I blame it on alcohol. If I drink I’m always up for a few hours in the middle of the night. And I’m quite sure they were doing a lot of that back in that time.
Ah yes. Having an evening drink, falling asleep at like 9PM, and then waking up wide awake at midnight to dick around for a few hours until finally falling back asleep at like 3 AM. It still happens to me from time to time.
Oh, so it's not just me. I've always interpreted it as the first sleep (hah) being my body being busy trying to sober up and the second sleep being the actual normal sleep now that the body can focus on something other than getting rid of all that poison.
Of course actual blood alcohol takes longer to go down than that but no matter how much I had, I'd invariably feel significantly more sober after the initial sleep than if I just stayed awake and stopped drinking.
Given that alcoholic drinks (especially various concoctions we'd hardly recognize as "beer" today) were fairly widespread especially when pure water was not always potable, I wouldn't be surprised if this didn't at least factor in for some of the reports. Then again this doesn't explain the observation of polyphasic sleep developing under experimental conditions.
> And I’m quite sure they were doing a lot of that back in that time.
Technically, they were all drinking alcohol because water was unsafe. However, beer at least had half the alcohol content that it has today and the wine was strongly watered. For women and children they even added water to the beer.
Googled it once. The information should still be available.