8 hour sleeping is a modern invention.
Imagine you are a denizen of the 18th century. It’s just past 8:30 P.M., you’ve got your night-cap on. You blow out your candles and fall asleep to the smell of the wax and the wick, which gently fills the air around your bed. Some hours pass. 2:30 AM. You awaken, grab your coat, and visit the neighbors because they, too, are up. Doing quiet reading, prayer, or even having sex. Well, apparently before the age of electricity, sleeping twice a night was completely ubiquitous.
Back in those times, we slept twice a night, getting up for an hour or two for recreation before heading back to bed until dawn.
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The existence of our sleeping twice per night was first uncovered by Roger Ekirch, professor of History at Virginia Tech.
His research found that we didn’t always sleep in one eight hour chunk.