The Sleep We Lost

It's Sunday, March twenty ninth, and welcome to HigherIQ. Last week we talked about how the weekend was invented. Two days off didn't exist until the twentieth century. The five day workweek was a negotiation between religion, hangovers, and a car manufacturer. It got us thinking: if the way we work was invented, was the way we sleep invented too? In 1697, a traveling court in London took a deposition from a nine year old girl named Jane Rowth. Her mother, she testified, had woken up after her "first sleep" and gone outside. The mother was later found dead. It was a grim document, but for a historian named Roger Ekirch, one detail jumped off the page. First sleep. The phrase was used casually, as if it needed no explanation. Ekirch, a professor at Virginia Tech, had never encountered the term. He started looking for more references. He found them everywhere. Over the next two decades, Ekirch uncovered more than two thousand references to "first sleep" and "second sleep" across a dozen languages, dating back as far as Homer's Odyssey in the eighth century BC. Virgil's Aeneid describes "the hour which terminates the first sleep, when the car of Night had as yet performed but half its course." Chaucer mentioned it. Medical texts prescribed it. Prayer books scheduled devotions for the gap between sleeps. A sixteenth century French physician named Laurent Joubert credited the fecundity of manual laborers to intercourse "after the first sleep," when couples "have more enjoyment and do it better." The pattern was consistent across centuries and cultures. People went to bed shortly after dark, slept for about four hours, woke for one to two hours, then slept again until dawn. The waking period between sleeps was not insomnia. It was expected. People used it to pray, reflect on dreams, talk with their bedfellows, tend to sick children, do small chores, or simply lie quietly in the dark. Monks rose at midnight to pray. Neighbors visited each other. Some people raided apple orchards. The period had names in multiple languages. In French, premier sommeil. In Italian, primo sonno. References to it appear not just in Europe but in records from Africa, South America, and Southeast Asia. Biphasic sleep wasn't a quirk of one culture. It was how humans slept. The evidence isn't purely historical. In 1992, psychiatrist Thomas Wehr at the National Institute of Mental Health ran an experiment. He put subjects in a room with fourteen hours of darkness per day, roughly simulating a long winter night without artificial light. At first, the participants slept for about eleven hours, presumably recovering from accumulated sleep debt. But after that initial phase, something shifted. Within a few weeks, every participant settled into biphasic sleep on their own. They slept for about four hours, woke for one to three hours in a calm, meditative state, then slept for another four hours. Nobody told them to do this. Nobody suggested it. Their bodies did it naturally, once the conditions that had been suppressing the pattern were removed. Wehr noted that the waking period between sleeps was characterized by unusual hormonal activity, including elevated levels of prolactin, the hormone associated with the peaceful feeling after orgasm. The subjects described the waking interval as restful, even pleasant. A 2017 study of an agricultural community in Madagascar without electricity found a similar pattern: people still mostly slept in two segments, rising around midnight. So what suppressed it? The same force that created the weekend: the Industrial Revolution. Before gas lighting, nightfall meant darkness. Real darkness, not the ambient glow of a city but an enveloping black that made the world outside your door essentially invisible. A single candle produced a feeble glow barely sufficient to read by. Going out after dark was dangerous, socially suspect, and widely associated with criminals and prostitutes. As late as the 1600s, it was common for people to empty chamber pots out of windows after sunset on the assumption that nobody respectable would be walking below. Sleep started shortly after dark because there was genuinely nothing else to do. Then, starting in the late 1700s, artificial light changed everything. A single gas lamp was roughly ten times as powerful as a candle. An electric bulb, introduced toward the end of the 1800s, was about a hundred times more powerful. London became the first city to install gas street lighting in 1807. Baltimore was the first in the United States, in 1816. By the mid 1800s, going out at night had become fashionable. Socializing pushed bedtimes later. And as bedtime got later, the two sleeps compressed into one. The waking period between them shrank. By the 1820s, Ekirch found that references to "first sleep" were already fading from the written record. By the end of the century, the consolidated eight hour block had become the standard, and middle of the night wakefulness had been reclassified as a medical problem. The Industrial Revolution didn't just compress sleep. It moralized it. Factory schedules demanded workers arrive at fixed times. In 1787, a New Hampshire man named Levi Hutchins built the first mechanical alarm clock specifically to wake himself for work. Sleep became something to be optimized, minimized, and controlled. Napoleon reportedly said that six hours of sleep was enough for a man, seven for a woman, and eight for a fool. Places that clung to traditional sleeping schedules were dismissed as backward. A London writer bragged that an ambitious person could steal "a march on the day and on one's fellow human beings, who are enjoying that second sleep." Parents were told to train children into unbroken sleep while their habits could still be shaped. The Harvard evolutionary biologist Daniel Lieberman has called the eight hour prescription a legacy of industrial era thinking, not biology. Field data from communities without electric light show typical nightly sleep of about six to seven hours, not eight. The American Academy of Sleep Medicine recommends "seven or more hours" for adults, a range that starts at seven, not a mandate of eight. Large scale studies consistently show a U-shaped relationship between sleep duration and health outcomes: both chronic short sleep and habitual long sleep are associated with higher risks. The bottom of the curve, the sweet spot, is around seven hours for most adults. The number eight, burned into public consciousness as the gold standard, has weaker scientific support than most people assume. Which brings us to the modern irony. We now live in a culture that obsesses over sleep more than any civilization in history. Sleep trackers on wrists and under mattresses. Weighted blankets. Melatonin supplements. White noise machines. Blue light glasses. Apps that score your sleep quality on a hundred point scale and send you notifications about how poorly you slept, which, research suggests, can actually make your sleep worse by increasing anxiety about it. The global sleep economy is worth over a hundred billion dollars. And yet the thing millions of people are most anxious about, waking up in the middle of the night, may not be a problem at all. It may be the oldest and most natural pattern of human sleep reasserting itself against a schedule that was imposed on us less than two hundred years ago. Ekirch has received thousands of emails from people who read his research and felt relief. Many had been diagnosed with middle of the night insomnia and were taking medication for it. Learning that their wakefulness had been normal for most of human history changed how they thought about their own bodies. As the sleep scientist Charles Czeisler at Harvard has put it, every time we turn on a light switch, we're effectively taking a dose of medicine that affects our circadian clock. The consolidated sleep we consider natural is the product of a world lit by electricity and organized by factory schedules. Remove those conditions, as Wehr's experiment did, and the older pattern comes back on its own. So if this comes up in conversation, here's how to think about it. The eight hour sleep block is less than two hundred years old. Before artificial light and industrial work schedules, humans slept in two shifts with a quiet waking period in between. References to this pattern go back to ancient Greece. When scientists recreated pre-industrial darkness in a lab, subjects reverted to biphasic sleep within weeks without being told to. Waking up at two in the morning and lying there for an hour isn't a disorder. For most of human history, it was just called the middle of the night. Stay informed, stay curious, and we'll see you tomorrow.