sleep?
I can understand big predators requiring sleep to conserve energy.
But why do humans need sleep? A group of humans who needed no or much less sleep could have easily outcompeted us.
You didn't evolve to drop dead from lack of sleep just to save a little energy. It would seem living bodies require constant maintenance, which can be done more efficiently when you power down the system.
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Anonymous2008-10-16 23:26
You need sleep to regenerate glycogen in your brain cells.
This much I remember from class.
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Anonymous2008-10-17 6:55
>>8,10
That seems a ridiculously crippling solution to a relatively trivial set of problems.
It's like the claim that testicles in many animals are on the outside of the body to keep the temperature low: it's not a satisfactory explanation.
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Anonymous2008-10-17 10:07
>>11
1) Did you not read the wikipedia article? We don't yet know what exactly the original purpose of sleep is for. It has only been in the last 5-10 years or so that we've actually made progress in understanding it.
2) You seem to be confused. Natural Selection does not work that way. There are no "solutions" in Natural Selection. Everything currently existing is merely the result of what has worked "good enough" for a species to survive with. The actual evolution of those features is a series of genetic accidents and not every change is for the better, nor is anything necessarily efficient.
3) As happens so often in Evolution, sleep has probably acquired additional purposes than what it was originally "developed" for. The observed memory functions could be indicative in this adaptation in species with larger brains. The original purpose may even have already been rendered unnecessary long ago by another process.
4) Not every species that sleeps is helpless and unaware of their environment. Traits like unihemispheric sleep (only one side of the brain is asleep) are quite common in birds and aquatic mammals. Other species have developed sleeping behaviors such as nesting that protects them (or gives them ample warning) from predators. Social species rarely all sleep at the same time, essentially having "gaurds", etc.
5) You haven't given an alternative "solution". Considering no one even knows what the "problem" actually IS, that isn't surprising. Since you don't know the reason and you obviously don't know what you're talking about in a larger sense, none of your arguments are valid.
External testicles are not the norm by any stretch of the imagination. Only a relatively few species have external testicles.
And the previous point applies. That is, all the "criticisms" I've seen against the temperature regulation hypothesis have been arguments from personal incredulity, a logical fallacy. Simply saying it isn't a "satifactory explanation" is not a valid argument. As I've said, Natural Selection and Evolution do not work that way.
Anyway, there are two other major hypotheses as well. Read the article.
>>12 1) Did you not read the wikipedia article? We don't yet know what exactly the original purpose of sleep is for.
And my point is that the explanations put forth here are unsatisfactory.
2) You seem to be confused. Natural Selection does not work that way.
Oh, shut the fuck up. I know how natural selection works, and if you had any experience with evolutionary biology besides reading the Wikipedia article on Gould, you'd know convenient short-hand when you saw it. My use of the word ``solution'' does not imply look-ahead or intelligence.
The original purpose may even have already been rendered unnecessary long ago by another process.
Something that renders an organism unconscious and vulnerable to attack for extended periods of time does not stick around after it's outlived its usefulness.
5) You haven't given an alternative "solution".
That's because I don't have one. I'm only pointing out the unsatisfactory nature of yours.
Since you don't know the reason and you obviously don't know what you're talking about in a larger sense, none of your arguments are valid.
lrn2logic, dipshit.
External testicles are not the norm by any stretch of the imagination. Only a relatively few species have external testicles.
I know. That was much of my point. The myth that external testicles exist for the sake of temperature regulation persists all the same, and it's not satisfactory for the same reason your bullshit explanations about sleep aren't.
That is, all the "criticisms" I've seen against the temperature regulation hypothesis have been arguments from personal incredulity, a logical fallacy.
Are you fucking kidding me? External testicles exist as advertising towards mates: the bearer can afford to keep something as important as testicles outside of his body, where they are easily damaged or lost, and therefore he is a strong mate. Similar to how the tails of many birds are actually significant handicaps to the birds themselves.
If you aren't even aware of this (now widely accepted) hypothesis (presumably because you get all of your information from woefully incomplete Wikipedia articles), perhaps you shouldn't be trying to lecture other people about how evolution works.
>>13
That's stupid, if your species don't already have external testicles, it's hardly going to woo the ladies when your mutant self suddenly pops them out.
And if you were stuck in that situation, it'd be an evolutionary triviality to pop them back in while replacing them with useless, brightly-colored flesh bags.
THE REAL ANSWER FROM SOMEONE WHO KNOWS WHAT THEY'RE TALKING ABOUT
But first, I'll just say that OP/13 is arrogant, ignorant, immature and delusional. Good job basing that entire post on logical fallacy, notably ad hominem attacks, while completely avoiding the couple actual points 12 brought up (especially bullets 3+4).
Anyway, sleep is not a genetic trait. That is, it is not something defined in DNA and so it is not passed down genetically and not subject to evolution. There are genes that manipulate the sleeping process, stuff like circadian rhythm modulations and unihemispheric tendencies, but nothing like an on/off switch for the sleeping "trait".
Sleep is a physical need, like eating or drinking. It is a part of the metabolic cycle. As organisms developed larger brains, the brains simultaneously adapted to optimize time spent sleeping for memory processing and such. The reason why we "tune out" the environment when we sleep seems to be because the pathways responsible for sensory input and processing are also used in these processes.
There are many hypotheses dealing with the subject, but that's the gist of it. Sleep isn't an evolutionary matter, it's a biochemical matter. You would know at least that much even just reading the wikipedia article that was already given.
However, the notion that sleep itself harms survivability is just plain wrong. Animals do not need all 24 hours in a day to do their survival bit: eat, drink, shit, piss, fuck, etc. That stuff takes up maybe half of their time, if that. So for the rest of the day, it makes sense to conserve energy and not run around and risk getting injured or eaten.
And as has already been said in this thread, most species have sleeping behaviors that help protect them. Nesting/burrowing, unihemispheric sleep, social groups, etc. Also, many species actually maximize survivability by hiding and sleeping when most of their predators are active.
And while I'm here:
>Something that renders an organism unconscious and vulnerable to attack for extended periods of time does not stick around after it's outlived its usefulness.
No. Sorry, but you have once again shown that you do not, in fact, know what you're talking about. Seriously, pick up a book on the subject.
As I've already said, sleep isn't genetic. It's biochemical. But there are literally thousands of evolutionary traits that have "outlived their usefulness", many of which are potentially fatal. Off the top of my head:
Cetaceans (animals in the order Cetacea like whales and dolphins) still have lungs. Besides the obvious inconvenience of having to resurface often, they also suffer from a type of decompression sickness known as "the bends". This is where Nitrogen from the lungs is forced into the bloodstream as bubbles as a result of a rapid change in atmospheric pressure. This is, of course, easily fatal. After a certain depth (depending on the physiology of the species), great care must be taken not to surface too quickly. This is not a problem for species with gills, and numerous species have actually re-evolved gills after previously evolving lungs.
A much more complicated example along similar lines would be the human respiratory system, which retains numerous "features" that are quite dangerous. The larynx/pharynx area, for example. Swallowing prevents breathing, breathing prevents swallowing, and until recently with the development of the Heimlich Maneuver, choking was the leading cause of accidental death.
Another human example concerns vitamin C. Nearly every single organism on Earth, plant and animal alike can produce it internally via biogenesis. Humans are among the small handful of species that can't. The gene for a certain enzyme is defectively mutated. The only reason it hasn't been catastrophically fatal is because vitamin C is abundant in our food sources. The body can only store a very limited supply of vitamin C, and so it must be constantly ingested.
I could go on and on, but I've got shit to do and I've already wasted enough time today. The point is that even if the trait severely damages survivability, that doesn't mean Evolution will necessarily take care of it.
>>17 Sleep isn't an evolutionary matter, it's a biochemical matter.
Incoherent, F--.
I can't believe you wrote a post of that length while still completely failing to understand a single thing about evolution.
Cetaceans (animals in the order Cetacea like whales and dolphins) still have lungs. (...) (bullshit about larynx)
I take it you don't have the slightest clue what a fitness landscape is, and why ``you can't get there from here'' is relevant here?
Another human example concerns vitamin C.
It's not a defect if it doesn't impact the organisms ability to breed. Human inability to produce vitamin C isn't an issue because we get it in our diet, like you said. The simple fact that animals do get eaten in their sleep shows that the analogy just doesn't apply in the case of sleep.
The point is that even if the trait severely damages survivability, that doesn't mean Evolution will necessarily take care of it.
You haven't demonstrated that at all. You are, in fact, ignorant and full of shit.
>>17
Describe to me the biochemical pathways that require or lead to sleeping then. Are these pathways not included in the DNA? If they are, then sleep is necessarily encoded in the DNA (just like eating and drinking). I'm pretty sure trees/bacteria don't sleep.
>>18
Did you even read? Choking? Nitrogen bubbles leading to pulmonary embolism?
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Anonymous2008-10-21 19:27
>>19 Did you even read? Choking? Nitrogen bubbles leading to pulmonary embolism?
Did you? You can't get there from here.
>>20
Hell is that supposed to mean? = Can't get from here to there? Where is "here" and "there"? Why not?
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Anonymous2008-10-22 7:40
>>21
A simple example: in humans and close cousins (I want to say all mammals, but I'm not actually sure), the ganglion cells are on the wrong side of the retina, so to get outside the eye and to the brain, they have to go through it, which is what the optic disc (or ``blind spot'') is. This is an artifact of our evolutionary history.
It would obviously be more advantageous to have an eye that has the ganglia at the back, as more light would reach the retina and there would be no blind spot (and squid and the like do have eyes like that), but there's no way to evolve that kind of eye from the ones we already have without going through intermediate steps that are worse than our current eye. Since evolution doesn't have foresight, that means that is never going to happen, because the individuals with the worse intermediate eyes would be outcompeted, so ``you can't get there from here''.
In terms of fitness landscapes, we're stuck on a sub-optimal peak in a fitness landscape, but we have no way to get to a higher peak, because it's impossible to move down.