There is an argument that it's historically common. http://en.wikipedia.org/wiki/Segmented_sleep#Segmented_sleep_as_a_historical_norm http://en.wikipedia.org/w

There is an argument that it's historically common. http://en.wikipedia.org/wiki/Segmented_sleep#Segmented_sleep_as_a_historical_norm http://en.wikipedia.org/wiki/Segmented_sleep#Segmented_sleep...