。从统计上看，食肉动物比被捕食动物有更多的有梦睡眠， 而被捕食动物更多地无梦睡眠。动物在有梦睡眠时，被有效地解除动 作水平，并且对外界刺激缺乏反应
4、。无梦睡眠则要浅得多。我们都看 到过猫和狗在显然的酣睡中，有一点响动耳朵就会竖起来。 The fact that deep dream sleep is rare among prey today seems clearly to be a product of natural selection, and it makes sense that today, when sleep is highly evolved, the stupid animals are less frequently immobilized by deep sleep than the smart ones. Bu
5、t why should they sleep deeply at all? Why should a state of such deep immobilization ever have evolved? Perhaps one useful hint about the original function of sleep is to be found in the fact that dolphins and whales and aquatic mammals in general seem to sleep very little. There is, by and large,
6、no place to hide in the ocean. 被捕食动物很少有深度的有梦睡眠，这看来显然是自然选择的结果。 而且这个点是有道理的：当睡眠高度进化以后，愚笨的动物比聪明的 动物更少在深度睡眠状态下丧失动作水平。但是动物为什么要进入深 度睡眠呢？为什么这样的无动作状态也会进化出来呢？海豚、鲸鱼以 及水生哺乳动物睡眠都极少，这个事实能够给睡眠的根本功能提供有 用的线索。海洋中是没有藏身之处的。 Could it be that, rather than increasing an animals vulnerability, the function of sleep is to d
7、ecrease it? Wilse Webb of the University of Florida and Ray Meddis of London University have suggested this to be the case. It is conceivable that animals who are too stupid to be quiet on their own initiative are, during periods of high risk, immobilized by the implacable arm of sleep. The point se
8、ems particularly clear for the young of predatory animals. This is an interesting notion and probably at least partly true. 会不会是这样，睡眠不但不增加动物受伤害的可能性，反而是减少了 这种可能性呢？佛罗里达大学的 Wilse Webb 和伦敦大学的 Ray Meddis 认为情况就是如此。能够想像得出，在危险的时刻，那些因为太愚笨 而不能自动保持安静的动物，会不由自主地变得动弹不得。这个点在 食肉动物的幼兽身上表现得特别明显。这是一个很有意思的看法，它 至少是部分准确的。
