Body needs sleep to repair itself and release hormones it probably wouldn't be a good idea to release when you're awake. Plus, your brain needs to rest.

5-10% is way down? lol

Even more evolutionarily advantageous to stay awake and hear the lion coming to get you inside the cave.


Evidence, please.

Not only have we failed to evolve to not need sleep, we haven't even evolved to be able to fly, live indefinitely or even breathe underwater! Evolution sucks.

Evolution isn't magic. The leap from a body that needs sleep to one that doesn't may be so huge that the mutation may never occur. Of course with mutations it's never impossible, just incredibly improbable. Maybe it would require the whole structure of the brain to be radically changed.

It's sort of like asking "Why haven't we gotten from A to B yet?" when you don't know how far away B is. You don't know what would be required in order for a creature to not need sleep.

people can take turns sleeping now, so I'd think something like night vision would be more desirable than unwinding the entire biological clock.

If sleep suddenly becomes a detriment to reproducing, those that sleep less will make more babies and sleeping lots will become less common.

Since that hasn't happened, it hasn't happened.

If it does happen, someone will probably ask "why have humans evolved to not need sleep" at some point. They might say so with bleary eyes.

We don't need to 'not sleep' to survive as a species.

This might be incorrect.. but from I understand in evolutionary terms, we haven't been around all that long and our environment has been fairly stable in the years we've been around. Again, from my limited knowledge of evolution I believe environment is the biggest factor in things changing in a species.

Look on the bright side, we sleep less than cats.

As in, referenced sources? Sorry. You can use take the time and use Google though, if you like. GH and testosterone, for one, are released during sleep.

And if you sleep deprive yourself long enough, you'd be the equivalent of alcohol intoxicated, focus and concentration wise. So that should hint towards your brain needing to rest and recover. But you're probably looking for specifics like what part of brain and the neurochemical interactions involved. I got no idea, dude.

Big brains. Humans sleep more than gazelles because we can afford to.

I assume you're not in graduate school, and have never given any sort of research talk. Making such a vague, unfounded statement like "brains need to rest" without being able to back it up is pretty middle-school lol. If YOU make an assertion, YOU need to be ready to back it up. So I will keep my position that there is little evidence that "brains need to rest."

I can almost see the boogers in your nostrils. Try to tone down the "you're beneath me" speak.

It almost sounds like you're biased against the idea that we need sleep. Fine, whatever. If you care so much to the contrary, look it up yourself. I'm not going to run an errand for you and provide a minimum number of references. I'm free to make the assertion. I'll take the F, professor.

Are you serious that you dont think your brain needs sleep? Or you just want to argue?

Just want to point out that just because we do lots of important stuff while we sleep it doesn't follow that that was the evotutionary driving force for sleeping.

Evolution is quite capable of making use of traits for other things and these other things can be highly fit.

It could be a fit predator-prey solution, maybe there was nothign useful to do with all those dinasours roaming around during tne day so better off hiding in a warm hole or maybe just that mum needs a rest and can only get it if the children sleep.

Most of our human characteristics were developed during the primitive early stage of human evolution. It could be that in humans, the sleep is state is less life-threatening and more conducive to survival then the awake state. Evolution is about species survival, and in particular, keeping a species alive long enough to reproduce. In the awake state, humans tend to move about in the relatively dangerous environment. Wakefulness may make humans, especially children, more susceptible to injury, disease, and to predators. Awake humans also burn more energy. The longer we are awake the more food and water we use up. Human sleep may simply be more conducive to life extension than being awake. Acoording to evolutionary theory, sleep may be characteristic more likley to be preserved rather than eliminated.

Even if we can establish that our (mammals') brains, right now, all absolutely need sleep, that wouldn't imply that all brains that could have evolved to do what ours do would need sleep. Yet the evidence we have is that those that exist, do (though to different extents). So we conclude, as a strong guess, that it's either difficult or impossible for a brain to evolve from what existed before mammals that does what our do without sleep.

Just why that is is another question.

(Note that I'm assuming that the hypothesis advanced in the post above this one is wrong — to me it seems unlikely that a need for sleep is a positive advantage, and far more likely that it is a disadvantage that's worth it.)