Thought this was interesting: (from a t-nation article of all places)
"In 2005, historian A. Roger Ekirch published a book named At Day's Close: Night in Times Past. In this book, Ekirch reveals what sleep looked like in pre-industrial times. Before there was electricity, before there were gaslights, people typically slept in two bouts they called first sleep and second sleep.
Within an hour or two after sunset, people would go to sleep, only to awaken about four hours later. Did they lie there and worry about taxes and their jobs and curse their circumstances? No, they got up and did household chores or visited with family or friends. They even used this time for sex.
Approximately two hours later, they'd go back to bed for another four hours or so.
Mind you, this was not social convention but innate physiology. It makes perfect sense, too, when you look at the rest of the animal kingdom. Almost all mammals that are active during the day, like chimps, giraffes, and yes by God, chipmunks, sleep in two distinct periods.
And when modern humans are freed from the time constraints imposed by modern life and modern lighting? They revert. Experiments where men are exposed to natural and artificial light for 10 hours a day and then confined to a dark room for 14 hours (similar to a winter's day and night) show that modern humans go back to segmented sleep. Likewise, anthropologists have observed similar segmented sleep patterns in certain modern African tribes."
Thoughts comments? I have to say I do find it interesting. Of course this assumes I go to bed at 7pm....which will never happen.