Discover mind-blowing human body facts you never knew before! From surprising abilities to hidden quirks, learn fascinating details about your body. #HumanBody #DidYouKnow Animation is created by Bright Side.
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FunTranscript
00:00:00People with albinism have little to no melanin, the pigment that colors hair, skin, and eyes.
00:00:06It's a rare condition to have.
00:00:08In the USA, just 1 in 18,000 to 20,000 people is albino.
00:00:14But ocular albinism is even more unique.
00:00:17Experts don't know exact numbers, but they think only 1 out of 50,000 individuals has
00:00:22it.
00:00:23If a person has ocular albinism, nothing but their eyes gets affected.
00:00:28Their skin and hair might be a bit lighter than those of their family members, but the
00:00:32difference isn't that big.
00:00:35Bright sunlight makes 17-35% of people sneeze.
00:00:39This phenomenon is called the photic sneeze reflex.
00:00:42In the Greek language, it's called sun sneezing.
00:00:46It happens when the nervous system misfires.
00:00:48When it happens, one of the nerves might get the reflexes wrong.
00:00:52And then, bright sunlight not only makes your pupils contract, but also activates the nose
00:00:58membranes.
00:00:59When natural, fair hair is rare in adults.
00:01:02It almost always darkens with age.
00:01:05People who are more likely to keep their hair color light are those living in the North.
00:01:10The Bajau is a group of nomadic people that live in the waters around the Philippines,
00:01:15Indonesia, and Malaysia.
00:01:17Thanks to a rare DNA mutation, they can stay underwater for up to 13 minutes.
00:01:23The Bajau people have evolved spleens that are way larger than average.
00:01:27This feature provides them with a genetic advantage.
00:01:30Sea nomads need it to hunt for fish or look for underwater stuff that can be used in crafts.
00:01:36A particular gene mutation results in super-dense bones that are almost impossible to break.
00:01:43They're several times tougher than the average person's bones.
00:01:47These people's skin is also less prone to aging.
00:01:50It might sound cool, but there are drawbacks.
00:01:53When such tough bones grow, they often put too much pressure on the nerves surrounding
00:01:58them and the brain.
00:02:00There are three kinds of cone cells in the average person's eyes.
00:02:04They help to recognize the colors in the blue, red, and green spectrums.
00:02:08Thanks to them, most people can distinguish around 1 million different shades.
00:02:13But those with tectochromacy have four cones in their eyes.
00:02:17This feature allows them to see up to 100 million different hues.
00:02:21However rare this vision anomaly is, it's still much more common in women than in men.
00:02:27By the way, most people with tectochromacy don't realize they see the world brighter
00:02:32than others.
00:02:33Only a bit more than 8% of people have counterclockwise hair whorls on their heads.
00:02:39A hair whorl can be single or double.
00:02:42Very few people have triple whorls, but those do exist.
00:02:46Not all experts agree with this theory, but some researchers claim there's a connection
00:02:51between handedness and the direction of a hair whorl.
00:02:55Left-handed people are 5 times more likely to have a counterclockwise whorl than those
00:02:59with the dominant right hand.
00:03:02Only 1 to 5 people in every 10,000 have an unusually shaped pupil.
00:03:07In most cases, it looks a bit like a keyhole or a cat's eye.
00:03:11This eye disorder is called iris coloboma.
00:03:15Scientists believe it's mostly genetic in origin.
00:03:19Supertasters are people who taste particular flavors more strongly than others.
00:03:23They have more taste buds.
00:03:25Those are small mushroom-shaped bumps littering the tongue.
00:03:28They're covered with taste receptors that tell your brain what you're eating.
00:03:33This feature also makes supertasters more sensitive to certain foods.
00:03:37For example, too sweet, bitter, or salty.
00:03:41They also have more pain receptors on their tongues.
00:03:44That's why such people avoid spicy food.
00:03:47The numbers vary around the world, but in general, 25-30% of people are supertasters.
00:03:54From 40-50% are average tasters, and 25-30% are non-tasters.
00:04:00Those have poor taste perception.
00:04:03Less than 1% of the world's population has a rare condition called dextrocardia.
00:04:08That's when the heart points toward the right side of the chest, not the left one.
00:04:13In rare cases, people with this unique quality have all their internal organs on the mirror
00:04:18image side of the body.
00:04:21Only 1 to 5 people in 10,000 have what's called perfect or absolute pitch.
00:04:26It's the ability to identify and recreate musical tones.
00:04:30This feature often runs in families.
00:04:33It's also more likely to occur in people who started their musical training before
00:04:37they turned 6.
00:04:40Ancient Greeks had stories about fire-breathing creatures called Chimeras.
00:04:44They were a fearsome mixture of a goat, lion, and snake.
00:04:48In real life, Chimeras are people who have two different sets of DNA.
00:04:53Scientists have recorded no more than 100 cases of human chimerism.
00:04:58The DEC2G mutation allows people to get away with just a few hours of sleep a night and
00:05:04still feel great.
00:05:07Short sleepers don't feel tired, and they never sleep in.
00:05:11Their usual wake-up time is 4 or 5 a.m.
00:05:14Wow, not me!
00:05:16Only up to 5% of people have this feature.
00:05:19Scientists from the University of California have also made an interesting discovery.
00:05:24They claim that people with the DEC2 mutation need less time to perform certain tasks than
00:05:30regular sleepers.
00:05:32Morton's toe is a foot structure where the second toe is longer than the first one.
00:05:38Only 3 to 22% of people in the world have their feet shaped this way.
00:05:43Michelangelo's David and the Statue of Liberty are among them.
00:05:47Unlike the majority of the world's population, 1.5% of people have just one palmar crease.
00:05:54That's the line running across your palm.
00:05:57Men are more likely to have a single palmar crease than women.
00:06:01Most often, this feature runs in families.
00:06:04Only 3% of people in the world have lines that form the letters X on both of their palms.
00:06:10In many cultures, this rare feature is believed to be a sign of a strong personality.
00:06:16One in every 500 people has an extra rib called cervical.
00:06:21The average human has two dozen ribs, 12 on each side of the body.
00:06:26But those lucky ones can have 25 or even 26.
00:06:31Excessive ribs are more often found in women.
00:06:33They're located in the cervical spine area and grow just above the collarbones.
00:06:39Their size can be different, from just barely developed to fully grown ones.
00:06:44In most cases, cervical ribs don't affect a person's well-being, unless they grow
00:06:49too large.
00:06:50In this case, they do cause discomfort.
00:06:53No more than 50 people have ever had Rh null blood type, so precious that it was nicknamed
00:07:00golden blood.
00:07:01It can be donated to people who have incredibly rare blood types and can't accept any other.
00:07:07For the first time, golden blood was discovered in an Australian Aboriginal woman.
00:07:13If you have a tiny hole near your ear, you're unique.
00:07:17It occurs in only 5% of people in the world.
00:07:20In the USA, less than 1% of people are born with this hole.
00:07:24In Asia and some parts of Africa, the number is a bit higher, from 4 to 10%.
00:07:30This feature is often inherited genetically.
00:07:33It can be present on one or both ears.
00:07:36This distribution is 50-50.
00:07:38The hole may go all the way through, or it can be a dimple, dent, or even a small lump.
00:07:45There's a theory that the little hole is an atavism, left from the times when all living
00:07:50beings had gills.
00:07:52There's a gene mutation that helps people keep their bad cholesterol levels extremely
00:07:56low.
00:07:57In this case, the gene instructs the body to produce a protein that curbs the amount
00:08:02of cholesterol in the blood.
00:08:04Unfortunately, only 2-3% of people have this useful ability.
00:08:10About 65% of the world's population have loop-shaped fingerprints.
00:08:15Only 30% of fingerprints are whorl-shaped.
00:08:18And only 5% of people have arch-shaped fingerprints.
00:08:22They can be plain or tinted arches.
00:08:25Around 35% of the world's population don't have to worry about the pain and inconvenience
00:08:30of wisdom teeth breaking through the gums simply because they don't have them.
00:08:35But around 5 million not-so-lucky people go through wisdom teeth removal every year.
00:08:42Some people have more than one row of eyelashes.
00:08:45This phenomenon is a genetic mutation called distichiasis.
00:08:49A person with this condition has a second set of eyelashes growing behind the first.
00:08:55All these thick, lush lashes sure look beautiful.
00:08:58But they can also cause some discomfort.
00:09:01Some hairs can start growing in the wrong direction, or in the place where an oil gland
00:09:06is supposed to be.
00:09:07It can cause irritation and tearing.
00:09:10Experts are sure that Tibetan people have genetically changed to be able to live at
00:09:14high altitudes.
00:09:16They have a gene that helps to adapt to falling oxygen levels amazingly fast.
00:09:21This evolutionary mutation has been one of the fastest ever recorded in people.
00:09:26It took a mere 3,000 years to develop.
00:09:32What?
00:09:33What's happening?
00:09:34You were so tired, couldn't wait for your face to hit that fragrant pillow.
00:09:38You could barely hold your head up at 9 p.m.
00:09:42Now you're just rolling around in bed, changing positions, everything so annoyingly sudden.
00:09:48Is it better to cover your feet or leave them uncovered?
00:09:51Should you sleep on your back, front, left, or right side?
00:09:55Ah!
00:09:56There's some moonlight coming through your window, so you take a peek at the other bed
00:10:01in the room.
00:10:02Your friend over there is sleeping so deeply.
00:10:05Asleep after about a minute.
00:10:06So unfair!
00:10:08You're spending the night because tomorrow, you're both taking a small trip to a nearby
00:10:12town.
00:10:13Of course, you'll have to get up at 5 a.m.
00:10:16Yay!
00:10:17Oh, and just look at the time now!
00:10:20Why can't you fall asleep?
00:10:22Why?
00:10:23Well, last week, you and a couple of friends went camping in the woods.
00:10:28And your struggles were similar.
00:10:30You got very tired after a long day of carrying all your stuff, walking around, preparing
00:10:35food, hours talking by the campfire.
00:10:38Your eyes were half-closed.
00:10:40You thought you'd fall asleep in seconds.
00:10:42But then… nothing.
00:10:44Eyes wide open, every little thing bothered you, and no sleeping position was right.
00:10:50So I ask you, why?
00:10:52The first-night effect, that's why.
00:10:54That's what you call it when you have sleep struggles in a new place.
00:10:59Sleep is a great thing, but evolution has made it a bit inconvenient for us from time
00:11:03to time.
00:11:04While sleeping, the brain actually shuts off for a couple of hours.
00:11:09That leaves you pretty unprotected.
00:11:11You can't spot any potential danger or defend yourself if something happens.
00:11:20There are animals, like dolphins and whales, that developed a sleeping system where only
00:11:25one part of their brain rests at a time.
00:11:28The other part is awake and ready to roll.
00:11:30We have a somewhat similar thing going on in our heads.
00:11:34Not that there are any dangers in your friend's room, although, when you think about all that
00:11:39dust under the bed, who knows what's hiding under there?
00:11:43We have certain instincts that showed up a long time ago, back when our ancestors lived
00:11:48in caves and knew that if they slept like there was no tomorrow, there might not be.
00:11:54That's why they also knew it wasn't safe to sleep outside their cave.
00:11:59That's most of the reason behind this first-night effect thing.
00:12:02If you sleep in your own bed, in a room you feel comfortable in, your brain is like, phew,
00:12:08okay, you're safe now.
00:12:10But if you go to a new place, nothing helps.
00:12:13Not even a comfy bed, a silky pillow, or the fact that you're at your good friend's place.
00:12:19Your brain knows you're far away from your cave, so it can't relax and let you fully
00:12:25fall asleep.
00:12:26It's a little bit like with dolphins.
00:12:28One part of our brain is resting, but the other is carefully listening in case something
00:12:33unpredictable happens.
00:12:35Your brain won't bother you with this half-the-brain-is-sleeping-and-half-not thing forever.
00:12:40When you spend two nights in a row in the same place, your brain is more likely to think,
00:12:45phew, it's safe here after all.
00:12:48Although that pile of dust still kinda worries me, and it'll probably let you fall asleep.
00:12:54The first-night effect is not that serious if you only experience it occasionally.
00:12:59But if you change locations really often, you could spend most of your time tired, unproductive,
00:13:05or facing some other issues.
00:13:07Our brain has some patterns that evolution gave it, but luckily, it's also quite flexible.
00:13:13You can trick it and help yourself overcome the first-night effect.
00:13:17Since your brain is afraid of the fact that you're in an unknown space, you can make it
00:13:22more familiar and show your brain everything's okay.
00:13:26You might bring something you like with you.
00:13:28Maybe your favorite pajamas, your pillow, that soft blanket you wouldn't change for
00:13:33the world.
00:13:34Do you usually drink warm milk before going to sleep?
00:13:38Do the same thing at your new place.
00:13:40Help your brain recognize it's time to relax.
00:13:44Go to sleep at the same time you usually do.
00:13:46Have some exercise rituals before bed?
00:13:49Yeah, me neither, but whatever routine you have before going to sleep, do it at this
00:13:54new place too.
00:13:56If you're booking a room at a hotel, try to find one that has a bed similar to the one
00:14:00you have at home.
00:14:02If you usually sleep in a double bed, it may feel weird sprawled out in a king size.
00:14:07Or just bring along your favorite pajamas, it's cheaper.
00:14:11Nothing you do is guaranteed to help, but it's worth a shot.
00:14:15Side note – don't you get annoyed when you meet someone who can just sleep anywhere?
00:14:20It feels really, really great to lie down, tuck yourself under a warm pile of blankets,
00:14:26and…
00:14:27Oops, sorry, mmm.
00:14:30Anyway, sleep's important.
00:14:32We literally need it to survive, just like we need food or water.
00:14:36We spend around one-third of our life sleeping.
00:14:39Scientists still don't know all the reasons why we sleep, but here's what they've
00:14:43got so far.
00:14:45We sleep to store energy.
00:14:468 hours of good sleep can produce enough energy for us to have an energetic, productive day.
00:14:53Our body needs to restore itself while sleeping.
00:14:56Hair and nails grow, muscles repair themselves.
00:14:59All that and more happens while you sleep, no effort needed.
00:15:04Then there's brain function.
00:15:06If you put a book under your pillow during the night hoping your brain will somehow read
00:15:10it and be prepared for tomorrow's final… not gonna happen.
00:15:14But if you study hard and take in a lot of facts, a good night's sleep can definitely
00:15:19help you remember everything.
00:15:22A brown bat sleeps almost 20 hours a day, while a giraffe only sleeps a tiny bit, usually
00:15:28in mini 5-minute power naps.
00:15:31That poor giraffe doesn't know what it's missing.
00:15:34Cats definitely know how to enjoy life – they spend two-thirds of their life sleeping.
00:15:39Randy Gardner set the record for the longest period without sleep in 1964.
00:15:44He was 17 when he stayed awake for 11 days, or 264 hours.
00:15:50Do not try this at home.
00:15:51Or anywhere.
00:15:53Peter Powers decided to set the opposite record and stayed asleep for 8 days straight.
00:15:59That's awesome.
00:16:00How come he didn't have to get up to use the bathroom?
00:16:04If you lie down in bed and fall asleep almost immediately, that means you're really, really
00:16:09tired and sleep-deprived.
00:16:10Ideally, it should take you around 10-15 minutes to fall asleep.
00:16:16There are two specific times each day we feel really tired – 2 a.m. and 2 p.m.
00:16:22That's when we feel like taking a nap after lunch, instead of getting on with our work.
00:16:27Show this video to your boss next time you're caught snoring in the office after your lunch
00:16:31break.
00:16:32We're actually the only mammals that delay sleep on purpose.
00:16:37And obviously the least cool mammals ever.
00:16:40Back in the day, only 15% of people dreamt in color.
00:16:44Now 75% of us do that.
00:16:47Some folks think it's because our TVs are in color nowadays.
00:16:51Speaking of, we spend around 2 hours in dreamland every night.
00:16:56But if you want to remember your dreams, you should write them down right after you wake
00:17:00up.
00:17:01Wait too long, and you'll forget all those awesome superpowers you had.
00:17:06Over the course of an average night, you might change sleeping positions around 20
00:17:11times.
00:17:12Your favored position can say a lot about your character.
00:17:16Lying on your back with your arms up by the pillow is called the starfish position.
00:17:21This type of sleeper tends to be a good listener and a selfless person who likes to help others.
00:17:26Also, this sleeper might let their guard down more easily.
00:17:31Then there's the free-faller position, where you're on your stomach with your hands up
00:17:35by the pillow and your head turned to the side.
00:17:38Some say these sleepers don't take criticism well and tend to be pretty direct.
00:17:43Finally, the yearner is when you lie on your side with both of your arms stretched out
00:17:48in front of you.
00:17:49This type of sleeper is a bit complex, but also very open-minded.
00:17:54They're slow to make a decision, but they stick to it once it's made.
00:17:58Now the kind and style of the jammies you wear to bed also says a lot, but we'll save
00:18:04that one for another video!
00:18:08Ok, look at yourself in the mirror.
00:18:13Yeah, right in the eye.
00:18:15See that little fold of tissue in the inner corner of both of your eyes?
00:18:19Well, get ready for this – it was actually once a third eyelid, or nictitating membrane.
00:18:25You can see it today in snakes or lizards, for example.
00:18:29The third eyelid was used for the same purpose as the other two, although it's unclear
00:18:33whether humans ever even had it fully grown.
00:18:36This membrane wasn't as thick as the two eyelids we have, and it could moisten the
00:18:41eye without obstructing the view.
00:18:44Right now, all we have left of it is this tiny fold in the corner of the eye, and most
00:18:49likely in the future we will lose it altogether.
00:18:52And maybe we'll finally stop waking up with that yucky crust that forms in our eyes overnight!
00:19:00While you're still in front of the mirror, look lower.
00:19:03Lower and lower still.
00:19:05Yeah, those are your toes!
00:19:07Say hello and goodbye!
00:19:09Scientists believe that, in some more or less distant future, we'll get rid of our toes
00:19:14completely.
00:19:16Our ancestors, the ancient primates, needed toes to climb trees more efficiently.
00:19:21They used both their hands and feet to grab tree branches.
00:19:25You can see it today in most monkeys and apes.
00:19:27They have longer and more flexible toes, along with flappier feet that allow them to
00:19:32get a hang on branches.
00:19:34Their feet mobility also lets them grab objects from the ground if necessary.
00:19:39For us humans, even lifting a pin we dropped on the floor with our toes is a complex task,
00:19:44but not for our primate relatives.
00:19:47Humans have evolved along a different route.
00:19:50We started walking upright and climbed down from trees, making rigid feet and shorter
00:19:55toes more of a necessity over time.
00:19:58Today, we still use our toes for balance when rolling from the balls of our feet to the
00:20:03tips of the toes, but our balance is now much more centered.
00:20:08It first moved towards our inner feet, which resulted in our pinky toes becoming so tiny,
00:20:13and the big toes, well, so big.
00:20:16As the balance moves away from the toes entirely, though, they're more likely to get fused
00:20:21together in the future.
00:20:23Now turn around and look at your gorgeous behind!
00:20:27If you've ever fallen off a skateboard or slipped on an icy patch, you must remember
00:20:31what a terrible thing it is to hit that tailbone on a hard surface.
00:20:36Luckily for us, scientists predict it's going to go away pretty soon in the course
00:20:41of evolution.
00:20:42A tailbone is a feature that was left to us by our primate ancestors too.
00:20:48But yet again, they needed their tails to achieve more mobility among tree branches,
00:20:53using them to fling themselves from tree to tree.
00:20:56It's hard to say when humans dropped the tail to never pick it back up, but facts are
00:21:01facts, the only thing we have reminding us of those glorious tree-jumping days is the
00:21:06pretty useless bone at the lower end of our backs.
00:21:10Okay, back to the face now.
00:21:13Open your mouth and say ahhh.
00:21:16If you're a lucky individual to have no wisdom teeth, then you can be proud knowing
00:21:21that you're a product of evolution going strong.
00:21:24As you might know, teeth are the only part of the human body that doesn't repair itself.
00:21:30So if you lost all your teeth back in the dark times with no dentists around, the only
00:21:35choice you had was to eat liquid food.
00:21:38Not cool.
00:21:40Dentists believe that nature gave us wisdom teeth as a replacement for old worn-out teeth
00:21:45we've had since childhood.
00:21:48That's why they grow so late in our lives.
00:21:50Today though, with all the progress dentistry has gone through, we tend to keep all or most
00:21:56of our teeth intact until a very old age.
00:21:59And even if we lose some, we can always replace them with new ones.
00:22:03That makes wisdom teeth a vestigial thing.
00:22:06And they seem to understand that, since more and more people never have to go through the
00:22:10ordeal of teething as grown-ups.
00:22:14Speaking of teeth, our entire jaw has been changing for the past, oh, 10,000 years, and
00:22:20is predicted to change even more quite soon.
00:22:23In fact, it's been the fastest changer of all our body parts.
00:22:28Back in the day, when early humans survived by hunting and gathering, they needed massive
00:22:33powerful jaws and bigger teeth to chew through raw meat and grind plants.
00:22:39As they came to cooking and then farming, their food became less tough, and so their
00:22:44jaws became smaller to fit the current needs.
00:22:48As time went by, our jaws shrank more and more, and they're likely to continue doing
00:22:53so in the future.
00:22:54With lots of processed foods that don't need much chewing, humans of the future are probably
00:22:59going to have more delicate facial features with thin jaw lines and smooth cheekbones.
00:23:06Some body parts are not going away, but making a comeback instead.
00:23:11A hundred years ago, Fabella, a tiny bone in the back of the knee, was only present
00:23:16in around 11% of people, and scientists thought it would disappear entirely pretty soon.
00:23:23But against all odds, the brave little bone has made it into the knees of a whopping 39%
00:23:29of modern people.
00:23:31It's still unknown why exactly the Fabella returned.
00:23:35But the most popular opinion is that we've grown taller and heavier than our ancestors.
00:23:41That much is true.
00:23:42As our diet became better and more nutritious, we learned to live longer and grow taller.
00:23:47We're now probably at the peak of our evolutionary height.
00:23:52And the Fabella might've appeared in our bodies to provide a smooth surface for the
00:23:56tendon behind the knee to slide on, reducing friction and lowering the chances of damage
00:24:02because of wear and tear.
00:24:05Speaking of becoming bigger, let's get you back to that mirror, shall we?
00:24:10Flux a little bit.
00:24:11Nice biceps there.
00:24:14But unfortunately, not as nice as your ancient ancestors were.
00:24:18Not everything about evolution is 100% good for us.
00:24:22It's just a set of features that adapt at best.
00:24:25And that's the case with our muscles.
00:24:28We've grown smaller and weaker with time, especially in our upper bodies.
00:24:33In ancient times, humans needed big and strong muscles to do a lot of handiwork.
00:24:39From hunting and schlepping their catch home to crafting tools and building shelters.
00:24:43Later, it didn't grow easier.
00:24:46Much the opposite, in fact, plowing fields and building complex structures required a
00:24:50lot of physical strength and endurance.
00:24:54As the technological progress started booming, physical capabilities gave way to brain power.
00:25:01And machines began doing a lot of work for us, most of it even better than us.
00:25:06We shifted more towards sedentary lifestyle, spending more and more time in front of computers.
00:25:12And our muscles have been growing steadily smaller, because we simply don't need them
00:25:17as much anymore.
00:25:19It's highly likely that, as the progress goes further, we'll become much slenderer
00:25:24and have more trouble gaining muscle mass.
00:25:28Our brain is of particular interest because it's been changing in a kind of a strange
00:25:33pattern.
00:25:34Our distant ancestors had a rather small brain at first, but the close relatives of humans,
00:25:40the Neanderthals, obtained a larger brain than the average modern human has.
00:25:46In the course of evolution, human brain grew larger.
00:25:50But in the more recent centuries, it started shrinking, and no one knows exactly why.
00:25:56Some experts say it might have to do with the change of our lifestyle and social connections.
00:26:02Early humans, especially hunter-gatherers, had to remember every plant and animal they
00:26:06saw, their properties, and how to use this or that thing.
00:26:11They were more generalist, having to learn everything their parents knew and find out
00:26:15more on their own.
00:26:17The modern human is more specialized in a certain area, delving deeper into some narrow
00:26:22subject while relying on their peers for the rest.
00:26:26Where ancient humans worked in groups in which anyone could potentially replace anyone else,
00:26:32we gather in teams, where each member has their own specific task and is irreplaceable.
00:26:38Still, brain size doesn't seem to matter that much, because orcas and elephants, for
00:26:44example, have bigger brains than us, which doesn't make them more intelligent.
00:26:48Happier?
00:26:49I'm guessing yes.
00:26:52And if we venture further into the unknown, meaning millennia from today, we might even
00:26:58develop some pretty unbelievable traits.
00:27:01Some go as far as to say that if the tendency for the sea levels to rise persists, humans
00:27:07might adapt to living in water.
00:27:10We might evolve to have webbed hands and feet to swim better, and develop gills to be able
00:27:15to breathe underwater.
00:27:17Or if we go into space and start colonizing other planets, we will inevitably have to
00:27:22adapt to their conditions.
00:27:24Mars, for instance, has lower gravity and a much colder climate.
00:27:29It will probably make humans taller and lighter, but also may cause them to grow much more
00:27:35body hair to keep warm.
00:27:38Other planets with stronger gravity and higher temperatures will, on the contrary, turn humans
00:27:43into stocky, sturdy, and likely hairless creatures.
00:27:47The possibilities are endless.
00:27:49Hey, maybe due to social media, we'll just turn into little blobs with big eyes and thumbs
00:27:54and not much else.
00:27:56So much better for texting.
00:27:58Hope not.
00:28:01Just one strand of hair can support about 3 ounces.
00:28:04On average, a person has about 150,000 strands.
00:28:08And when your hair is working as a team, it can support about 12 tons.
00:28:13That's two elephants.
00:28:14Not counting the peanuts.
00:28:16Your brain generates electricity, and it'd be enough to light up a small light bulb.
00:28:21If you could only figure out how.
00:28:24It doesn't hurt to cut your nails or hair, because the only part that's alive is under
00:28:28the skin.
00:28:29Also, nails grow faster in summer than in winter, even in places where there's not
00:28:34much difference between the seasons.
00:28:36Also, nails grow faster on your writing hand.
00:28:39Probably because you use it more often, and that stimulates the nails more.
00:28:44It looks like the pinky finger is weak, but that's not true at all.
00:28:48Without it, you'd lose 50% of your hand strength.
00:28:50It usually works together with your ring finger to provide power.
00:28:54The other three are more for grabbing stuff.
00:28:57Oh, and just like fingerprints, your tongue has a unique print too.
00:29:02But you can't use it to unlock your phone, at least not yet.
00:29:05Also, your tongue has a lot of fat in it.
00:29:08If you gain weight, your tongue does too.
00:29:12There's acid in your stomach that breaks down food.
00:29:15The acid is so strong that it could eat right through a piece of wood.
00:29:19The total length of all blood vessels in an adult is close to 100,000 miles.
00:29:25That's 4 times around the equator.
00:29:27In your lifetime, you produce enough saliva to fill two swimming pools.
00:29:33Our ancestors needed goosebumps to make their body hair stand on end and scare away any
00:29:38bad guys.
00:29:39We don't need that anymore, but we still get them because we haven't evolved enough
00:29:43yet to get rid of this feature.
00:29:46You probably never noticed, but you mostly only breathe through one nostril at a time.
00:29:51Every few hours, the nostrils switch jobs.
00:29:54That's why only one nostril gets stuffy when you have the flu.
00:29:58Most people think they have 5 senses, but that's not true.
00:30:02Scientists don't yet know themselves, but they think there's more than 20.
00:30:06There's sight, hearing, touch, smell, and taste.
00:30:09And there are other senses like time, hunger, and thirst.
00:30:14Then there's proprioception, the sense of where your body is in space.
00:30:19Your brain can't always tell the difference between intense happiness and intense sadness.
00:30:25It gets that you're experiencing a very strong emotion, but sometimes it gets a bit
00:30:29confused.
00:30:30That's why you might cry when you're very happy.
00:30:34Your eyes stay about the same size your whole life, but your nose and ears don't.
00:30:38That'd be so weird.
00:30:41Back in the day, all humans had brown eyes.
00:30:44Other eye colors developed as a result of a random mutation.
00:30:48Scientists think that while the first humans appeared on Earth around 6 million years ago,
00:30:52the first blue-eyed person appeared only 10,000 years ago.
00:30:56So it's pretty likely that all blue-eyed people on the planet have the same ancestor.
00:31:02Uncle Bob!
00:31:04All bones in the human body are connected to each other except one.
00:31:08The hyoid bone is U-shaped and located at the base of the tongue holding it in place.
00:31:15Bones are stronger than steel.
00:31:17A strong healthy bone could, in theory, handle the weight of 5 pickup trucks.
00:31:22Still, they're not the strongest body part.
00:31:25The strongest is tooth enamel.
00:31:28It's made of a bunch of different materials that make it damage-resistant.
00:31:32Teeth live a long time, lasting for hundreds of years.
00:31:35But of course, you still need to take care of them.
00:31:38They're the only body part that can't heal itself.
00:31:42Your heart works non-stop and beats around 3 billion times over the course of your lifetime.
00:31:49Just like your heart, your tongue never takes a vacation.
00:31:53Even when you sleep, it helps push saliva down your throat.
00:31:56By the way, where do you rest your tongue?
00:31:59If you keep it on the bottom of your mouth, you're doing it wrong.
00:32:03This posture might lead to some neck and jaw pain.
00:32:06If you keep it jammed up against your teeth, you're doing it wrong too.
00:32:09It can cause your teeth to shift and might lead to a bad bite.
00:32:13Instead, try to keep it sort of halfway, about a half an inch away from your teeth.
00:32:19We can't breathe and swallow at the same time.
00:32:22That's because whatever we swallow and the air we breathe travel down the same path,
00:32:27at least at first.
00:32:28It's like there's a little guy directing traffic down there.
00:32:32Your eyes can breathe.
00:32:34The cornea is the only body part that doesn't have a direct blood supply.
00:32:38It gets oxygen right from the air.
00:32:40That's why when it's dry outside, your eyes might get a bit itchy.
00:32:46Everyone dreams.
00:32:47Some people say they've never dreamt a night in their life, but they just never remember
00:32:52any of their dreams.
00:32:53Some scientists think that the dreaming stage is followed by an active forgetting stage.
00:32:59It's probably because dreams aren't exactly full of important information, and our brain
00:33:03needs to clean up some extra space for something more useful.
00:33:08Those who are lucky enough to remember their dreams still end up forgetting about half
00:33:12within 5 minutes of waking up, and after 10 minutes, it's usually gone for good.
00:33:19When you blush, the lining of your stomach turns red too.
00:33:22It happens because blood starts to flow around more when you're embarrassed, as your body
00:33:27gets ready for something stressful to happen.
00:33:30Your face and stomach lining get more of it, turning them red.
00:33:33Also, humans are the only animals who can blush, or at least the only ones where you
00:33:38can see it so obviously.
00:33:41During one lifetime, the average human grows 590 miles of hair.
00:33:46The average man, if he never shaved, would have a 30-foot-long beard.
00:33:51Hair grows a little faster in warm climates because heat stimulates faster circulation
00:33:55in our bodies.
00:33:57Everything you'd ever need to know about you is all written down in one strand of hair.
00:34:03From a single hair, a scientist could tell you what you've been eating your whole life
00:34:07and what kind of environment you've lived in.
00:34:09On average, one human eats their way through 100,000 pounds of food in one lifetime.
00:34:15That's like 10 big hippos worth of food!
00:34:19Lips are one of the most sensitive parts of the human body.
00:34:22They have loads of nerve endings, even more than your fingers.
00:34:25Also, lip skin is very thin, so you can actually see the blood capillaries inside.
00:34:31That's why lips are red or pink, unlike the rest of your body.
00:34:35Lips are also very sensitive to sun damage, so remember to apply sunscreen on them.
00:34:41It'll help to preserve their health and fullness over time.
00:34:45In addition to your fingerprints, your iris, and your tongue, your lips are also unique.
00:34:51The total surface of your lungs is about the same as a tennis court.
00:34:56Coughs and sneezes are real fast-travelers.
00:34:58A cough can get up to 50 mph, a sneeze is even faster – almost 100 mph.
00:35:06Unless you use your fingers to help you, it's impossible to sneeze with your eyes open.
00:35:11Scientists don't really know what's going on there.
00:35:13Some say it's just a reflex, so you can't control it.
00:35:17Others think it happens to shield your eyes from whatever's flying out.
00:35:22All humans literally glow.
00:35:24The light comes from your body heat.
00:35:26It's actually a thousand times less intense than you're capable of seeing, but still
00:35:30awesome.
00:35:33The largest flash drive in the world is actually your brain.
00:35:37Well, anyone's brain.
00:35:38The neurons in it combine together in such a way that your storage capacity is about
00:35:43a million gigabytes.
00:35:45It's enough to hold 3 million hours of movies.
00:35:48That's like a 300-year-long movie night.
00:35:51Hey, pass the popcorn!
00:35:53You start feeling thirsty when you lose about 1% of your body weight.
00:35:58If you lose 5%, you might even feel like fainting.
00:36:02Fingers don't have muscles that make them move.
00:36:05The muscles that do that are located in the palm and the forearm.
00:36:09The word muscle actually comes from the old Latin word for mouse.
00:36:13That's what the Romans thought their biceps looked like.
00:36:16On average, in their lifetime, a person walks about 110,000 miles.
00:36:22That's 4 times the distance around our planet, or half the distance from the Earth to the
00:36:26Moon.
00:36:27So, remember to wear comfortable shoes.
00:36:30Well, here's some fats you'll find hard to digest.
00:36:35Your stomach has a pretty incredible capacity, being able to hold up to half a gallon of
00:36:40liquids.
00:36:41That's like a whole large bottle of Coke.
00:36:44It's pretty hard to estimate how much hard food you can eat because it's processed
00:36:49with your teeth before it gets to your stomach.
00:36:51There's definitely not enough room for a turkey, but a good-sized chicken would probably
00:36:56fit in it.
00:36:58If you were asked where your stomach was, you would probably point to your tummy.
00:37:03Sorry, that's wrong.
00:37:04It's actually up here, hidden in between your ribs.
00:37:10Scientists believe that the appendix will disappear eventually.
00:37:13Nobody really knows why we need it, but some researchers claim it might've existed to
00:37:18help our ancestors digest tree bark.
00:37:21Because it's no longer part of our daily diet, the appendix isn't necessary and can
00:37:26disappear from our bodies without any consequences.
00:37:30The appendix isn't the only obsolete part of our body.
00:37:34Wisdom teeth aren't that useful either.
00:37:36Yeah, they used to come in handy whenever our ancestors lost some of their teeth.
00:37:41But the only thing they help us lose now is the money we spend extracting them.
00:37:47Almost all of our body is covered with hairs, even if we don't notice them.
00:37:51They grow even in the belly button.
00:37:54Their purpose is to catch lint.
00:37:55Check it out.
00:37:57See?
00:37:59Your liver acts as your own personal bodyguard, protecting you from toxins and many other
00:38:04things you don't want hanging around in your body.
00:38:06It's also pretty indestructible and can even regenerate.
00:38:12Only about 43% of you is actually you.
00:38:16Over 50% of the cells in your body belong to tiny little creatures that mainly live
00:38:21in your gut.
00:38:22Still, even though your own cells are fewer than microbial ones, there are, on average,
00:38:28about 100 trillion of them in you.
00:38:30See?
00:38:31You're not alone.
00:38:34With this in mind, your own genes are less than half of what you really consist of.
00:38:39If you take all the microbes dwelling within your body and count their genes, you'll
00:38:43find between 2 to 20 million.
00:38:48If you sleep, it doesn't mean all of your body sleeps.
00:38:51In fact, sometimes your brain has to work even harder when you're asleep.
00:38:55It needs to process tons of information, and reports usually take a lot of time.
00:39:02The nose definitely gets a good rest while you're sleeping.
00:39:05Amazingly, your sense of smell basically deactivates at night.
00:39:10You wouldn't even be bothered if there was a really terrible smell in your bedroom.
00:39:14No comment.
00:39:16The nose is probably one of the most underappreciated parts of the body.
00:39:21We wouldn't even be able to enjoy eating without it.
00:39:24About 80% of the taste of any food is thanks to the nose and its ability to recognize odors.
00:39:30If you hold your nose while eating, you will taste almost nothing.
00:39:34With no sense of smell, you're likely to recognize food mostly by texture.
00:39:39So an onion might seem no different than a big refreshing apple.
00:39:43Yeah, try that and leave me a comment on how that goes.
00:39:48Scientists used to believe we could distinguish about 10,000 smells, but they were wrong.
00:39:54Recent research showed that people are actually able to distinguish between more than a trillion
00:39:59smells.
00:40:00We also remember them better than anything else, and smells can even evoke some distant
00:40:05memories.
00:40:07Your nose just doesn't help you breathe and catch odors.
00:40:10It filters the air for sensitive throats and lungs.
00:40:14If we inhale dry air, the nose moistens it, cools it, and heats it if it's necessary.
00:40:20Also the nose cleans the air of dirt.
00:40:24When you age, your brain is gradually reducing in size.
00:40:28By age 75, it's much smaller than at 30, and it starts shrinking by the age of 40.
00:40:34It happens to everyone, and doesn't affect your mental strength in any way.
00:40:40Our brain can store only 7 bits in its short-term memory.
00:40:44Don't even try to compare your brain with a phone capacity, not even the one you had
00:40:48back in 2005.
00:40:50That's why you can't even learn a phone number by heart.
00:40:54Our short-term memory functions just like a chalkboard.
00:40:57You can get some information, but sooner or later, you run out of space.
00:41:02To check your working memory capacity, try this test.
00:41:05Ask a friend to write a list of 10 words and read it to you.
00:41:09Most people recall 7 or fewer items from that list.
00:41:14Your RAM, or working memory, is an essential thing that we need to perform almost any everyday
00:41:20activity, including basic conversations, surfing the net, and even petting your dog.
00:41:27Our strongest and emotional memories are often fake.
00:41:31The central memory gives us the confidence to believe that we remember everything, even
00:41:35though most of the details are made up in our heads.
00:41:40Not only your brain shrinks as you get older, you too shrink dramatically.
00:41:44The bones get more brittle, the backbone gets compressed.
00:41:48A similar thing happens when you rest at night.
00:41:51Your bones kinda relax too.
00:41:53Because of this, you wake up taller in the mornings than you are at the end of the day.
00:41:59Among mammals, only humans can walk on two legs for their entire lives.
00:42:04You might think that kangaroos or gorillas move in the same way, but kangaroos use their
00:42:09tail as a third leg, and gorillas use their long arms to keep balance.
00:42:16Your bones take part in metabolism too.
00:42:18Since they mostly consist of calcium, when there's not enough of this element in your
00:42:22blood, bones start shedding it into the bloodstream, balancing your body.
00:42:27The same reaction works in reverse too.
00:42:30When there's too much calcium in your blood, it goes into the bones to be stored for later.
00:42:36The only bone to have a sense of humor in your body is inside your upper arm.
00:42:40That's why it's called the humerus.
00:42:43Okay, I made that one up.
00:42:45Moving along…
00:42:47The only bones that never grow are found in our ears.
00:42:51We can hear thanks to these tiny bones because they have adapted to transmit sound vibrations.
00:42:57Doctors call them the oscular chain.
00:42:59One of these hearing bones, the stapes, is the smallest bone in your entire body.
00:43:04It's no larger than a grain of rice.
00:43:08Our height, shape of our body, and skin color depend a lot on where our ancestors used to
00:43:14live.
00:43:15But we can adapt to new conditions even within our own lifespan.
00:43:19For example, if you move from plains to the mountains, you'll eventually develop more
00:43:24red blood cells to compensate for the lack of oxygen.
00:43:28And naturally, if you move from a colder climate to a hotter and sunnier one, your skin will
00:43:33get darker to adapt.
00:43:36Our lifespan is programmed within our cells.
00:43:39They constantly renew and divide, but they have a sort of internal timer that stops at
00:43:44some point.
00:43:45Some cells also stop reproducing sooner than others.
00:43:49On average, cells cease dividing when we reach the age of 100.
00:43:53That means, if we could find a way to trick ourselves into turning off the timer, we could
00:43:58potentially live forever.
00:44:01Body fat isn't just a nuisance.
00:44:04It acts as insulation material, energy reserve, and shock absorber.
00:44:08Your body sends the most fat into your waist region because that's where your internal
00:44:13organs are.
00:44:14If something happens to you, this layer of fat might protect your vitals from irreparable
00:44:19damage.
00:44:20Heads up!
00:44:21Your skull isn't a single bone.
00:44:25It actually consists of 28 different bones, many of which are fused together to protect
00:44:30your brain.
00:44:31The mandible, or the lower jaw, is the only skull bone that isn't fixed to the bone
00:44:36around it.
00:44:37It's attached with connective tissues and muscles.
00:44:40This is what makes it so mobile – you can move it in any direction you like.
00:44:44You can actually masticate with your mandible!
00:44:47Another word for chewing!
00:44:49You see, the strongest muscles in your body aren't in your arms or legs – they're
00:44:54in your head!
00:44:55The masseter is the main muscle responsible for chewing, and it needs to be the strongest
00:44:59for you to eat normally.
00:45:01And you know those muscles that allow you to move your ears?
00:45:05Those are temporalis, located above your temples.
00:45:08They also help you chew your food.
00:45:10Now, we've got two really fast muscles – they control the eyelid closing.
00:45:17In fact, they're the fastest muscles in our body.
00:45:20Eyes are fragile and need protection, so the reflex that protects them needs to be as fast
00:45:25as lightning.
00:45:26These muscles can shut the eyelids in less than a tenth of a second.
00:45:32People with double-jointed thumbs can bend them backward.
00:45:35It looks super unusual, and very few people can do it.
00:45:38Still, it's totally okay.
00:45:40Even though it looks painful, it actually doesn't hurt at all for someone with a double-jointed
00:45:44thumb.
00:45:47We recognize only purple-blue, green-yellow, and yellow-red colors.
00:45:52Everything else is a combination of these three.
00:45:55It's impossible to calculate how many of these combinations the human eye sees, because
00:46:00every single person has slight vision differences.
00:46:04But it's about 1 million combinations on average.
00:46:07You see?
00:46:08Oh, the phone's ringing.
00:46:13Must be something urgent.
00:46:14At 11 p.m.?
00:46:16Only all the gadgets in the house are silent.
00:46:19It's your ears that are ringing.
00:46:21We can also hear some hissing, whistling, buzzing, and even roaring.
00:46:25But all this noise doesn't have an external source.
00:46:29That's why it's known as phantom sounds.
00:46:32They can occur in one or both ears, constantly or from time to time.
00:46:37They're usually most noticeable at night when nothing distracts you.
00:46:41Hearing noise in your ears is called tinnitus.
00:46:44It's quite common and affects 15-20% of people.
00:46:48Tinnitus starts in the part of your inner ear shaped like a snail.
00:46:51It's called the cochlea.
00:46:55Your middle ear picks up sound waves.
00:46:57They get translated into electrical impulses in the inner ear.
00:47:01Then, sensory nerves carry these impulses to your brain.
00:47:05If your inner ear works incorrectly, your brain can misinterpret the sounds.
00:47:11Tinnitus occurs when there are some changes in the cochlea's nerve.
00:47:14They can be caused by loud noise, like chainsaws, jackhammers, loud music, or shouting.
00:47:21Tinnitus can start after a head, neck, or ear injury, or after you begin to take certain
00:47:26medications.
00:47:27You can also hear ringing in your ears if you have some blood pressure issues.
00:47:31Elsewhere, in the amazing human body, some of the bacteria living in your gut can produce
00:47:37electricity!
00:47:38Shocking!
00:47:39They give off electrons, and this creates tiny electrical currents.
00:47:44That's likely to be the bacteria's backup system, their way to generate energy.
00:47:49Humans are the only animals that have chins.
00:47:52Even our closest genetic relatives, gorillas and chimps, lack this small piece of bone
00:47:57that extends forward from the jaw.
00:47:59Their lower jaws slant down and back from their front teeth.
00:48:04Scientists still haven't figured out this mystery.
00:48:06The opinions about why people are made this way differ.
00:48:09Some researchers think chins help us chew our food.
00:48:12Others are sure they have something to do with speaking.
00:48:15A few of us think it's simply a special place to grow a goatee.
00:48:20Blinking keeps your eyes clean and moist.
00:48:22But that's not all.
00:48:24Every time you blink, you take a micro-nap.
00:48:27Researchers from Washington University have found out that blinking makes your attention
00:48:32sharper and works as a teeny recharge.
00:48:37Ever seen tiny dots traveling in squiggly lines, especially when you're looking at
00:48:41a bright blue sky?
00:48:43These dots are only visible for a second or so and might look like itty-bitty worms.
00:48:48Those are your white blood cells moving through the capillaries in front of the retina.
00:48:53That's the light-sensitive tissue at the back of your eyes.
00:48:56Curiously, most people don't even notice the dots unless asked to pay attention.
00:49:02The pineal gland in your brain handles the production of melatonin.
00:49:06That's the very hormone that regulates your sleep patterns.
00:49:10The gland looks like a pine nut, and that's how it got its name.
00:49:15The human brain is 73% water, and the same is true about the heart.
00:49:19That's why if your brain loses even 2% of liquid, you start to feel tired.
00:49:25It also makes your memory worse, shortens your attention span, and puts a dampener on
00:49:30your mood.
00:49:32By the way, your brain makes sure you don't drink too little or too much water.
00:49:37If you swallow some liquid, your mouth and throat start to fire signals to your brain,
00:49:42telling it to stop drinking.
00:49:43Otherwise, you'd be gulping down water for the entire 10 to 60 minutes it takes the liquid
00:49:49to get to your cells.
00:49:51Your eyes can see something for a mere 13 milliseconds, and your brain will already
00:49:56process this image.
00:49:57For comparison, the average blink lasts from 100 to 400 milliseconds.
00:50:03Even though the tongue isn't the strongest muscle in your body, it never gets tired.
00:50:08That's because of the way it's built.
00:50:10It's made up of 8 interwoven muscles.
00:50:13But unlike other muscles in your body, these aren't situated around a supporting bone.
00:50:18The tongue's structure is similar to an elephant's trunk or an octopus's tentacles.
00:50:26Your body emits visible light.
00:50:29That's why they call me sunny.
00:50:32You're the brightest at 4 p.m., and your glow is the least visible at 10 a.m.
00:50:37Unfortunately, this glowing is a thousand times less intense than what your eyes can
00:50:41see.
00:50:43Sweat is mostly water mixed with proteins, sugars, ammonia, and a lot of other stuff.
00:50:49It even contains tiny amounts of trace metals, like copper, zinc, nickel, iron, and so on.
00:50:55What makes sweat taste salty is the sodium it contains.
00:50:59Plus, the more salt you eat, the saltier your sweat is.
00:51:03Your body's trying to get rid of the excess, and the fastest way is to sweat it out.
00:51:08In an adult, the blood makes up 7-8% of the total body weight.
00:51:13About 55% of your blood is liquid plasma.
00:51:17The rest is red and white blood cells and platelets.
00:51:20They form clots and prevent bleeding.
00:51:23You can't swallow and breathe at the same time.
00:51:26The food you swallow and the air you breathe go down the same part of your throat at first.
00:51:32Only a bit deeper, the passage splits into the esophagus, for food and liquid, and trachea,
00:51:37for air.
00:51:39When you swallow, your airway gets automatically closed off.
00:51:42This prevents you from accidentally inhaling food.
00:51:46But occasionally, it still happens.
00:51:49Your brain sometimes generates more than 48 thoughts in just one minute.
00:51:54That's almost 3,000 thoughts per hour and 69,000 per day!
00:51:59Fingernails grow faster on the dominant hand.
00:52:02If you use your right hand more, you'll have to trim nails on it more often.
00:52:07Fingernails also grow more quickly in the summer and during the day.
00:52:11You might keep in memory up to 10,000 different faces.
00:52:14Sure, it varies from person to person, and the average number is 5,000.
00:52:19It doesn't mean you can put a name to each of these faces.
00:52:23It's only about recognizing the features.
00:52:26You might try to hide the truth, but your nose will always give you away.
00:52:31When a person tells a lie, the temperature around their nose and in the inner corners
00:52:35of their eyes goes up.
00:52:37This phenomenon is known as the Pinocchio effect.
00:52:43Women have more taste buds on the surface of their tongues than men do.
00:52:47It's one of the reasons why 35% of ladies and only 15% of guys are supertasters.
00:52:54Those are people who feel flavors more strongly than others.
00:52:57Your teeth are the only part of your body that can't repair itself.
00:53:02But the enamel they're covered with is one of the toughest things in the human body.
00:53:07Your heartbeat often syncs with the music you're listening to.
00:53:10If a piece has a continuous increase in volume or tempo, like rock, it can make your heart
00:53:15rate faster.
00:53:17Some classic music lowers heart rate and blood pressure.
00:53:20This phenomenon affects everyone from professional musicians to amateurs and music lovers.
00:53:27There are 2 to 5 million sweat glands on your body.
00:53:30The sweat they produce is of two different kinds – stress sweat and regular sweat.
00:53:35Hey, don't sweat the small stuff, huh?
00:53:38The sweat caused by stress has fatty acids and proteins in it.
00:53:43And the regular sweat is mostly made up of water, salt, and a tiny bit of other substances.
00:53:48It's actually possible to brush your teeth too thoroughly and hard.
00:53:53This can wear down the enamel and make your teeth super sensitive to cold and hot foods.
00:53:59If you walked in the same direction for 12 hours a day, you would need around 800 days
00:54:04to travel around the globe.
00:54:06And don't forget your rubber boots for the ocean parts.
00:54:10If your stomach acid made contact with your skin, it would most likely eat a hole in it.
00:54:16All because of hydrochloric acid.
00:54:18This type of acid is incredibly potent.
00:54:21It can easily dissolve some metals, for example, magnesium or zinc.
00:54:27Hydrochloric acid is the main component of the gastric acid your stomach produces.
00:54:31It protects your immune system and gets rid of viruses and bacteria in the food you eat.
00:54:36This acid also helps your body break down, digest, and absorb all kinds of nutrients,
00:54:42including proteins.
00:54:44Your lips look red because there is a great concentration of miniature blood capillaries
00:54:49right below the skin.
00:54:52Your pinky is a powerful little thing.
00:54:54Without it, your hand would lose a significant part of its power.
00:54:58Your index and middle fingers cooperate with your thumb to grab and pinch.
00:55:03And your pinky, together with your ring finger, provides grip strength.
00:55:08The fattest organ in your body is your brain.
00:55:12Fat makes up at least 60% of its dry weight.
00:55:15This quality got the brain to the Guinness World Records.
00:55:19The organ contains around 25% of your body's cholesterol, which is vital for the brain's
00:55:24well-being.
00:55:25So, is that where the term fat head comes from?
00:55:30Your skeletal cells never stop regenerating.
00:55:33That's why you get a new skeleton every 10 years or so.
00:55:37This process slows down with age, and the regeneration takes longer.
00:55:41That's one of the main reasons why bones become thinner.
00:55:45And there's a newly discovered type of brain cells crucial for visual search.
00:55:50They're called target cells.
00:55:52Without their help, you wouldn't be able to spot an acquaintance in a crowd or your
00:55:56dog in the park.
00:55:57Interestingly, target cells don't care what the thing you're searching for looks like.
00:56:02All they want to know is whether an object is your target or not.
00:56:06Hey, it's not picky!
00:56:11Whenever we yawn, we use the muscles in our mouth and tongue, and the contact can squeeze
00:56:17some of the saliva-producing glands.
00:56:19As a result, we might squirt a tiny stream of saliva without even noticing it, but it'll
00:56:25reach out a foot or more.
00:56:27I had a friend in college who could do that at will.
00:56:30It was impressive.
00:56:32It turns out that saliva is basically filtered blood.
00:56:36Blood is processed thanks to special glands, and special cells absorb its properties.
00:56:41After that, the blood becomes saliva.
00:56:44Moving on, if your brain were a USB drive, it would be totally insane.
00:56:50Our brain capacity is somewhere between 10 and 100 terabytes.
00:56:55Some scientists claim the full spectrum can reach 2.5 petabytes.
00:57:00Sounds like a dog snack, doesn't it?
00:57:02When the size of the full English version of Wikipedia was calculated back in 2010,
00:57:08it was only 5.6 terabytes.
00:57:11Our body heat can boil a half a gallon of water in 30 minutes, even when we're idle.
00:57:17We should try that.
00:57:19Our brain can perform up to 10 quadrillion operations per second with 10 watts of power
00:57:25only.
00:57:26A computer that could do the same would need about 1 gigawatt of power.
00:57:30This amount could power up to 300,000 houses.
00:57:35Your memory is affected by your body position.
00:57:38For example, you're much more likely to recall a situation where you waved to someone
00:57:43if you stand and wave again.
00:57:46Your brain has millions of neurons.
00:57:48They're all different, and the speed of connection between them is different too.
00:57:53That's why you can recall some information faster than others.
00:57:58Our nerve impulses, though, are super slow compared to the speed of electricity.
00:58:03Neurons can speed up to 275 mph, even slower than the world's fastest car.
00:58:09Still, it's pretty fast because your brain needs to respond to stuff like pain or tickles.
00:58:16The brain itself, by the way, can't feel pain.
00:58:19It has no nerve endings of its own.
00:58:23People with red-colored hair are 1% of all people.
00:58:262% are natural blondes.
00:58:29So yeah, most people you see with these hair colors have dyed hair.
00:58:33Black is the most common hair color in the world.
00:58:38Hair is not only strong but also elastic.
00:58:42It can stretch about 30% of its length when it's wet.
00:58:46The average hair growth rate is 6 inches per year.
00:58:50So if you never cut your hair until you're, say, 80 years old, your hair will have grown
00:58:55up to 480 inches, about the height of a 4-story building.
00:58:59Still, it's not quite possible because our hair length is programmed genetically.
00:59:06A human eye resembles a car engine.
00:59:08Both of them need liquid for good lubrication.
00:59:12The engine needs oil, and the eye needs tears.
00:59:15To make sure the eyes work right, tears are distributed all over them.
00:59:20That's why we blink more than 10,000 times a day.
00:59:24The eye muscle is the fastest muscle in our bodies.
00:59:27We can blink 5 times per second and even more.
00:59:31We spend about 6 seconds blinking every minute.
00:59:35During the day, we spend 30 minutes in complete darkness just because we close the eyes, not
00:59:40even including the time when we sleep.
00:59:44The only part of the human body that doesn't get any nutrients from blood is the cornea
00:59:49of the eye.
00:59:50The only thing it needs to work well are tears and fluid in front of your eyes.
00:59:56Most scientists agree that tears that appear out of emotion are a unique human feature.
01:00:01No other animal is capable of crying because of sadness or joy.
01:00:07The pupils narrow and expand in order to control the incoming light.
01:00:11If there's a lot of light, they narrow the passage for light so as to not harm the
01:00:16vision.
01:00:17In the dark, the pupils expand to capture as much light as possible.
01:00:22Now back to our mouths.
01:00:24The tongue has a lot of muscles, and some of them constrain only when you're learning
01:00:29a new language.
01:00:31A human bite almost always becomes infected because of all the bacteria that live in our
01:00:36mouth.
01:00:37In this sense, we're quite close to hyenas.
01:00:41Your bones are designed to be used a lot daily, and some of them can absorb two or
01:00:46even three times your body weight.
01:00:48That's impressive, but your teeth are even stronger.
01:00:52When you bite something, the teeth can exert incredible pressure, up to 200 pounds.
01:00:58By the way, the enamel is considered to be a part of your skeletal system.
01:01:04Our body is about 60% water, and it can be found even in bones.
01:01:09About 25% of the human bone mass is made of water.
01:01:15Hydrochloric acid in our stomach, also known as the most important defender of the immune
01:01:20system, helps get rid of dangerous food toxins, viruses, and bacteria you get with the food
01:01:26you eat.
01:01:27Even the stomach itself can be digested by this acid, but the mucous membrane protects
01:01:32it.
01:01:34Even if you brush your teeth twice a day and never forget about mouthwash, your mouth still
01:01:39stays one of the dirtiest parts of the human body.
01:01:43Millions of bacteria live inside it.
01:01:46The good news is that most of these bacteria are good for the body and protect it from
01:01:51bad bacteria and viruses.
01:01:55People and giraffes have similar necks.
01:01:58A person has the same amount of neck vertebrae as a giraffe has.
01:02:02The difference, though, is about the length.
01:02:05Giraffe vertebrae are about 10 inches long.
01:02:08Our spine can withstand pressure of up to 1,000 pounds.
01:02:12It would withstand an adult zebra.
01:02:16But please don't try it at home, there are no zebras there after all.
01:02:21When you lie down on your back and elevate the knees, the pressure on your spine is about
01:02:2625 pounds.
01:02:28Not a zebra for sure, but a good-sized cat.
01:02:31Our spine is also very flexible.
01:02:34If we could bend it, it could possibly form two-thirds of a complete circle.
01:02:38Are we like snakes then?
01:02:41In the morning, you're taller than in the evening.
01:02:44While sleeping, you're no longer affected by the force of gravity.
01:02:48And your spine stretches, giving you up to half an inch in height.
01:02:52Too bad you become shorter by daytime, though.
01:02:56A rollercoaster actually tosses your organs around.
01:02:59So when you feel like your stomach's falling down, it's actually flipping inside your
01:03:03body.
01:03:05You think your fingerprints are the only unique thing in your body?
01:03:08Well, they're not.
01:03:10Your tongue print and your smell are also one of a kind.
01:03:14If anyone sniffs you, it's reason enough to get suspicious.
01:03:18If all of your blood vessels were stretched into a single line, boy that would hurt.
01:03:24But it would go around the Earth more than twice.
01:03:27An impressive feat that you wouldn't see because, well, you can't live without your
01:03:31blood vessels.
01:03:33You think you rest while you're asleep, but, in fact, your brain doesn't.
01:03:38It's actually more active at night than during the day, processing all the info you've collected.
01:03:44So have some respect!
01:03:48The human liver is the busiest organ of the body.
01:03:51It has over 500 functions, and not all of them are even clear to the scientists.
01:03:57Ever wonder why you feel so sleepy after lunch?
01:04:00Well, that's because of your circadian rhythms, which have 24-hour cycles, demand you have
01:04:06a nap after 7 hours of being awake, and food just adds to this effect.
01:04:12Simple.
01:04:13Toothache and headache are linked together thanks to the trigeminal nerve.
01:04:18It goes through the jaw right to the head, so when you feel tooth pain, it usually goes
01:04:23hand-in-hand with that in your head.
01:04:27You lose calories doing literally anything.
01:04:30A healthy 8-hour sleep, for example, makes you lose up to 800 calories.
01:04:35And yes, you spend energy even while eating.
01:04:39Like all mammals, we have a diving reflex that slows down or even stops some bodily
01:04:45functions to keep us from drowning.
01:04:48That refers to heart rate too.
01:04:50A person can go without food for more than 20 days.
01:04:53However, if you don't sleep for 10 days, your body will simply stop functioning.
01:04:59Talking about sleep, the average person forgets 90% of their dreams.
01:05:04And maybe that's a good thing.
01:05:06Otherwise, imagine how crazy the world would've been.
01:05:10The color of your dreams is affected by the TV you watched as a kid.
01:05:15If you're of an older generation that watch black-and-white TV, you'll see monochrome
01:05:20dreams more often than not.
01:05:23If you're used to color television, your dreams will also be colorful.
01:05:28Out of every 10,000 people on Earth, one person has their organs mirrored, or reversed from
01:05:34their usual and customary positions.
01:05:37That is, their liver would be larger on the left side, and the right kidney would be a
01:05:41bit superior to the left one.
01:05:44Speaking of kidneys, your left one is a bit more elevated than your right.
01:05:49That's because the liver is larger on the right side of your body.
01:05:53People with light-colored eyes, blue or green, are better at tolerating pain than those with
01:05:58dark eyes.
01:06:00Scientists think it might be related to melanin that affects the color of the eyes.
01:06:05The length of your foot is similar to that of your forearm.
01:06:09Don't believe me?
01:06:10Go check!
01:06:11I'll wait right here.
01:06:12Nah.
01:06:14Hey, check it out!
01:06:15Your bones are designed to be used a lot every day.
01:06:18Some of them can absorb the force of 2 or even 3 times your body weight!
01:06:23That's impressive, but your teeth are even stronger.
01:06:26When you bite something, they can withstand incredible pressure – up to 200 pounds!
01:06:31By the way, the enamel is considered to be a part of your skeletal system.
01:06:36Whenever you rotate your hand, the bones inside your forearm cross.
01:06:41Grab hold of your arm and turn your palm to face first upward and then downward.
01:06:46You'll make sure it's true!
01:06:48Not only is your body 60% water, your bones contain some liquid too.
01:06:53About 25% of the human bone mass is made up of water.
01:06:57The human eye has something in common with a car engine.
01:07:01They both can't work properly without various liquids.
01:07:04The eye needs tears as much as the engine needs oil.
01:07:07Tears should be evenly spread over the surface of your eye.
01:07:11That's why you blink up to 20,000 times a day.
01:07:14And your eyelid plays the role of a windshield wiper.
01:07:17The only part of the human body that doesn't get any nutrients from blood is the cornea
01:07:22– the clear front surface of the eye.
01:07:25Instead, it's fed by tears on the outside and special fluids on the inside.
01:07:30When you blush, it means there's increased blood flow in your body.
01:07:34And then, not only your cheeks, but also your stomach lining gets somewhat red.
01:07:39It's because it has plenty of blood vessels.
01:07:41When there's more blood than usual in them, the lining blushes.
01:07:45Your stomach lining gets replaced every 3-4 days.
01:07:48This prevents the organ from eating itself.
01:07:51The digestive acids there are exceptionally powerful.
01:07:55People can accidentally swallow small objects, such as glass, plastic items, coins, and many
01:08:01others.
01:08:02Normally, they don't cause any harm and pass through the digestive tract within 48
01:08:07hours.
01:08:08So, any quantities of plastic you might consume by mistake won't harm you.
01:08:12But your stomach will have problems with digesting grass.
01:08:16Grazing animals have special teeth and stomachs to process raw leaves and grass.
01:08:21People aren't equipped that way.
01:08:24The stomach is the most important protector of the immune system.
01:08:27It contains hydrochloric acid.
01:08:30This acid gets rid of dangerous food toxins, viruses, and bacteria that come along with
01:08:34the food you eat.
01:08:36The stomach itself would be digested by this strong acid if the mucous membrane didn't
01:08:41protect it.
01:08:42You've got two really fast muscles.
01:08:45They control your eyelids closing.
01:08:47They're the swiftest in your body.
01:08:49Your eyes are fragile and need protection.
01:08:51When a special reflex is triggered, for example, when something suddenly touches your eye,
01:08:57these muscles only need 1 tenth of a second to shut the eyelids.
01:09:02Men usually blink more than men.
01:09:03Plus, the older you get, the more frequently you do it.
01:09:07By the way, when you watch a movie with a friend, you both blink in unison.
01:09:12Do you think you owe your firm handshake to your strength workouts?
01:09:16It's more likely thanks to your pinky.
01:09:19Just kidding.
01:09:20And still, the pinky is the strongest finger out there.
01:09:22It's responsible for 50% of the entire hand's strength.
01:09:27But the most used finger is the thumb.
01:09:30If a person loses it, their hand becomes 40% less agile.
01:09:34Oh, and the thumb has its own pulse, thanks to the artery running through it.
01:09:39Your big toes carry more than 40% of your weight, more than all the other toes combined.
01:09:45All in all, all your toes are a big deal.
01:09:47They provide support and balance when you walk.
01:09:50And when you run, they help you to be faster.
01:09:53No more than 2% of people have natural red hair.
01:09:57They're followed by blondes, about 3%, and all kinds of brown shades, about 11%.
01:10:03But the world's most common hair colors are black and dark brown.
01:10:08Hair is almost indestructible.
01:10:10It can be burned or affected by strong acids.
01:10:13But that's pretty much all you can do to destroy it.
01:10:17Your hair usually stops growing at a certain length.
01:10:19And since a hair lives for 2 to 7 years, its length doesn't normally exceed 42 inches.
01:10:26Well that to this lady from China, who got to the Guinness World Records with the longest
01:10:31hair ever.
01:10:32In 2004, it was a bit more than 18 feet 5 inches long.
01:10:37Wow, what a drag!
01:10:39Nails can grow staggeringly long too.
01:10:42Some of the longest nails in the world belong to this guy from India.
01:10:46Their combined length was 29 feet 10 inches, which is almost as long as a London double
01:10:51decker.
01:10:52The man cut them off back in 2018.
01:10:56Nails do help us catch small objects and peel stickers off.
01:11:01But that's not all.
01:11:02If you didn't have a rigid structure to press against, you wouldn't be able to understand
01:11:06how firmly you should hold things.
01:11:09Not only your hair and nails, but also your liver can grow.
01:11:13It's the largest internal organ by mass.
01:11:16The liver can fully regenerate from only 51% of its original mass back to the full size.
01:11:23At the same time, constant damage to the liver will result in scars.
01:11:28The largest organ in your whole body is the skin.
01:11:31It makes up more than 15% of your total body weight.
01:11:35People lose 30,000 to 40,000 skin cells every single minute.
01:11:40It adds up to 9 pounds of skin cells a year.
01:11:43You know that dust in your house?
01:11:45Well, now you know where some of it comes from.
01:11:49The tongue isn't the only organ that helps you recognize taste.
01:11:53Your nose also plays a critical role in this process.
01:11:57It's often said the nose is responsible for 75 to 95% of your taste perception.
01:12:03Try holding your nose next time you eat.
01:12:05Gnaw on an onion or eat some smoked fish.
01:12:08It's not that you won't feel any taste at all, but it's gonna be way blander.
01:12:14Your taste buds won't work properly if your mouth is too dry.
01:12:18You simply won't feel the taste until the food is covered in saliva.
01:12:22It contains enzymes, which are complex protein molecules.
01:12:25They start to break down your food as soon as it gets into your mouth.
01:12:29A recent study has found out that people can distinguish more than a trillion smells.
01:12:35You tend to remember odors better than sounds or images.
01:12:38That's why smells can evoke distant memories.
01:12:41When you're asleep, you don't feel any odors.
01:12:44Your sense of smell basically deactivates at night.
01:12:48Even if there's some terrible stench in your bedroom, you won't notice it.
01:12:52I'm sure my dog is relieved to hear that.
01:12:55The color of your dreams seem to be affected by the TV you watched as a kid.
01:13:00If it was black and white, you'd probably see monochrome dreams more often than not.
01:13:05If you're used to color television, your dreams are likely to be colorful.
01:13:10What kind of dreams did people in the Middle Ages have then?
01:13:14Hearts that say knee?
01:13:16Your heart can give you away when you lie by starting to beat faster.
01:13:20Women's hearts are usually smaller than men's.
01:13:22That's why they have to work harder and make more beats.
01:13:25Otherwise, they won't be able to pump enough blood.
01:13:29Even if you brush your teeth twice a day and never forget about mouthwash, your mouth still
01:13:34remains one of the dirtiest parts of your body.
01:13:37Millions of bacteria live there.
01:13:39The good news is that most of them are good for your health.
01:13:43They protect your body from bad bacteria and viruses.
01:13:47The second dirtiest place is your belly button.
01:13:49You don't really use it after you were born.
01:13:52So this forlorn area accumulates all kinds of germs, sweat, and dirt.
01:13:57The belly button has over 2,300 bacterial species, and it does need extra attention.
01:14:04They say eyes don't grow with the rest of the body.
01:14:07Well, it's not 100% true because the eyes aren't fully developed until you're about
01:14:1321.
01:14:14But the absolute growth champions here are your ears and nose.
01:14:18They never stop growing.
01:14:20Wow, what was that thing about elephants again?
01:14:22Must've been a different video.
01:14:25If all your blood vessels were stretched into a single line, dang, you would be in a really
01:14:30tough spot.
01:14:31But they would go round the Earth four times.
01:14:35You can't tickle yourself, no matter how hard you try.
01:14:38You've just checked that and failed, haven't you?
01:14:41That's because your brain warns you that you're about to be tickled, which it can't
01:14:45do if it's someone else.
01:14:47Ever wondered why you feel so sleepy after lunch?
01:14:51One of the reasons is your circadian rhythm, which runs on a 24-hour cycle.
01:14:55It demands that you have a nap 7 hours after waking up, and the food just adds to this
01:15:01effect.
01:15:02As simple as that.
01:15:03Oh, excuse me, it's time!
01:15:07Most people are sure that humans only have five senses, but that's not entirely true.
01:15:12Taste, touch, smell, sight, and hearing aren't the only ones we have.
01:15:18Scientists claim that people have between 9 and 20 senses in total.
01:15:22These include thermoception, the sense of warmth, equilibrioception, the sense of balance.
01:15:29There's also the sense of time, although not everyone seems to have that last one.
01:15:34We used to think that there were just eight different blood types, but in reality, there
01:15:38are over 30 known blood group systems.
01:15:41Here on the Bright Side, our favorite blood group is B-positive.
01:15:45Get it?
01:15:46For every pound of fat you gain, you generate one mile of new blood vessels to supply oxygen
01:15:52and nutrients to your body.
01:15:54Your stomach produces a new lining every six days to avoid digesting itself.
01:16:00Nerve cells transmit 1,000 nerve impulses a second.
01:16:04They travel between 1 and 268 miles per hour.
01:16:08Our DNA contains 100,000 viruses.
01:16:12Scientists have discovered one that goes back 100 million years.
01:16:16Your body emits visible light.
01:16:18You're the brightest at 4 p.m., and your glow is the least visible at 10 a.m.
01:16:23Unfortunately, this glowing is 1,000 times less intense than what your eyes can see.
01:16:29Sweat is mostly water mixed with proteins, sugars, ammonia, and a lot of other stuff.
01:16:35It even contains tiny amounts of trace metals like copper, zinc, nickel, iron, and so on.
01:16:41What makes sweat taste salty is the sodium it contains.
01:16:45Plus, the more salt you eat, the saltier your sweat is.
01:16:49Your body's trying to get rid of the excess, and the fastest way is to sweat it out.
01:16:54If you walked 2 miles per hour, you'd have to walk for 20 hours straight to lose 1 pound.
01:17:00And it would take you 518 days and 8 hours to circle the equator.
01:17:05Earwax isn't actually wax.
01:17:08It contains fat, skin cells, sweat, and dirt.
01:17:12Your brain gets three times bigger over the first year of life and reaches its full maturity
01:17:16when you're 25.
01:17:1860% of it is fat.
01:17:21Your brain generates around 23 watts of electrical power, which is enough to run a small light bulb.
01:17:28Humans can't really multitask.
01:17:30Your brain can't perform more than one action at the same time.
01:17:34It switches between them, which doesn't save time as you might think, but increases the
01:17:39possibility you'll do something wrong and makes the process longer.
01:17:43When you have an exam to take or you're at work trying to focus on an important task,
01:17:48try chewing gum.
01:17:50Research showed it can help you stay concentrated for longer on tasks that require your full attention.
01:17:56Studies even say that it's a better test aid than caffeine.
01:17:59There's nothing special in the gum, but the act of chewing wakes your brain up.
01:18:04The effect doesn't last long, though, just for 20 minutes.
01:18:07Embryos develop fingerprints at 3 months.
01:18:11Your bones are four times harder than concrete.
01:18:14The strongest bone in your body is the femur.
01:18:16It can support up to 30 times the weight of a grown-up person.
01:18:20Even crazier is that our bones are made up of composite material, meaning they're both
01:18:24hard and elastic at the same time.
01:18:28Sunburn is the result of radiation exposure.
01:18:31When your body's natural defense mechanism gets overwhelmed trying to fight UV rays,
01:18:36a toxic reaction occurs that results in sunburn.
01:18:39Goosebumps are an evolutionary reflex left over from our ancestors.
01:18:44The release of adrenaline made their hair stand up, and they look scarier to approaching predators.
01:18:50Your body produces 1 to 3 pints of saliva every day.
01:18:53It helps you digest food and fights off infections.
01:18:57You also have a lot of bacteria in your mouth.
01:18:59Yeah, that's right.
01:19:00The average amount of bacteria in a person's mouth is almost the same as the number of
01:19:04people living on Earth.
01:19:06That's hard to digest.
01:19:08Each human has roughly 150,000 hairs on their head.
01:19:12Every strand grows around one-half an inch per month.
01:19:15If we added the growth from each hair, it would measure the distance of 10 miles in
01:19:19just one year.
01:19:21Your hair is also a lot stronger than you think.
01:19:24A single strand can hold 3 ounces, which is the weight of an apple.
01:19:28If we combine the strength of all the hair on your head, it could support the weight
01:19:32of two elephants.
01:19:33Hey, let's try it.
01:19:35The beating sound your heart makes is the clap of valve leaflets opening and closing.
01:19:41Your heart doesn't replicate itself unless you have an injury.
01:19:44Your corneas are the only part of your body that don't get blood.
01:19:48They get oxygen directly through the air.
01:19:51When you're sitting or standing upright, it's easier for you to recall some positive
01:19:55memories that make you feel good.
01:19:57Some believe it's because sitting up with your back flat boosts blood flow and your
01:20:01brain gets more oxygen, which helps it function better.
01:20:05The man who has the deepest voice in the world, and that's definitely not me, can produce
01:20:10sounds that humans, including him, can't hear at all.
01:20:14But elephants can hear those sounds.
01:20:17Veins look blue because light has to go through layers of skin and fat to reach them.
01:20:23Your skin scatters a lot of the red portion of white light before it reflects the blood.
01:20:28This leaves only the blue light to bounce back to your eyes.
01:20:31A person who has anosmia is unable to detect smells.
01:20:36Antosmia is the opposite condition, when someone smells an odor that isn't actually there.
01:20:42The human brain has 100 billion neurons.
01:20:45It's 73% water, and the same is true about the heart.
01:20:49That's why if your brain loses even 2% of its liquid, you start to feel tired.
01:20:54It also makes your memory worse, shortens your attention span, and puts a dampener on
01:20:59your mood.
01:21:00The earliest known person to have had blue eyes lived in the Stone Age, 7,000 years ago.
01:21:06Your right kidney is probably smaller and sits lower down than your left kidney to make
01:21:11room for your liver.
01:21:13By the way, your brain makes sure you don't drink too little or too much water.
01:21:18After you swallow some liquid, your mouth and throat start to fire signals to your brain,
01:21:23telling it to stop drinking.
01:21:24Otherwise, you'd keep gulping down water for the entire 10-60 minutes it takes the liquid
01:21:29to get to your cells.
01:21:31Your eyes can see something for a mere 13 milliseconds, and your brain will already
01:21:36process this image.
01:21:38The average blink lasts from 100 to 400 milliseconds.
01:21:42Even though the tongue isn't the strongest muscle in your body, it never gets tired.
01:21:47That's because of the way it's built.
01:21:49It's made up of 8 interwoven muscles.
01:21:52The tongue is the only muscle with ends not connected to bone.
01:21:56Other muscles join two bones at both ends because that's how we pull and make a motion.
01:22:02There are around 700 different species of bacteria in your mouth.
01:22:06Over 6 billion of them live there.
01:22:09Your skin is your largest organ.
01:22:12It can cover the surface area of two bath towels.
01:22:15It accounts for around 16% of body weight and is around 22 square feet.
01:22:20If you typed 60 words per minute for 8 hours a day, it would take you 50 years to type
01:22:26the human genome.
01:22:28You get tired pretty quickly when you're out in the heat.
01:22:31This happens because your body is trying really hard to keep itself cool, which puts a lot
01:22:35of extra work on it.
01:22:37So you get exhausted and tired, even if you don't do anything physically demanding.
01:22:43Your body has 78 organs, but only 5 of them are essential for survival.
01:22:48The brain, liver, kidney, lungs, and heart.
01:22:52Oh, the phone's ringing.
01:22:54Must be something urgent.
01:22:55At 11pm.
01:22:57Only all the gadgets in the house are silent.
01:22:59It's your ears that are ringing.
01:23:02You can also hear some hissing, whistling, buzzing, and even roaring.
01:23:06But all this noise doesn't have an external source.
01:23:10That's why it's known as phantom sounds.
01:23:12They can occur in one or both ears, constantly or from time to time.
01:23:17They're usually most noticeable at night, when nothing distracts you.
01:23:21Women have more taste buds on the surface of their tongues than men do.
01:23:25That's one of the reasons why 35% of ladies and only 15% of guys are super tasters.
01:23:31Those are people who feel flavors more strongly than others.
01:23:35Left-handed people usually prefer to chew on the left side.
01:23:39And right-handed people, well, you guessed it, chew on the right.
01:23:43Even if your fingerprints are damaged, they'll grow back in the same unique pattern.
01:23:48When breathing, a single lung only uses 5% of the oxygen you've inhaled.
01:23:56You can't recall a memory all by itself.
01:23:59When you're trying to think of one detail, like the color of the t-shirt your friend
01:24:03was wearing the other week, you'll remember some other details too.
01:24:07For example, the place where you saw him, things you were talking about.
01:24:12The hippocampus is the part of your brain that stores memories.
01:24:16It usually packs them together, including multiple small details.
01:24:21On average, taste buds last 10 days, clusters of sensory cells in your tongue.
01:24:26The buds that are closer to the surface are more short-lived.
01:24:30That's the reason you don't have to wait for too long to be able to taste again after burning
01:24:33your tongue.
01:24:36One theory says deja vu is some sort of a brain processing lag.
01:24:41Scientists think it might happen when your brain is transferring information from one
01:24:44side to the other, and there's a split-second delay in that process.
01:24:49That means that your brain gets the same information twice and processes it as the event that happened
01:24:54before.
01:24:56Only 30% of people can flare their nostrils, and one-third can bend their thumb backward.
01:25:03Some people can produce a roaring noise in their heads.
01:25:07All they have to do is tense their ears or jaws.
01:25:10There's a small muscle in the ear.
01:25:12It dampens loud sounds, like when you're chewing.
01:25:15But some people can flex that muscle, and that creates an audible rumble.
01:25:21Your fingertips are sensitive, but hundreds of times less so than your lips.
01:25:27You inhale lots of different types of debris, including 700,000 of your own skin flakes.
01:25:32And that's only in a day.
01:25:35A hypnic jerk is a twitch you can experience when falling asleep.
01:25:40It's an abrupt muscle movement that comes during the non-REM sleep phase.
01:25:44It can create an illusion of falling.
01:25:48One of the theories is that, when you're dozing off, your brain sees the relaxing of your
01:25:52muscles as a sign you're in trouble and really falling.
01:25:55So it sends signals to the muscles to protect you by tensing up.
01:26:01Synesthesia is a special and rare ability where people can taste music or hear colors.
01:26:06Only one in every 2,000 people has it.
01:26:11For some people, cilantro may taste similar to soap because the plant contains a chemical
01:26:15used in soap making.
01:26:17But only 4 to 14% of the world's population have special genes that can detect it.
01:26:2318% of people can move both ears at the same time, while 22% can move one ear at once.
01:26:31People who do it use weak vestigial muscles we got from the ancestor humans, who had this
01:26:35in common with cats.
01:26:39Bruises change their color over time.
01:26:41A bruise appears because there's bleeding under the skin.
01:26:44Tiny blood vessels get crushed, and some blood gets trapped in there.
01:26:48In the beginning, a bruise is red because the blood is rich in oxygen.
01:26:52But then it turns purple, green, yellow, or even gray when the levels of oxygen drop.
01:26:59Sweat doesn't smell itself.
01:27:01The unpleasant odor is caused by bacteria on your skin.
01:27:05When sweat comes out of the pores on your body, the bacteria breaks it down into acids.
01:27:09What most deodorants actually do is get rid of the bacteria on your skin.
01:27:15People used to dream in black and white much more than today.
01:27:18That's because they watched black and white TV.
01:27:22Blue cheese is another thing that affects your dreams and makes them more vivid.
01:27:27Eggshells might be used for growing new human bones.
01:27:30Certain eggshells contain calcium carbonate, which is something you also have in your bones.
01:27:37The food on the plane is likely to taste different than on the ground.
01:27:40That's because you lose up to 30% of your taste bud sensitivity due to the dryness and
01:27:45pressure in the cabin.
01:27:47It's especially true about salty and sweet foods.
01:27:51Your nostrils don't work with the same efficiency all the time.
01:27:54When you breathe, one nostril does most of the work, and they switch every couple of
01:27:58hours.
01:28:00You wouldn't be able to taste food without saliva.
01:28:03Your taste buds have chemoreceptors that recognize different flavors, but they need some liquid
01:28:07for those flavors to bind into their molecules.
01:28:10Also, you can't taste things saliva doesn't dissolve.
01:28:15The brain can't actually feel pain.
01:28:18It does have a pain center, but it doesn't have pain receptors itself.
01:28:22When your head hurts, you can feel it because of the nerves, tissues, and blood vessels
01:28:26around your brain.
01:28:29A single human hair can support 3.5 ounces of weight.
01:28:32That's how much two candy bars weigh.
01:28:36Toenails grow almost four times more slowly than fingernails that get more exposure and
01:28:41are used more frequently.
01:28:43There must be at least some photos where you have red eyes.
01:28:46When the camera's flash goes off, your eyes aren't prepared for such an influx of light.
01:28:51Your pupils remain dilated, which is why the light gets reflected off the red blood vessels
01:28:55of the choroid.
01:28:57This is a layer of tissue at the back of your eye that nourishes your retina.
01:29:02The right lung is bigger than the left one because your body needs to make some room
01:29:05for the heart.
01:29:07Your teeth are the only part of your body that can heal itself.
01:29:12The masseter is the strongest muscle you have, based on its weight.
01:29:16Together with the rest of the raw muscles, it can close your teeth with a force of 200
01:29:20pounds on the molars and 55 pounds on the incisors.
01:29:26Onions produce a special chemical irritant.
01:29:29It stimulates special glands in your eyes, causing them to release tears.
01:29:34Your nose can memorize up to 50,000 different scents and detect more than one trillion of
01:29:39odors.
01:29:41We all have our unique smell, except for identical twins.
01:29:45This smell is partly determined by genetics, but it also depends on your diet, hygiene,
01:29:50and the environment.
01:29:53Eating snow is not the best way to stay hydrated.
01:29:55Your body needs too much energy to turn it into water.
01:29:59Snow can provide a bit of hydration, but it'll also lower the temperature of your body, which
01:30:04isn't the best scenario if you're trying to survive harsh winter conditions.
01:30:09You burn somewhere between 100 and 200 calories per hour while standing.
01:30:14Sitting burns 60 to 130 calories, depending on your height, weight, gender, and age.
01:30:22Brain freeze is an annoying ice cream headache.
01:30:25That's how your brain tells you to slow down and maybe stop eating something that's so
01:30:29cold.
01:30:30The main purpose of eyelashes is to shield your eyes and protect them from sand, moisture,
01:30:35dust, and debris in the air.
01:30:37Your eyelashes sense when something comes up too close to your eyes, like an insect
01:30:41flying toward you, and trigger your blink reflex.
01:30:45Blinking also helps when you need to flush out some tiny particles or debris stuck in
01:30:49your punk dot.
01:30:51Those are small openings you have in your eyelids.
01:30:53That's where the tears get pumped out.
01:30:56Your eyebrows stop sweat from running directly into your eyes.
01:31:00Your skin there, and the shape of your bones also work together to direct the sweat toward
01:31:04the sides of your face.
01:31:07We're not the fastest, strongest, or biggest in the animal kingdom, but we're the best
01:31:11at long-distance running.
01:31:13That's because we have long legs, and our bodies can lose excess heat through sweating.
01:31:18Even long ago, our ancestors hunted animals by chasing them for long periods of time.
01:31:23Eventually, it wore smaller creatures out.
01:31:27Five basic senses are taste, touch, sight, sound, and smell.
01:31:32But people have more senses than that.
01:31:35Proprioception is when your body is aware of its parts and their position, even if you
01:31:39don't see them.
01:31:40Like if your arm is behind your back, you know it's there.
01:31:43If you were an octopus, you wouldn't know it, because these creatures don't know their
01:31:47arms exist if they can't see them.
01:31:49Thermoception is your ability to sense temperature.
01:31:53Equilibrioception is a sense of balance.
01:31:55You also have gnosisception, which means you can feel pain.
01:31:59Then there's chronoception.
01:32:00That's how you can sense time passing by.
01:32:04There are even more senses found in the animal kingdom.
01:32:07Electroreception and magnetoreception.
01:32:10But people don't have those.
01:32:13You can't see your taste buds.
01:32:15Those little bumps on the tongue are lingual papillae.
01:32:18There are four kinds of them.
01:32:20Circumvalate, foliate, fungiform, filiform.
01:32:25They are all covered with taste buds, except for the last one, filiform.
01:32:29This one is responsible for the sense of touch in your tongue.
01:32:34Your pinky holds 50% of the total strength in your hand.
01:32:39Your liver is a very important organ that works a lot and is responsible for 500 individual
01:32:44functions.
01:32:45Up to 10% of it is made of fat.
01:32:48The liver can regenerate.
01:32:51You can burn calories when you take a hot bath, as many as you would if you took a half
01:32:55hour walk.
01:32:58People mostly need 7 minutes to fall asleep.
01:33:00This time gets shorter if you've just had a large tasty meal.
01:33:05On average, the heart is as big as your fist.
01:33:08It beats 115,000 times and pumps around 2,000 gallons of blood a day.
01:33:16Alright, quick question.
01:33:18Do you think you know everything about your own body?
01:33:21Are you sure?
01:33:22Well, how about the fact that 25% of an adult's bones are in their feet?
01:33:27Or that taste buds aren't actually those bumps on your tongue?
01:33:30Well, get ready for some eye-openers!
01:33:32Ow!
01:33:33No, no, we're really not going to open someone's eyes.
01:33:37I don't do surgery here on the bright side.
01:33:40Well, maybe in a future video.
01:33:42Anyway, here we go with a big batch of biological background bots to boggle your brain.
01:33:48Your stomach gets a new lining every 3-4 days.
01:33:51This way, your body prevents the stomach from digesting itself.
01:33:56Your brain contains more than 86 billion nerve cells, which are joined with one another by
01:34:00100 trillion connections.
01:34:02That's many more than the number of stars in our home Milky Way galaxy.
01:34:07By the way, if you decided to count all those numerous nerve cells in your brain, it would
01:34:12take you up to 3,000 years.
01:34:14Better get started!
01:34:16Your fingernails grow faster on your dominant hand.
01:34:19In other words, if you write with your right hand, you'll have to trim those nails more
01:34:23often.
01:34:24Your fingernails also grow faster in the summer and during the day.
01:34:28When your brain sends messages to different parts of your body, the signals travel along
01:34:33your nerves at a speed of up to 270 mph.
01:34:37That's way faster than a sports car!
01:34:39People spend more than 4 years of their lives eating.
01:34:42Wow, is the restaurant service that slow?
01:34:45Just kidding!
01:34:47The fastest muscles in your body are those that make your eyes blink.
01:34:51Their contraction speed is one blink in less than one hundredth of a second.
01:34:55In a day, you can blink more than 15,000 times.
01:35:00In their lifetime, the average person processes more than 100,000 pounds of food.
01:35:05That's more than the weight of 7 elephants combined.
01:35:08And how do you eat an elephant?
01:35:09Yep, one bite at a time.
01:35:12If someone decided to uncoil the human DNA, the whole thing would stretch for 10 billion
01:35:17miles, which is 40,000 times more than the distance between the Earth and the Moon.
01:35:22If you don't have insomnia, you're likely to spend around one third of your life asleep.
01:35:27But there are creatures that sleep even more.
01:35:30For example, for a dog, this time is 44% of their life.
01:35:35And for a python, 75%.
01:35:38During just one day, all the blood in your body travels more than 12,000 miles.
01:35:43That's half as long as the distance around Earth.
01:35:46Your skeleton will renew itself completely within 10 years.
01:35:50And yes, without surgery.
01:35:53An adult uses around 200 muscles to make just one step.
01:35:57And don't tell me I don't work out enough!
01:36:00Every minute your body sheds more than 3,000 skin cells.
01:36:04That's almost 200,000 skin cells per hour and more than 9 pounds per year.
01:36:09Hey, it's the shedding skin cells weight loss plan!
01:36:13But don't worry, you still have about 300 million skin cells at any given moment.
01:36:18Plus, your skin completely renews itself every 28 to 30 days.
01:36:23The liver is the only human organ that can regenerate completely.
01:36:27As little as 25% of the original liver weight can get back to its full size.
01:36:33Skin cells create a lot of dust, not only under your bed, but also in the Earth's atmosphere.
01:36:39If someone collected all the flaked-off skin cells floating in the air, this dust would
01:36:43weigh up to a billion tons.
01:36:46It's 150 times the weight of the Great Pyramid.
01:36:49How's that for a comparison?
01:36:51Now, you won't see your taste buds by the naked eye because they're too tiny.
01:36:56The small bumps most people take for taste buds are called papillae.
01:37:00Real taste buds are on top of these hair-like projections.
01:37:04By the way, taste buds also have a very short life cycle.
01:37:08They live for no longer than 10 to 14 days, so they get a very short taste of life.
01:37:14The average person has more than 100,000 hairs on their head.
01:37:18And since this hair grows about 6 inches per year, it'll make more than 40 feet in a lifetime!
01:37:25Some people can hear their eyeballs moving inside the eye sockets.
01:37:29That must be no fun.
01:37:31Unlike other parts of your body, your ears and nose never stop growing.
01:37:36That must be no fun.
01:37:38Your skin wrinkles if you stay in the water for too long, but not because it absorbs water.
01:37:43When your body's wet, wrinkled fingers and toes provide you with a better grip.
01:37:48You know, like when the treads on your car tires grip the road better when they're new?
01:37:53Your eyes are an amazing instrument.
01:37:55They can distinguish between 10 million different colors.
01:37:59Your brain uses more than 20% of your body's energy, even when you're resting.
01:38:04When you're asleep, it still consumes almost as much power as when you're awake.
01:38:08It also burns about 330 calories per day at that!
01:38:12An adult person has about 25% of all their bones in their feet.
01:38:18Most of them are tiny but crucial.
01:38:20If these bones are out of alignment, so is the rest of the body.
01:38:24You breathe around 20,000 times a day.
01:38:27Try not to stop.
01:38:28I actually set a personal best record today for consecutive days breathing, and I plan
01:38:33to top that tomorrow.
01:38:36Human bones are a real paradox.
01:38:38They're almost 5 times stronger than a steel bar with the same width, but can fracture
01:38:42on impact and are rather brittle.
01:38:46Fingers don't have muscles that can make them move.
01:38:48All the muscles that move the finger joints are located in the forearm and palm.
01:38:54Your body contains more than 37 trillion cells.
01:38:57Earth has more than 7 billion inhabitants.
01:38:59It means that there are over 5,000 times more cells in your body than people on our planet.
01:39:06It surely depends on your lifestyle and on how much you move, but the average person
01:39:10will walk up to 110,000 miles in their lifetime, which is half as long as the distance from
01:39:16Earth to the Moon, or more than 4 times longer than the distance around our planet.
01:39:22If a person has anosmia, also called smell blindness, they can't distinguish and detect
01:39:28smells.
01:39:29But they can still be smelly.
01:39:32You start feeling thirsty when water loss is 1% of your body weight.
01:39:37More than 5%, and you may faint.
01:39:39Water loss that's bigger than 10% of the body weight and dehydration can end a person,
01:39:45if you know what I mean.
01:39:46The strongest muscle in your body based on its weight is your jaw muscle.
01:39:51Mine is way overdeveloped.
01:39:54At any moment, 50,000 cells in your body are getting replaced by new ones.
01:39:58Boy, that sounds like a company I used to work for.
01:40:02By the end of their life, the average person can recall up to 150 trillion pieces of information,
01:40:08except where they left their car keys.
01:40:10Even if fingerprints are badly damaged, they can still grow back with their original pattern.
01:40:16Your most powerful sneeze can travel at a speed of more than 100 miles per hour, almost
01:40:21as fast as a skydiver in free fall.
01:40:24The average person has about 250 hairs in each eyebrow.
01:40:28These hairs get completely replaced every 4 months.
01:40:32Your brain's memory capacity is equivalent to about 4 terabytes on a hard drive, which
01:40:37is more than 8 million photos.
01:40:40People are the only living creatures that can naturally sleep on their backs.
01:40:44Even apes usually sleep in a sitting position, leaning on something.
01:40:49Your longest bone is your thigh bone, not your funny bone, and the tiniest one is in
01:40:54your ear.
01:40:55It's shorter than a grain of rice.
01:40:57The largest organ in your body is your skin.
01:41:00Despite being thin, it weighs a surprising 9-11 pounds.
01:41:04That's the weight of a healthy and well-fed house cat.
01:41:08Your skull may feel like it's all in one piece, but in fact, it consists of 29 different
01:41:14bones.
01:41:15The only part of your body that can't heal itself is your teeth.
01:41:19What a shame.
01:41:21Right-handed people tend to chew most of their food on the right side of their mouths, while
01:41:25the left-handed opt for the other side.
01:41:29Out of all people who can move their ears, only 30% can move just one ear.
01:41:35Such talent!
01:41:37Every person has dimples on their lower back.
01:41:40But in some people, they're more pronounced than in others.
01:41:43These dimples appear in places where the pelvis is connected with the sacrum, so their existence,
01:41:48even if it's not apparent, makes sense.
01:41:51Your right lung is shorter than the left one because it has to leave some room for your
01:41:56liver.
01:41:57The left lung, on the other hand, is narrower since it has to make space for the heart.
01:42:02A male's lungs can usually hold more air than a woman's.
01:42:06Surprisingly, you burn more calories when you're sleeping than when you're watching
01:42:10TV.
01:42:11Actually, that should tell you something helpful.
01:42:15By the time you turn 60, you're likely to lose 50% of your taste buds.
01:42:21Your hair grows twice faster when you're traveling by plane.
01:42:25It has to do with higher atmospheric pressure.
01:42:28The muscles that help your eyes focus make around 100,000 movements a day.
01:42:33If you want to make your leg muscles move as much, you'd need to walk 50 miles.
01:42:38When you listen to music, your heart starts beating in sync with it.
01:42:43Ay-yi-yi, about 6% of people can vibrate and rapidly shake their eyeballs back and forth.
01:42:49It doesn't mean something's not right with their eyes, it's just a unique trick they
01:42:53can perform.
01:42:54Good at parties, I suppose.
01:42:56Your bones are designed to be used a lot daily, and some of them can absorb two or even three
01:43:00times your body weight.
01:43:02That's impressive, but your teeth are even stronger.
01:43:05When you bite something, the teeth can exert incredible pressure, up to 200 pounds.
01:43:11By the way, the enamel is considered to be part of your skeletal system.
01:43:15Your stomach has a pretty incredible capacity, being able to hold up to half a gallon of
01:43:20liquid, a whole large bottle of Coke.
01:43:23It's pretty hard to estimate how much hard food you can squeeze into your stomach, since
01:43:27the food is processed with your teeth before it gets inside.
01:43:30There's definitely not enough room for a turkey, but a good-sized chicken will probably fit it.
01:43:36Whenever you rotate your hand, the bones inside it actually intersect.
01:43:41Grab your hand and verify it.
01:43:42Yeah, not very useful.
01:43:44Now, show me where your stomach is.
01:43:46If you're pointing at your tummy, sorry, but it's wrong.
01:43:50It's up here, hidden between your ribs.
01:43:53Fun fact about bones.
01:43:54You know that your body is about 60% water, right?
01:43:57What's new here is that your bones are in this too.
01:44:00About 25% of the human bone mass is made up of water.
01:44:05Scientists believe that the appendix isn't here to stay.
01:44:08Nobody really knows why we need it, but some researchers claim it helped our ancestors
01:44:12process the tree bark they were eating.
01:44:15As it's no longer part of our daily diet, the appendix can disappear from our bodies
01:44:19without any consequences.
01:44:22A human eye has some resemblance to a car engine.
01:44:25They both need various liquids to perform properly.
01:44:28An engine needs gasoline, and an eye needs tears.
01:44:31In order to work well, the tears should be thoroughly distributed all over the eye.
01:44:36That's why we blink up to 20,000 times a day.
01:44:39So a lid is a bit of a windshield washer.
01:44:42Almost all of our body is covered with hairs, even if we don't notice them.
01:44:46They grow even in the belly button.
01:44:48Their purpose is to catch lint.
01:44:50The only part of the human body that doesn't get any nutrients from blood is the cornea
01:44:55of the eye.
01:44:56Instead, it's fed by tears and fluid in the front of your eyes.
01:45:00If you never knew you had a personal bodyguard, look deeper.
01:45:04Your liver is your security guard, protecting you from toxins and many other things you
01:45:08don't want to have.
01:45:10It's also pretty indestructible and can even regenerate.
01:45:14When you blush, it means there's an increased blood flow in your body.
01:45:18Not only do your cheeks get somewhat red, but your stomach lining too.
01:45:22It's because it has plenty of blood vessels, and when there's more blood than usual, it
01:45:26turns red.
01:45:28Only about 43% of you is actually you.
01:45:31There are over 50% tiny little creatures that mainly live in your gut and other body parts
01:45:36without ever leaving it.
01:45:38Still, even though your own cells are fewer than microbial ones, there are, on average,
01:45:43about 100 trillion of them in you.
01:45:46Let's count them.
01:45:47You start.
01:45:48Your stomach has a lining replaced every 3-4 days.
01:45:52That's done to stop it from eating itself.
01:45:54The digestive acids we've got can be pretty damaging.
01:45:58One thing that surely rests while you're sleeping is your nose.
01:46:01You just won't smell anything nasty in your sleep.
01:46:04The thing is that your sense of smell basically deactivates at night.
01:46:08If there's some really terrible smell in your bedroom, you won't even be bothered.
01:46:13We can accidentally digest small objects, such as plastic items, glass, coins, and many
01:46:18other small objects.
01:46:20They pass their way through the digestive tract within 48 hours.
01:46:23Really, just trust me on this one.
01:46:25You have better things to do.
01:46:28We used to believe we could distinguish about 10,000 smells.
01:46:31Nope.
01:46:32Recent research showed that people were able to distinguish more than a trillion smells.
01:46:37We also remember them better than anything else, and smells can even evoke some distant
01:46:42memories.
01:46:43We can digest tiny quantities of plastic, but the human digestive system can't really
01:46:48bear grass.
01:46:49Grazing animals have special teeth and several stomachs to process raw leaves and grass,
01:46:54while we have none of that stuff.
01:46:57But don't feel bad – among mammals, only humans can always walk on two hind limbs and
01:47:02keep that posture for their entire lives.
01:47:04You might object that kangaroos or gorillas move in the same way, but the roos use their
01:47:09tail as a third leg, and gorillas use the help of their long arms to keep balance.
01:47:15The stomach is the most important defender of the immune system.
01:47:18Hydrochloric acid in our stomach kills dangerous food toxins, viruses, and bacteria that get
01:47:24in there with the food you eat.
01:47:26This acid can digest even the stomach itself, but the mucous membrane protects it.
01:47:31Body fat isn't just a nuisance – it acts as insulation material, energy reserve, and
01:47:36shock absorber.
01:47:37Your body sends the most fat into your waist region because that's where your internal
01:47:41organs are.
01:47:42If something happens to you, this layer of fat might as well protect your vitals from
01:47:47irreparable damage.
01:47:48We've got two really fast muscles – they control the eyelid closely.
01:47:53These are the fastest muscles in our body.
01:47:56Eyes are fragile and need protection.
01:47:57That's why, when the reflex is triggered, these muscles shut the eyes within about 100
01:48:02milliseconds.
01:48:03That's not more than 0.1 second!
01:48:06We recognize only purple-blue, green-yellow, and yellow-red colors.
01:48:11Everything else is a combination of these three.
01:48:13It's impossible to calculate how many of these combinations the human eye sees because
01:48:18every person has slight visual differences, but it's about 1 million combinations on
01:48:23average.
01:48:24Even if you brush your teeth twice a day and never forget about mouthwash, your mouth still
01:48:29stays one of the dirtiest parts of the human body.
01:48:33Millions of bacteria live inside it.
01:48:35The good news is that most of these bacteria are good for the body and protect it from
01:48:40bad bacteria and viruses.
01:48:42The second dirtiest place is the belly button, and it's probably because it's the first
01:48:47ignored place.
01:48:48The thing is, we don't really use them after we're born, so this forlorn area accumulates
01:48:54all kinds of germs, sweat, and dirt.
01:48:57The belly button has over 2,300 bacterial species, and it does need extra attention.
01:49:03You think you owe your strong handshake to all your strength workouts?
01:49:07Well, you're more likely to owe it to your pinky.
01:49:10Just kidding.
01:49:11Anyway, a pinky is the strongest finger out there.
01:49:14This humble finger is responsible for 50% of your hand strength.
01:49:18Still, the most used finger is the thumb.
01:49:21It takes to itself 40% of the hand's action.
01:49:24Well, it probably makes it the most important finger too.
01:49:28Two more humble helpers are your toes that carry about 40% of your weight.
01:49:33If you've ever heard that humans don't really need their toes, don't believe it.
01:49:36They're also the main pushers when you walk.
01:49:40Tomatoes have more genes than humans.
01:49:42This shouldn't concern you, though, because it's not the number of genes that matters,
01:49:46but the complexity of their connections.
01:49:49Nails don't only help us catch random objects and peel the stickers off.
01:49:53If you didn't have a rigid structure against which to press, you wouldn't be able to
01:49:57judge how firmly to hold anything.
01:50:00Our hair color is easily explained by genes.
01:50:03There are not more than 2% of people with naturally red hair.
01:50:07They're followed by blondes, about 3%.
01:50:10And all the varieties of brown shades, only about 11%.
01:50:14The vast majority goes to black hair, including very dark brown.
01:50:19Yeah, your hair can stop growing at a certain length.
01:50:21A hair usually grows from 2 to 7 years, so usually it doesn't exceed 42 inches.
01:50:27Well, tell that to this gal from China who broke all the hair records with the longest
01:50:32hair ever.
01:50:33In 2004, her hair was 18 feet, 5.5 inches long.
01:50:38Rapunzel, where have you been, girl?
01:50:41When we laugh, think, look at something, dream, move, or do some other activity with our body,
01:50:47small electrical and chemical signals run between neurons along those connections.
01:50:52Our brain is always active, sometimes even more when we're sleeping than when we're
01:50:57awake.
01:50:58And by that, neurons make and send more information than all the phones in the whole world.
01:51:03You're sitting somewhere outside, and an insect lands on your leg.
01:51:07Your skin has sensory neurons, and they quickly send the message to your brain at an impressive
01:51:12speed, 150 miles per hour.
01:51:15The brain sends back the message to your leg to shake the insect off very fast, and
01:51:19the speed that information travels is even bigger, 200 miles per hour.
01:51:26Toenails grow around 4 times slower than your fingernails.
01:51:29This happens because we do more things with our hands compared to feet, which is why we
01:51:33cause more trauma to our fingernails.
01:51:35There's a high possibility your right hand has different types of microbes than the left
01:51:40one.
01:51:41This happens because they cover our skin from head to toe, and their variety depends on
01:51:46our skin thickness, humidity, temperature, texture, and chemistry, which can change as
01:51:51we use our right and left hands in different ways.
01:51:54Our nails and hair are made of keratin, which is a material we find in certain body parts
01:51:59of some other animals as well.
01:52:01For instance, claws, hooves, horns, wool, fur, feathers, beaks, turtle shells, and porcupine
01:52:08quills.
01:52:09Our body is made of stardust.
01:52:12Really!
01:52:13The more complex elements in our body can only come about through supernovas.
01:52:17The first stars were just gassy lumps that were drawn together and, at some point, started
01:52:22the process of combustion.
01:52:25This finally led to a nuclear reaction in its center.
01:52:28Stars that were there right after the Big Bang were over 50 times bigger than our Sun
01:52:32is now.
01:52:33Inside of them, there was a constant process of making the elements, and those large stars
01:52:38were burning their fuel faster.
01:52:40Most of the elements in the human body were formed in those stars over billions of years,
01:52:44so you could realistically say that part of you is immortal.
01:52:49Cool, huh?
01:52:51There's more nerve cells and connections in your brain than there's stars in the Milky
01:52:57Way.
01:52:58If you decided to count them all, it'd take you 3,000 years.
01:53:02To make it easier for you, you have about 100 billion neurons in there.
01:53:06The brain can't actually feel pain.
01:53:09It does have a pain center, but it doesn't have pain receptors itself.
01:53:13When your head hurts, you can feel it because of the nerves, tissue, and blood cells around
01:53:17your brain.
01:53:18Your RAM, or working memory, is an essential thing that we need to perform almost any everyday
01:53:24activity, including conversations, surfing the net, and even petting your dog.
01:53:29Our strongest and emotional memories are often fake.
01:53:32The central memory gives us the confidence to believe that we remember everything, even
01:53:36though most of the details are made up in our heads.
01:53:40When we laugh, think, look at something, dream, move, or do some other activity with our body,
01:53:46small electrical and chemical signals run between neurons along those connections.
01:53:51And by that, neurons make and send more information than all the phones in the whole world.
01:53:58You're sitting somewhere outside and an insect lands on your leg.
01:54:01Your skin has sensory neurons and they quickly send the message to your brain at an impressive
01:54:06speed, 150 miles per hour.
01:54:09The brain sends back the message to your leg to shake the insect off very fast, and the
01:54:14speed that information travels is even bigger, 200 miles per hour.
01:54:19Our brain can store only 7 bits in its short-term memory.
01:54:24Don't even try to compare your brain with a phone's capacity, not even the one you had
01:54:28back in 2005.
01:54:30That's why you can't even learn a phone number by heart.
01:54:33Our short-term memory functions just like a chalkboard.
01:54:36You can get some information, but sooner or later, you run out of space.
01:54:40To check your working memory capacity, try this test.
01:54:43Ask a friend to write a list of 10 words and read it to you.
01:54:48Most people recall 7 or fewer items from the list.
01:54:52Synesthesia is a special and rare ability when people can taste music or hear colors.
01:54:59Only 1 in every 2,000 people has it.
01:55:03Five basic senses are taste, touch, sight, sound, and smell, but people have more senses
01:55:09than that.
01:55:11Proprioception is when your body is aware of its parts and their position, even if you
01:55:16don't see them.
01:55:17Like if your arm is behind your back and you know it's there.
01:55:21If you were an octopus, you wouldn't know it, because these creatures don't know their
01:55:25arms exist if they can't see them.
01:55:28Thermoception is your ability to sense temperature.
01:55:32Equilibrioception is a sense of balance.
01:55:35You also have gnosisception, which means you can feel pain.
01:55:39Then there's chronoception.
01:55:41That's how you can sense time passing by.
01:55:44There are even more senses found in the animal kingdom, but people don't have those.
01:55:50You can't recall a memory all by itself.
01:55:52When you're trying to think of one detail, like the color of the t-shirt your friend
01:55:56was wearing the other week, you'll remember some other details too.
01:56:00For example, the place where you saw him, things you were talking about.
01:56:05The hippocampus is the part of your brain that stores memories.
01:56:08It usually packs them together, including multiple small details.
01:56:13On average, taste buds last 10 days.
01:56:17One theory says, déjà vu is some sort of a brain processing lag.
01:56:22Scientists think that it might happen when your brain is transferring information from
01:56:25one side to the other, and there's a split-second delay in that process.
01:56:30That means that your brain gets the same information twice and processes it as the event that happened
01:56:35before.
01:56:36It can create an illusion of falling.
01:56:39One of the theories that when you're dozing off, your brain sees the relaxing of your
01:56:43muscles as a sign you're in trouble and really falling.
01:56:47So it sends signals to the muscles to protect you by tensing up.
01:56:52You can physically see your nose, but the brain chooses to ignore it, otherwise it would
01:56:56stand in the way of your vision.
01:56:58Plus, it would be out of focus.
01:57:01Brain freeze is an annoying ice cream headache.
01:57:03That's how your brain tells you to slow down and maybe stop eating something that's so
01:57:07cold.
01:57:10People mostly need 7 minutes to fall asleep.
01:57:13This time gets shorter if you've just had a large tasty meal.
01:57:17People used to dream in black and white much more than today.
01:57:20That's because they watched black and white TV.
01:57:24Around 12% of people can't dream in color nowadays.
01:57:28All your muscles relax at the same time, right after you've fallen asleep.
01:57:32Your brain thinks you're about to fall asleep and sends quick signals to all of your muscles
01:57:36to awaken them.
01:57:37That's why it sometimes feels like you're literally falling.
01:57:41The hypnic jerk is a twitch you can experience while falling asleep.
01:57:45It's an abrupt muscle movement that comes during the non-REM sleep phase.
01:57:50If you sleep, it doesn't mean all your body sleeps.
01:57:53In fact, sometimes, your brain has to work even harder when you're asleep.
01:57:57It needs to process tons of information, and reports usually take a lot of time.
01:58:04By the time you wake up, you'll have forgotten 50% of your latest dream.
01:58:08After 10 minutes, you won't remember 90% of it.
01:58:12When you blush, your stomach lining goes red along with your face.
01:58:16It happens because your sympathetic nervous system's causing an increased blood flow
01:58:20throughout the body.
01:58:22Your hair follicles have the same receptors as your nasal passages.
01:58:25That's why your hair can detect scents, too.
01:58:28Sandalwood can help you develop that superpower.
01:58:32The nose definitely gets a good rest while you're sleeping.
01:58:35Amazingly, your sense of smell basically deactivates at night.
01:58:39You wouldn't even be bothered if there was a terrible smell in your bedroom.
01:58:43No comment.
01:58:44When you age, your brain is gradually reducing in size.
01:58:48By age 75, it's much smaller than at 30.
01:58:51And it starts shrinking by the age of 40.
01:58:54It happens to everyone, and it doesn't affect your mental strength in any way.
01:58:59No matter how hard you try, you'll never be able to tickle yourself.
01:59:03It's because your brain prepares the body for tickling and helps you avoid the typical
01:59:07laughing reaction.
01:59:11We recognize only purple-blue, green-yellow, and yellow-red colors.
01:59:16Everything else is a combination of these three.
01:59:19It's impossible to calculate how many of these combinations the human eye sees, because every
01:59:24single person has slight vision differences.
01:59:27But it's about 1 million combinations on average.
01:59:30You see?
01:59:33Heads up!
01:59:34Your skull isn't a single bone.
01:59:36It actually consists of 28 different bones, many of which are fused together to protect
01:59:41your brain.
01:59:43The strongest muscles in your body aren't in your arms or legs.
01:59:46They're in your head.
01:59:48The masseter is the main muscle responsible for chewing, and it needs to be the strongest
01:59:53for you to eat normally.
01:59:55And you know those muscles that allow you to move your ears?
01:59:58Those are temporalis.
02:00:00Located above your temples, they also help you to chew your food.
02:00:04Now we've got two really fast muscles.
02:00:06They control the eyelid closing.
02:00:08In fact, they're the fastest muscles in our body.
02:00:12Eyes are fragile and need protection, so the reflex that protects them needs to be as fast
02:00:17as lightning.
02:00:18These muscles can shut the eyelids in less than a tenth of a second.
02:00:24Our body is made of stardust.
02:00:27Really!
02:00:28The more complex elements in our body can only come about through supernovas.
02:00:33The first stars were just gassy lumps that were drawn together and, at some point, started
02:00:38the process of combustion.
02:00:40This finally led to a nuclear reaction in its center.
02:00:44Stars that were right there after the Big Bang were over 50 times bigger than our sun
02:00:49is now.
02:00:51Inside of them, there was a constant process of making the elements, and those large stars
02:00:56were burning their fuel faster.
02:00:58Most of the elements in the human body were formed in those stars over billions of years
02:01:03ago.
02:01:04So you could realistically say that part of you is immortal.
02:01:07Cool, huh?
02:01:09That's it for today!
02:01:10So, hey, if you pacified your curiosity, then give the video a like and share it with your
02:01:14friends!
02:01:15Or, if you want more, just click on these videos and stay on the Bright Side!