[dj_mc_merlin]

I believe this theory is largely thought false nowadays, or phrased too strongly at least.

I myself have weird sleep cycles. I prefer to stay up into the night and wake up around 12:00, but I vary my sleeping hours by up to 4 hours or so. I go to sleep when I feel like it, and don't feel much discomfort by falling asleep at different times. It leads to weird situations - especially in winter - where I might not see the sun more than a couple hours in 3 days despite being up and around a lot. I don't experience a lot of 'two sleeps', but they do occasionally happen.

[xhrpost]

I've heard that this theory is true, I've also heard that it is a myth that it is true, and I've even heard that it is a myth that it is a myth.

[dj_mc_merlin]

Hehe, yes. Since the literature is split I can offer my anecdata from living in low light conditions (in the mountains of Eastern Europe with no electricity):

It happens rarely. But enough times that one might notice it. If you experiment with lucid dreaming, you realize that the time you usually wake up is in between your REM cycles at the 4 hour mark. If you take a 15 minute break from sleep in your bed at this time, then fall asleep while trying to keep your mind awake (by, say, counting backwards, or just "willing it"), you can fall directly into a lucid dream. If you try this at the beginning of your sleep, you just fall into a long sleep paralysis and hypnagogia session. Your next REM cycle is too far away.

So, yes, it's real. But I think it's more likely that it was experienced much like nowadays, as a rare occurrence rather than a standard.

[huetius]

An interesting data point: even today, the Liturgy of the Hours, which is the regiment of prayer for Christian monks and nuns, contains prayers for the middle of the night.

[Der_Einzige]

Intuitionistic logic, in MY HN? Blasphemy!

[boomboomsubban]

>this theory is largely thought false nowadays, or phrased too strongly at least.

What theory? The article doesn't really claim that this kind of sleep is better or more natural, just that it was incredibly common. Is the idea that it was common now thought to be false?

[notahacker]

I don't know about commonly thought to be false because I'm not sure it's commonly thought about at all, but it's a theory with considerable weaknesses

Ekirch hypothesis: Early humans had two distinct phases of sleep with an important gap between. Lack of in-depth discussion or even a name for that gap in any language is actually evidence of it being so common it wasn't worth commenting on. It disappeared - again without comment - because of widely available artificial light, although it actually makes less sense to dedicate midnight hours to stuff like household chores and reading in the middle of the night without easy light sources, especially in northern European summer when it's about the only time there isn't daylight.

Null hypothesis: early humans slept much like today's humans, sometimes waking or being woken in the night, occasionally even intentionally but generally not making a big deal of it and trying to sleep through. People sometimes described periods of broken sleep as "first sleep", "second sleep" and even "third sleep" but commentary on the practise of biphasic sleep and importance of midnight waking is harder to find because most people didn't do it that way. A lot of references to "first sleep" can be found if you search digitized records with that string and its foreign language equivalents, but so can references to obviously non-systematic things like "first injury" or "first marriage". You can't generalise human behaviour in the absence of electricity from one tribe that does have a midnight break when numerous others studied don't.

[sooheon]

> Null hypothesis: early humans slept much like today's humans [...]

That's a terrible null hypothesis, as there is no reproducible, controllable test for it, other than a time machine.

A better one might be "people exposed to pre-industrial revolution photoperiods (<12h per day) will settle into a biphasic sleep pattern".

This was empirically tested with a small N (https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2869.1992...). At least it's testable.

[notahacker]

Specifying that as something isn't directly testable, it's better that a bold new theory should actually be the null hypothesis isn't how science works! We've observed a lot of populations with little or no natural light and there is no reason to cherry pick the one or two which actually conform to Ekirch's proposed "standard" form of sleep. I mean, for a start, assuming "pre industrial revolution photoperiods" generally matched the ones in Wehr's study involves pretending that seasons don't exist in most of the places Ekirch's soured material came from!

[axiolite]

A much better study:

https://www.theatlantic.com/science/archive/2015/10/the-many...

[sooheon]

Better in what dimension? It's not a repeatable intervention, it's not controlled, it's observational. It's not a study on the same null hypothesis.

[notahacker]

If your claim concerns common habits of populations with limited or no artificial light sources, observational studies of multiple populations with no artificial light sources is a superior way of assessing it than a prior study which imposed very specific periods of light deprivation on a study sample accustomed to nightly routines governed by available light to see how their behaviour changed.

[int_19h]

> A lot of references to "first sleep" can be found if you search digitized records with that string and its foreign language equivalents, but so can references to obviously non-systematic things like "first injury" or "first marriage"

This hypothesis would also have to explain why we don't say things like "first sleep" anymore, even though we do say things like "first injury" or "first marriage".

[notahacker]

We don't talk about first sleeps but you'll still find plenty of modern references to "first sleep", "second sleep" and even "third sleep" in modern text too, from book titles to scholarly articles on sleep cycles

[jfengel]

It has always struck me as an unlikely hypothesis. While I'm not a historian, I do get some insight into the Elizabethan period in particular by a very close familiarity with its plays. Shakespeare never mentions it, and he does talk about sleep quite a bit.

One example that comes to mind, from Henry V:

    But, like a lackey, from the rise to set
    Sweats in the eye of Phoebus and all night
    Sleeps in Elysium

Hal doesn't say "All night sleeps in Elysium except for that bit where he wakes up in the middle of it". He's explicitly referring to untroubled, continuous sleep for most people (as compared to his own insomnia from worry about his kingdom).

I haven't done an exhaustive survey, but I don't believe Shakespeare characters ever wake in the middle of the night unless there is something to disturb them. They may drink late, or chimneys may come crashing down around them, but nobody ever says "Hey, see you in a few hours when we're both awake".

This is obviously far from conclusive. But the man writes about sleep often enough that I'd have expected at least some hint of it.

[wolverine876]

> Early humans

This article is about the 17th century (with some references going back further). Does Ekirch write also about early homo sapiens? Earlier ancestors? I am not nitpicking, just wondering if that term is used intentionally.

[Izkata]

> or even a name for that gap

From the article:

> The period of wakefulness that followed was known as "the watch"

Other terms for that time of night:

The witching hour (which almost sounds like a corruption of "the watch") - https://en.wikipedia.org/wiki/Witching_hour

Wee small hours - https://en.wiktionary.org/wiki/wee_small_hours

[notahacker]

Erkich's own words, both his original paper and his website, acknowledge the lack of a distinct name. He suggested generic terms "watch" and "watching" may have been used throughout a long period of British history to describe the hypothesised universal period of wakefulness based on one primary source each. One appears to be a prayer which refers to "between one morning watch and another" without hinting what a "morning watch" is, another is a devotional text calling on people to watch their first waking thoughts are set on God, where there are rather obvious alternative interpretations of the words "watch" and "first"...

The notion of "witching hour" is predicated on the idea that spirit activity takes place when most people are asleep, and "the wee small hours" is a reference to the entire period between midnight and dawn. If the closest word a language had to "lunch" was "afternoon", I'd probably conclude that culture generally didn't have an important midday meal!

https://sites.oxy.edu/clint/physio/article/SleepWeHaveLostPr... https://sites.google.com/vt.edu/roger-ekirch/sleep-research/...

[axiolite]

> The article doesn't really claim that this kind of sleep is better or more natural

It does:

"the benefits of dividing up sleep"

"single periods of slumber might not be 'natural'."

THIS article soft-peddles such claims biphasic sleep is better and more natural ONLY because those theories have been largely discredited since it was first put forward. Try an older article:

"Ekirch believes many sleeping problems may have roots in the human body's natural preference for segmented sleep"

"a consolidated eight-hour sleep may be unnatural"

https://www.bbc.com/news/magazine-16964783

> Is the idea that it was common now thought to be false?

Yes, that part is likely false, too:

https://www.theatlantic.com/science/archive/2015/10/the-many...

[quietbritishjim]

> The article doesn't really claim that this kind of sleep is better or more natural, just that it was incredibly common. (Emphasis mine.)

For a start, the article suggests that it wasn't just common but actually the dominant pattern of sleep, but the evidence seems a bit thin on that. Moreover, it says that "Ekirch began to suspect that the method had been ... an ancient default that we inherited from our prehistoric ancestors". But I seem to remember an anthropologist on a TV programme (many years ago so I forget which one sadly) saying this isn't obvserved in isolated tribal cultures today, so we can reasonable expect that our pre-agriculture anscestors wouldn't have slept this way.

Edit: A reply to a sibling comment found a good citation: https://www.theatlantic.com/science/archive/2015/10/the-many... Interestingly, like the BBC article it mentions Ekirch as the proponent of the two sleeps theory. So I wonder if the whole idea is the pet theory of this one person.

[rtsil]

The "it was incredibly common" part is the theory. I don't know if anyone else besides Roger Ekirch supports it, which doesn't mean it's false of course. Our ignorance of things past is gigantic and not helped by the fact that history (and stories) tend to be constantly rewritten.

[wruza]

I used to sleep like this too, for around 15 years (20-35yo). Then I began to experience many-day insomnias, or inability to wake up until my body feels like it. Troubles with digestion, immune system, motivation and mental state in general (all interlinked). Checking my hormone levels was like rolling dice every time. My endocrinologist, gastroenterologist, neurologist, psychotherapist all told me that if I don't correct my sleep cycles and get married, I'll suffer even more. I did the former half a year ago and feel much better.

It doesn't have to be connected, maybe my health would deteriorate independently of sleep or alone factors, but doctors say that it puts you into the risk group at the very least. I'd say be careful, but 5-10 years ago I'd also waved it away as irrelevant :)

[the_only_law]

This would almost work for me, except one of the “when I feel like sleeping” times aligns with the peak of workday, and “when I fell perfectly awake and refreshed” is too late.

[dj_mc_merlin]

It was like that for me too when I worked 9-5 (or more like 6). Now I work "biphasal" days so to speak, from 12:00-16:00 and sometime later in the evening for a couple hours. I find that splitting it up helps me be more productive, I have more of my "software development energy" to spend. I'm lucky that my work offers very flexible hours since we hire around the globe and nobody in my team minds that I review their MRs in the middle of the night.

I usually use the day hours as "open office time" for support requests and meetings, and the later time as "proper work time". This helps me avoid context switches.

[dylan604]

Too late for whom? Apparently, not for you. With WFH, taking a nice little siesta isn't impossible (and anecdotally sounds like its more common than some would like to admit). Of course, forced to work in an office makes it harder, and probably surrounded by bosses much less sympathetic to the concept.

[nottorp]

> I prefer to stay up into the night and wake up around 12:00, but I vary my sleeping hours by up to 4 hours or so. I go to sleep when I feel like it, and don't feel much discomfort by falling asleep at different times.

Yep. Exactly the same here. I tend to wake up 7-9 hours after I go to sleep (usually between 00-04:00) no matter when that happens. With very rare occurences of two part sleep. No side effects by 45, but I do exercise.

Come to think of it, I may get two part sleep more often than I think, because I do wake up during the sleep period. But most of the time I ignore it and fall asleep again in a couple minutes.

[a_square_peg]

Yeah - I'm currently reading 'Why We Sleep' by Matthew Walker (excellent book by the way) and it mentions that this theory has been debunked.

[honkdaddy]

I haven't read Why We Sleep yet, but I do remember a post[1] on here a while ago which found issue with some of the books' claims. YMMV

[1] https://news.ycombinator.com/item?id=21546850

[a_square_peg]

Oh wow, that's interesting. Will take a look - thanks for the info.

[Edit] - Ok, I read the review and I can see why you added YMMV.

[daneel_w]

It may be thought of false, but historic documents from many European countries mention and detail it as the common habit. There is no theory or claim about its benefits, just that it was habitual.

[naikrovek]

what theory? the article is about a person who found copious evidence for this.

"two sleeps" was pure fact for a very long time.

[jgilias]

I used to be an adventurer like you, then I got kids.