新托福 考试写作考生想拿高分，“肚子里必须有点墨水”，背上一篇两篇优秀范文，以备不时只需。以下这篇范文的题目是：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 pre
