The "two-sleep" system (two periods of sleep at night, separated by wakefulness)

Zaria Gorvett, The forgotten medieval habit of 'two sleeps', BBC Future, Jan 9, 2022. Much of the article is apparently based on, Roger Ekrich, At Day's Close: A History of Nighttime.

In the 17th Century, a night of sleep went something like this.

From as early as 21:00 to 23:00, those fortunate enough to afford them would begin flopping onto mattresses stuffed with straw or rags – alternatively it might have contained feathers, if they were wealthy – ready to sleep for a couple of hours. (At the bottom of the social ladder, people would have to make do with nestling down on a scattering of heather or, worse, a bare earth floor – possibly even without a blanket.)

At the time, most people slept communally, and often found themselves snuggled up with a cosy assortment of bedbugs, fleas, lice, family members, friends, servants and – if they were travelling – total strangers.

To minimise any awkwardness, sleep involved a number of strict social conventions, such as avoiding physical contact or too much fidgeting, and there were designated sleeping positions. For example, female children would typically lie at one side of the bed, with the oldest nearest the wall, followed by the mother and father, then male children – again arranged by age – then non-family members.

A couple of hours later, people would begin rousing from this initial slumber. The night-time wakefulness usually lasted from around 23:00 to about 01:00, depending on what time they went to bed. It was not generally caused by noise or other disturbances in the night – and neither was it initiated by any kind of alarm (these were only invented in 1787, by an American man who – somewhat ironically – needed to wake up on time to sell clocks). Instead, the waking happened entirely naturally, just as it does 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 just about anything and everything after they awakened from their first sleep," says Ekirch.

Under the weak glow of the Moon, stars, and oil lamps or "rush lights" – a kind of candle for ordinary households, made from the waxed stems of rushes – people would tend to ordinary tasks, such as adding wood to the fire, taking remedies, or going to urinate (often into the fire itself).

For peasants, waking up meant getting back down to more serious work – whether this involved venturing out to check on farm animals or carrying out household chores, such as patching cloth, combing wool or peeling the rushes to be burned. One servant Ekirch came across even brewed a batch of beer for her Westmorland employer one night, between midnight and 02:00. Naturally, criminals took the opportunity to skulk around and make trouble – like the murderer in Yorkshire.

But the watch was also a time for religion.

For Christians, there were elaborate prayers to be completed, with specific ones prescribed for this exact parcel of time. One father called it the most "profitable" hour, when – after digesting your dinner and casting off the labours of the world – "no one will look for you except for God”.

Those of a philosophical disposition, meanwhile, might use the watch as a peaceful moment to ruminate on life and ponder new ideas. In the late 18th Century, a London tradesman even invented a special device for remembering all your most searing nightly insights – a "nocturnal remembrancer", which consisted of an enclosed pad of parchment with a horizontal opening that could be used as a writing guide.

But most of all, the watch was useful for socialising – and for sex.

As Ekirch explains in his book, At Day's Close: A History of Nighttime, people would often just stay in bed and chat. And during those strange twilight hours, bedfellows could share a level of informality and casual conversation that was hard 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'd had a long day of manual labour, the first sleep took the edge off their exhaustion and the period afterwards was thought to be an excellent time to conceive copious numbers of children.

Once people had been awake for a couple of hours, they'd usually head back to bed. This next step was considered a "morning" sleep and might last until dawn, or later. Just as today, when people finally woke up for good depended on what time they went to bed.

Ekirch also references bi-phasic sleep in the classical era.

Biphasic sleep is common among among animals as well.

"There are broad swaths of variability among primates, in terms of how they distribute their activity throughout the 24-hour period," says David Samson, director of the sleep and human evolution laboratory at the University of Toronto Mississauga, Canada. And if double-sleeping is natural for some lemurs, he wondered: might it be the way we evolved to sleep too?

The move away from biphasic sleep happened during the Industrial Revolution:

"Artificial illumination became more prevalent, and more powerful – first there was gas [lighting], which was introduced for the first time ever in London," says Ekirch, "and then, of course, electric lighting toward the end of the century. And in addition to altering people's circadian rhythms. artificial illumination also naturally allowed people to stay up later."

However, though people weren't going to bed at 21:00 anymore, they still had to wake up at the same time in the morning – so their rest was truncated. Ekirch believes that this made their sleep deeper, because it was compressed.

As well as altering the population's circadian rhythms, the artificial lighting lengthened the first sleep, and shortened the second. "And I was able to trace [this], almost decade by decade, over the course of the 19th Century," says Ekirch.

I mention multiphasic sleep in other posts, such as:

• Reading The Human Swarm 5: Night-time action and brain-to-brain coupling [Shazam!!]
• Sleep: 8 continuous hours is a cultural convention, not a natural need

H/t Tyler Cowen.