[quote name='Fat Rich' timestamp='1379938791' post='2218413']
Secondly, there's some historical evidence that we never used to sleep right through the night, there are references to "First sleep" and "second sleep" in some old literature and paintings of people up and about during the night.
[/quote]
Yes, I read something about that recently... before gas/electric lighting, people without access to large amounts of candle-power (everyone except the chandelier-toting aristocracy?) Would go to bed when it got dark, when wake up (and do what?!) four hours later.