Why has nothing evolved to not need sleep?

[-RA-]

An animal that does not need to sleep would be at a huge advantage over all other animals as animals are more vulnerable when asleep, so why are there none that have done that?

(i think i am correct in saying that all animals sleep)

 

[jim mcnamara]

Probably not correct - either of your assumptions.

-- more vulnerable

One view of sleep is that it EVADES predators. Example: human night vision is very poor compared to a lion. If humans sleep in a group, maybe in a tree, they are much safer than bumping around in darkness and walking right into the midst of a pride of lions to beome lion chow.


-all animals sleep (my definition of sleep is an altered brain state that shuts off or reduces incoming stimuli, not just a period when an animal waits for a meal to hop by):

example -
Animals like pit vipers - snakes that are active in darkness or daytime. They slow down only when they are digesting food, or temperatures are out range for functioning.

Otherwise, they are on the alert 24X7 when hunting. I do not know of any research that shows an altered brain state for snakes. By this I mean the reptilian equivalent of sleeping 'delta' waves, or REM sleep. Or even if snakes even have sufficient "higher" brain function to show altered brain states.

Anybody else know about snake EEG patterns?

 

[-RA-]

One view of sleep is that it EVADES predators. Example: human night vision is very poor compared to a lion. If humans sleep in a group, maybe in a tree, they are much safer than bumping around in darkness and walking right into the midst of a pride of lions to beome lion chow.

but they would be a lot safer if they were awake up the tree at night tham if they were all asleep up a tree. Animals are more vulnerable when they sleep, that's the very reason why they have to dig a burrow, or climb a tree in the first place.

-all animals sleep (my definition of sleep is an altered brain state that shuts off or reduces incoming stimuli, not just a period when an animal waits for a meal to hop by):

thats similar as to how i would describe sleep, although i would tend to call it an altered state of conscious.

i should have been more specific, why do all mammals sleep even though they have all evolved separately.

 

[mgb_phys]

i should have been more specific, why do all mammals sleep even though they have all evolved separately.

They all evolved from a common ancestor - that was probably nocturnal and hid in a burrow all day. If you are hiding in hole during the day it makes sense to reduce your energy demands by slowing down that calorie hungry brain so that when you do go out looking for food you don't need to find so much.

I would expect to see a reduction in hours slept as go from small to large animals.

 

[jim mcnamara]

-RA-

Okay, lose the tree. That's a non-sequitur response, you know.

Try a personal experiment.

Go to a field where you cannot see any electric lights closer than 100 yards or so. Go out on a dark moonless night.

Try to walk about. You will personally experience why some researchers think being awake at night and moving around was a bad idea for early humans. While you are stumbling around, pretend there are predators nearby. They can silently run 40mph, too. And you are on the menu.

You will also learn why lots of "primitive" people use walking sticks.

 

[-RA-]

Go to a field where you cannot see any electric lights closer than 100 yards or so. Go out on a dark moonless night.

Try to walk about. You will personally experience why some researchers think being awake at night and moving around was a bad idea for early humans. While you are stumbling around, pretend there are predators nearby. They can silently run 40mph, too. And you are on the menu.

point taken, although i think i'll leave the experiment for someone else to try!. I suppose that is a good reason for mammals with bad night vision; but what about animals that hunt at night, as well as the day? they still sleep periodically.

If you are hiding in hole during the day it makes sense to reduce your energy demands by slowing down that calorie hungry brain so that when you do go out looking for food you don't need to find so much.

i can understand that aswell, but i also can't see why we have to sleep to replenish our brains in the first place. An animal with a brain that 'replenishes' as it is use, and so would never need to rest, would be at a much bigger advantage than animals that do rest. I would have thought that over time some animals would have developed to not need sleep as it would be so advantageous.

I guess in an indirect way i am asking why exactly do animals need sleep so badly in the first place.

 

[mgb_phys]

It depends wether you sleep to replenish your brain (ie. allow chemicals to be built up or waste products to be removed ) or it is purely a low power state to save energy.

Cats sleep most of the time - to save energy, you might as well ask why they haven't evolved to chase and eat prey 24hours a day.

 

[-RA-]

It depends wether you sleep to replenish your brain (ie. allow chemicals to be built up or waste products to be removed ) or it is purely a low power state to save energy.

what does sleep do out of those two options then?

i'm not sure if I'm saying this right, but i still can't see the real reason for sleep. If it was to replenish your brain why do you need to sleep for your brain to do that?, your brain builds up chemicals and removes waste products when you are awake aswell. If sleep is a low power state to save energy that implies that every animal has evolved to be inefficient at storing energy, and so has to sleep to save this energy. So if an animal evolved to become twice as efficient at using energy than its predecessors it should sleep for half the time. surely that's not correct?

 

[Count Iblis]

A long time ago on some science program I heard about a theory of how sleep is thought to have evolved. You have to go back way back to the pre-Cambrium. Just imagine that you have different primitive sea creatures that do not sleep. They eat and they use the energy from what they eat to find food move around etc. There is competition between different species. This drives the organisms toward the limit of their capabilities.

If you are a predator, then the prey will make sure you need to go beyond your maximum sustainable limit to catch them. This will then cause you to need a resting period of low activity to compensate for high activity periods.

Since sleep has evolved so long ago, it is basically hard wired into our system. When we are awake we function at a level that is simply not sustainable on the long run. You can think of undoing the necessity of sleep, but then the same dynamics of our early ancestors that led to the evolution of sleep will still apply: If you could somehow change your biology and go witout sleep and do theoretical physics 24 hours a day, then you could tweak your biological system a bit and obtain a system that can do physics much better for 10 hours but will need rest and sleep to recover.

 

[TVP45]

An animal that does not need to sleep would be at a huge advantage over all other animals as animals are more vulnerable when asleep, so why are there none that have done that? (i think i am correct in saying that all animals sleep)

I think it is correct to say many scientists are unsure whether insects really sleep or not.

How do you know that not sleeping would be an advantage? At this point, we are still not clear on why we need sleep (except that almost all people who do not sleep will fairly quickly die) and so cannot assess what, if any, advantage sleep provides.

 

[Proggle]

Here's my personal take on it:

I think sleep evolved because it was, at a given point in evolutionary history, more energetically efficient than being awake all day. That means, it was better to go into a low-energy consumption state at night than trying to find food or mating in poor lighting conditions (keep in mind that this happened long before eyes evolved to their current level).

After this happened, a further advantage could be gained by those species that performed certain vital functions while sleeping, say tissue repair, allowing all energy to be focused to productive activities during the day. As the number of these "sleep activities" grew in number, it became increasingly difficult for future species to be able to "evolve" out of sleep. So the evolutionary adaptation for taking advantage of the fact that other species were sleeping was to become nocturnal, not to abandon it altogether.

 

[TVP45]

I see your point. Rather like trying to evolve flying once we had dense bones.

 

[arildno]

jim:
Why should a creature stumble about in the dark rather than just sit quietly up in a tree?
The crucial distinction is between
1. the resting, but awake (i.e, alert) creature and the

2. the resting creature fallen asleep (i.e, inattentive).

1. would be the best choice, from the perspective of natural selection.


However, as to the original question:

It is not enough for natural selection that some other state would be a better adaptation to the environment; it must also be an ATTAINABLE state.
(The gradient in evolution can't be too large).

 

[scott_alexsk]

Who says they would be stumbling about in the darkness, couldn't they simply evolve to see in the dark.

 

[Proggle]

Who says they would be stumbling about in the darkness, couldn't they simply evolve to see in the dark.

To see in the dark you need:

- A lens, otherwise you simply won't gather enough light.
- A diaphragm (pupil), otherwise you'll go blind in daylight.
- A large number of sensitive photoreceptive cells.

If something like that had evolved instead of a mechanism for sleep, creationists would actually have a point.

 

[Moonbear]

Okay, I'm going to back up a few steps here. While everyone is speculating on the benefits/risks of not sleeping, there's a fundamental misunderstanding of evolution and natural selection in the opening post that needs to be addressed.

An organism cannot choose to evolve in a certain direction, or to acquire a particular trait. It doesn't matter how wonderful it might be, if a mutation that would permit it has never occurred, it can't happen.

However, as has been speculated above, it's possible that such a mutation HAS occurred, and turned out to NOT be adaptive, in which case it quickly disappeared from the gene pool again.

 

[Proggle]

Okay, I'm going to back up a few steps here. While everyone is speculating on the benefits/risks of not sleeping, there's a fundamental misunderstanding of evolution and natural selection in the opening post that needs to be addressed.

An organism cannot choose to evolve in a certain direction, or to acquire a particular trait. It doesn't matter how wonderful it might be, if a mutation that would permit it has never occurred, it can't happen.

However, as has been speculated above, it's possible that such a mutation HAS occurred, and turned out to NOT be adaptive, in which case it quickly disappeared from the gene pool again.

The point I'm trying to make is that we may be so far down the path of depending on sleep that a mutation that disables it may not be feasible.

If an organism that doesn't sleep is born, it is very likely it will die, as systems that are supposed to function during that time are unlikely to have mutated to compensate for the change. This makes a one-step leap from sleep to no sleep extremely unlikely.

You may say "An animal could start sleeping less, and eventually abandon it." but if those intermediary states provide a disadvantage in survivability, even if the final state is better, the evolutionary path that leads that way will not be followed.

 

[Moonbear]

The point I'm trying to make is that we may be so far down the path of depending on sleep that a mutation that disables it may not be feasible.

If an organism that doesn't sleep is born, it is very likely it will die, as systems that are supposed to function during that time are unlikely to have mutated to compensate for the change. This makes a one-step leap from sleep to no sleep extremely unlikely.

You may say "An animal could start sleeping less, and eventually abandon it." but if those intermediary states provide a disadvantage in survivability, even if the final state is better, the evolutionary path that leads that way will not be followed.

I have no problem with any of those concepts presented. I just wanted to make sure that the OP clearly understands how natural selection works, since their statement sounded like there was a more fundamental misconception that needed clarifying.

 

[-RA-]

I have read that the part of sleep that is the important part is REM sleep, the part where you dream. Is this the only part of sleep that is really needed? or are the other less active phases just as important? i would imagine tests have been done on REM's comparitive importance to other phases, i just can't find any.

 

[arildno]

I have read that the part of sleep that is the important part is REM sleep, the part where you dream.

Correction:
It is that phase of sleep from which an awoken person is able to remember that he dreamt something.

Is this the only part of sleep that is really needed? or are the other less active phases just as important? i would imagine tests have been done on REM's comparitive importance to other phases, i just can't find any.

I know of no specific REM-deprivatory sleep experiments that could be used to provide evidence for that hypothesis.
While it certainly is a scientific hypothesis, I do not think we have the ability to carry out the necessary experiments to give us the answers to it, at the present.

 

[-RA-]

Is it true that the pineal gland produces the drug DMT at night, which is the chemical that gives us our dreams. Apparently (according to doctor Rick Strassman, and others) when a person is approaching death, the pineal gland releases DMT, thus accounting for much of the imagery reported by survivors of near-death experiences.

It is a very strong hallucinogen, the type that shamans have used to visit, what they call, the 'spiritworld' for centuries. Is it that dreams are a milder version of this experience as less DMT is released by the brain?

 

[Cincinnatus]

Interesting, I've heard of endogenous DMT before, but I don't think I'd heard it varied in concentration during sleep. Do you have a reference for that by any chance?

 

[-RA-]

I am no expert on this but I think that the fact that there is DMT produced in the brain is well known, but as it is used up very quickly by the brain compared to most other drugs it is very hard to test where it originates without being unethical to living people. Whether it originates from the pineal gland is just a hypothesis at the moment until it is proved/disproved in the future.

"Since these same Psychoactive tryptamines occur in humans, it is possible that their activity may be promoted by the actions of endogenous beta-carbolines for normal psychological processes; e.g. the production of visual / emotive imagery in sleep. The periodic altering of consciousness in sleep may even be necessary for the maintenance of normal mental health, since only a few days of sleep deprivation will result in a seepage of hallucinatory phenomena into the waking state."

From Tryptamines, Beta-carbolines and You. Dr J.C. Callaway, Dept. of Pharmaceutical Chemistry, University of Kuopio, Finlandstrassmans book of the original research into the drug; http://www.rickstrassman.com/pages/dmt/ (i reccomend the book he wrote about peoples experiences, 'DMT: the spirit molecule')

some similar topic journal articles that he often sites; http://www.rickstrassman.com/pages/writings/

 

[TVP45]

I have read that the part of sleep that is the important part is REM sleep, the part where you dream. Is this the only part of sleep that is really needed? or are the other less active phases just as important? i would imagine tests have been done on REM's comparitive importance to other phases, i just can't find any.

The link below gives an excellent starting point for learning about sleep. The brief answer to your question is that there is a normal range for each phase of sleep and deprivation of any of them can be life-threatening.
http://www.ninds.nih.gov/disorders/brain_basics/understanding_sleep.htm

 

[-RA-]

Interesting, I've heard of endogenous DMT before, but I don't think I'd heard it varied in concentration during sleep. Do you have a reference for that by any chance?

I found some good papers about endogenous DMT;

http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&list_uids=6792104&cmd=Retrieve&indexed=google
http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=pubmed&dopt=AbstractPlus&list_uids=3412201
http://cat.inist.fr/?aModele=afficheN&cpsidt=3071296
http://leda.lycaeum.org/?ID=16837

there are plenty of reasons to expect that all animals produce DMT in their pineal gland, but i don't think any direct studies have been done to test for this. Certainly not on humans anyway.

 

[MagikRevolver]

Simple answer is evolution occurs on a need to basis. There is no direct or immediate need to evolve past sleep, thus we haven't evolved past sleep. Also, sleep is an evolution in itself. "Most animals, and probably most living organisms, exhibit a circadian rest-activity rhythm. It is possible that sleep may have evolved from rest to allow more flexibility within this rather rigid rhythm of rest and activity. Researchers think that sleep arose to allow organisms to conserve and restore their energy." (Irene Tobler, University of Zurich)

 

[Nexus555]

An animal that does not need to sleep would be at a huge advantage over all other animals as animals are more vulnerable when asleep, so why are there none that have done that?

(i think i am correct in saying that all animals sleep)

Sorry if I repeat anyone, for I didn't read all the responses.

Sleep isn't a survival skill with respects to dodging predators. We need sleep for replenishing energy and resting our muscles. Every animal needs this, in some way, shape or form. Insects do this, but they are only brief second pauses. Dolphins shut off half of their brain at a time to do this.

Another good reason is to conserve our energy. In nature, if all animals were awake at all times, they would constantly have to be hunting and eating. When animals go to sleep, this gives them time to rest (as I've said above,) slow down the organs and conserve their energy.

This has nothing to do with being eaten. Though some animals are nocturnal to take advantage of the night scene.

 

[-RA-]

I know of no specific REM-deprivatory sleep experiments that could be used to provide evidence for that hypothesis.
While it certainly is a scientific hypothesis, I do not think we have the ability to carry out the necessary experiments to give us the answers to it, at the present.

I have just found that exact experiment in a documentary. And it gives some very strong evidence for dreaming to be a form of pshchedelic trip due to endogenous DMT, as when the subjects were deprived of REM sleep they started to hallucinate and see patterns when they were awake. The brain certainly does seem to need this drug very frequently, and it seems very important to all animals.

you can see it in a short clip here; EDIT: clip does not work anymore.

The question arrises, why do all animals need this psychedelic so much? what purpose do you think it plays?

 

[Count Iblis]

I have just found that exact experiment in a documentary. And it gives some very strong evidence for dreaming to be a form of pshchedelic trip due to endogenous DMT, as when the subjects were deprived of REM sleep they started to hallucinate and see patterns when they were awake. The brain certainly does seem to need this drug very frequently, and it seems very important to all animals.

you can see it in a short clip here;

The question arrises, why do all animals need this psychedelic so much? what purpose do you think it plays?

I don't think the specific details are so important. Just think in terms of competition between (biological) machines. The machines have to repair themselves which limits the average performance. A machine that can run on turbocharge for a while and then needs extra repair will outperform a similar machine that doesn't have this option. Also, during the turbocharge phase the system will be optimized for doing the specific tasks it is designed for while during the rest phase the system can be optimized to do the self repair work more efficiently.

So, I think that sleep is more a game theoretical issue that leads to sleep being a universal phenomenon independent of the biological details. If we find complex living organisms on some other planet that work via totally different chemistry it will probably also have sleep cycles.

 

[moe darklight]

I don't think the specific details are so important. Just think in terms of competition between (biological) machines. The machines have to repair themselves which limits the average performance. A machine that can run on turbocharge for a while and then needs extra repair will outperform a similar machine that doesn't have this option. Also, during the turbocharge phase the system will be optimized for doing the specific tasks it is designed for while during the rest phase the system can be optimized to do the self repair work more efficiently.

So, I think that sleep is more a game theoretical issue that leads to sleep being a universal phenomenon independent of the biological details. If we find complex living organisms on some other planet that work via totally different chemistry it will probably also have sleep cycles.

yea, this makes sense. If you look at the lifestyle of animals on earth, it is composed of only short spurts during which the animal's full potential or energy is required; during the rest (and majority) of its time, this energy is not needed. ... an animal that is always "on" and does not need periods of rest to repair itself would have to be going full blast all day long... in other words, it would have to be constantly on the hunt for nutrients. this seems rather impractical and inefficient... it's also not hard to see how such an animals would do quite poorly during even the shortest periods during which nutrients are not plentiful.

an animal that saves its energy and only goes full blast when in immediate danger or while hunting or doing whatever it needs to do to survive is much more efficient and likely to survive.RELATED QUESTION: do single-celled organisms and simpler multi-celled organisms rest? at what point along the complexity chain does the need for sleep and rest begin?