前面是讲：deep dream sleep差不多是（顶级）捕猎者的专利，因为理论上它们可以高枕无忧；
后一句是讲：即使（顶级）捕猎者，譬如狮子老虎，也有危险期（譬如幼年期），而幼年期的（顶级）捕猎者“高枕无忧一动不动”有可能是避免了它们乱动反而陷入悲剧（譬如被其它捕猎者看到吃掉）的一种演化。这里的stupid是too young to be smart的缘故。

嗯，我又把上下文多延伸阅读了些，发现我前面理解得不准确。

原文这段其实在强调：睡眠导致动物不能动弹反而是在一些高风险期（譬如捕猎者的幼年期）保护了动物。所以说这个是个有趣的观点而且至少部分为真。

然后，原文又说这种想法并不能解释全部。譬如，为何几乎没有自然天敌的狮子也演化出需要睡觉（指不动的深度睡眠）？。。。然而，因为在※※长河中，现在在食物链顶层的动物也可能以前也是被捕猎的对象。。。

总之，原文主要在生物演化层面分析动物的睡眠，国内考试文貌似主要在讲睡眠这一具体事项上。
本帖最后由 ColorPig 于 2020-9-16 16:45 编辑

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搜到的可能的国外原文

There is some recent evidence that the two types of sleep, dreaming and dreamless, depend on the lifestyle of the animal.

Truett Allison and Domenic Ciccheti of Yale University have found that predators are statistically much more likely to dream than prey, which are in turn much more likely to experience dreamless sleep. These studies are all of mammals and apply only to differences between, not within, species. In dream sleep, the animal is powerfully immobilized 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. It is also commonly held that when sleeping dogs move their legs in a kind of running pattern, they are dreaming of the hunt.

The fact that deep dream sleep is rare among prey today seems clearly to be a product of natural selection. But organisms that are largely prey today may have had ancestors that were predators, and vice versa. Moreover, predators are generally organisms with larger absolute brain mass and ratio of brain to body mass than their prey. It makes sense that today, when sleep is highly evolved, the stupid animals are less frequently immobilized by deep sleep than the smart ones. But 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, no place to hide in the ocean. Could it be that, rather than increasing an animal’s vulnerability, the function of sleep is to decrease it? Wilse Webb of the University of Florida and Ray Meddis of London University have suggested this to be the case. The sleeping style of each organism is exquisitely adapted to the ecology of the animal. 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.

供更详细的上下文参考：https://www_bibliotecapleyades_net/ciencia/sagan/ciencia_sagan_dragon06.htm 本帖最后由 ColorPig 于 2020-9-16 10:58 编辑

记得原文里把sleep分为 deep dream sleep （有梦的深度睡眠，不易醒），dreamless sleep（无梦浅睡，易醒）
显然不同的两种睡眠是此段文章（或者说动物睡眠演化研究）的重点。

而且哪种动物演化出（习惯性）哪种睡眠方式为主，和是捕猎者还是被捕猎者都密切相关。

By the way，阅读这些科技英语，其实和科学与逻辑密不可分（也可以借用英语学习中的术语“上下文”）。

Good points!   

看了下原文，大致意思“受毫不留情的睡眠（之手/魔爪）所控，故而动弹不得”。

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 seems particularly clear for the young of predatory animals; not only are baby tigers covered with a superbly effective protective coloration, they also sleep a great deal.

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k版

看迷糊了

That's a good suggestion

哈哈，马兄，不按快门机身会生锈、镜头会长绿毛毛的。

还得感谢k版两年前号召学英语引发了俺的学习热情！到现在感觉兴趣还保持的可以，觉得也算是娱乐及健身吧，效果倒不是太关注。等天凉快了赶紧去按快门，到歪楼向诸位老兄请教。