History delves into how our past sleep schedules challenge the idea that anything, even our biological needs, truly transcends historical boundaries.
For much of recorded history, humans have actually slept eight hours, but in two distinct phases of approximately four hours each. As scholar Roger Ekirch uncovered through his exhaustive historical study of literature, art, and diaries, people would once head to bed when it got dark, sleep for four hours, wake for a while, and slide into a “second sleep” for another four hours. People didn’t just toss and turn along in between their two sleep sessions: they would contemplate their dreams, read by candlelight, or have sex.
Writers from Livy to Plutarch to Virgil to Homer all referred to this structure, as well as medieval Christian and African tribal cultures. But the “biphasic sleep” pattern, which was governed by the natural timing of nightfall and sunrise, didn’t last in the modern era.
