In hunter-gatherer societies, bedtime typically occurred two hours after sundown and waking occurred before dawn.

“they typically go to bed about an hour and a half to two hours after sundown so around sort of 8:30 9 o'clock they usually get about seven seven and a half hours of sleep at night and then they have a siesta like nap in the afternoon to make it up to around about a total of nine hours”

“what they would typically do is they would maybe sleep just six six and a half hours at night and then they would make the rest up and they”

“particularly during the summer months they will typically have an afternoon nap right in the time zone that you just described and this is the very much the mediterranean siesta-like behavior”

“what they would typically do is they would maybe sleep just six six and a half hours at night and then they would make the rest up and they would get into that exact same sort of territory by way of the nap so they would take it in these two chunks”

“in those individuals it means what the word states which is it's the middle of the night for them midnight because they usually go to bed maybe two hours after sundown and they're asleep you know by let's say 9 p.m in in the evening or 8 30 and then they're awake you know just a little bit before dawn”

“what seems to wake them up is not necessarily daylight it's the change in temperature because there's a rise in temperature that seems to happen before daylight starts to break and it seems to be it's the temperature change that they are much more buckled to in terms of regulation of their sleep weight rhythm”

“the natural point of middle point of sleep, the middle phase sort of time of that eight to nine hours sleep phase, came somewhere between midnight and 1:00 p.m.”

“That seems to be a thermal trigger for them getting sleepy and falling asleep.”