comment: >
  
  This is not true at all. We’ve created, buildings, cities, communities, doors, doors with locks, ring cameras, and a police state that quite effectively discourages and prevents situations requiring humans to evolve sleep awareness.
  We evolved in communities of 100-150ish members, when one group or person is sleeping, other community members stay awake to protect the sleeping.
  We could also get into domestication of dogs and other animals.
  We could also talk about the way humans jolt out of a dead sleep into a survival / high alert state. 
  /showerthoughts is full of ideas that seem interesting but just are not true in anyways. OP post has 2400 upvotes…does anybody out there have critical thinking skills? Fuck.
context: This is a friendly reminder to read our rules.
  Remember, /r/Showerthoughts is for showerthoughts, not "thoughts had in the shower!"
  (For an explanation of what a "showerthought" is, please read this page.)
  Rule-breaking posts may result in bans. >
  
  Like other mammals, humans live in groups and have security systems that protect the group.  Like a locked door.  Or 500 years ago, someone in the village or tribe that slept in the day and was awake at night. >
  
  That's probably why some people have a intrinsic tendency to wake up really early while others are the opposite. Diversity within a group probably worked as some sort of defence mechanism. Nowadays we are just lazy when we have a hard time going to sleep early/waking up early. :) >
  
  There is indeed a theory proposed a number of years ago in psychology and sociology which speculates that the reason older people tend to have more trouble sleeping and require less sleep per night has to do with exactly this. The idea being that older people are more likely to nap during the day when the younger portion of  the village would be busy doing tasks and chores that older people are less able to do. Then, at night, older people are more easily awakened by external threats like animals, invaders, or impending natural disasters and would then go about rousing the people to counter or escape the threat. 
  They also pointed out men tend to wake more easily to when disturbed by sounds with bass and tend to lose more high frequency hearing range as they age. Women tend to be more readily awakened by higher pitch sounds like a baby crying, and tend to lose more in the lower frequency ranges as they age. 
  I wish I could provide a source on this but I do not remember which podcast I was listening to at the time. I can only say that it was around 2018 and I was doing a ton of research on sleep disorders, sleep apnea, PAP therapies, and generally all things having to do with sleep hygiene when I came across a podcast with a research scientist talking about it from a historical/evolutionary perspective. I've never been able to find a paper about this online despite having looked again just now. 
  It seems very plausible though, considering that, in the past, many generations often lived with each other and this would have niched the roles somewhat. >
  
  My personal take away from this is that humans weren't meant to survive alone but as part of a community. >
  
  The only thing we have going for us that isn't related to living in groups is our ability to chase anything to death >
  
  Also throwing! No one throws like a human. Our hunting game went to another level when throwing spears got involved. >
  
  And even MORE extreme when we learned how to throw sharp rocks SUPER fast through a metal cylinder by using gunpowder >
  
  We basically got really good at throwing rocks >
  
  Deadly yeets >
  
  Many animals have existed much longer than humans and are the same way. Yet to see a dog or wolf or bear spray acid from its ass as a defense mechanism and remain asleep after. Because that self-defense mechanism is called "waking up" >
  
  You were so close. One could say that domestication of dogs was our way of evolving our self-defense while sleeping. >
  
  One could say it, sure.... Wouldn't make much sense tho. >
  
  This doesn’t really make sense. By your logic, couldn’t someone just argue that we’ve actually evolved so greatly on other levels (technologically, engineering, etc) that we now have the luxury of being totally vulnerable while we sleep because we’ve created safety systems like enclosed domiciles? Isn’t that just a perfect example of evolution? >
  
  OP doesn't understand evolution >
  
  That's made clear by their implication that 200,000 years is even remotely meaningful in evolutionary terms. >
  
  I actually didn’t even think of that but you’re beyond right >
  
  200k years is a blink in terms of evolutionary timelines >
  
  Depends on the species. Some bacteria evolve so quickly that it's the cause of antibiotics failing. >
  
  In the ancient past, it was called a watch. Each watch was 3 hours then rotated to the next person on watch.  But you're right though. We sleep more soundly in modern times. >
  
  Reminds me of ftxs in the army. Or missions in general >
  
  Bro why you getting down voted LMAO >
  
  Idk it's true.
  Someone stays up guarding SI, or even in garrison they watch the building aka staff duty or cq. Then they get a rest day after. >
  
  All animals are vulnerable while they sleep. Some sleep in holes in the ground, others sleep in trees. Some sleep in packs. Humans alarm their town houses and keep baseball bats by the bed >
  
  This post complexity misunderstands what evolution is. Evolution is not some ordered system that tries to solve problems or “improve” the species. It’s the result of completely random mutations that just by chance happen to provide some benefit, such that the individuals with that mutation are more likely to live and pass it in to future generations.
  Humans haven’t evolved some specialized defense mechanism during sleep because either: the random mutations just never happened or some mutations happened but they provided no added survival benefit beyond what the rest of the species had.
  Edit: added some clarification >
  
  Yeah OP acting like we're supposed to become gods after years of evolution. You can go through centuries of evolution and still make zero forward progress. >
  
  Speak for yourself. In my sleep I have:
  
  Physically punched the air on multiple occasions, waking up my wife, barely missing her.
  Physically kicked the air on multiple occasions, waking up my wife, hitting her in the shin once.
  Yelled “FUCK YOU!” extremely loud, waking up my wife.
  Gotten out of bed, walked into another bedroom, woken up my dad, told him the toilet was broken, went into his bathroom, pooped, and left it there.
  
  If some shit’s going down (literally), I’ll stay asleep, but I’ll wake you up. >
  
  I bit my bf in my sleep, just woke up to him yelling. Does that count as sleep defence? >
  
  Depends on what he was doing to you in your dream at the time. >
  
  I was fighting a woman and woke up with my mouth clamped to his shoulder. Very weird experience >
  
  Who won? >
  
  Who's next?
  You decide!
  Epic Dream Battles of History! >
  
  My defensive mechanism whilst I sleep is a lock on my front door. >
  
  So, fun fact: Different people naturally have different circadian rythms. Some people are better suited to being morning people, others function better when staying up until 4-5 in the morning and waking up mid afternoon.
  In other words, human communities have physiologically adapted to leaving some people up at night (presumably to keep watch and wake everybody else up if a tiger is stalking the camp (though now that we don't have to worry about Saber Tooth cats anymore, most of those night people are now working bar and Taco Bell night shifts). >
  
  I wake up every morning to the tic-tac sound of my dog's claws because if I don't, she will do her business inside. So I'd say our hearing is a pretty decent defense mechanism. >
  
  I remembe listening to a Mr. Ballen podcast about a girl who was camping and wolk up midway through a fox eating the top of her head. I think there was a similar one about a polar bear too. Depending on the stage of sleep we are in we can be pretty unaware of the world around us. >
  
  You raise a good point about sleep stages but then last night? My dog woke me a little after midnight (only 3 hours into sleep!) and she really had to go so, perhaps there's an override for some of us caused by specific sounds and/or known dangers. The most common of these would be a baby crying, I would guess.  Any parents out there who can concur? >
  
  How is it even possible to reply to so many answers that get you so consistently downvoted? Like, at some point reassess bro >
  
  If I had to guess, I’d say OP is downvote farming.  Either that or extremely stupid, but I’m honestly leaning toward downvote farming.  One likes to think this level of stupid isn’t possible. >
  
  Some people are also so insecure that they are completely unable to say “oh, I guess I was wrong!” Without damaging their ego.
  Case and point: OP >
  
  Hey! The phrase is actually 'case in point'. Because it means "In this point (argument/example) you can see my case at work." >
  
  Oh, I guess I was wrong! 
  Thanks! >
  
  Admitting you made a small mistake and updating your knowledge? How dare you. >
  
  there's also an evolutionary mix of night- and day-active people. some stay up late naturally and some wake up early naturally >
  
  We have defensive mechanisms, some more than others. Even while sleeping, even little but unusual sounds can wake you up. When suddenly waking up people breathe in violently, boosting the amount of oxygen in the blood, raising the heart rate. The Eyes, which are closed during sleep, can see better even without light in the dark. This trick was used by Pirates and on other Ships. The Eyepatch wasn't cause of a lost Eye, when they needed to go suddenly inside the ship, where only little light source where possible, they changed the Eyepatch and used the Eye which was under it to see better. Higher heart rate means a higher production of Adrenaline which allows faster reaction from Muscles. Also, when panicking, more blood get pumped into the extremities, the legs to assure fleeing. All these defensive mechanisms are from a time we needed them like 200.000 years ago, we use them now instinctively. These mechanics are good enough to survive, so we didn't need to develop new or different once. An animal which reached it's peak of evolution don't need to evolve until the surroundings change and make it more difficult to survive. >
  
  Other than the intelligence to build shelters and form social groups and societies where some can keep watch and protect the group while most sleep >
  
  That is because we grew smarter. Most animals do not sleep as deeply as humans due to having to be on their guard against predators. Humans who learned how to communicate effectively who learned how to create weapons and shelters can now sleep more deeply. >
  
  We evolved to be social creatures, which is the defence. By living in groups/packs with watchers we didn't need to evolve any further innate defences. >
  
  People have touched on a lot of great points but one I think deserves mentioning is that humans when asleep aren’t really in as much danger as you’d think. 
  Firstly, there’s not much in the environment that actually poses a threat to humans from a predation standpoint. Yes lions exist and have been known to hunt us but think about the circumstances surrounding when most humans would have gone to sleep. They would likely be back at camp which was probably either a cave or some other defensible place, we would be surrounded by other humans who likely would come to our mutual defense, and also humans for quite a bit of that 200k years had access to fire which would hurt in top of the arrows and javelins. It makes much more sense for a predator to wait for a human to leave that place either alone or in a much smaller group to go pick berries or whatever and snatch them then. 
  Secondly the threat from other humans throughout most of those 200k years was probably not as significant as you’d expect. There wasn’t that many of us and we were spread out across Afro-Eurasia, running into another group was probably less walking dead and more oh thank god someone I’m not related to.
  Humans wherever they have been for the last 200k years have either been one of or the apex predators of that landscape and while yes we sleep 1/3 of our lives away other predators do that too and you don’t see any of us sneaking up on a them any time soon. >
  
  Simple. You can't sleep when enemies are nearby. So if you fall asleep that means it's safe. >
  
  I understood this reference. >
  
  200,000 years of evolution is like trying to boil water in 3 seconds. Evo is really really, and I mean reaaaaaaally slow >
  
  OP you sound like your learning about the world and your curiosity is commendable, but I don’t think you understand how evolution works >
  
  I’m quite sure that if there were things that wanted to eat you prowling around where you sleep, you would be woken up by sounds in the night more often than you would if there weren’t any things that wanted to eat you around. >
  
  My girls got spayed recently, all of a sudden i was shooting awake at 4 am because on of them removed their cone, and my instincts just woke me up. Another time in the past, i went to sleep, suddenly i was standing by my fridge that i couldn't see from my bed. I hadn't shut the door properly earlier so it was open, i just done food shopping so it all woulda gone bad. So that's twice now my body has awoken me when something's wrong haha >
  
  Houses. We built houses. That’s about the most comprehensive defense mechanism possible. We even have automated motion alerts, artificial lighting, sirens, cameras, and (possibly illegally) traps. No other animal has nearly as well-guarded of a sleeping spot. >
  
  So my raging insomnia is an evolutionary defence mechanism then? >
  
  Yes, you would have been the night watchman. For animals that live in groups it's useful survival-wise to have some of them not feel like sleeping when the others do. >
  
  It’s believed that snoring is actually a sleep defense mechanism. The sound of it coming from a cave would suggest that a large creature lives inside >
  
  we learned to build homes and live indoors.  We are a lot less vulnerable than we were 200,000 years ago, actually. >
  
  We have built houses and communities and laws al for this.
  ​
  Not only that the intinct of waking up to a strange sound close to you is very real. >
  
  I disagree. Humans developed cooperation to keep watch while others sleep, fire to ward off predators, and dogs to help alert to danger. >
  
  Does OP know that humans were not the first species to sleep? >
  
  The two security doors and the concrete walls which I'm currently behind of would like to disagree. >
  
  The same can be said for many species but humans specifically have evolved a brain capable of great subconscious foresight. Obviously there will always be occasions where people think they are safe asleep and get hurt and or killed but we have a population of eight billion encounting for a reason.
  Most people do millions of calculations subconsciously and obviously deem it safe to sleep at a particular time in a particular place. The brain is really fascinating. >
  
  Try to sneak up on me while I sleep. You will have to bypass multiple locked doors and booby traps after that. >
  
  
  Craft shelter/burrow
  Pack tactics such as rotating sleep schedules 
  Insomnia
  Buddy system >
  
  Because we evolved to live in groups and at some point starting keeping dogs around as an alarm. >
  
  Ok but all animals are like that. Everything that has a brain, sleeps vulnerably.  So that's more like 500 million years of evolution >
  
  Maybe I’m just sleep deprived, but this makes total sense, my insomnia isn’t a problem its proof I’m more advanced than the rest of humanity. >
  
  "200,000 years of evolution"
  This isn't a whole lot of time for any significant amount of evolution to take place. It took like 5 million to get sweating down. >
  
  It also doesn't really describe evolution right, since life has been evolving since it began. It's not like humans started doing it just in the last 200,000 years. >
  
  As animals, our defense mechanism was to sleep in packs and maybe have someone guarding.
  Nowadays we got more complex mechanisms. >
  
  we do have a defense mechanism, it’s called other people. But since society forces all those people stay awake at night to be asleep as the same time as the rest of us, we got rid of that mechanism ourselves >
  
  If only we had some sort of structures to keep us safe and other people to form “communities” of some sort… >
  
  Humanity actually did evolve a defense mechanism for this: the night owl.
  Approximately one-third of the human population has a circadian rhythm that does not match the rest of the human race, and across them all, cover all hours of the night. This is why night shifts exist, now that we have electricity to light them.
  I am one such person. I work best if I go to sleep at 2 AM and wake at 10 AM, and I feel most awake at 4 to 8 PM, then get another burst of energy at 11 PM. In a tribe, I'd be the first of two or three night shift guards.
  Sadly, my job likes everyone on the same schedule, so I'm forced to wake up at 4 AM. My brain doesn't like that, though, so I still often only get to sleep between 10 and midnight, despite how tired I may be. >
  
  1) most animals don’t. Unless they already have passive protection systems(porcupine came to mind)
  2) we evolved past the general need for it long ago. Probably around the time we figured out how to lock doors. >
  
  I'm pretty sure that before we had locks the defense mechanism was communal living. A few people probably stayed up and kept watch. Then they passed down their genes all the way to me, and thanks to them I hate getting up early in the morning or going to bed early at night. But hey, your ancestors are welcome for their survival LOL. >
  
  Humans did evolve a defense mechanism, it’s called society. I can sleep safely because I live a house with a lock on the door, and other humans stay awake during the night to patrol the streets and watch out for potential threats. 
  The best defense was the friends we made along the way. >
  
  The “defense mechanism” is having a social group that can watch out for you while you sleep.
  Humans sleep deeper than most other animals, and don’t need to sleep as long. >
  
  Babies actually have pretty advanced and complicated defense mechanisms known as “parents”