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!
There is an astronomical difference between vestigial organs/nerves/what have you, and a required biological function which renders the individual totally incapacitates and utterly vulnerable for 6-10 hours. Especially considering the "natural" state of things where even giving the benefit of the doubt you will avoid predators which can kill humans, you may be sleeping under a rock or a tree and susceptible to bugs, rodents, germs, etc. I don't feel that your rebuttal really, well, rebutted his point.
It seems like a big difference but it occurred very early on in the evolution of life, so it's a disadvantage shared by all animals.
How about another example: mammalian females giving birth through their pelvises. This caused the deaths of countless women and children throughout human history. It's not as much of a problem for other mammals but it's a huge problem for humans. We've had to advance modern medicine to the point where we can safely perform major surgery (caesarian section) in order to mitigate it.
The book Sapiens has a few pages on this. Essentially, the thought seems to be that we're an edge case that's been able to jointly optimize for intellect/large brains and small efficient bodies by overcoming the limits on brain size imposed by vaginal birth. This in part explains our relative immaturity at birth. We're vulnerable and require constant care for the first few years of life. Compare this with other mammals such as calves which are able to walk roughly at birth.
> It seems like a big difference but it occurred very early on in the evolution of life, so it's a disadvantage shared by all animals.
It's possible that you could have sleepless neurons. But they would be so different than neurons we are stuck with that we might need to wait few billion years for them to show up.
Well the environemnt greatly changes in a 24 hour period which would have had a large affect on the evolution of agents. Typically for a period of each day its dark and cold, not a very efficient time for an agent to operate on average. Perhaps its more effective to be productive during the time when they can see easily, and its warm so cold blooded agents can operate and then an ecosystme builds around these things etc and its no longer about jst the physical ebvironment but the ecological niche an agent is operating in. So no point being active at night if the flowers aren't awake, and the bugs that feed off the nectar aren't there, and thus your food isn't about.
These kind of evolution arguments are really common but seem super shaky to me.
Saying "if it was better, it would've happened already" assumes humans are perfectly evolved right now, and negates any possibility of future evolution. That argument would be just as valid a 5000 years ago as it is now but presumably humans have evolved since then. Genes mutate randomly, selection pressures change, things in our environment might affect the way genes mutate - its much more complex.
Yea, evolution is just a good enough result based on current stimuli. Even if the output is great and near perfect, the "perfect" is still based on the requirements of the environment.
This isn't about humans though, but life in general. Mostly everything sleeps, theres been a lot of time for something to evolve that would both be intelligent and not need sleep, and yet there isn't.
5000 years isn't remotely close enough for sleeplessness to evolve, more like a few million. Its not so much why do humans sleep, but why do apes? Why does anything?
That seems just a little bit of an absolutist straw-man, though. Exaggerating further for effect: Nobody's saying sleep is a universal constant imposed by fundamental timeless physical law.
Whatever is going on must be important, and not easy to avoid without serious trade-offs.
There are plenty animals that have all but eliminated sleep; giraffes, elephants, dolphins to name a few, can get away with very short bouts of sleep. Others perfect the Unihemispheric slow-wave sleep, I've even seen studies that humans do this to a lesser degree when sleeping in unfamiliar surroundings.
The majority of our hominid evolution was in Africa, where we likely developed night time sleep patterns as a defense to the big cats developing better night vision. Other benefits like social interactions, heat-conservation, even directly procreation; As well as the diminished usefulness of any work, from hunting to building in darkness would all play a roll.
I find it fascinating that we likely also developed a fear of the dark as a response to the big cats developing better night vision in exactly the same way gazelles developed better hearing and faster legs.
Maybe, but maybe not. Evolution only has to be better suited to the current environment, but it doesn't necessarily need to result in perfect creatures.
Creatures could have developed the day/night awake/resting cycle independent of sleep just because at night you want to conserve energy to stay warm, and it's difficult to hunt at night.
Once creature developed day/night modality, taking advantage of that time to run repair processes would be an evolutionary advantage.
The question isn't why people sleep, it's why can't creatures run repair processes 24/7? If they could do that, then evolving to not need sleep would be a lot easier.
Evolution is essentially an optimization algorithm, and like many such algorithms, it can get stuck in localized maximums.
Suppose there exists a far better brain design, but all the brain designs that are part way between the current design and that design are far worse. Any mutation that steps toward the better design will be selected against.
Genetic algorithms esp. punctuated equilibrium ones can and will skip over local minima. It might take very specific environmental conditions (fitness function) though, so is not quite guaranteed.
Based on the article's description, that wouldn't really fit the definition of "getting rid of sleep", as this "half sleep" severely impairs the brain functionality.
It does make sense in the context of a somewhat hostile environment, where constant awareness is required, but it wouldn't benefit humans as much.
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.
It may not, if any such system is very energetically taxing, or would confer a host of other issues. Such a system would, downsides taken into account, have to confer a net advantage. It may be that sleep in some form is best system with the fewest downsides.
The downsides of sleep are more severe for aquatic air-breathers, and, as some other comments have already pointed out, it appears to have already been eliminated in that case.
This is only true if you redefine "sleep" in a certain technical way. This redefinition is supported by phenomena such as the dolphin closing one eye during that eye's half-sleep cycle, but it is not obviously appropriate in all contexts.
In addition to higher energy requirements, anabolism can increase the probability of tumours. Additionally, metabolism creates mutagenic oxygen compounds. It may be that separating metabolic and anabolic states in time (wake and sleep) allows these nasties to be cleaned away before the risky business of cellular division takes place.
In the book "Why We Sleep" the author (Dr Matthew Walker) gives such a strong set of reasons that he says the wonder is why we ever bother to be awake.
It's a very thorough book and certainly convinces you of the tremendous benefits of sleep.
Actually, sleep would have been evolutionarily beneficial to us since we can't see well at night and it would keep us out of way of predators at night. Sleep wouldn't be a drawback, it would be a benefit to our survival.
It's why hamsters are nocturnal. Their predators hunt during the day, so they sleep during the day and play at night.
Evolutionary theory would say the hamsters that like to play during the day got eaten so that only those who slept during the day got to mate and pass on their genes, etc.
If you think sleep is a drawback for humans, trying visiting a forest at night without a flashlight.
So, why would sleep be benefitial to non-nocturnal animals? That is, I think the parent is saying that sleep must be very important because almost all animals sleep. If sleep wasn’t very important, a lot more animals wouldn’t sleep.
Depends on what we're debating. Are we debating whether or not humans need sleep? Or simply that beings with similar brain "design" need sleep? Perhaps due to a flaw in our (Animals) common ancestors we developed sleep to overcome other negative traits. Which is to say that sleep is simply one flaw to compensate for another flaw.
Given the path evolution takes it seems a stretch to ever consider it best, perfect, good or anything other than "it worked just enough at the time". Just enough being the key. All we know is that sleep didn't disrupt animals enough to entirely fail the evolutionary test. However plenty of garbage features go along with more powerful features. One in isolation is not proof of it's perfection, I would think.
There is no denying that sleep is beneficial and I agree with that assertion. I was specifically addressing his point about the drawbacks of sleep - "There are several survival drawbacks from sleep, as it leaves one vulnerable.".
Sleep wasn't a liability to our survival, especially our ancestors. It actually aided in our survival. Human beings who were active at night would have been the vulnerable ones as they would attract predators and were more likely to perish as a result. Especially considering out vision would be limited in the dark.
In short, sleep kept us away from the dangers at night.
Imagine a hypothetical state of pseudo-sleep that causes us to withdraw during the night (the same as normal sleep), except we keep our eyes open/ stay alert.
We are just as hidden from predators, but now even more equipped to defend ourselves.
Therefore it seems difficult to deny that sleep itself has some form of rejuvenative benefit.
Who is denying that sleep has rejuvenative benefit? I'm not. I know that sleep has a rejuvenative benefit.
Please try reading my comment or following the thread. I'll paste it here : "I was specifically addressing his point about the drawbacks of sleep - "There are several survival drawbacks from sleep, as it leaves one vulnerable."."
In other words, sleep has rejuvenative benefits and it keeps us away from predators. Sleep can have many benefits. You can stay up all night, but you'd miss out on the rejuvenative benefits of sleep. Or you can safely tuck away and sleep and gain benefits of safety and rejuvenation.
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.
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.
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.
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).
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.
> 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.
