Don: (YAWN)

Yael: Get enough sleep last night, Don?

D: I probably got too much, in fact. I went to sleep at my usual time, 8 p.m. Then I slept      until about one, woke up for a few hours, did some reading, then went back to sleep      for a few hours until it was time to wake up.

Y: It sounds like you might have a sleep disorder, Don.

D: I know it sounds strange, but there's actually nothing abnormal about the way I sleep.      In fact, the typical eight hour uninterrupted sleep is what's really unnatural.

Y: Come again?

D: See, until about two hundred years ago most people slept as they had for thousands      of years. Since there was no bright source of artificial light, people went to sleep      when it got dark. They'd naturally wake up during the middle of the night for a few      hours. Then they'd go back to bed for what was called the "morning sleep."

Y: And how do we know this?

D: It's science, Yael. Researchers re-created conditions for pre-historic sleep in a lab.      After a few days of going to bed around 8 p.m., subjects began to experience      segmented sleep. They'd wake up around one or two, lie in bed quietly for a few      hours, and then fall back asleep. Animals in the wild are known to do this as well.

Y: So I guess our world of artificial light and all-night supermarkets has changed the way      we sleep.

D: It's true. But in pre-industrial cultures around the world people still sleep in short      bursts instead of through the night.

Y: Interesting. So how do you feel?

D: A little sleepy.  

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