What is the best title of the passage? A. Three kinds of Loneliness B. Loneliness and Diseases C. Loneliness and Social Contacts D. Chronic Loneliness B 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 the 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 stop its activity at night and to wake up at dawn the next morning. According to the evolutionary theory of sleep, evolutionary equipped us with a regular pattern of sleeping and walking for the same reason. Theory does not deny that sleep provides some important restorative functions. It merely says that evolutionary 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 a familiar, safe place, but we sleep lightly, if at all, when we fear that bears will nose into the tent. The evolutionary theory explains the differences in sleep among creatures. Why do cats, for example, sleep so much, while horses sleep so little? Surely cats do not need five times as much repair and restoration as horse 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. Horse must spend over, they cannot afford to sleep too long or too deeply, because their survival depends on their ability to run away from attackers. 【查看更多】
