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 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 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 animals vulnerability, the University of Florida and Ray Middies 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.
体坛英语资讯:AFC Asian Cup: Group stage ends with Oman, Vietnam advancing last
你愿意为知识付费吗?
体坛英语资讯:South Korea beat China 2-0 to finish top of Group C at Asian Cup
娱乐英语资讯:Interview: Bollywood film actress Rani Mukerji calls for more Indo-China film production
体坛英语资讯:Preview: Ronaldo poses main threat to Atleticos European ambitions
国际英语资讯:OSCE envoy notes lack of progress in resolving conflict in Ukraine
皮特低调参加前妻生日派对?这是要闹哪样
国内英语资讯:State Council releases vocational education reform implementation plan
国内英语资讯:Chinese investors could help build Kenya into regional manufacturing hub: lobby
机场中转未登机 汉莎航空起诉乘客并索赔
国内英语资讯:Chinas C919 jetliner to speed up test flights in 2019
这个售价650美元的“思考箱”在推特上火了!里面都有啥?
貌美如花的人变老是什么感觉?
貌美如花的人变老是什么感觉?
娱乐英语资讯:Kacey Musgraves, Childish Gambino take top awards at 2019 Grammys
体坛英语资讯:Ice hockey gaining popularity ahead of Beijing 2022 Winter Games
国内英语资讯:Commentary: Egregious accusations ignore basic facts on Xinjiang
体坛英语资讯:Ajax narrow margin with PSV to four points
比伯也在治疗抑郁症? 明星的状态你真的想不到
国际英语资讯:Polish president says U.S. troop increase in Poland can be expected
国际英语资讯:Feature: Fresh construction projects spring up amid improved security in Iraq
国内英语资讯:Vice premier urges solid efforts for biodiversity conservation
My Loneliness 我的孤独
促进肠道健康的简单方法
国际英语资讯:Sudanese president declares 2019 as year for peace in Sudan
国际英语资讯:Brazils Bolsonaro released from hospital after 17 days
有哪些知识最毁三观?
致情人配偶的一封信
国际英语资讯:Death toll rises to 15 in Nigeria campaign rally stampede
苹果窃听漏洞竟是由14岁孩子发现的!震惊到我了
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |