[janereinheimer]

“Most people need somewhere in the negihborhood of 8 hours sleep a night ...”

The average amount of time that adults slept at the turn of the century (1900s) was 9-1/2 hours a night. The fact that we’ve turned that back to an average of 8 hours a night says a lot about cultural expectations.

Cave studies put research participants at about 10 hours when they are left to their own devices and without any external cues to tell them what time it is or how much time has passed since they last slept.

— Jane

[tlj18]

That is extremely interesting. Apparently, our modern electrified age has reduced the amount of sleep that is considered normal and acceptable. Some people might say that sleeping 12 hours a day is laziness, but once you are asleep, aside from alarms, there isn't much you can do about it. I can sleep through a lot. Well, a good Soldier is said to be able to sleep whenever he can....

Just not for half the day, though.

[GovernmentShrinker]

True, although external cues (daylight, temperature changes, birds making noise, etc.) are a natural part of our sleep/wake cycle system, so I don’t know that the results one gets when they’re removed provide any reliable information about what amount of sleep is “natural”. And of course, at the turn of the century, the vast majority of people were still spending most of their day engaged in fairly vigorous manual labor of one sort of another, and quite possible needed more sleep than if they’d been leading a less physically demanding life.

One thing that is certainly natural is to sleep more in the winter (i.e. when nights are longer), and less in the summer. That is a factor that’s been pretty much wiped out by the combination of convenient electric lighting everywhere, and work and school schedules which are fixed year-round.