First Sleep and Second Sleep: Did Our Ancestors Sleep Differently?

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Are We Doing It Wrong?

For much of European history, many people did not sleep in one long block. Historical records describe a “first sleep” starting a few hours after dark, a quiet waking period around midnight, and then a “second sleep” until morning. That does not mean your eight-hour night is wrong. Studies of modern hunter-gatherers show that one main block of sleep is also common and natural. The most useful lesson is reassuring: waking briefly in the night is normal, and worrying about it often does more harm than the waking itself.

Here is what the historical evidence shows, what sleep experiments and field studies have added, why the pattern faded, and what it means if you lie awake at 3 a.m.

The discovery of “first sleep” and “second sleep”

The idea comes mainly from A. Roger Ekirch, a historian at Virginia Tech. While researching nighttime in pre-industrial Europe, he kept finding casual references to a first and second sleep in diaries, court depositions, medical texts, prayer books and literature. He published his findings in a 2001 paper in the American Historical Review, and in 2005 in the book At Day’s Close: Night in Times Past, which draws on more than 500 references from sources ranging from Homer to accounts of 20th-century African societies.

What persuaded him was not just how often the phrases appeared, but how ordinary they seemed to the writers. As Ekirch put it to the BBC:

“It’s not just the number of references – it is the way they refer to it, as if it was common knowledge.” — A. Roger Ekirch

According to his reading of the sources, people typically went to bed two hours or so after dusk, slept for three or four hours, woke for an hour or more, and then slept again until dawn. The whole pattern stretched across a long winter night of roughly twelve hours in the dark.

What people did in the hours between

The waking interval was not treated as insomnia. It was simply part of the night. Ekirch’s sources describe people using it to pray, reflect on their dreams, talk quietly with a bed partner, tend the fire, check on animals or children, have sex, and sometimes visit neighbours. Some prayer manuals of the period even offered special prayers for this hour.

Physicians also had views on the matter. Some advised couples that the time after the first sleep was best for conceiving a child, because the body was rested. Others recommended lying on one side for the first sleep and the other for the second, in line with the medical thinking of the day.

Because candles and oil were expensive, most of this happened in darkness or by firelight. That detail matters: long, dark winter nights seem to have been one of the conditions that allowed the pattern to exist.

The darkness experiment that seemed to confirm it

A laboratory study added weight to the historical case. In the early 1990s, psychiatrist Thomas Wehr at the US National Institute of Mental Health had volunteers spend 14 hours of each day in darkness for about a month, roughly the length of a winter night without artificial light. The published account describes seven healthy men; popular articles often give a larger number.

After an initial period of catching up on sleep, the men drifted into a split pattern: about four hours of sleep, two to three hours of calm wakefulness, then another four hours of sleep. Wehr noticed that the waking interval was quiet and restful rather than stressful, and press reports of the study noted that hormone levels during it reportedly resembled those of a meditative state.

It is a striking result, but it comes from a handful of people in an artificial setting. It shows that long nights can produce segmented sleep, not that everyone is built to sleep that way.

Why segmented sleep faded

Ekirch found that references to first and second sleep began to disappear from the late 17th century, first among the wealthy in northern European cities, and by the early 20th century the idea had largely vanished from everyday speech. Several changes pushed in the same direction.

  • Street lighting. Paris began lighting its streets in 1667, and other cities followed. Historian Craig Koslofsky, who has written about this “nocturnalisation” of Europe, describes how the night gradually changed from a time associated with danger and disorder into one for socialising and entertainment.
  • Cheaper artificial light. Gas and later electric lighting shortened the period people spent in darkness, compressing the night.
  • Industrial time. Factory work, fixed shifts and clocks encouraged a view of sleep as one efficient block. Some 19th-century advice writers even treated lying awake as a sign of illness or laziness.

Ekirch suggests that a common modern complaint, waking in the middle of the night and struggling to get back to sleep (often called sleep maintenance insomnia), may partly be an echo of the older pattern. That is a reasonable idea, but it is a hypothesis, not a proven cause.

What hunter-gatherer studies found

If segmented sleep were the single “natural” human pattern, you would expect to see it in societies living without electricity. In 2015, a team led by Gandhi Yetish and UCLA sleep researcher Jerome Siegel tested this with wrist sensors on 94 people in three pre-industrial societies: the Hadza of Tanzania, the San of Namibia and the Tsimane of Bolivia.

They found that people usually slept in one main block, about 5.7 to 7.1 hours a night. They tended to stay up several hours after sunset, often woke before sunrise, rarely napped, and seemed to time their sleep more by falling night temperatures than by darkness. Siegel summed up the surprise:

“Their sleep is actually on the low end of what’s been recorded in our modern society.” — Jerome Siegel, PBS NewsHour, 2015

Ekirch questioned whether these equatorial groups, with shorter nights, tell us much about long northern European winters. And a later study, published in 2017, did find segmented sleep in a farming community without electricity in Madagascar. The fair conclusion is that human sleep is flexible. Long nights and darkness can encourage two sleeps; other conditions favour one.

If you wake at night: myths and practical steps

A few common beliefs deserve a rethink:

  • Myth: any waking in the night means something is wrong. Brief awakenings between sleep cycles are normal, and most people do not remember them. Oxford circadian neuroscientist Russell Foster has said he reassures patients that waking at night can be a throwback to this older pattern.
  • Myth: we should all switch to two sleeps. There is no good evidence that deliberately splitting your night, or following online polyphasic schedules, improves health.
  • Myth: more time in bed always helps. Lying awake for long periods can teach the brain that bed is a place for worrying.

If you wake and cannot drift off again, these habits, in line with NHS advice, often help:

  • Keep the room dark and quiet, and avoid checking the time repeatedly.
  • If you feel restless or anxious, get up and do something calm in dim light, such as reading, then return to bed when you feel sleepy.
  • Avoid screens, alcohol, caffeine and large meals close to bedtime, and avoid long daytime naps.
  • Get up at the same time every day, even after a poor night.

If poor sleep has lasted for months or is making daily life hard to cope with, talk to a doctor. Cognitive behavioural therapy for insomnia is an effective, drug-free option that doctors often recommend.

Sources: Segmented sleep (Wikipedia); PBS NewsHour, “Paleo ancestors didn’t sleep better than us” (15 October 2015); NHS, Insomnia; Stephanie Hegarty, “The myth of the eight-hour sleep”, BBC News (2012); The New York Times on Thomas Wehr’s study (1995). Earlier versions of this story by Arjun Walia at Collective Evolution and Slumberwise.

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