History and Science indicate that before modern lighting, people used to sleep a few hours, wake up for a few and then go back to sleep and later wake up to start their day. Often when people wake up in the middle of the night these days they stress over getting back to sleep when this may indeed be a normal cycle of humans.
http://slumberwise.com/science/your-...leep-like-you/
An English doctor wrote, for example, that the ideal time for study and contemplation was between “first sleep” and “second sleep.” Chaucer tells of a character in the Canterbury Tales that goes to bed following her “firste sleep.” And, explaining the reason why working class conceived more children, a doctor from the 1500s reported that they typically had sex after their first sleep.