history of sleep patterns: History shows humans once slept twice a night — here’s why we don’t anymore
Before electric lights and factory schedules reshaped daily life, people often split their nights into two separate sleeps and thought nothing about it.
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Were people really sleeping in two shifts?
For centuries, people in Europe, Africa, and Asia followed a pattern often described as “first sleep” and “second sleep.” After nightfall, families would go to bed early. After a few hours, they would wake up naturally for an hour or more before returning to bed by morning.
Historical letters and diaries show that this period of mid-wakefulness was commonplace. It wasn’t a restless tossing and turning. It was the expected time and the realized time that gave the night a clear midpoint. Long winter evenings felt less endless when broken into two manageable parts.
During this silence, some people stood up to stir the fire or check on the animals. Others stayed in bed to pray or ponder dreams. Many used the tranquil darkness to read or write. Some even visited neighbors or spoke softly to family members. For couples, waking up in the middle of the night was often a time for intimacy. References to this pattern go back a long way in the literature. The ancient Greek poet Homer and the Roman poet Virgil speak of “an hour that terminates the first sleep,” showing how common interrupted sleep once was.
How artificial light and industry changed sleep
The disappearance of the “second sleep” occurred in the last two centuries. People stayed up late as kerosene lamps, kerosene lamps, and eventually electric lights extended the night. Instead of going to bed shortly after sunset, nights became productive time.
Bright light after dark does more than help us see. It alters our internal clock, our circadian rhythm, and makes us less likely to wake up naturally in the middle of the night. Even typical room lighting before bed can delay the release of melatonin, pushing sleep to later hours, according to a report by Science Alert.
Then came the Industrial Revolution. Factory work encouraged rigid schedules and combined rest blocks. By the early 20th century, the old two-sleep rhythm had been replaced by spending eight hours straight in bed.
But when researchers recreated long winter nights in sleep labs by removing clocks and artificial evening lights, many participants naturally fell back into two sleep episodes with a quiet waking period in between.
A 2017 study in a farming community in Madagascar without electricity found that people still tended to sleep in two blocks and often woke up around midnight, according to a report by Science Alert.
Why does light shape our feelings about time and sleep?
Light is more than illumination; It stabilizes our sense of time. In winter, weaker and later morning light makes circadian adaptation more difficult. Morning light contains higher levels of blue wavelengths, which are particularly effective at stimulating cortisol and suppressing melatonin, according to a report by Science Alert.
Without strong light cues, whether in caves, time-isolated laboratories, or arctic winters, people often lose track of the passing days. Many people count time completely incorrectly. In places with prolonged darkness, time can feel suspended.
Research also shows that mood plays a role in how we experience time. In virtual reality experiments matching scenes from the United Kingdom and Sweden, participants watched short clips set at different times of day and light levels. Two-minute intervals were longer in evening or low-light scenes than in bright daytime scenes. The increase in time was most noticeable among participants who reported feeling depressed.
This flexibility of time perception is important at 3 o’clock in the morning. Anxiety and low light can cause minutes to drag on. Without a cultural expectation of a natural midnight interval, people often focus on the clock, and the longer they watch it, the longer their wakefulness seems.
Is it really normal to wake up at 3 am?
Sleep clinicians note that brief awakenings are common, especially during phase transitions and sleep periods close to REM sleep, which are associated with vivid dreams. Often it is our reaction that determines whether it will be upsetting or not.
Cognitive behavioral therapy (CBT-I) for insomnia recommends getting out of bed after being awake for about 20 minutes and doing a quiet activity, such as reading a book in dim light, before returning to bed while drowsy. Experts also recommend turning off the watch and stopping time tracking overnight, according to a report by Science Alert.
Understanding that fragmented sleep was once typical can change perspective. Waking up at night is not necessarily a malfunction. In many ways, the compression of modern life into a single block is a deeply human pattern.
FAQ
Did people really wake up in the middle of the night on purpose?
Yes. Historical records show that many people expect a period of natural awakening between “first” and “second” sleep.
Why do we sleep in one block now?
Artificial lighting and industrial work schedules gradually replaced fragmented sleep with a single, consolidated eight-hour pattern.
