Funny, I came to the comments to say the same. Segmented sleep is a theory all from writings of a "second sleep". I imagine for some small groups this may have

Funny, I came to the comments to say the same. Segmented sleep is a theory all from writings of a "second sleep". I imagine for some small groups this may have existed but seems extremely unlikely as a normal behavior. BBC went as far as to write "The Myth of the 8 hour sleep" http://www.bbc.com/news/magazine-16964783 http://www.bbc.com/news/magazine-16964783 without citing any anthropologist or medical insight. I imagine however, prior to modern society, humans took naps more often, especially in agrarian societies after particularly laborious days.