Why has nothing evolved to not need sleep?

[Reality Check]

What I'm asking, in an indirect way, is why do animals have to shut themselves off from the rest of the world at all. I can see all the advantages of sleep, but not why you have to become unconsious (rather alter your state of consciousness) to achieve these. I dont see why the part of sleep where you become not aware of your surroundings is a neccissary component. This apsect only serves as a disadvantage.

The reason for an animal altering its state of consciousness is to achieve the advantages of sleep that you already know about. If you want to get the maximum energy advantage from a period of rest then reducing all activity (including sensory input) is needed. It does not serve as a disadvantage. It serves as a balance between an advantage (gain in energy) and disadvantage (risk of predation).
The level of rest can even go beyond mammalian sleep to hibernation.

Read the post from Iomiller about how most animals are light sleepers.

My expectation is that the level of sleep will vary according to the security of the animal, e.g. bats hanging from the roof of a cave are fairly secure and so sleep deeply; primates sleeping in trees are fairly secure and so would deeply; deer sleeping on the ground are less secure and so sleep lightly.

 

[sol invictus]

So plants are animals now eh?

Why in the world would you edit your post to ask such a bizarre question? Certainly it doesn't relate anything I said... are you making "mistakes" again?

I dont see why the part of sleep where you become not aware of your surroundings is a neccissary component. This apsect only serves as a disadvantage.

Why do you keep repeating this this obvious falsehood?

Evolution favors genes whose creatures reproduce them successfully. It doesn't matter if many of those creatures get eaten so long as enough survive to reproduce. If, hypothetically, sleeping results in a greater risk of premature death but at the same time a much greater chance of reproducing if you survive, it would probably be favored by evolution. So the presumption your question is based on is false.

What would be more interesting would be to ask what functions sleep serves, why some species or individuals sleep more or less than others, etc.

 

[Madalch]

I seem to recall reading that dolphins (and possibly other cetations) sleep with half a brain at a time.

My students do that, too, starting about ten minutes into my lectures.

 

[Polgara]

There is a Harvard Nursing Study that indicates that if humans had sleep deprivation their hypothalamic-pituitary-adrenal axis, cortisol, etc. become overworked and out of balance which causes all kinds of ugly ramifications regarding the function of the nervous system.

Many animals are biologically structured in a similar fashion.

I will provide the research shortly.

 

[schlitt]

What an odd post. This thread is about the way that sleep has evolved within darwins evolution, and the advantages and disadvantages of it. I certainly wasn't trying to have a poke at evolution.

You should be careful, sarcasm is lost on some, people may think your actually a creationist, or perhaps even worse, your one of those people that think that evolution is just a theory, and so by default God must exist Whatever the hell 'god' means.

As I said on the last page, incase you missed it: It's possible that such a mutation to reduce sleep and increase the percentage of the day animals are awake and aware by performing the job of sleep while fully conscious HAS occurred, and turned out to NOT be adaptive, in which case it quickly disappeared from the gene pool again. The reson why this was not an advantage and died out is the underlying question.

My apologies Zeuzzz. I got the wrong impression from the first page and assumed we had another DOC on our hands.

 

[DanishDynamite]

An animal that does not sleep would be at a huge advantage over all other animals as animals are more vulnerable when asleep. Animals go through all the hassle of digging a burrow, or climbing a tree so they are safe when they sleep.

So why have none evolved to counter this large disadvantage and perform the jobs that sleep does while in an awake state?

An excellent question.

We currently don't know exactly why animals need to sleep. We can measure that it is detrimental to them if they are hindered in sleeping, but why this is the case, we don't know.

 

[Ron_Tomkins]

Why has nothing evolved to not need sleep?

I gotta take a nap right now, but I'll get back at you with that later.

 

[Tortan]

I didn't read through the whole thread as it is quite lengthy even at only three pages. I have read some posts, and I am in agreement with the hypothesis that sleep is needed to conserve and/or regain energy.

I think of it this way:

Say we have a large sample of nondescript creatures. Some of these creatures have a period in which they sleep to regain their energy so they can operate at near or 100% capacity. Meanwhile, there are creatures that operate at less capacity at all times. They have to operate at a lower capacity because they constantly need to refuel themselves. Kind of like a panda, who needs to eat a lot in the run of a day just to maintain itself. These "slower" creatures will spend a disproportionate amount of time eating and maintaining their energy level while in a fully conscious state, just to remain awake 24/7, compared to sleeping critters.

In the wild, unless the creatures that operate at less capacity are cunning, they will be easy prey for those who can operate at a higher energy level, if the other animal uses them as food. If they both eat the same food, this means that the sleeping creatures can easily cover the ground needed for their food requirements for the day in shorter time, and still have energy left over for other things, like mate, provide food for others and not just themselves, and explore.

Who knows, maybe we did have critters that didn't sleep at all before. Maybe they eventually stopped acting in the daytime all together and became some of the nocturnal animals we have today? Speculation, I know, but just some random thoughts.

 

[DanishDynamite]

You can rest your body constantly by just lying down, but the rest makes no difference at all in regard to your well-being. If you lie down for 3 days, yet don't sleep, you will be a wreck after the 3 days.

It is the sleeping itself which renews you. Why this is so, we don't know.

 

[Zeuzzz]

The reason for an animal altering its state of consciousness is to achieve the advantages of sleep that you already know about. If you want to get the maximum energy advantage from a period of rest then reducing all activity (including sensory input) is needed. It does not serve as a disadvantage. It serves as a balance between an advantage (gain in energy) and disadvantage (risk of predation).

I see what your saying, but the argument that an animal after sleep performs better is not really answering the question. The problem here is that evolution should have selected for an animal that didn't sleep yet still performed. There is not one animal in the world that seems to have taken this path. So, since this has not happened, there seem only a few reasons 1) oops 2) it's not actually more beneficial to survival 3) sleep is above and more important to life that evolutionary processes.

My vote goes with 3). And it would be real interesting to find out why this is, but I dont think anyone really knows for sure.

 

[Zeuzzz]

Found this, which is essentially about the same thing:

http://everything2.com/e2node/Evolution%20of%20sleep

You are certainly more vulnerable when you sleep, and death is a particularly strong selective force, so it would seem quite obvious that sleeping would be selected against. On the flipside, the advantages of sleeping are hightened levels of performance during wake time. Imagine if you had a mechanic living in your garage who would fix your car every night. You could drive it like a maniac during the day, knowing that at night, your little mechanic/elf would make your car nice and new the next morning. For an animal, the advantage is that the body can focus energy on being active during periods of activity, and focus energy on repair during periods of sleep.

While the disadvantage of being killed in one's sleep is more of a direct problem for prey than for a predator, both parties benefit from sleeping. The predator is a better hunter after a long rest and the prey is more likely to survive if chased after a refreshing nap. Still, extra energy alone isn't enough of a selective advantage for sleep. If energy for activty was the only necessity, why wouldn't a predator reverse sleeping schedule and become nocturnal, while its diurnal prey is napping?[.....]

He says that he thinks that animals have not evolved to do hunt 24/7 as the ability to hunt sleeping prey confers too large of a short-term advantage, and would render the Predator-prey relationship un-stable. Which, is a valid argument in the sense that predators that didn't sleep would probably end up killing all the prey that they need to eat, and so then die out themselves; but this still doesn't really solve the question, as you could argue that to counter this the prey could/should have evolved to be aware 24/7 to aid their defense against predators.

 

[Zeuzzz]

It seems that the brain is in fact more than capable of performing the jobs that sleep is thought to do (whatever they may be) while in an awake state. Which makes the question why we have to shut ourselves off and become unaware of our surroundings for so long even more puzzling. To me anyway. I should have been a sleepologist, its a fascinating area

http://www.sciencedaily.com/releases/2006/03/060329085308.htm

Asleep Or Awake We Retain Memory

ScienceDaily (Mar. 29, 2006) — Sleeping helps to reinforce what we've learned. And brain scans have revealed that cerebral activity associated with learning new information is replayed during sleep. But, in a study published in the open access journal PLoS Biology, Philippe Peigneux and colleagues at the University of Liege demonstrate for the first time that the brain doesn't wait until night to structure information. Day and night, the brain doesn't stop (re)working what we learn.

So thats sort of addressed the memory aspect, it appears you dont seem to actually require loss of awareness for memory as your brain is more than capable of structuring information while awake, and as others have pointed out the energy aspect we can gain from simply resting, becoming unaware of your surroundings is not an essential part of this; so what other reasons are there for sleep?

 

[EHocking]

Originally Posted by 3point14
I seem to recall reading that dolphins (and possibly other cetations) sleep with half a brain at a time.

My students do that, too, starting about ten minutes into my lectures.

You might have to ask yourself if the cause of this entirely the students' fault.

 

[Reality Check]

I see what your saying, but the argument that an animal after sleep performs better is not really answering the question. The problem here is that evolution should have selected for an animal that didn't sleep yet still performed. There is not one animal in the world that seems to have taken this path. So, since this has not happened, there seem only a few reasons 1) oops 2) it's not actually more beneficial to survival 3) sleep is above and more important to life that evolutionary processes.

My vote goes with 3). And it would be real interesting to find out why this is, but I dont think anyone really knows for sure.

I vote for 4):
There are many different environments on the Earth. Two of them are daylight and nighttime. Species evolve to be fitter for their environments (niche differentiation). Thus there is a general split between nocturnal and diurnal species with some intermediate temporal differentiation. A nocturnal species is at a disadvantage during daytime. A diurnal species is at a disadvantage during nighttime. Thus individuals that reproduce have reduced the risk. A strategy to reduce the risk is to find a secure location. If you are in a secure location then why waste energy being awake? If you are in a less secure then why waste energy being fully awake? If you are in a herd then why should all members be awake?

Sleep is not "above and more important to life that evolutionary processes". It is evolutionary processes that create the biological processes that make sleep an advantage for a species (i.e. allows individuals to reproduce more).

 

[Zeuzzz]

I vote for 4):
There are many different environments on the Earth. Two of them are daylight and nighttime. Species evolve to be fitter for their environments (niche differentiation). Thus there is a general split between nocturnal and diurnal species with some intermediate temporal differentiation. A nocturnal species is at a disadvantage during daytime. A diurnal species is at a disadvantage during nighttime.

Not necissarily. An animal that evolved to have no preference to day or night would be at a greater advantage than those that just stick to one. Most nocturnal predators hunt nocturnal prey and diurnal predators hunt diurnal prey. They have evolved this way, not because this approach in itself is an advantage; but because they have to sleep. Which again makes option c) the most likely in my mind.

If you are in a secure location then why waste energy being awake?

Because if a predator comes in to your secure location, it would be an advantage to be awake and aware of the predator than asleep and ignorant of it. The very reason why they are in this secure location to begin with is because they have to sleep

If you are in a less secure then why waste energy being fully awake?

You dont have to be asleep to save energy. You can rest and still be aware of your surroundings, which would be an advantage to non aware sleep. Its the non awareness bit that puzzles me.

If you are in a herd then why should all members be awake?

So they can all individually be aware of predators.

Sleep is not "above and more important to life that evolutionary processes". It is evolutionary processes that create the biological processes that make sleep an advantage for a species (i.e. allows individuals to reproduce more).

I think you have this backwards. It seems (to me anyway) that sleep comes first, and evolutionary processes evolve around this, for the reasons I gave above. If evolution came before and was more important than sleep, sleeping should have been selected against as species evolved to confer the advantgaes of retaining an awake state. The problem is that evolution should have selected for an animal that didn't sleep yet still performed. It hasn't.

 

[sol invictus]

My own summary is that the whole question is nonsensical. You might as well ask why living things are ever awake. The answer is that they evolved that way because it allowed them to occupy a niche.

Totally unrelated comparison.

Not according to this article in Progress in Neurobiology:

The cause of sleep is a complex question, which needs first, a clear distinction amongst the different meanings of a causal relationship in the study of a given behavior, second, the requisites to be met by a suggested cause, and third, a precise definition of sleep to distinguish behavioral from polygraphic sleep. This review aims at clarifying the meaning of the question and at showing the phylogenetic origin of the mammalian and avian sleep. The phylogenetic appearance of sleep can be approached through a study of the evolution of the vertebrate brain. This began as an undifferentiated dorsal nerve, which was followed by the development of an anterior simplified brain and ended with the formation of the multilayered mammalian neocortex or the avian neostriate. The successive stages in the differentiation of the vertebrate brain produced, at least, two different waking types. The oldest one is the diurnal activity, bound to the light phase of the circadian cycle. Poikilotherms control the waking from the whole brainstem, where their main sensorymotor areas lie. Mammals developed the thalamocortical lines, which displaced the waking up to the cortex after acquiring homeothermy and nocturnal lifestyle. In order to avoid competence between duplicate systems, the early waking type, controlled from the brainstem, was suppressed, and by necessity was turned into inactivity, probably slow wave sleep. On the other hand, the nocturnal rest of poikilotherms most probably resulted in rapid eye movement sleep. The complex structure of the mammalian sleep should thus be considered an evolutionary remnant; the true acquisition of mammals is the cortical waking and not the sleep.

 

[Reality Check]

Not necissarily. An animal that evolved to have no preference to day or night would be at a greater advantage than those that just stick to one. Most nocturnal predators hunt nocturnal prey and diurnal predators hunt diurnal prey. They have evolved this way, not because this approach in itself is an advantage; but because they have to sleep. Which again makes option c) the most likely in my mind.

But then there is niche differentiation. Night and day are niches..

Because if a predator comes in to your secure location, it would be an advantage to be awake and aware of the predator than asleep and ignorant of it. The very reason why they are in this secure location to begin with is because they have to sleep

No - they are in the secure location to avoid the predators and so have the freedom to sleep.

You dont have to be asleep to save energy. You can rest and still be aware of your surroundings, which would be an advantage to non aware sleep. Its the non awareness bit that puzzles me.

You can rest but sleep is better at saving energy.

So they can all individually be aware of predators.

They do not need to be individually be aware of predators. All they need is a warning from a guard animal, e.g. troops of baboons and meercats have sentinels, or from an another individual being eaten.

I think you have this backwards. It seems (to me anyway) that sleep comes first, and evolutionary processes evolve around this, for the reasons I gave above. If evolution came before and was more important than sleep, sleeping should have been selected against as species evolved to confer the advantgaes of retaining an awake state. The problem is that evolution should have selected for an animal that didn't sleep yet still performed. It hasn't.

You seem to have forgotten that bacteria do not sleep. We evolved from bacteria. Therefore sleep did not come first. It evolved.
Also evolutionary processes do not "evolve around" processes like sleep. That sounds more like Lamarckism. Evolution is mutation of inheritable traits + natural selection.

 

[Wowbagger]

Zeuzz,
One thing you have to keep in mind: Evolution hardly ever provides solutions we humans would recognize as optimal. Evolution works in a more haphazard, cludgy manner, with no forsight into the future, and heavy reliance on past evolutionary heritage.

Just because you think it would be advtantageous for animals to never sleep, does not mean nature is going to agree.

I say it would be better for gazelles to run four times faster, and for us humans to grow extra limbs when we lose some. But, in the real world, there are constraints on perfection.

Like I said: The level of sleep and waking time probably varies over time: Animals will sleep more often, when they can get away with it; and stay awake more often when they need to; depending on selection pressures of the given enviornment, over time.

 

[BenBurch]

Reality Check,

Yes, sleep evolved, but as I noted above, it might have evolved as an unavoidable side effect of neural processing. Not all things that evolve are or can be beneficial - in these cases the organism does what it can to negate the negative effects, like sleeping lightly, sleeping with half of the brain, sleeping in very short intervals, etc. But having a neural processing structure is SO beneficial that the bad side effects were not enough to prevent it from being a winning strategy.

 

[quarky]

Apologies if this has been mentioned already;

Disciplined meditators often require less sleep. However, they need to be skilled at obtaining a thought free mental state, and a completely stable and comfortable body posture.