It also seems sketchy to me how much this seems to trace back to one guy's book. Most of what I can find on the internet cites the 2005 book
At Day's Close: Night in Times Past by Roger Ekirch. Not saying his book is wrong, but it'd be nice if there were more sources (and there could be, but his book is just the one anyone knows about). Btw, if you're curious, I found
this. It's the Ekirch guy briefly arguing against a paper that claimed bimodal sleep was only a thing in very high latitudes because of very long nights during the winter. Gives a sense of how much is known about this topic. Plus it's interesting and somewhat amusing.
Compiled in one book the case is indeed thin and yet taking it over spread like wildfire.
When I first read someting about it it felt like making sense for two resons:
A. I read a lot of everything including stuff from old medieval-early modern annals, courtcases, letters, diaries browsing through that when interested in someting (else). Enough patchy confirmation there for plausibility
B. In todays world there is a lot to do about "sleep disorders" mainly people having difficulty to fall asleep or people waking up in the middle of the night and not able to fall asleep easily again. Especialy older people.
Ad B:
Well... what is normal ???
If that 8 hour is normal... waking up in the middle of the night is a disorder
If that breaking your sleep in the middle of the night is normal.... getting that 8 hours uninterrupted is a cultural imposement.
Well, what does that mean? 50% of people did this? 10%? Seven nights a week? One night a week?
So why not assuming diversity ?
Diversity from differences between people, between what you did the day before (physical, stress, kind of food and when), between other ageing phases of your life (and body metabolism). etc.
If I walk my (little) dog.. if we meet a lot of other dogs with all the social interactions... or/and meet a lot of people/kids at the small shopping centre... when we come home she is going to sleep flat out.
When it is raining and walking the dog is shorter and little interaction happens she also goes sleeping afterwards... but when I make myself a coffee an hour later she already wants to play with me. And getting my hands free for other stuff I learned that she will keep on disturbing me unless I give her at least a quarter of an hour game play with fighting over fluffy pets, ball, hide-seek play games, etc.
Ad A
* In medieval time people slept a lot more together in one bed (because of room, warmth, etc). A little baby needed breast milk and made ofc loudly clear when (and mothers had all the time babies).
Not much of that "holy special" bedroom cultus we have now, where anti-snoring devices and earplugs are selling well.
* Chickens were everywhere in medieval time (eggs also a currency unit) including roosters with their cockrow. And cockrow is not only at dawn ! Goes on through the night starting with the "midnight" cockrow roughly around 1 AM. Really handsome as time indicator throughout the night for the vigils (watches). The traditional medieval sundial does ofc not work during the night and clockworks are Renaissance period. Makes me wonder whether wild chicken roosters do the same, or this is part of the domestication effects of chickens (earlier laying eggs, more flesh when adult, less agressive to us or other chickens, etc). Chickens BTW great to keep your yard free of mice and other vermin and eating up food (cooking) remains before they rot..
* You mentioned already prayers. Christianity took over the Jewish tradition of several prayers a day, but in monasteries this blossomed to a whole system since around 400-600 AD. The midnight prayer one of them as part of that highly prescriptive system with many (ideological and identity) changes over time. Bookprinting good for prayerbooks and the tradition was kept up in some way in early protestantism.
etc, etc
