Did Humans Used to Sleep Twice a Day?

Did humans used to sleep twice a day?

Yes, for most of human history prior to the Industrial Revolution, people commonly slept in two distinct segments known as biphasic or segmented sleep.

This pattern consisted of a “first sleep” shortly after dusk, followed by an hour or two of wakefulness, and a “second” or “morning sleep” until dawn.

The Watch

The period between the two sleeps, often called “the watch,” was not typically spent in bed. It was a calm, productive, or social time for activities like reading, writing, praying, chatting, or checking on household items.

Widespread Practice: Evidence from diaries, medical texts, and literature spanning centuries indicates this was normal across Europe, Africa, Asia, and the Americas.

Shift to Modern Sleep Pattern

With the rise of the Industrial Revolution and increased artificial lighting (streetlights, lamps), this pattern shifted towards the continuous eight-hour, monophasic sleep cycle dominant today, starting with the upper classes in the late 17th century.

Scientific Backing: Studies have shown that when humans are removed from artificial light sources, they naturally revert to this two-phase sleep pattern.

This historical, segmented approach meant that wakefulness during the night was once considered normal rather than a sign of insomnia.