There’s a great question and answer column in this week’s TIME Magazine, talking all about sleep. Here’s an excerpt of one of the questions, and the corresponding answer:
You point out it’s difficult to understand how sleep evolved. What are some theories about why people sleep?
There’s no “sleep bone” that people have been able to locate or find. So ultimately we really don’t know how people used to sleep. James McKenna, a doctor who specializes in infant sleep at Notre Dame, believes early on that people probably slept in trees. How many hours did people sleep then? How many hours are we sleeping now — is it far fewer hours now than then? That type of thing is very hard to track.