It was around eleven o'clock in the evening, April 13, 1699, in a small village in the north of England.
Nine-year-old Jane Root opened her eyes and squinted into the moody evening shadows.
She and her mother had just woken up from a short sleep.
Mrs. Rout got up and went to the hearth of their modest home, where she began to smoke a pipe.
Just then, two men appeared by the window.
They shouted and instructed her to get ready to go with them.
As Jane later explained in the courtroom, her mother had clearly been expecting visitors.
She went with them willingly - but first she whispered to her daughter to "lay still, and she will come again in the morning".
Maybe Mrs. Rout had some nightly errand to finish.
Or maybe she was in trouble and knew that leaving the house was a risk.
In any case, Jane's mother failed to keep her promise - she never returned home.
That night, Mrs. Rout was brutally murdered, and her body was discovered in the following days.
The crime was never solved.
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Almost three hundred years later, in the early 20s, the historian Roger Church walked through the arched entrance to the Public Record Office in London - an imposing Gothic building that housed the National Archives of the United Kingdom from 1838 to 2003.
There, among endless rows of ancient parchments and manuscripts, he found Jane's testimony.
And something about that struck him as strange.
Originally, Ikirch was researching a book on the history of the night time, and at the time he reviewed records spanning the era between the early Middle Ages and the Industrial Revolution.
He was afraid to write a chapter on sleep, thinking that it is not only a universal need - but also a biological constant.
He was skeptical that he would find anything new.
So far, he has found court testimony particularly instructive.
"They are a wonderful resource for social historians," says Ikrich, a professor at Virginia Tech University in the US.
"They comment on activities that are often unrelated to the crime itself."
But as he read Jane's guilty plea, two words seemed to echo a particularly tantalizing detail of life in the 17th century that he had never encountered before - "the first dream".
"I can quote the original document almost verbatim," says Ikirch, whose delight at his discovery is palpable even decades later.
In her testimony, Jane describes how, just before the men arrived at their house, she and her mother woke up from their first night's sleep.
There was no further explanation - the broken dream was just stated as if it was completely unremarkable.
"She said it as if it was completely normal," says Ikirch.
The first dream implies the second dream - a night divided into two halves.
Was this just a family quirk or something more?
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Omnipresence
Over the following months, Ikirch searched the archives and found many more references to this mysterious phenomenon of double sleep, or "biphasic sleep" as he later called it.
Some were quite mundane, such as the mention of the weaver John Coburn, who simply casually slipped it into his testimony.
But others were darker, like Luke Atkinson from the East Riding of Yorkshire.
He managed to squeeze in an early-morning murder between two sleeps in one night - and according to his wife, he often used that time to visit other people's houses for sinister deeds.
When Ikirč expanded his search to include online databases of other written records, it soon became clear that the phenomenon was more widespread and common than he had imagined.
To begin with, the first dreams are mentioned in one of the most famous works of medieval literature, Geoffrey Chaucer's Canterbury Tales (written between 1387 and 1400), which is presented as a storytelling competition between a group of pilgrims.
They are also described in the work of the poet William Baldwin, Beware of the cat (1561) - a satirical book considered by some to be the first novel, which centers on a man who learns to understand the language of a group of terrifying supernatural cats, one of whom, a mouse killer, is on trial for promiscuity.
But that's just the tip of the iceberg.
Ikirč found occasional references to the double sleep system in all possible forms, with hundreds of appearances in letters, diaries, medical textbooks, philosophical writings, newspaper articles, and plays.
The practice even turned into ballads, such as Old Robin of Portingale.
"... i when you wake up from the first dream, you will make a warm drink, and when you wake up from the next dream, your sadness will subside... ".
Biphasic sleep was not unique to England - it was widely practiced throughout the pre-industrial world.
In France the initial dream was "premier somme". In Italy it was "primo sono".
In fact, Ikirch found evidence of the habit in locations as far-flung as Africa, South and Southeast Asia, Australia, South America, and the Middle East.
A colonial report from Rio de Janeiro, Brazil, from 1555 describes how the inhabitants of Tupinambo had dinner after their first sleep.
Others - from 19th-century Muscat, Oman - explained that the locals would retire to their first sleep before ten o'clock in the evening.
And far from a medieval idiosyncrasy, Ikirch began to suspect that this method had been the dominant way of sleeping for millennia—an ancient standard inherited from our prehistoric ancestors.
The first record that Ikirch found was from the eighth century BC, in the 12.109-line Greek epic Odyssey, while the last hints of its existence date back to the early 20th century, before it somehow fell into oblivion.
How did that work? Why did people do this?
And how could something that was once completely normal be so completely forgotten?
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A free moment
In the 17th century, sleeping through the night looked something like this.
As early as nine to eleven o'clock in the evening, those lucky enough to afford it would begin to descend on mattresses stuffed with straw or rags - alternatively, the mattresses might have been stuffed with feathers, if the owners were wealthy - ready to sleep for a few hours.
(At the bottom of the social ladder, people would have to be content to nestle on patches of heather or, worse, on the bare dirt floor—perhaps even without a blanket.)
In those days, most people slept together and often found themselves snuggled up with a comfortable assortment of bed bugs, fleas, lice, family members, friends, servants and - if they were traveling - complete strangers.
To minimize any discomfort, sleeping involved a series of strict social conventions, such as avoiding physical contact or fidgeting too much, and there were certain sleeping positions.
For example, the female children would usually lie on one side of the bed, the oldest closest to the wall, then the mother and father, then the male children - again arranged by age - then those who are not members of the family.
A few hours later, people would begin to wake up from this primal sleep.
Night wakings usually lasted from eleven to about one after midnight, depending on what time they went to bed.
It was mostly not caused by noise or other disturbances in the night - nor was it triggered by any kind of alarm (these were only invented in 1787 by an American who - somewhat ironically - had to wake up in time to sell watches).
Instead, waking up happened completely naturally, just like in the morning.
The period of wakefulness that followed was known as "the watch"—and it was a surprisingly useful window in which to get things done.
"(The records) describe how people did almost anything and everything after waking up from their first sleep," says Ikrich.
Under the dim glow of the moon, the stars, and oil lamps or "bulbs"—a kind of candle for ordinary households, made from waxed cane stalks—people would tend to ordinary tasks, such as adding wood to the fire, taking medicine, or going to urinate.
For the peasants, waking up meant getting back to more serious work - whether that involved going to check on the animals on the farm or doing household chores such as mending cloth, combing wool or peeling reeds for kindling.
Ikirch remembered a maid who, one night, between midnight and two in the morning, even prepared a load of beer for her employer from Westmoreland.
Of course, criminals have taken the opportunity to sneak around and cause trouble - like the Yorkshire murderer.
But the hour was also a time for religion.
For Christians there were elaborate prayers to be completed, with special prescribed prayers for exactly this part of the time.
One father called it the "most profitable" hour, when - after you have cooked dinner and discarded the labors of the world - "no one will be looking for you but God".
Meanwhile, those of a philosophical disposition could use the watch as a quiet moment to reflect on life and brainstorm new ideas.
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At the end of the 18th century, a London merchant even invented a special device for remembering all your most useful nocturnal ideas - a "night notebook", which consisted of a closed parchment with a horizontal opening that could be used as a writing guide.
But most of all, the watch was useful for socializing - and for sex.
As Ikirch explains in the book At Day's Close: A History of Nighttime, people would often just stay in bed and chat.
And during those odd twilight hours, bedfellows could share a level of informality and casual conversation that was difficult to achieve during the day.
For husbands and wives who managed to navigate the logistics of sharing a bed with others, it was also a convenient interval for physical intimacy.
If they had a long day of physical work, the first sleep eliminated their exhaustion and later it was considered to be an excellent period for conceiving a large number of children.
After people had been awake for a few hours, they would usually go back to bed.
This next step was considered "morning" sleep and could last until dawn or later.
Just like today, when people finally wake up depends on what time they went to sleep.
An ancient adaptation
According to Ikrich, there are references to the double sleep system that was observed during the classical era, which suggests that it was already common then.
It was casually inserted into the works of such famous figures as the Greek biographer Plutarch (from the first century AD), the Greek traveler Pausanias (from the second century AD), the Roman historian Livy and the Roman poet Virgil.
Later, the practice was adopted by Christians, who immediately saw the potential of the hour as an opportunity to recite psalms and confessions.
In the sixth century AD, Saint Benedict required monks to rise at midnight for these activities, and the idea eventually spread across Europe - gradually making its way to the masses.
But humans aren't the only ones who have discovered the benefits of partitioning sleep - it's widespread in nature, with many species resting in two or even several separate parts.
This helps them stay active at the most convenient times of the day, such as when they are most likely to find food, and avoid ending up as a snack themselves.
One example is the ring-tailed lemur.
These iconic Madagascar primates, with eerie red eyes and erect black-and-white tails, have remarkably similar sleep patterns to pre-industrial humans—they're "cathemeral," meaning they're awake day and night.
"There are wide ranges of variability among primates in terms of how they distribute their activity over a twenty-four-hour period," says David Samson, director of the Human Sleep and Evolution Laboratory at the University of Toronto, Mississauga, Canada.
And if double sleeping is natural for some lemurs, he wondered: Is this the way we evolved to sleep, too?
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Ikirč had the same premonition for a long time.
But for decades, there was nothing concrete to prove it — or shed light on why it might have disappeared.
Then, back in 1995, Ikirch was reading on the Internet late one night when he came across a New York Times article about a sleep experiment from a few years earlier.
The research was conducted by Thomas Ware, a sleep scientist at the National Institute of Mental Health, and involved fifteen men.
After an initial week of observing their normal sleep patterns, they were deprived of artificial light at night to reduce their hours of "daylight"—either natural or electrically generated—from the usual sixteen hours to just ten.
The rest of the time, they were locked in a bedroom with no light or window, and completely enveloped in velvety blackness.
They were not allowed to play music or exercise - and instead were encouraged to rest and sleep.
At the beginning of the experiment, all men had normal nighttime habits - they slept in one continuous shift that lasted from late evening until morning.
Then something incredible happened.
After four weeks of ten-hour days, their sleep patterns changed - they no longer slept in one section, but in two halves of roughly the same length.
They were interrupted by a period of one to three hours in which they were awake.
Measurements of the sleep hormone melatonin showed that their circadian rhythms had also adjusted, so their sleep had changed on a biological level.
Ver reinvented biphasic sleep.
"That (reading about the experiment) was, apart from my wedding and the birth of my children, probably the most exciting moment of my life," Ikrich says.
When he emailed Ware to explain the remarkable correspondence between his own historical research and the scientific study, "I think I can tell you he was just as excited as I was," he says.
Recently, Samson's research supported these findings—with an exciting twist.
Back in 2015, along with collaborators from many other universities, Samson recruited local volunteers from the remote community of Manadena in northeastern Madagascar for the study.
The location is a large village located in the hinterland of a national park - and there is no electricity infrastructure, so the nights are almost as dark as they have been for millennia.
The participants, who were mostly farmers, were asked to wear an "actimeter" - a sophisticated activity-detecting device that can be used to track sleep cycles - for ten days to track their sleep patterns.
"What we found was that [in those without artificial light] there was a period of activity just after midnight from about one to one-thirty in the morning," says Samson.
"Then they would go back to sleep and be inactive until they wake up at six in the morning, which usually coincides with sunrise."
As it turns out, biphasic sleep never completely disappeared - it still lives on in parts of the world today.
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New social pressure
Together, this research also gave Ikirch the explanation he craved for why most of humanity abandoned the two-sleep system starting in the early 19th century.
As with other recent changes in our behavior, such as the shift towards time dependence, the answer was the industrial revolution.
"Artificial lighting became more prevalent and more powerful - first there was gas (lighting), which was first introduced in London," says Ikirch, "and then, of course, electric lighting at the end of the century.
And in addition to changing people's circadian rhythms, artificial lighting also naturally allowed people to stay up late."
However, even though people no longer went to bed at nine in the evening, they still had to wake up at the same time in the morning - so their rest was shortened.
Ikirch believes that this made their sleep deeper because it was compressed.
In addition to changing the circadian rhythms of the population, artificial lighting made the first sleep longer and the second shorter.
"And I was able to track (this), almost decade by decade, throughout the 19th century," Ikrich says.
Intriguingly, Samson's study in Madagascar included a second part - in which half of the participants were given artificial light for a week, to see if they made any difference.
And in this case, the researchers found that it had no effect on their segmented sleep patterns.
However, the researchers point out that a week may not be enough for artificial light to lead to major changes.
So the mystery continues…
Even if artificial lighting is not entirely to blame, by the end of the 20th century the division between the two sleeps had completely disappeared - the industrial revolution had not only changed our technology, but also our biology.
New anxiety
One of the main side effects of much of humanity's changing sleeping habits is a change in attitudes.
For one thing, we quickly began to shame sleepers and developed a preoccupation with the connection between early waking and productivity.
"But for me, the most satisfying aspect of all of this," says Ikrich, "relates to those who suffer from insomnia in the middle of the night."
He explains that our sleep patterns are now so altered that any awakening in the middle of the night can send us into a panic.
“I don't want to make light of it - indeed, I suffer from a sleep disorder myself. And I take medicine for it…”.
But when people learn that this may have been perfectly normal for millennia, he finds that their anxiety is somewhat reduced.
However, before Ikirc's research leads to the development of the Paleo diet, and people start throwing away lamps—or worse, artificially dividing sleep into two parts with an alarm clock—he wants to emphasize that abandoning the two-sleep system does not mean that the quality of our sleep is worse today.
Despite near-constant headlines about the prevalence of sleep problems, Ikirc has previously argued that, in some ways, the 21st century is the golden age of sleep.
It's a time when most of us no longer have to worry about being killed in bed, freezing to death or getting lice, when we can doze off without pain, the threat of fire or the fear of strangers sneaking up next to us.
In short, individual sleep periods may not be "natural".
And yet, neither fancy ergonomic mattresses nor modern hygiene.
"More seriously, there is no going back to the old ways because the conditions have changed," says Ikirc.
So we may be missing out on confidential midnight bed chats, psychedelic dreams and late-night philosophical revelations - but at least we won't wake up covered in angry red bites.
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