
Sleep helps to repair damaged DNA in neurons, scientists find - puttycat
https://www.theguardian.com/science/2019/mar/05/sleep-helps-to-repair-damaged-dna-in-neurons-scientists-find
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rhema
One argument I've heard: if evolution could get rid of sleep, it would have a
long time ago. There are several survival drawbacks from sleep, as it leaves
one vulnerable. It must be important!

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imustbeevil
Definitely today sleep prioritizes healing resources over active resources and
it certainly seems beneficial to have that happen. But I'd contend that a
system that can constantly be active _and_ healing would be an evolutionary
improvement that _will_ occur over time.

Evolution is kind of like Economics; it's not rational, and it's not currently
in equilibrium.

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omalleyt
That would take extra calories, that's where the balance is

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abootstrapper
Too bad I can’t spend my calorie surplus on the no sleep extra healing
evolution upgrade.

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scotty79
My pet theory was that natural neural networks have built in learning
mechanism that is prone to over-fitting. The way nature is overcoming the
problem is periodically disconnecting inputs and outputs from the neural
network and letting it trigger randomly for some time to add a bit of noise.

But it seems that more and more evidence shows up that sleep is just clean-up
time for the brain.

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puttycat
Original paper:
[https://www.nature.com/articles/s41467-019-08806-w](https://www.nature.com/articles/s41467-019-08806-w)

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gnode
I think it's premature to assume that sleep is essential to any essential
mechanism that occurs during it. It's similar to assuming that if a smartphone
downloads and applies updates when it's charging and on WiFi, that external
power and WiFi are vital to the updating mechanism.

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Protostome
The fact that sleep is essential is something that is very easily observed.
Sleep deprivation results in a relatively quick death (days - weeks), even
faster than starvation.

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gnode
By essential, I don't mean that we depend on it, but that it is evolutionary
unavoidable. It may be physically possible for a given process to be performed
during wake, yet we are only able to perform it during sleep, because we had
already evolved to sleep and thus the process could be optimised in such a way
as to become dependent on it.

If we're trying to answer the question of why complex animals evolved to sleep
in the first place, then we'd have to find processes which depend inherently
on sleep (or at least are enhanced by it).

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Protostome
I agree with your statement - that doesn't mean that there isn't a way around
sleep. If we imagine the fitness vs. evolutionary traits as multi-dimensional
landscape, it could be that we're stuck on a very deep local minimum. It
doesn't mean that there's not a deeper local minimum few blocks away :-)

It just means that sampling evolutionary traits that lead us out of that local
minima, is very expensive from a fitness perspective.

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gnode
> it could be that we're stuck on a very deep local minimum

I think that's likely.

Also, in cases where being able to be awake continually (e.g. high predation
or flying over water) animals have evolved unihemispheric sleep, which is
likely a shorter evolutionary path and largely satisfies the selective
pressure, making it less likely for sleep to be entirely evolved away.

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LifeLiverTransp
Sleep is when you descend from a vegetable who lacks diggestable light food
during the night.

