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Unirt's avatar

Thank you! Some comments:

1. Early life may have occurred deep in the oceans fuelled by the warmth of the Earth so the creatures were not really interested in the sun, probably only developed circadian rhythms later when they colonised the upper water layers (er, sorry, this was not really necessary, just had to say it out).

2. I've lately been a bit confused by this topic: the anthropologists have been claiming that hunter-gatherers are opportunistic sleepers, who sleep whenever they can and want and overall much less than us; infants have no circadian rhythms whatsoever and are only trained by parents to have these; many peoples have siestas at noon and therefore totally different sleep-wake patterns than once-per-day sleepers. Yet the sleep patterns of contemporary men in 'advanced' societies are highly heritable and hard to change. This is a contradiction, I can't solve it.

3. "SUN SUN SUN SUN SUN"

Sun? You mean the small shiny thing we see once a week through a frosty mist?

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Experimental Fat Loss's avatar

> Sun? You mean the small shiny thing we see once a week through a frosty mist?

You must be British? :D

I've seen various claims about sleep in hunter-gatherers, but the few studies I actually saw where they tested this, most of them slept pretty much exactly like us. They did not sleep all the time, they did not sleep way less, most did not regularly nap (although more in the summer!), they did not have "2 sleeps" with a long waking period in between. They pretty much slept like we do.

That said; a siesta can make sense, as can a "second sleep"/night activity time. I could imagine for example if it's too hot to comfortably sleep soon after sunset, you would go to bed later, and if it's too hot/bright out to keep sleeping enough too early, maybe you just get tired enough around noon?

And if it's dark for 16h a day in the winter, you can't possibly sleep that entire time. So unless you're a night owl or lark, it could spontaneously develop in a way where you sleep from say 9-12, stay up for a few hours, then sleep some more.

About the baby thing; I think their circadian rhythm is biologically set, it's not training by the parents. Just like our rhythm changes as we age, it's completely bonkers the first few months or years until it becomes what we'd consider "normal."

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