Why Did Humans Use to Sleep Twice a Night?

Do you wake up at 3 a.m. and can't fall back asleep? For centuries, many people in Europe slept in two parts: a "first sleep", an hour or so awake in the middle of the night, then a "second sleep". A historian found more than 500 old references to it. So what happened to it, what did a sleep experiment in long darkness show, and how do people who live without electricity sleep today? 0:00 Why do you wake up at 3 a.m.? 0:31 The historian who found "first sleep" 1:18 How a two-sleep night worked 1:43 What people did in the middle of the night 2:21 The month-long darkness experiment 3:06 Why the two sleeps disappeared 4:21 Light still changes our sleep 4:37 People who live without electricity 5:50 The Hadza night watch 6:34 Putting the clues together 6:53 The debate isn't over 7:11 What it means for your 3 a.m. What time do you usually wake up at night? Tell me in the comments, and subscribe for more stories about how people really lived. Sources: BBC News Magazine (2012), "The myth of the eight-hour sleep" - https://people.uncw.edu/imperialm/unc... A. Roger Ekirch, "Connecting the segments of sleep", Past & Present (2015) - https://pastandpresent.org.uk/connect... Open Culture (2022), "People in the Middle Ages Slept Not Once But Twice Each Night" - https://www.openculture.com/2022/01/p... Thomas Wehr (1992), "In short photoperiods, human sleep is biphasic", Journal of Sleep Research - https://en.wikipedia.org/wiki/Thomas_... Scientific American blog, "What is a natural sleep pattern?" - https://www.scientificamerican.com/bl... Wright et al. (2013), camping and the internal clock - https://www.sciencenews.org/article/c... Yetish et al. (2015), Hadza, San and Tsimane sleep (UCLA) - https://www.uclahealth.org/news/relea... Samson et al. (2017), Hadza night watch (Duke University) - https://today.duke.edu/2017/07/live-g... Boyce (2023), "Have we lost sleep?", Medical History - https://www.cambridge.org/core/produc... Ekirch (2024), "Reflections on 'Have we lost sleep?'", Medical History - https://www.ncbi.nlm.nih.gov/pmc/arti... NHS Fife, "Dealing with insomnia" - https://www.nhsfife.org/services/all-... This video is for general information, not medical advice. If you're exhausted every day, talk to a doctor. Music: "Tratak" by Jesse Gallagher, "Pure Potentiality" by Benjamin Martins and "Sleep Music No. 1" by Chris Haugen (YouTube Audio Library). #Sleep #History #FirstSleep #Insomnia #SleepScience #HumanHistory #Biphasic