Evolution of sleep
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.
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 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. The fact that deep dream sleep is rare among pray today seems clearly to be a product of natural selection, and it makes sensethat 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 genera 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 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 quite 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. This is an interesting notion and probably at least partly true
2017英语六级口语考试练习(4):睡眠的进化.doc正在阅读:
游记作文400字08-05
广西理工职业技术学院2021高考录取通知书查询入口08-04
学校开学典礼活动总结四篇08-19
革命传统教育活动心得体会600字:革命传统教育活动心得体会【四篇】07-06
2023年江苏省苏州市太仓市中小学社会实践基地招聘财务助理员公告08-11
2022年重庆口腔执业医师医学综合考试时间:8月19日-20日【附机考考试规则】08-20
2017上半年重庆教师资格初中信息技术学科知识与教学能力真题及答案(Word版)08-23