I htink this fits what you intend? It’s been discussed before, most recently:
This guy is putting out a revision of his book about historical biphasic sleep. He had been critiqued for having a fairly low sample size. He’s unearthed a few more:
https://www.cnn.com/2022/01/09/health/sleep-history-wellness-scn/index.html
At this point I’d say “compelling,” not “convincing.” It might be more accurate to write that prior to the “industrial revolution” [itself not a clear term–one of my profs argued that the IR didn’t begin until the 1950s] the timing of sleep didn’t matter too much, so sleep cycles just didn’t matter and therefore people didn’t try to regulate them as much.
