Second Sleep: How Our Ancestors Slept in Two Phases

Before electric lights changed everything, people commonly slept in two distinct periods with a wakeful hour between them. Explore the fascinating history of segmented sleep and what it means for us today.

The idea that we should sleep in one uninterrupted eight-hour block is surprisingly modern. For most of human history, people practiced what was known as "first sleep" and "second sleep"—a natural pattern of two distinct sleep periods separated by a wakeful interval. This historical sleep pattern challenges many of our assumptions about what "normal" sleep looks like.

The Discovery of Segmented Sleep

Historian Roger Ekirch's groundbreaking research, published in his book "At Day's Close: Night in Times Past," revealed that references to "first sleep" and "second sleep" appear in hundreds of historical documents spanning centuries and cultures.

These references appeared in:

  • Court depositions and legal records
  • Medical texts and health guides
  • Personal diaries and letters
  • Literature and poetry
  • Prayer books and religious texts

The consistency of these references suggests that segmented sleep was so common it was simply assumed—like eating lunch, it didn't need explanation.

How Segmented Sleep Worked

The First Sleep

People would go to bed shortly after dusk, following the natural light cycle:

  • Timing: Usually 2-3 hours after sunset
  • Duration: Approximately 3-4 hours
  • Sleep type: Likely dominated by deep sleep

The Waking Period

Between first and second sleep, people experienced 1-2 hours of quiet wakefulness:

  • Activities: Prayer, meditation, reading, conversation
  • Physical needs: Using the chamber pot, tending the fire
  • Intimacy: Historical records suggest this was a preferred time for couples
  • Mood: Often described as calm and reflective

Importantly, this waking period wasn't viewed as insomnia or a sleep problem—it was simply part of the normal night.

The Second Sleep

After the waking interval, people returned to sleep:

  • Duration: Another 3-4 hours
  • Waking: At dawn or shortly before
  • Sleep type: Likely more REM sleep

What Ended Segmented Sleep?

The Rise of Artificial Lighting

The transition away from segmented sleep began with:

  • 1600s-1700s: Improved oil lamps and candles made evening activities possible
  • 1800s: Gas lighting illuminated city streets and homes
  • Late 1800s: Electric light bulbs completed the transformation

With reliable evening lighting, people began staying up later, consolidating their sleep into a single period.

Industrial Revolution Changes

Factory schedules demanded workers wake at fixed times regardless of natural light:

  • Work shifts began standardizing daily schedules
  • Time became more regimented with clocks and schedules
  • Sleep was compressed to maximize working hours
  • Efficiency became prized over natural rhythms

Cultural Shifts

By the early 20th century:

  • Consolidated sleep became the expected norm
  • Waking at night began to be seen as abnormal
  • Medical experts started treating middle-of-night wakefulness as a disorder
  • The concept of "insomnia" as we understand it emerged

Scientific Support for Segmented Sleep

The Wehr Experiment

In the 1990s, psychiatrist Thomas Wehr conducted an illuminating experiment:

  • Subjects were exposed to 14 hours of darkness nightly (mimicking pre-electric conditions)
  • After adjustment, participants naturally fell into a segmented sleep pattern
  • They slept in two ~4-hour blocks with 1-2 hours of quiet wakefulness between
  • The waking period featured a unique, almost meditative brain state

This suggests that biphasic sleep may be hardwired into human biology, suppressed only by artificial light exposure.

Prolactin Release

During the waking interval in Wehr's subjects, prolactin levels were elevated—similar to states seen during meditation. This hormonal pattern may explain historical descriptions of the waking period as peaceful and reflective rather than anxious.

What This Means for Modern Sleep

Reframing Middle-of-Night Wakefulness

Understanding segmented sleep history can change how we view nighttime awakenings:

  • It may be natural: Brief nighttime wakefulness isn't necessarily a disorder
  • Anxiety compounds the problem: Worrying about being awake makes it harder to return to sleep
  • Acceptance helps: Treating wakefulness as normal rather than problematic can reduce stress

When It's Still a Problem

That said, not all nighttime wakefulness is benign:

  • If you can't fall back asleep and feel exhausted
  • If wakefulness is caused by pain, sleep apnea, or other disorders
  • If it significantly impacts your daytime functioning
  • If it's accompanied by anxiety or racing thoughts

These situations warrant evaluation and potentially treatment.

Could You Practice Segmented Sleep Today?

Potential Benefits

  • May reduce anxiety about nighttime wakefulness
  • Creates a quiet period for reflection, creativity, or intimacy
  • Could align better with natural circadian rhythms for some people
  • Offers flexibility for those with non-traditional schedules

Practical Challenges

  • Modern schedules: Most work and school schedules assume consolidated sleep
  • Light exposure: We'd need to limit evening light significantly
  • Screen time: Digital devices make evening dimness impractical for many
  • Social expectations: Evening activities often extend past natural sunset bedtimes

A Modified Approach

Rather than fully adopting historical sleep patterns, you might:

  • Accept brief nighttime awakenings as normal rather than fighting them
  • If you wake at night, avoid screens and bright lights
  • Use the time for quiet, relaxing activities (reading, meditation)
  • Don't check the clock—this increases anxiety
  • Consider biphasic sleep with an afternoon nap as a more practical alternative

Activities for the Waking Period

If you find yourself awake between sleep periods, historical and modern options include:

Reflective Activities

  • Meditation or prayer
  • Journaling or writing
  • Gentle stretching or yoga
  • Breathing exercises

Low-Stimulation Tasks

  • Reading (physical books, not screens)
  • Knitting or handcrafts
  • Planning or organizing (with dim light)
  • Listening to quiet music or podcasts

What to Avoid

  • Bright lights or screens
  • Checking email or social media
  • Work that causes stress
  • Eating substantial meals
  • Caffeine or alcohol

Historical Quotes About Second Sleep

Historical documents reveal how embedded segmented sleep was in daily life:

"Don Quixote followed nature, and being satisfied with his first sleep, did not solicit more."

— Miguel de Cervantes, Don Quixote (1615)

"He knew this, even in the horror with which he started from his first sleep, and threw up the window to dispel it by the presence of some object."

— Charles Dickens, Barnaby Rudge (1840)

These casual references demonstrate that first and second sleep were commonly understood concepts requiring no explanation.

Frequently Asked Questions

Was everyone in history practicing segmented sleep?

It appears to have been the dominant pattern in pre-industrial Western societies. Other cultures had varying practices, but the two-sleep pattern was widespread where studied.

Why don't we naturally fall into segmented sleep today?

Artificial light, especially blue light from screens, suppresses melatonin and keeps us awake later. We then consolidate sleep to fit within the shortened night period.

Is segmented sleep healthier than consolidated sleep?

There's no evidence that one is inherently healthier than the other, as long as total sleep needs are met. The key is getting adequate, quality sleep in whatever pattern works for your life.

Should I try to switch to segmented sleep?

For most people in modern society, this would be impractical. However, understanding the history can help reduce anxiety about occasional nighttime wakefulness.

Is waking up at 3 AM related to historical sleep patterns?

Possibly. The timing would align with the gap between first and second sleep for someone who went to bed around 9-10 PM. However, regular 3 AM waking can also indicate other issues worth investigating.

Did children practice segmented sleep?

Historical records suggest children often slept through the night, while adults practiced segmented patterns. Children's higher sleep needs may have made the pattern less relevant for them.

How did people time their sleep without clocks?

Natural light cycles, church bells, animal sounds (roosters), and internal rhythms guided sleep timing. People were more attuned to these natural cues without artificial lighting.

Conclusion

The history of segmented sleep offers a valuable perspective on our modern sleep struggles. While we may not return to sleeping in two distinct phases, understanding that consolidated eight-hour sleep is a relatively recent invention can help us approach our own sleep with more flexibility and less anxiety.

If you occasionally wake during the night, remember that this pattern has deep historical roots. Instead of panicking, consider whether a calm, quiet waking period might actually be a natural part of human sleep—one that we've only recently forgotten.

Whether you prefer consolidated sleep or are curious about biphasic patterns, the most important thing is finding an approach that leaves you feeling rested and meets your body's needs. Use our Sleep Calculator to optimize your sleep timing within whatever pattern works best for your modern life.