The current sleep guidelines by the National Sleep Foundation recommends that the average adult get seven to nine hours of sleep each night. For us modern sleepers, it's normal to assume we'd need to get those z’s all in one uninterrupted snooze.
But for humans living in the pre-industrial era, sleep was an entirely different affair.
Writing in a 2001 paper, historian Roger Ekirch proposed that, “until the modern era, up to an hour or more of quiet wakefulness midway through the night interrupted the rest of most Western Europeans.”
