Fairly interesting article about sleep in the latest SA Mind. Sleep has never been easy for me, so I'm always interested in learning more about it. As it turns out, we're the only mammal that seems to want to try and sleep for a continuous period of time. Even odder, it now seems that until recently (several hundred years ago, with artificial nighttime illumination) in fact most people did not necessarily sleep 8 straight hours at night. Instead, they'd sleep for 4, then wake up to have sex, family time, do some chores around the farm, or whatever, then back to sleep for another 4 hours before getting up. The writers actually postulate that it's only the demands of an 8am work start time that now force most people to try and do the 8-in-a-row version of sleep, since there is no longer really 11-12 hours available at night to get 8 hours of sleep.
They also mention in this article something that I've always found extremely interesting: that left to our own devices, the human internal clock runs in a 25 hour cycle. Not 24. This has been proven by locking subjects into dark rooms for weeks and weeks. Everyone operates on a 25 hour cycle, naturally - but when exposed to the earth's 24 hour cycle, we grudgingly adjust. No wonder everyone's grumpy - we innately feel that we're being cheated out of 1 hour each and every day we live!
I'm really struggling to come up with a natural-selection based reason why we'd have a 25 hour cycle. Did the earth once (recently) have a 25 hour day? Maybe we're actually from a different planet with a 25 hour day? ;) This is one of those things that's going to bug me until they figure it out.
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