This is basically what Matthew Walker (https://en.wikipedia.org/wiki/Matthew_Walker_(scientist)) sort of alludes to in his book, "Why we sleep". It's a good book. He specifically mentions hydras as well (iirc)... he's a neuroscientist who is a crazy maniac about sleep and he cites newest research and delivers a very clear message of urgency.
Lots of fascinating stuff there, highly recommend if you're interested.
In my view (of his view) - that in many cultures we see today, we've come to vastly underestimate the importance of sleep. For example, we've removed afternoon naps from workday routine (with field evidence showing effects on health such as heart disease (against comparative groups who haven't stopped taking naps - but not lab-controlled I think) etc.) We sleep less.[2]
We shouldn't be asking what's the purpose of this pesky thing called sleep (which evolution turns to always incorporate into animal life, however inconvenient it is[1]; to route around the inconveniences as it were, rather than the other way around). We should rather be asking, is there a single function which isn't improved by sleep (Walker thinks no). End of preach rant :)
[1]: e.g.: some birds appear to sleep in patterns such as when there's a row of birds sleeping, the two birds at each end sleep with one hemisphere each - but opposite ones - so that the field of vision is maximised. At midpoint in time however they swap places. The rest of the birds sleep with both hemispheres. That sounds pretty cool.
[2]: though apparently there's criticism directed at Walker re: this, and re: him not mentioning that mortality appears to increase beyond the 7 hour mark (but I'm just learning this, so basically, just a fair warning not to take all of this at face value, there's nuance).
Regarding mortality and the 7 hour mark, this is such unfortunate bullshit, that keeps being propagated by people who should know better. Ill people sleep more (even if you catch a cold, once you get past the peak, you sleep more for a few days) because their body requires more recovery.
In chronically ill people this continues for a long time and the body never is able to catch up to the problem it's trying to solve.
But despite all the "correlation not causation" mantras repeated by everyone, we keep citing this as if we decide to sleep a bit more that'll make it more likely to die, which is nonsense.
Ah okay, so basically you're saying that the mortality vs > 7 hour sleep time correlation claim hasn't normalized / accounted for other parent causes (e.g. chronic illness and other things affecting / disturbing sleep quality)? I'm a noob here, but if that is the case, that is very unfortunate and frustrating.
I've not seen a single study to demonstrate causative link, or conclusively eliminate other variables (which is frankly quite impossible anyway).
Unfortunately a lie repeated a thousand times (by media) becomes truth. And it's just too juicy of a news to say "sleeping too much bad for health". Especially managers, they love that kind of news ;-)
BTW my frustration is pointed at general media and society, not you in particular, I wasn't clear.
In toddlers and in very elderly, the sleep-wake cycle can no longer be full 24 hours due to decreased/lower abilities of your body to “buffer” for that amount of time. So a single well defined afternoon sleep can be good.
I wouldn’t call that “naps”. That’s not what it is.
Lots of fascinating stuff there, highly recommend if you're interested.