Oh, there’s tons of evidence for this, largely in the writings of pre-electricity figures who clearly treated the subject as common knowledge. Advice manuals from the time even indicate that this was the best time for couples to conceive.
Modern tribes without access to continuous light actually still sleep like this too, which is fascinating.
Modern tribes without access to continuous light actually still sleep like this too, which is fascinating.
https://www.bbc.com/news/magazine-16964783