1994年1月英语四级 - 阅读理解A

Suppose we built a robot to explore the planet Mars. We provide the robot with seeing detectors to keep it away from danger. It is powered entirely by the sun. Should we program the robot to be equally active at all times? No. The robot would be using up energy at a time when it was not receiving any. So we would probably program it to cease its activity at night and to wake up at dawn the next morning.
假设我们造了一个机器人探索火星。我们为机器人提供了视觉探测器，使其远离危险，完全由太阳提供动力。我们应该对机器人进行编程，使其在任何时候都同样活跃吗？不。机器人在没有接收到任何能量的时候会消耗掉能量。所以我们可能会安排它在晚上停止活动，第二天早上醒来。

According to the evolutionary theory of sleep, evolution equipped us with a regular pattern of sleeping and waking for the same reason. The theory does not deny that sleep provides some important restorative functions. It merely says that evolution has programmed us to perform those functions at a time when activity would be inefficient and possibly dangerous. However, sleep protects us only from the sort of trouble we might walk into; it does not protect us from trouble that comes looking for us. So we sleep well when we are in familiar, safe place, but we sleep lightly, if at all, when we fear that bears will nose into the tent.
根据睡眠的进化理论，出于同样的原因，进化为我们提供了规律的睡眠和清醒模式。该理论并不否认睡眠提供了一些重要的恢复功能。它只是说，进化已经安排我们在活动效率低下且可能危险的时候执行这些功能。然而，睡眠只能保护我们免受可能遇到的麻烦；它并不能保护我们免受寻找我们的麻烦。所以，当我们在熟悉、安全的地方时，我们会睡得很好，但当我们担心熊会钻进帐篷时，我们会睡得很轻。

The evolutionary theory accounts well for differences in sleep among creatures. Why do cats, for instance, sleep so much, while horses sleep so little? Surely cats do not need five times as much repair and restoration as horses do. But cats can afford to have long periods of inactivity because they spend little time eating and are unlikely to be attacked while they sleep. Horses must spend almost all their waking hours eating, because what they eat is very low in energy value. Moreover, they cannot afford to sleep too long or too deeply, because their survival depends on their ability to run away from attackers.
进化论很好地解释了生物之间睡眠的差异。为什么猫睡得那么多，而马睡得那么少？当然，猫不需要像五倍于马的修复。但猫可以长时间不活动，因为它们很少花时间吃饭，睡觉时也不太可能受到攻击。马几乎醒着的时候都要吃东西，因为它们吃的东西能量很低。此外，他们不能睡得太久或太深，因为他们的生存取决于他们逃离攻击者的能力。