Earlier quoted context omitted.
You are right (and very observant) that this is mostly Ekrich when you dig into it. I didn't realise this until quite recently, and I too had assumed there was a lot more work about this. But what he's found in literature is pretty consistent, and biphasic sleep was once quite normal in a specific context: the siesta. It's dying out in continental Europe alas -- a lost cultural touchstone -- and in the contemporary W…
Question for people who sleep like this: do you live with anyone? How do they tolerate it? I can't imagine it's great to wake up to your roommate scraping pans in the kitchen on odd nights.
I tried it and it worked, but I have a family and no, it didn't work for them, so I stopped. Couldn't get a schedule right that allowed me to be with the family for normal social interaction times, AND be at work when THEY expected me to be available for the work-team.
So I had to go to a socially acceptable "norm".