Why we stopped sleeping twice a night

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For much of history, people didn’t sleep in a single eight-hour block. In diaries, medical texts and court records from pre-industrial Europe and beyond, nights were often split into a “first sleep,” a quiet waking hour or two, then a “second sleep.” That middle spell, sometimes called the “watch”, was used for prayer, conversation, reading, sex, or simple reflection in the dark. Historian Roger Ekirch’s archival work, and a small NIMH experiment where volunteers lived without artificial light and naturally drifted into two sleep bouts, helped revive awareness of this older pattern.

How light and schedules squeezed the night

So why did segmented sleep fade? In a word: light, followed by schedules. Gaslight and then electric bulbs stretched evenings, delaying melatonin release and nudging bedtimes later. Once mornings stayed the same because factory whistles, rail timetables and office hours didn’t budge, the long winter night that once accommodated two sleeps got squeezed into a single block. Over the 19th and 20th centuries, the cultural ideal of “a solid night’s sleep” took root, reinforced by schooling, commuting and mass media.

Is biphasic sleep “more natural”?

It’s better to say it’s a normal human option that emerges under long, dark nights. It wasn’t universal; season, latitude and lifestyle mattered. Modern reviews find little support for extreme polyphasic schedules, but they also note that waking calmly for a short period at night isn’t pathological. For many, it’s just a remnant of that older rhythm.

What to do if you wake at 2-3 am

What’s the practical takeaway today? Don’t panic if you wake up briefly around 2-3 am. Treat it like a normal blip: keep lights low, avoid clocks, and do something quiet if needed. To reduce awakenings over time, dim screens two hours before bed, get bright morning light, keep a steady schedule, and anchor caffeine, alcohol and heavy exercise for earlier in the day.

The biology for segmented sleep is still there; modern lighting and social clocks simply push most of us toward one consolidated night.