INTERESTING NOTE in the HISTORY of SLEEP:


Before the industrial revolution humans were sleeping in a biphasic way. There was a 1st and a 2nd sleep. The 1st or deep sleep would occur a bit after dusk. It would last around 2-4 hours. After that, there would be a break of 2 hours in which people would socialize, meditate about their dreams or simply rest. A 2nd sleep (morning sleep) would then start - this would finish by dawn. Most of our bodies still have memory of this system and tend to go back to it. This is how we are still designed and will be for some time.


Before the invention of agriculture, which allowed us to become sedentary only 10,000 years ago, night sleep was even more segmented. We were preys and would have to be more vigilant. That's how we slept or didn't sleep for 99% or more of our history as a species. That's a mark / code / software we all carry.


Side note: How come do we know so little about what we do during about 1/3 our lifetime - sleep.