A scientist from the United States found evidence that earlier people were sleeping at least two times less. 8 hour sleep as "the norm" has come to us only after the invention of electricity.
If from time immemorial phase of the human dream lasts 4 hours, in ancient times people did a one-hour break between them. During this period people read prayers, talked, watched.
Study author Roger Ekirch believes that such a revival among the nights are very useful for the human body.
Some even visited during such hours between sleep, the author was able to collect over 500 ancient documentary evidence of such a regime. So taking into account breaks were spent on sleep Colo 9 hours.
But then it was invented electricity, so to prolong the evening was easy, but it has been extended by reducing night time waking, that people gradually switched to continuous 8 hour sleep, which is now all doctors recommend as the norm. But to return to the old "natural" form of sleep is easy enough to hold in the dark about 14 hours, then people will Wake up every 4 hours.
This experiment has been conducted by the author, and even a group of volunteers.