5 ms·

Why We Sleep

79 points by blatherard 11y ago

netman21 11y ago
I have an alternative answer to that question. Mammals evolved to sleep because those young that gave their parents a rest survived childhood. Seems obvious to any parent. :-) Imagine a puppy that never stopped. Its mother would abandon it.
- carsongross 11y ago
  Cute, but just turn the darwinian crank: the mother that didn't abandon it would then have super-puppy offspring that would be able to secure far more resources for themselves and their offspring. The obvious advantages of not sleeping indicates to me that there is a deep connection between sleep and our waking performance. If there weren't why the hell would it have persisted across so many creatures for so long. I am confused by the fact that human young keep parents awake so much: it seems like a delicate time to be introducing poor cognitive performance into the mix. But then a lot of things confuse me when I apply straight forward darwinian thinking.
  - zyrthofar 11y ago
    I like to think that we evolved sleep because it's better, in the wild, to be still and silent in the dark, than move around and make noise. Since we can barely see in the dark and can't do anything anyway, wouldn't it be preferable to minimize the time spent defenseless against predators with better night vision? Staying still seems like a good strategy a lot of times, when most animal visions, night vision or not, is based on movement. It doesn't answer, though, why the top of the food chain need to sleep too.
    - ricree 11y ago
      It also doesn't explain why the effects of sleep are so strong, when an instinct for watchful stillness would have been every bit as effective for that purpose.
    - jqm 11y ago
      Maybe if we hadn't been sleeping we would have evolved the ability to see in the dark by now.
  - logfromblammo 11y ago
    Toothed whales (incl. dolphins) can apparently sleep with just half their brain at a time, while remaining alert with the other half. Thus, there exists a solution in nature wherein the creature experiences the benefits of both regular sleep and continuous alertness. The rarity of the solution suggests that sleep is more important for most mammals, except in niches where a prolonged loss of consciousness could lead to drowning, or being eaten by sharks. Also recall that as social, tribal animals, modern humans relied on aunts and grandmothers to relieve exhausted mothers for all of prehistory. Separate homes for smaller family units and wider geographic dispersal of family members are relatively recent developments. I wouldn't expect biological adaptations to the practice to appear any time soon. I think the most likely event is that we will discover and use a pharmaceutical remedy for sleep deprivation in parents, possibly by studying dolphin brains.
    - kayman 11y ago
      Similar to meditation perhaps.
- winternewt 11y ago
  That doesn't explain why the parents need to sleep, though.
  - simonsquiff 11y ago
    It does, it's the vestigial remnants of whatever makes the baby sleep...
    - ars 11y ago
      There are plenty of neonatal behaviors that stop as the child gets older. Why would sleep be the exception?
ommunist 11y ago
Why would anyone want to "be productive" if he or she can just ... hm, sleep!
- venomsnake 11y ago
  Story of my college years ...
guelo 11y ago
I hate it when I solve programming problems while sleeping. It makes me feel like I'm working for free on my time off. They're only supposed to be renting my brain for part of the day.
- csorrell 11y ago
  It's even worse when all that time sleeping is spent failing to solve the programming problem...
- dsp1234 11y ago
  I hate it when I code the solution when I'm sleeping, then I wake up and am forced to code it again for real. It's like the ultimate failure to Ctrl+S
- elwell 11y ago
  Start your own startup and you won't have this problem.
septerr 11y ago
Tldr: When we sleep, our brains process the events of the day and pick out things to stow away in our long term memory. Maybe as a side-effect of this processing, they also aid problem solving - after a good night's sleep, you are able to find solutions to the previous day's problems faster (than you would, if you hadn't had the sleep). As we sleep, our brains clear away toxins that accumulate during our awake time. These toxins may be culprits behind neuro degenerative diseases. There seems to be a correlation between sleep deprivation and cardiovascular diseases.
- at-fates-hands 11y ago
  >> Maybe as a side-effect of this processing, they also aid problem solving. This is an interesting side effect considering when I have a tough coding problem, it keeps my brain churning for hours and it keeps me from falling asleep. It's clear your subconscious comes to the forefront as your conscious part of your brain turns off during sleep. Having your subconscious solving complex problems is fascinating to me. I'm wondering how you could activate this on purpose, without having these issues keep you awake at night when you consciously can't let go of a problem. The implications of this are pretty cool if you could pull it off.
  - deleted 11y ago
    [deleted]
- jacobolus 11y ago
  Sleep also somehow helps the immune system do its thing properly. After a night without sleep or a few days with insufficient sleep, the immune system is partly compromised. As one example, multiple people I know with chronic virus-caused skin conditions (like warts, herpes, ...) have symptoms when they don’t get sufficient sleep. I know a couple people whose arthritis kicks into high gear after insufficient sleep. Sleep also definitely has a large effect on mood, I assume at least partly through the mix of stress hormones produced; many people I have known closely become extremely emotional and irritable when they haven’t had enough sleep. Others become emotionally detached/withdrawn (at least, by outward appearances).
wyager 11y ago
It is, I think, often more enlightening to ask the question "why do we awaken"? I wonder if, a long time ago, some animal evolved the ability to enter brief periods of elevated activity. This was obviously highly advantageous for e.g. escaping predators, so over time this animal evolved to sustain this temporary boost for longer periods. Today, animals can sustain this boosted state for the majority of their lifetime. It is merely a matter of perspective that leads us to consider wakefulness to be "normal" and sleep to be something out of the ordinary.
- jacquesm 11y ago
  You already answered the question: if you keep on sleeping you're vulnerable and being vulnerable over a longer period of time equates to certain death. So we awaken to stay alive when the cover of night disappears.
- sudoherethere 11y ago
  So plants are just sleeping animals, sort of. I kind of like this.
- dharma1 11y ago
  Some animals sleep the majority of their lives - some bats for instance http://chartsbin.com/view/1923 http://chartsbin.com/view/1923
stuartd 11y ago
This is where f.lux - https://justgetflux.com https://justgetflux.com - is so great. After sunset in your location it gradually bleeds blue light from your display: also at work I use it to just orange-ify the display a bit at a constant rate - because work is lit by fluorescents - and on a bright monitor it noticeably reduces eyestrain.
vernon99 11y ago
There's a pretty convincing theory that says that while we sleep, brain is processing signals from our internal organs instead of processing the sensory input. Experimentors were triggering impulses in monkey stomach and seeing them activate some areas of the brain that are normally used in the cognitive process. That way brain inspects the organism and balances it's functions. One of the side effects of this theory is that our dreams are just an interpretation of these signals. Like your liver signals trigger some areas of the brain and that produces the weird imaginery we call dreams. Can't find the link to that paper right away.
- vernon99 11y ago
  Found some publications, the theory is called The Visceral Theory of Sleep, spearheaded by Ivan Pigorev. Intro: http://www.researchgate.net/publication/271920141_The_Visceral_Theory_of_Sleep http://www.researchgate.net/publication/271920141_The_Viscer... Cortical visual areas process intestinal information during slow-wave sleep: http://onlinelibrary.wiley.com/doi/10.1111/nmo.12052/abstract http://onlinelibrary.wiley.com/doi/10.1111/nmo.12052/abstrac...

79 points by blatherard 11y ago

I have an alternative answer to that question. Mammals evolved to sleep because those young that gave their parents a rest survived childhood. Seems obvious to any parent. :-) Imagine a puppy that never stopped. Its mother would abandon it.

carsongross 11y ago
Cute, but just turn the darwinian crank: the mother that didn't abandon it would then have super-puppy offspring that would be able to secure far more resources for themselves and their offspring. The obvious advantages of not sleeping indicates to me that there is a deep connection between sleep and our waking performance. If there weren't why the hell would it have persisted across so many creatures for so long. I am confused by the fact that human young keep parents awake so much: it seems like a delicate time to be introducing poor cognitive performance into the mix. But then a lot of things confuse me when I apply straight forward darwinian thinking.
- zyrthofar 11y ago
  I like to think that we evolved sleep because it's better, in the wild, to be still and silent in the dark, than move around and make noise. Since we can barely see in the dark and can't do anything anyway, wouldn't it be preferable to minimize the time spent defenseless against predators with better night vision? Staying still seems like a good strategy a lot of times, when most animal visions, night vision or not, is based on movement. It doesn't answer, though, why the top of the food chain need to sleep too.
  - ricree 11y ago
    It also doesn't explain why the effects of sleep are so strong, when an instinct for watchful stillness would have been every bit as effective for that purpose.
  - jqm 11y ago
    Maybe if we hadn't been sleeping we would have evolved the ability to see in the dark by now.
- logfromblammo 11y ago
  Toothed whales (incl. dolphins) can apparently sleep with just half their brain at a time, while remaining alert with the other half. Thus, there exists a solution in nature wherein the creature experiences the benefits of both regular sleep and continuous alertness. The rarity of the solution suggests that sleep is more important for most mammals, except in niches where a prolonged loss of consciousness could lead to drowning, or being eaten by sharks. Also recall that as social, tribal animals, modern humans relied on aunts and grandmothers to relieve exhausted mothers for all of prehistory. Separate homes for smaller family units and wider geographic dispersal of family members are relatively recent developments. I wouldn't expect biological adaptations to the practice to appear any time soon. I think the most likely event is that we will discover and use a pharmaceutical remedy for sleep deprivation in parents, possibly by studying dolphin brains.
  - kayman 11y ago
    Similar to meditation perhaps.
winternewt 11y ago
That doesn't explain why the parents need to sleep, though.
- simonsquiff 11y ago
  It does, it's the vestigial remnants of whatever makes the baby sleep...
  - ars 11y ago
    There are plenty of neonatal behaviors that stop as the child gets older. Why would sleep be the exception?

ommunist 11y ago

Why would anyone want to "be productive" if he or she can just ... hm, sleep!

venomsnake 11y ago
Story of my college years ...

guelo 11y ago

I hate it when I solve programming problems while sleeping. It makes me feel like I'm working for free on my time off. They're only supposed to be renting my brain for part of the day.

csorrell 11y ago
It's even worse when all that time sleeping is spent failing to solve the programming problem...
dsp1234 11y ago
I hate it when I code the solution when I'm sleeping, then I wake up and am forced to code it again for real. It's like the ultimate failure to Ctrl+S
elwell 11y ago
Start your own startup and you won't have this problem.

septerr 11y ago

Tldr: When we sleep, our brains process the events of the day and pick out things to stow away in our long term memory. Maybe as a side-effect of this processing, they also aid problem solving - after a good night's sleep, you are able to find solutions to the previous day's problems faster (than you would, if you hadn't had the sleep). As we sleep, our brains clear away toxins that accumulate during our awake time. These toxins may be culprits behind neuro degenerative diseases. There seems to be a correlation between sleep deprivation and cardiovascular diseases.

at-fates-hands 11y ago
>> Maybe as a side-effect of this processing, they also aid problem solving. This is an interesting side effect considering when I have a tough coding problem, it keeps my brain churning for hours and it keeps me from falling asleep. It's clear your subconscious comes to the forefront as your conscious part of your brain turns off during sleep. Having your subconscious solving complex problems is fascinating to me. I'm wondering how you could activate this on purpose, without having these issues keep you awake at night when you consciously can't let go of a problem. The implications of this are pretty cool if you could pull it off.
- deleted 11y ago
  [deleted]
jacobolus 11y ago
Sleep also somehow helps the immune system do its thing properly. After a night without sleep or a few days with insufficient sleep, the immune system is partly compromised. As one example, multiple people I know with chronic virus-caused skin conditions (like warts, herpes, ...) have symptoms when they don’t get sufficient sleep. I know a couple people whose arthritis kicks into high gear after insufficient sleep. Sleep also definitely has a large effect on mood, I assume at least partly through the mix of stress hormones produced; many people I have known closely become extremely emotional and irritable when they haven’t had enough sleep. Others become emotionally detached/withdrawn (at least, by outward appearances).

wyager 11y ago

It is, I think, often more enlightening to ask the question "why do we awaken"? I wonder if, a long time ago, some animal evolved the ability to enter brief periods of elevated activity. This was obviously highly advantageous for e.g. escaping predators, so over time this animal evolved to sustain this temporary boost for longer periods. Today, animals can sustain this boosted state for the majority of their lifetime. It is merely a matter of perspective that leads us to consider wakefulness to be "normal" and sleep to be something out of the ordinary.

jacquesm 11y ago
You already answered the question: if you keep on sleeping you're vulnerable and being vulnerable over a longer period of time equates to certain death. So we awaken to stay alive when the cover of night disappears.
sudoherethere 11y ago
So plants are just sleeping animals, sort of. I kind of like this.
dharma1 11y ago
Some animals sleep the majority of their lives - some bats for instance http://chartsbin.com/view/1923 http://chartsbin.com/view/1923

stuartd 11y ago

This is where f.lux - https://justgetflux.com https://justgetflux.com - is so great. After sunset in your location it gradually bleeds blue light from your display: also at work I use it to just orange-ify the display a bit at a constant rate - because work is lit by fluorescents - and on a bright monitor it noticeably reduces eyestrain.

vernon99 11y ago

There's a pretty convincing theory that says that while we sleep, brain is processing signals from our internal organs instead of processing the sensory input. Experimentors were triggering impulses in monkey stomach and seeing them activate some areas of the brain that are normally used in the cognitive process. That way brain inspects the organism and balances it's functions. One of the side effects of this theory is that our dreams are just an interpretation of these signals. Like your liver signals trigger some areas of the brain and that produces the weird imaginery we call dreams. Can't find the link to that paper right away.

vernon99 11y ago
Found some publications, the theory is called The Visceral Theory of Sleep, spearheaded by Ivan Pigorev. Intro: http://www.researchgate.net/publication/271920141_The_Visceral_Theory_of_Sleep http://www.researchgate.net/publication/271920141_The_Viscer... Cortical visual areas process intestinal information during slow-wave sleep: http://onlinelibrary.wiley.com/doi/10.1111/nmo.12052/abstract http://onlinelibrary.wiley.com/doi/10.1111/nmo.12052/abstrac...