65+ Body Facts I Had to Fact-Check to Believe

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Transcript

00:00:00I've tried this one myself too. Pinch your elbow as hard as you can. You barely feel

00:00:05pain. How come? Well, different areas of your skin have different nerve endings. Our bodies

00:00:12are designed to be more sensitive to pain in places that are at higher risk of getting

00:00:16damaged. Those important parts have more nerve endings so that we're more alert and able

00:00:21to protect ourselves. And thick skin, like that on elbows, has fewer pain detectors.

00:00:27Now I'm not talking about the tingling, jolting pain you can feel when you hit your elbow

00:00:32against something. Oh, that feels almost like your entire arm has been electrocuted. It's

00:00:37not a feeling I would consider funny. But it comes from the funny bone. Now the funny

00:00:42bone isn't actually a bone. It's a nerve that starts in your spine, goes through your

00:00:47neck, through your elbow, and through your fingers. Its real name is the ulnar nerve.

00:00:53It's one of the three primary nerves in your arm, and it provides sensation to the fingertips.

00:00:59Your ulnar nerve is well-protected by muscle, fat, and bone. But there's one spot at your

00:01:04elbow where this nerve is exposed, and that spot is… yeah, the funny bone. A different

00:01:10but real version of Achilles' story, huh? Okay, so now you know why it hits so different

00:01:16when you bump your funny bone and why you feel nothing when you pinch your elbow.

00:01:21Now the next phenomenon is related to socially awkward moments. Okay, maybe not entirely.

00:01:26It might happen when your crush gives you a compliment. I'm talking about blushing.

00:01:32Now I'm not sure those butterflies in your stomach exist when you're in love. But I'm

00:01:37sure of this, when you blush, your stomach lining also turns red. Yeah, I've looked.

00:01:43The stomach lining is the tissue that protects your stomach walls from the acid inside. When

00:01:48you blush, it also turns red because blushing happens when the blood rises to the surface

00:01:53of the skin. This affects the stomach too. Now this is a natural process, a physiological

00:01:59response to the change in your emotions. Now since we're talking about the stomach, it

00:02:04might be a good time to mention that the stomach fluid has the ability to melt a steel table.

00:02:10Yep, this means the acid would be able to digest your internal organs. Luckily, the

00:02:15stomach lining prevents this from happening.

00:02:18Number three is about letting you know that you can glow in the dark. Now don't turn

00:02:22off the lights just yet, you can't see it with the unaided eye. These visuals of glittering

00:02:27human bodies come from ultra-sensitive cameras. Japanese scientists were the first to capture

00:02:33the images of human bioluminescence. Only ultra-sensitive cameras can reveal that our

00:02:38bodies emit tiny amounts of light because this light is a thousand times weaker than

00:02:43the human eye can detect. Apparently, all living creatures produce a small amount of

00:02:48light thanks to the chemical reactions in their cells. Humans are newly added to this

00:02:54list. The researchers had been photographing the upper bodies of the volunteers for several

00:02:59days. The results showed that the amount of emitted light followed a 24-hour cycle. The

00:03:04glow is at its highest in late afternoon and lowest late at night. Plus, the brightest

00:03:10light is emitted from the cheeks, forehead, and neck. Interestingly, this does not correspond

00:03:15with the brightest areas caught by thermal cameras.

00:03:19Did you know you're a little bit taller in the morning than you are later at night? Yes,

00:03:23I've been measuring you. Seriously. This height difference is related to gravity. Its

00:03:29force compresses the cartilage in your spine and knees when you stand up or sit down throughout

00:03:34the day. But when you're lying down, your spine decompresses and relaxes. That's why

00:03:40when you wake up in the morning after resting in bed all night, you're taller. The increase

00:03:45in height is not even above an inch, so don't bet on who is taller after hearing this information.

00:03:51Fun fact, astronauts returning from a mission are a few inches taller than they usually

00:03:56are on Earth. It's because of the lack of gravity on the International Space Station.

00:04:01They don't remain that tall forever, though. When they're on the Earth again, gravity

00:04:05gradually squeezes them back down to their usual height.

00:04:10Let's get back to the organ we've already spoken about – the skin. Yes, the skin is

00:04:14an organ. In fact, it's the largest organ in your body. It contributes to about 15%

00:04:20of your body weight. What else does this organ do, besides covering your body? It performs

00:04:25vital functions. For instance, it protects your body from external physical and biological harm.

00:04:31Plus, it prevents excessive water loss. I can't help wondering what other surprises

00:04:36the human body has in store for us. But right now, let's move on to the animal planet.

00:04:43Owls don't have eyeballs. Instead, they have something called eye tubes. Their rod-shaped

00:04:48eyes do not move in their sockets as our eyeballs do. That's why owls would have to move their

00:04:54entire bodies to look around. But moving their torsos would make some noise, and other animals

00:04:59would hear it. So, owls have evolved to have necks that can twist to around 270 degrees,

00:05:06and they move super silently. But why the concern? Well, night vision requires large corneas to get

00:05:13as much light as possible. This is the main reason why most nocturnal animals, such as the slow

00:05:18loris or tarsier, have big eyes. For owls, it works a little differently. Since they have small

00:05:24heads, such large eyes wouldn't be able to fit inside. Now, even though these creatures don't

00:05:30have eyeballs, they have three sets of eyelids. One set is for blinking, one is for sleeping,

00:05:35and the last one is for keeping their eye tubes clean. So, do the owls give a hoot about that?

00:05:41Yes, yes they do. Moving on from nocturnal animals to the ones you're more familiar with.

00:05:47Meow. Cats have an extra organ that allows them to taste scents in the air.

00:05:52This organ is called Jacobson's organ or the vomeronasal organ. Jacobson's organ is located

00:05:58inside the cat's nasal cavity and opens into the roof of the mouth. This organ can detect

00:06:04specific chemicals by using nerves that lead directly to the brain. That's not a regular

00:06:09sniffing though. The odor receptors of Jacobson's organ aren't designed to catch ordinary smells.

00:06:14They detect chemicals that have no odor at all. In other words, cats can detect undetectable

00:06:20smells. It's not just this. Jacobson's organ increases the sense of smell. For instance,

00:06:27when kittens need to find their mother's milk, imagine there are two mother cats and four

00:06:32kittens. Kittens can distinguish their mother from the other grown-up cat with the help of

00:06:36their sense of smell. Now, when two people meet, they assess each other's body language.

00:06:42Cats can usually do this by sniffing each other's heads. This greeting releases pheromones

00:06:47that can tell a lot about one cat to the other. Like what the other feline likes to eat or if

00:06:52they are healthy or not. They can even evaluate whether the other cat is happy or moody. All

00:06:58thanks to Jacobson's organ. Now, another fact about cats. Their nose has distinct ridges that

00:07:04look like a pattern. Similar to our fingerprints, every cat has a unique nose print. It can be used

00:07:10as a form of identification. Okay, cat, we can nail you for breaking the vase. We have your nose

00:07:16prints all over it. Now, do you want to cut a deal? Just tell us what you know about the dog

00:07:21and that chewed-up DVD. Dog lovers, no, I didn't forget about you. Here's a myth you've probably

00:07:28heard. Dogs are colorblind. But they aren't. However, it is true that the color range they

00:07:34can detect is limited compared to the spectrum humans can see. Their color palette consists

00:07:39mostly of yellows, blues, and violets. Our reds, greens, and oranges are not noticeable to them.

00:07:46Now, this one is about turtles. These animals cannot leave their shells and get back whenever

00:07:51they want. In fact, they are completely attached to their shells. These shells grow with turtles,

00:07:57similar to the human skin. A turtle's shell consists of 50 bones. It also includes a skeleton

00:08:03with the spine and rib cage. So, they go on vacation with it. It's kind of like an RV

00:08:09that you can't get rid of. Wow, just one strand of hair can support about 3 ounces. On average,

00:08:15a person has about 150,000 strands. And when your hair is working as a team, it can support about

00:08:2212 tons. That's two elephants. Um, not counting the peanuts. Your brain generates electricity,

00:08:29and it'd be enough to light up a small light bulb, if you could only figure out how.

00:08:34It doesn't hurt to cut your nails or hair, because the only part that's alive is under the skin.

00:08:40Also, nails grow faster in summer than in winter, even in places where there's not

00:08:44much difference between the seasons. Also, nails grow faster on your writing hand,

00:08:50probably because you use it more often and that stimulates the nails more.

00:08:54It looks like the pinky finger is weak, but that's not true at all. Without it, you'd lose

00:08:5950% of your hand strength. It usually works together with your ring finger to provide power.

00:09:05The other three are more for grabbing stuff. Oh, and just like fingerprints, your tongue

00:09:11has a unique print too. But you can't use it to unlock your phone, at least not yet.

00:09:16Also, your tongue has a lot of fat in it. If you gain weight, your tongue does too.

00:09:22There's acid in your stomach that breaks down food. The acid is so strong that it could eat

00:09:27right through a piece of wood. The total length of all blood vessels in an adult is close to

00:09:33100,000 miles. That's 4 times around the equator. In your lifetime, you produce enough saliva to

00:09:40fill two swimming pools. Our ancestors needed goosebumps to make their body hair stand on end

00:09:48and scare away any bad guys. We don't need that anymore,

00:09:51but we still get them because we haven't evolved enough yet to get rid of this feature.

00:09:56Now, you probably never noticed, but you mostly only breathe through one nostril at a time.

00:10:02Every few hours, the nostrils switch jobs. That's why only one nostril gets stuffy when you have the

00:10:07flu. Most people think they have 5 senses, but that's not true. Scientists don't yet know

00:10:14themselves, but they think there's more than 20. There's sight, hearing, touch, smell, and taste,

00:10:20and there are other senses like time, hunger, and thirst. Then there's proprioception,

00:10:26the sense of where your body is in space. The brain can't always tell the difference

00:10:32between intense happiness and intense sadness. It gets that you're experiencing a very strong

00:10:38emotion, but sometimes it gets a bit confused. That's why you might cry when you're very happy.

00:10:44Your eyes stay about the same size your whole life, but your nose and ears don't. That'd be so weird.

00:10:51Back in the day, all humans had brown eyes. Other eye colors developed as a result of a

00:10:56random mutation. Scientists think that while the first humans appeared on Earth around 6

00:11:02million years ago, the first blue-eyed person appeared only 10,000 years ago.

00:11:07So, it's pretty likely that all blue-eyed people on the planet have the same ancestor.

00:11:13Uncle Bob!

00:11:15All bones in the human body are connected to each other except one. The hyoid bone is

00:11:21U-shaped and located at the base of the tongue holding it in place.

00:11:26Bones are stronger than steel. A strong healthy bone could, in theory, handle the weight of 5

00:11:32pickup trucks. Still, they're not the strongest body part. The strongest is tooth enamel. It's

00:11:39made of a bunch of different materials that make it damage-resistant. Teeth live a long time,

00:11:44lasting for hundreds of years. But, of course, you still need to take care of them.

00:11:49They're the only body part that can't heal itself.

00:11:53Your heart works non-stop and beats around 3 billion times over the course of your lifetime.

00:12:00Just like your heart, your tongue never takes a vacation. Even when you sleep,

00:12:04it helps push saliva down your throat. By the way, where do you rest your tongue? If you keep

00:12:10it on the bottom of your mouth, you're doing it wrong. This posture might lead to some neck and

00:12:15jaw pain. If you keep it jammed up against your teeth, you're doing it wrong too. It can cause

00:12:21your teeth to shift and might lead to a bad bite. Instead, try to keep it sort of halfway, about a

00:12:27half an inch away from your teeth. We can't breathe and swallow at the same time. That's

00:12:33because whatever we swallow and the air we breathe travel down the same path, at least

00:12:38at first. It's like there's a little guy directing traffic down there. Your eyes can breathe. The

00:12:45cornea is the only body part that doesn't have a direct blood supply. It gets oxygen right from

00:12:50the air. That's why when it's dry outside, your eyes might get a bit itchy. Everyone dreams. Some

00:12:58people say they've never dreamt a night in their life. But they just never remember any of their

00:13:03dreams. Some scientists think that the dreaming stage is followed by an active forgetting stage.

00:13:10It's probably because dreams aren't exactly full of important information,

00:13:14and our brain needs to clean up some extra space for something more useful.

00:13:19Those who are lucky enough to remember their dreams still end up forgetting about half within

00:13:245 minutes of waking up, and after 10 minutes, it's usually gone for good.

00:13:29When you blush, the lining of your stomach turns red too. It happens because blood starts to flow

00:13:35around more when you're embarrassed, as your body gets ready for something stressful to happen.

00:13:40Your face and stomach lining get more of it, turning them red. Also, humans are the only

00:13:46animals who can blush, or at least the only ones where you can see it so obviously.

00:13:50During one lifetime, the average human grows 590 miles of hair. The average man,

00:13:57if he never shaved, would have a 30-foot-long beard. Hair grows a little faster in warm climates

00:14:03because heat stimulates faster circulation in our bodies. Everything you'd ever need to know

00:14:08about you is all written down in one strand of hair. From a single hair, a scientist could tell

00:14:14you what you've been eating your whole life and what kind of environment you've lived in.

00:14:19On average, one human eats their way through 100,000 pounds of food in one lifetime.

00:14:25That's like 10 big hippos worth of food. Lips are one of the most sensitive parts

00:14:30of the human body. They have loads of nerve endings, even more than your fingers. Also,

00:14:35lips' skin is very thin, so you can actually see the blood capillaries inside. That's why lips are

00:14:41red or pink, unlike the rest of your body. Lips are also very sensitive to sun damage.

00:14:47Remember to apply sunscreen on them. It'll help to preserve their health and fullness over time.

00:14:56In addition to your fingerprints, your iris, and your tongue, your lips are also unique.

00:15:02The total surface of your lungs is about the same as a tennis court.

00:15:06Coughs and sneezes are real fast travelers. A cough can get up to 50 miles per hour. A sneeze

00:15:13is even faster – almost 100 miles per hour. Unless you use your fingers to help you,

00:15:18it's impossible to sneeze with your eyes open. Scientists don't really know what's going on

00:15:24there. Some say it's just a reflex, so you can't control it. Others think it happens to shield

00:15:29your eyes from whatever's flying out. All humans literally glow. The light comes from

00:15:36your body heat. It's actually a thousand times less intense than you're capable of seeing,

00:15:41but still awesome. The largest flash drive in the world is

00:15:46actually your brain. Well, anyone's brain. The neurons in it combine together in such a way

00:15:52that your storage capacity is about a million gigabytes. It's enough to hold 3 million

00:15:58hours of movies. That's like a 300-year-long movie night. Hey, pass the popcorn!

00:16:04You start feeling thirsty when you lose about 1% of your body weight. If you lose 5%,

00:16:10you might even feel like fainting. Fingers don't have muscles that make them move.

00:16:15The muscles that do that are located in the palm and the forearm. The word muscle actually comes

00:16:22from the old Latin word for mouse. That's what the Romans thought their biceps looked like.

00:16:27On average, in their lifetime, a person walks about 110,000 miles. That's 4 times the distance

00:16:34around our planet or half the distance from the Earth to the Moon. So, remember to wear

00:16:39comfortable shoes. Alright, quick question. Do you think you know everything about your own body?

00:16:46Are you sure? Well, how about the fact that 25% of an adult's bones are in their feet?

00:16:52Or that taste buds aren't actually those bumps on your tongue? Well, get ready for some eye-openers!

00:16:58Ow! No, no, we're really not going to open someone's eyes. I don't do surgery here on

00:17:04the bright side. Well, maybe in a future video. Anyway, here we go with a big batch of biological

00:17:10background bots to boggle your brain. Your stomach gets a new lining every 3-4 days.

00:17:16This way, your body prevents the stomach from digesting itself. Your brain contains more than

00:17:2286 billion nerve cells, which are joined with one another by 100 trillion connections. That's

00:17:28many more than the number of stars in our home Milky Way galaxy. By the way, if you decided to

00:17:34count all those numerous nerve cells in your brain, it would take you up to 3,000 years.

00:17:39Better get started! Your fingernails grow faster on your dominant hand. In other words, if you write

00:17:45with your right hand, you'll have to trim those nails more often. Your fingernails also grow

00:17:50faster in the summer and during the day. When your brain sends messages to different parts of your

00:17:56body, the signals travel along your nerves at a speed of up to 270 miles per hour. It's way

00:18:02faster than a sports car! People spend more than 4 years of their lives eating. Wow, is the restaurant

00:18:09service that slow? Just kidding! The fastest muscles in your body are those that make your

00:18:14eyes blink. Their contraction speed is one blink in less than one hundredth of a second. In a day,

00:18:21you can blink more than 15,000 times. In their lifetime, the average person processes more than

00:18:28100,000 pounds of food. That's more than the weight of 7 elephants combined. And how do you

00:18:33eat an elephant? Yep, one bite at a time. If someone decided to uncoil the human DNA,

00:18:40the whole thing would stretch for 10 billion miles, which is 40,000 times more than the

00:18:45distance between the Earth and the Moon. If you don't have insomnia, you're likely to spend around

00:18:50one-third of your life asleep. But there are creatures that sleep even more. For example,

00:18:56for a dog, this time is 44% of their life, and for a python, 75%. During just one day,

00:19:04all the blood in your body travels more than 12,000 miles. That's half as long as the distance

00:19:10around Earth. Your skeleton will renew itself completely within 10 years. And yes, without

00:19:16surgery. An adult uses around 200 muscles to make just one step. And don't tell me I don't

00:19:23work out enough. Every minute your body sheds more than 3,000 skin cells. It's almost 200,000

00:19:30skin cells per hour and more than 9 pounds per year. Hey, it's the shedding skin cells weight

00:19:36loss plan! But don't worry, you still have about 300 million skin cells at any given moment.

00:19:43Plus, your skin completely renews itself every 28 to 30 days.

00:19:48The liver is the only human organ that can regenerate completely. As little as 25% of

00:19:54the original liver weight can get back to its full size. Skin cells create a lot of dust,

00:20:00not only under your bed, but also in the Earth's atmosphere. If someone collected all the flaked

00:20:05off skin cells floating in the air, this dust would weigh up to a billion tons. It's 150 times

00:20:12the weight of the Great Pyramid. How's that for a comparison? You won't see your taste buds by the

00:20:18naked eye because they're too tiny. The small bumps most people take for taste buds are called

00:20:24papillae. Real taste buds are on top of these hair-like projections. By the way, taste buds

00:20:30also have a very short life cycle. They live for no longer than 10 to 14 days, so they get a very

00:20:37short taste of life. The average person has more than 100,000 hairs on their head. And since this

00:20:44hair grows about 6 inches per year, it'll make more than 40 feet in a lifetime. Some people can

00:20:50hear their eyeballs moving inside the eye sockets. Wow, that must be no fun. Unlike other parts of

00:20:57your body, your ears and nose never stop growing. Wow, that must be no fun. Your skin wrinkles if

00:21:04you stay in the water for too long, but not because it absorbs water. When your body's wet,

00:21:09wrinkled fingers and toes provide you with a better grip. You know, like when the treads on

00:21:14your car tires grip the road better when they're new. Your eyes are an amazing instrument. They

00:21:20can distinguish between 10 million different colors. Your brain uses more than 20% of your

00:21:26body's energy, even when you're resting. When you're asleep, it still consumes almost as much

00:21:32power as when you're awake. It also burns about 330 calories per day at that. An adult person has

00:21:39about 25% of all their bones in their feet. Most of them are tiny but crucial. If these bones are

00:21:45out of alignment, so is the rest of the body. You breathe around 20,000 times a day. Try not

00:21:52to stop. I actually set a personal best record today for consecutive days breathing, and I plan

00:21:58to top that tomorrow. Human bones are a real paradox. They're almost five times stronger than

00:22:05a steel bar with the same width, but can fracture on impact and are rather brutal. Fingers don't

00:22:11have muscles that can make them move. All the muscles that move the finger joints are located

00:22:16in the forearm and palm. Your body contains more than 37 trillion cells. Earth has more than 7

00:22:23billion inhabitants. It means that there are over 5,000 times more cells in your body

00:22:29than people on our planet. It surely depends on your lifestyle and on how much you move,

00:22:35but the average person will walk up to 110,000 miles in their lifetime, which is half as long

00:22:40as the distance from Earth to the Moon, or more than four times longer than the distance around

00:22:45our planet. If a person has anosmia, also called smell blindness, they can't distinguish and detect

00:22:52smells, but they can still be smelly. Sorry. You start feeling thirsty when water loss is 1% of

00:23:00your body weight, more than 5%, and you may faint. Water loss is bigger than 10% of the body weight,

00:23:07and dehydration can end a person, if you know what I mean. The strongest muscle in your body,

00:23:13based on its weight, is your jaw muscle. Yeah, mine is way overdeveloped. At any moment,

00:23:2050,000 cells in your body are getting replaced by new ones. Boy, that sounds like a company I

00:23:25used to work for. By the end of their life, the average person can recall up to 150 trillion

00:23:31pieces of information, except where they left their car keys. Even if fingerprints are badly

00:23:37damaged, they can still grow back with their original pattern. Your most powerful sneeze can

00:23:42travel at a speed of more than 100 mph, almost as fast as a skydiver in free fall. The average

00:23:49person has about 250 hairs in each eyebrow. These hairs get completely replaced every 4 months.

00:23:57Your brain's memory capacity is equivalent to about 4 terabytes on a hard drive, which is more

00:24:02than 8 million photos. People are the only living creatures that can naturally sleep on their backs.

00:24:09Even apes usually sleep in a sitting position, leaning on something. Your longest bone is your

00:24:15thigh bone, not your funny bone, and the tiniest one is in your ear. It's shorter than a grain of

00:24:21rice. The largest organ in your body is your skin. Despite being thin, it weighs a surprising 9-11

00:24:29pounds. That's the weight of a healthy and well-fed house cat. Your skull may feel like it's

00:24:34all in one piece, but in fact, it consists of 29 different bones. The only part of your body that

00:24:41can't heal itself is your teeth. What a shame! Right-handed people tend to chew most of their

00:24:47food on the right side of their mouths, while the left-handed opt for the other side. Out of all

00:24:55people who can move their ears, only 30% can move just one ear. Such talent!

00:25:02Every person has dimples on their lower back. But in some people, they're more pronounced than in

00:25:07others. These dimples appear in places where the pelvis is connected with the sacrum,

00:25:12so their existence, even if it's not apparent, makes sense. Your right lung is shorter than the

00:25:18left one because it has to leave some room for your liver. The left lung, on the other hand,

00:25:24is narrower since it has to make space for the heart. A male's lungs can usually hold more air

00:25:29than a woman's. Surprisingly, you burn more calories when you're sleeping than when you're

00:25:35watching TV. Actually, that should tell you something helpful. By the time you turn 60,

00:25:42you're likely to lose 50% of your taste buds. Your hair grows twice faster when you're traveling by

00:25:49plane. It has to do with higher atmospheric pressure. The muscles that help your eyes

00:25:54focus make around 100,000 movements a day. If you want to make your leg muscles move as much,

00:26:00you'd need to walk 50 miles. When you listen to music, your heart starts beating in sync with it.

00:26:08The distance between your outstretched arms is your height. You renew your skeleton every 10

00:26:13years. You lose around 100 hairs every day, and that's totally normal. Humans are the only

00:26:21creatures who sleep on their backs for a long time. Koalas, like humans, have their own unique

00:26:26fingerprints. In a lifetime, the average person will walk the equivalent of 3 times around the

00:26:32world. A person can have from 250 to over 1,000 hairs in each eyebrow. Your eyebrows also have a

00:26:40lifespan – about 4 months for all the hairs to fall out and be replaced by new ones. Thank goodness!

00:26:47Your eyes are the only organ that doesn't grow with age. Human DNA is 96% similar to a chimpanzee,

00:26:5490% similar to a cat, 70% to a slug, and 50% to a banana. That has appeal! You share 99.9% of your

00:27:04DNA with any random person on the planet. Your heart is the size of your fist. Your brain – two

00:27:11clenched fists. When you listen to music, your heartbeat syncs with its rhythm. You can't swallow

00:27:17and breathe at the same time, trust me on that one. There are as many nerve cells in your brain

00:27:22as there are stars in our galaxy – about 100 billion. The popular belief that people only use

00:27:2810% of their brain power is nothing but a myth. Even when you're resting or sleeping, more than

00:27:34a tenth of your brain is working. You're more likely to get attracted to a person who thinks

00:27:38and looks the same as you. The belief that opposites attract isn't true. Your nose and ears

00:27:44are the only parts of your body that never stop growing. The human brain generates enough

00:27:49electricity to power a small light bulb. If your eye was a digital camera, it would have a resolution

00:27:56of 576 megapixels. Your tongue prints are also unique to you, but let's not lick the scanner.

00:28:03Scientists at the University of Pittsburgh found that blue- and green-eyed people are

00:28:07less sensitive to pain than brown-eyed people. But lighter-colored eyes are more light-sensitive

00:28:12than dark ones. The microorganisms in the human body outnumber cells 10 to 1.

00:28:18Aye-aye-aye! About 6% of people can vibrate and rapidly shake their eyeballs back and

00:28:24forth. It doesn't mean something's not right with their eyes, it's just a unique trick they

00:28:28can perform. Good at parties, I suppose. Fun fact about bones. You know that your

00:28:33body is about 60% water, right? What's new here is that your bones are also in this too.

00:28:39About 25% of human bone mass is made up of water. Not all of your brain's regions are active all the

00:28:46time, but most work on this or that task 24-7. Every two minutes, people all over the world

00:28:53take more pictures than they did in the entire 19th century. However, there's nothing said about

00:28:58today's photos being any better. People are kind of programmed to return favors. This instinct

00:29:04probably developed when people needed to help one another to survive.

00:29:08Studies have proved that sneezing is your nose's way to reset. A sneeze reboots the

00:29:13cells that line the insides of your nose. They're called cilia. Sneezing is also one of the first

00:29:19defenses against bacteria and other, you know, unwanted stuff. When the delicate nose lining

00:29:25gets tickled with a foreign substance, like pollen, dirt, or dust, it sends a signal to

00:29:30your brain. The brain informs your body it's time to sneeze. The part of your brain that's

00:29:36responsible for vision is actually in the back of your head. The right side of your brain controls

00:29:42the vision on the left side, and vice versa. Okay, put down your phone and pay attention.

00:29:48Multitasking is actually impossible. Your brain only allows you to switch between different tasks

00:29:54really fast, but not to do them at the same time. Such contact switching isn't ideal either.

00:30:00Studies show that, in this case, people make mistakes much more often. Plus, they need twice

00:30:06as long as usual to do things. So, focus! There is one exception, though. When you're

00:30:12engaged in some physical activity you've done many times before, you can simultaneously perform

00:30:18a mental task. That's why you can easily walk up the stairs or take a shower and think about

00:30:23problems at work. Food tastes better when someone else has made it. That's why a sandwich from a

00:30:29cafe looks more appetizing, even though you used the same ingredients. One study suggests it's

00:30:35because it takes time to make yourself a meal, so when you're ready to dig in, you don't feel all

00:30:41that excited. Your body contains enough blood vessels to wrap around the planet two and a half

00:30:46times. You spend 4 months in each year asleep. In a lifetime, you rack up 26 years. Only 6 of

00:30:54those years will be spent dreaming. We forget 50% of a dream within 5 minutes of waking up.

00:31:0010 minutes later, it's 90%. Each cell in your body contains 1.5 gigabytes of information.

00:31:07Do the math for your 100 trillion cells and see that you're one powerful walking computer.

00:31:13Your brain cools down when you yawn. Your ears work even when you're asleep, but your brain

00:31:18ignores the incoming information. The bumps on your tongue aren't taste buds, they're called

00:31:24papillae. Not all papillae contain taste buds, but those that do have 1 to 5 in each. The atoms

00:31:31in your body are 99% empty, and yet you feel full after dinner. How is that? The brain grows for the

00:31:39first 18 years of life and then gets 5% smaller every 10 years after the age of 40. Well, that

00:31:46explains a lot, don't you think? We spend 10% of our waking hours with our eyes closed just from

00:31:51blinking. The muscles that work your fingers are actually in your forearm. Your foot is the same

00:31:57length as your forearm. Same ratio with your thumb and nose. Your toenails grow 3 times slower than

00:32:04your fingernails. Your lungs aren't identical. The right one has 3 lobes, and the left one has 2.

00:32:10Your hair grows faster when you're sleeping. The only thing that grows faster than hair

00:32:14is bone marrow. Your body releases enough heat in a half an hour to boil 2 quarts of water.

00:32:21Your brain uses 20% of the energy your body generates. Your body uses more energy to cool

00:32:27itself on hot days than to warm up when it's cold. People can go much longer without food

00:32:32than without sleep. Stomach acid can dissolve metal. It's so strong that the stomach has to

00:32:38create a new lining every 3-4 days. So, what's eating you? Your stomach.

00:32:44In terms of muscle, your tongue is like an elephant trunk and an octopus arm. That's

00:32:49just wrong. Your nails are made of the same stuff as a rhino's horn and a horse's hoof.

00:32:54And the rhino wants it back. We have nails to protect our fingertips. Without them,

00:33:00you wouldn't be able to grip things as well. You use 200 muscles just to take one step,

00:33:05and 50 muscles just to use chopsticks. You use only 2 fingers to play chopsticks.

00:33:12Most people speak about 125 words per minute. The brain can process 800 in the same time.

00:33:18Me, I can go 185 with wingus up to 250. Your skin completely renews itself every 27 days.

00:33:26Now, you can't tickle yourself. Your brain already knows of your intentions and prepares

00:33:31your body for it. Humans are the only species with an outline that separates the lips from

00:33:36the surrounding skin. Half the bones in your body are in your feet and hands. C'mon, let's share,

00:33:42guys! Finally, cornflakes have more genes than people do. Your cereal has 32,000. You have 20,000.

00:33:51Your memory is affected by your body position. For example, you're much more likely to recall

00:33:56a situation where you waved to someone if you stand and wave again. Your brain has millions

00:34:02of neurons. They're all different. And the speed of the connection between them is different too.

00:34:07That's why you can recall some information faster than others. The brain itself, by the way,

00:34:13can't feel pain. It has no nerve endings of its own. People with red-colored hair are 1% of all

00:34:20people. 2% are natural blondes. Yeah, most people you see with these hair colors have dyed hair.

00:34:26Black is the most common hair color in the world. A human eye resembles a car engine.

00:34:32Both of them need liquid for good lubrication. The engine needs oil, and the eye needs tears.

00:34:38To make sure the eyes work right, tears are distributed all over them. That's why we blink

00:34:43more than 10,000 times a day. Well, your body can do incredible things on its own,

00:34:49but you may also have features that make you stand out even from the largest crowd. Having

00:34:54extremely long eyelashes, having an additional joint in your fingers, or not having any lines

00:35:00on your palms but one. You name it. So let's find out how unique you are. Many people can roll their

00:35:07tongue, so it's a pretty lame party trick. But only about 15% can twist their tongue into a clover

00:35:14shape. How about a tongue bouquet? Only about 3% of all people on Earth have an X-shape on

00:35:21both of their palms. Look at yours. Maybe you're the lucky one. Some say it's a sign of a strong

00:35:27character, by the way. Can you cross your eyes so that they look at each other? Some people,

00:35:33about 6% of the world's population, can vibrate both their eyes and their sockets. Looks strange,

00:35:39but it's actually really quick moving of the eyes back and forth,

00:35:43so it depends on the strength of your eye muscles. You could train that if you wanted.

00:35:49Ducks, seagulls, platypuses – all these creatures have one thing in common – webbed feet. Same as

00:35:55about half a percent of the people in the world. The most common occasion among these lucky guys

00:36:02is that the second and third of their toes have a web between them that connects them.

00:36:07Some rare individuals have finger joints that are so flexible they can bend both inwards and

00:36:13outwards. It's unknown how many people can do that, but you could check if you're one of them,

00:36:18of course. There's an unknown number of people who have an extra joint in one or more of their

00:36:24fingers. It bends like a normal one and doesn't cause any discomfort. There's a condition where

00:36:31the remains of a membrane that formed while a person was still inside the womb still cover

00:36:36part of their eye pupil. It makes the pupil look like it has a blot right in the middle

00:36:42with strands going in every direction, attaching to the iris. Around 2% of people have a lazy eye.

00:36:49It's a condition that appears before birth when the brain focuses on the development of one eye

00:36:54more than the other. As a result, one eye basically looks in a different direction

00:36:59from what it should be. There's a little muscle in your jaw that muffles the sound of your

00:37:05chewing typically, and it's usually relaxed. But when you flex it intentionally, you can create a

00:37:12roaring sound in your head. Only about 16% of people can actually do that intentionally, though.

00:37:18But why would you? Can you flare your nostrils at will? If so, you're in about a third of people

00:37:24in the world that can do that. We actually flare our nostrils unintentionally quite often,

00:37:30but only a few can move those nose muscles as they want. Your eyes focus and unfocus on their

00:37:37own all the time. But about half of the population of our planet can control them. They can relax the

00:37:43eye muscles, make the eyes unfocus, and look in different directions. Now, all of us can raise

00:37:50our eyebrows. It's one of the things our mimics allow us. But only some can move one eyebrow at a

00:37:56time. Also, if you can raise one eyebrow, it's usually one and the same. You're an even rarer

00:38:02individual if you can move either of your eyebrows at will. By the way, people who can do that can

00:38:09also often move their ears, either one or both. Hypermobile hands are a rare thing as only about

00:38:175% of people have them. This condition allows them to bend their hands and fingers backward,

00:38:22and some of them can even grab things with the back of their hand.

00:38:26A less fortunate but no less rare thing is being tongue-tied. It's when your tongue is literally

00:38:32tied harder than usual to the bottom of your tongue. Around 5% of people have it, and it does

00:38:38cause some inconveniences, unfortunately. Another 5% of the human population are secretly elves.

00:38:46Maybe not exactly, but these rare individuals have pointy ears that strongly resemble elfin ones.

00:38:54This is caused by an extra fold at the tip of the ear, and the reason for it is still unknown.

00:39:00About 4% of people have a clubbed thumb. It's a thumb that's about two-thirds of the standard

00:39:05length and is flatter and broader at the tip. Dreams usually come in color, but about 12%

00:39:12of the world's population see them in black and white. Scientists believe this is related to the

00:39:18emergence of color television. Before it appeared, about 75% of the people saw their dreams in black

00:39:24and white instead. Widow's peak is a triangular shape of hair right above the middle of your

00:39:31forehead, and it's a rare occasion too. Only about 12% of people have it. Also, it's a genetic thing,

00:39:38so it usually runs in families. Amber eyes, which are a sort of a mix between yellow and brown,

00:39:45are a more frequent color than green or gray ones. About 5% of people have amber eyes,

00:39:51while green-eyed people make up 2%, and gray eyes occur in less than 1%. You might think it's not

00:39:58the case, but gray eyes just often get confused with blue ones, which occur in about 9% of people.

00:40:05If you have a dark ring around the iris of your eyes, you're one of less than a third of the

00:40:10world's population to have a dark, limbal ring. It also becomes more prominent in people as they age,

00:40:16so even if you don't have one now, you'll have it later on in your life.

00:40:22Talon cusps happen in around 4% of people. They're small bumps on the back of the teeth

00:40:27that usually occur randomly and look like little nails.

00:40:32Not only do you have a dominant hand, but a dominant eye. Only about a third of people are

00:40:37left-eye dominant. To check which category you belong to, stretch out your hands in front of

00:40:43you and make a diamond shape with them, connecting the tips of your index fingers and thumbs.

00:40:48Center some object in that shape and close your left eye. If the thing remains centered,

00:40:54you're right-eye dominant, and if not, you're left-eye dominant.

00:40:59Less than 1% of people miss a nail from birth. It's a genetic condition that literally prevents

00:41:05you from developing a nail entirely. Still, sometimes it's only part of a nail that's missing.

00:41:11A select few people, also less than 1%, have an eyeball scar. The vitreous pulls away from the

00:41:18retina, and it causes the pupil to sometimes lose its round shape and a line that looks like a scar

00:41:25appears on the iris. Another group of people have exceptionally long eyelashes. There's a

00:41:31condition that can make them extra thick or curly or have more pigment too, making your eyes much

00:41:37more expressive. There's a rare and usually genetic condition that literally makes your skin blue.

00:41:44In people who have it, hemoglobin, the protein that carries and distributes oxygen to the body,

00:41:50can't effectively release it into the tissues. As a result, the skin bears a bluish tint,

00:41:56and the lips become purple. Most of us have patterns of creases criss-crossing our palms.

00:42:02But about 1.5% of people have only one prominent crease, while the rest are much less visible.

00:42:10Less than 1% of people with light hair have a single streak of dark hair on their heads.

00:42:16This occurs due to increased melanin production in the area. The pigment that makes our eyes,

00:42:21hair, and skin lighter or darker depends on its amount in those parts. Similarly, when there's

00:42:27an area on your hand that got less melanin than it should have, you get a patch of white hair.

00:42:33It can also occur in an eyebrow or in the eyelashes of one eye.

00:42:38Now, have you found any rare things that you probably have? Or have you met someone

00:42:43whose appearance is hard to forget? Please do share in the comments!

00:42:49Well, here's some fats you'll find hard to digest. Your stomach has a pretty incredible capacity,

00:42:56being able to hold up to half a gallon of liquids. That's a whole large bottle of coke!

00:43:02It's pretty hard to estimate how much hard food you can eat because it's processed with your teeth

00:43:07before it gets to your stomach. There's definitely not enough room for a turkey,

00:43:11but a good-sized chicken would probably fit in it. If you were asked where your stomach was,

00:43:17you would probably point to your tummy. Sorry, that's wrong. It's actually up here,

00:43:22hidden in between your ribs. Scientists believe that the appendix will disappear eventually.

00:43:28Nobody really knows why we need it, but some researchers claim it might've existed to help

00:43:34our ancestors digest tree bark. Because it's no longer part of our daily diet,

00:43:39the appendix isn't necessary and can disappear from our bodies without any consequences.

00:43:44The appendix isn't the only obsolete part of our body. Wisdom teeth aren't that useful either.

00:43:50Yeah, they used to come in handy whenever our ancestors lost some of their teeth.

00:43:55But the only thing they help us lose now is the money we spend extracting them.

00:44:00Almost all of our body is covered with hairs, even if we don't notice them.

00:44:04They grow even in the belly button. Their purpose is to catch lint. Check it out. See?

00:44:11Your liver acts as your own personal bodyguard, protecting you from toxins and many other things

00:44:16you don't want hanging around in your body. It's also pretty indestructible and can even regenerate.

00:44:23Only about 43% of you is actually you. Over 50% of the cells in your body belong to tiny little

00:44:31creatures that mainly live in your gut. Still, even though your own cells are fewer than microbial

00:44:37ones, there are, on average, about 100 trillion of them in you. See? You're not alone.

00:44:44With this in mind, your own genes are less than half of what you really consist of.

00:44:49If you take all the microbes dwelling within your body and count their genes,

00:44:53you'll find between 2 to 20 million. If you sleep, it doesn't mean all of your body sleeps.

00:45:00In fact, sometimes your brain has to work even harder when you're asleep.

00:45:05It needs to process tons of information, and reports usually take a lot of time.

00:45:10The nose definitely gets a good rest while you're sleeping. Amazingly, your sense of smell basically

00:45:16deactivates at night. You wouldn't even be bothered if there was a really terrible smell

00:45:21in your bedroom. No comment. The nose is probably one of the most under-appreciated parts of the

00:45:27body. We wouldn't even be able to enjoy eating without it. About 80% of the taste of any food

00:45:34is thanks to the nose and its ability to recognize odors. If you hold your nose while eating,

00:45:40you will taste almost nothing. With no sense of smell, you're likely to recognize food mostly

00:45:45by texture. So, an onion might seem no different than a big refreshing apple.

00:45:52Scientists used to believe we could distinguish about 10,000 smells,

00:45:55but they were wrong. Recent research showed that people are actually able to distinguish

00:46:01between more than a trillion smells. We also remember them better than anything else,

00:46:06and smells can even evoke some distant memories. Your nose just doesn't help you breathe and catch

00:46:12odors. It filters the air for sensitive throats and lungs. If we inhale dry air, the nose moistens

00:46:19it, cools it, and heats it if it's necessary. Also, the nose cleans the air of dirt.

00:46:25When you age, your brain is gradually reducing in size. By age 75, it's much smaller than at 30,

00:46:33and it starts shrinking by the age of 40. It happens to everyone and doesn't affect

00:46:37your mental strength in any way. Our brain can store only 7 bits in its short-term memory.

00:46:44Don't even try to compare your brain with a phone capacity, not even the one you had back in 2005.

00:46:50That's why you can't even learn a phone number by heart. Our short-term memory functions just

00:46:55like a chalkboard. You can get some information, but sooner or later, you run out of space.

00:47:01To check your working memory capacity, try this test. Ask a friend to write a list of 10 words

00:47:07and read it to you. Most people recall 7 or fewer items from that list.

00:47:13Your RAM, or working memory, is an essential thing that we need to perform almost any

00:47:18everyday activity, including basic conversations, surfing the net, and even petting your dog.

00:47:25Our strongest and emotional memories are often fake. The central memory gives us the confidence

00:47:30to believe that we remember everything, even though most of the details are made up in our heads.

00:47:36Not only your brain shrinks as you get older, you too shrink dramatically. The bones get more

00:47:42brittle. The backbone gets compressed. A similar thing happens when you rest at night. Your bones

00:47:48kinda relax too. Because of this, you wake up taller in the mornings than you are at the end

00:47:53of the day. Among mammals, only humans can walk on two legs for their entire lives. You might

00:48:00think that kangaroos or gorillas move in the same way, but kangaroos use their tail as a third leg,

00:48:07and gorillas use their long arms to keep balance. Your bones take part in metabolism too. Since they

00:48:14mostly consist of calcium, when there's not enough of this element in your blood, bones start shedding

00:48:19it into the bloodstream, balancing your body. The same reaction works in reverse too. When there's

00:48:25too much calcium in your blood, it goes into the bones to be stored for later. The only bone to

00:48:31have a sense of humor in your body is inside your upper arm. That's why it's called the humerus.

00:48:37Okay, I made that one up. Moving along. The only bones that never grow are found in our ears.

00:48:44We can hear thanks to these tiny bones because they have adapted to transmit sound vibrations.

00:48:50Doctors call them the oscular chain. One of these hearing bones, the stapes, is the smallest bone in

00:48:56your entire body. It's no larger than a grain of rice. Our height, shape of our body, and skin color

00:49:03depend a lot on where our ancestors used to live. But we can adapt to new conditions even within our

00:49:09own lifespan. For example, if you move from plains to the mountains, you'll eventually develop more

00:49:16red blood cells to compensate for the lack of oxygen. And naturally, if you move from a colder

00:49:22climate to a hotter and sunnier one, your skin will get darker to adapt. Our lifespan is programmed

00:49:28within our cells. They constantly renew and divide, but they have a sort of internal timer that stops

00:49:35at some point. Some cells also stop reproducing sooner than others. On average, cells cease

00:49:41dividing when we reach the age of 100. That means, if we could find a way to trick ourselves

00:49:47into turning off the timer, we could potentially live forever.

00:49:55Body fat isn't just a nuisance. It acts as insulation material, energy reserve, and shock

00:50:01absorber. Your body sends the most fat into your waist region because that's where your internal

00:50:07organs are. If something happens to you, this layer of fat might protect your vitals from

00:50:12irreparable damage. Heads up! Your skull isn't a single bone. It actually consists of 28 different

00:50:20bones, many of which are fused together to protect your brain. The mandible, or the lower jaw, is the

00:50:26only skull bone that isn't fixed to the bone around it. It's attached with connective tissues and

00:50:31muscles. This is what makes it so mobile. You can move it in any direction you like. You see,

00:50:37the strongest muscles in your body aren't in your arms or legs. They're in your head. The masseter

00:50:42is the main muscle responsible for chewing, and it needs to be the strongest for you to eat normally.

00:50:49And you know those muscles that allow you to move your ears? Those are temporalis,

00:50:54located above your temples. They also help you chew your food.

00:50:58Now, we've got two really fast muscles. They control the eyelid closing. In fact,

00:51:04they're the fastest muscles in our body. Eyes are fragile and need protection, so the reflex that

00:51:10protects them needs to be as fast as lightning. These muscles can shut the eyelids in less than

00:51:15a tenth of a second. People with double-jointed thumbs can bend them backward. It looks super

00:51:21unusual, and very few people can do it. Still, it's totally okay. Even though it looks painful,

00:51:27it actually doesn't hurt at all for someone with a double-jointed thumb.

00:51:32Now, we recognize only purple-blue, green-yellow, and yellow-red colors. Everything else is a

00:51:38combination of these three. It's impossible to calculate how many of these combinations

00:51:43the human eye sees, because every single person has slight vision differences. But it's about

00:51:501,000,000 combinations on average. You see?

00:51:57The phone's ringing. Must be something urgent. At 11 PM? Only, all the gadgets in the house are

00:52:03silent. It's your ears that are ringing. You can also hear some hissing, whistling,

00:52:08buzzing, and even roaring. But all this noise doesn't have an external source.

00:52:14Ooh, that's why it's known as phantom sounds. They can occur in one or both ears, constantly or

00:52:21from time to time. They're usually most noticeable at night when nothing distracts you. Hearing

00:52:27noise in your ears is called tinnitus. It's quite common and affects 15-20% of people.

00:52:33Tinnitus starts in the part of your inner ear shaped like a snail. It's called the cochlea.

00:52:38Your middle ear picks up sound waves. They get translated into electrical impulses in the inner

00:52:46ear. Then, sensory nerves carry these impulses to your brain. If your inner ear works incorrectly,

00:52:53your brain can misinterpret the sounds. Tinnitus occurs when there are some changes in the

00:52:58cochlea's nerve. They can be caused by loud noise, like chainsaws, jackhammers,

00:53:04loud music, or shouting. Tinnitus can start after a head, neck, or ear injury or after you begin to

00:53:10take certain medications. You can also hear ringing in your ears if you have some blood

00:53:15pressure issues. Elsewhere in the amazing human body, some of the bacteria living in your gut

00:53:22can produce electricity. Shocking! They give off electrons, and this creates tiny electrical

00:53:28currents. That's likely to be the bacteria's backup system, their way to generate energy.

00:53:34Humans are the only animals that have chins. Even our closest genetic relatives,

00:53:39gorillas and chimps, lack this small piece of bone that extends forward from the jaw.

00:53:45Their lower jaws slant down and back from their front teeth.

00:53:49Scientists still haven't figured out this mystery. The opinions about why people are made this way

00:53:54differ. Some researchers think chins help us chew our food. Others are sure they have something to

00:53:59do with speaking. A few of us think it's simply a special place to grow a goatee.

00:54:05Blinking keeps your eyes clean and moist. But that's not all. Every time you blink,

00:54:10you take a micro-nap. Researchers from Washington University have found out that

00:54:16blinking makes your attention sharper and works as a teeny recharge.

00:54:21Ever seen tiny dots traveling in squiggly lines, especially when you're looking at a bright blue

00:54:26sky? These dots are only visible for a second or so and might look like itty-bitty worms. Those

00:54:33are your white blood cells moving through the capillaries in front of the retina. That's the

00:54:38light-sensitive tissue at the back of your eyes. Curiously, most people don't even notice the dots

00:54:45unless asked to pay attention. The pineal gland in your brain

00:54:49handles the production of melatonin. That's the very hormone that regulates your sleep patterns.

00:54:55The gland looks like a pine nut, and that's how it got its name.

00:55:00The human brain is 73% water, and the same is true about the heart. That's why if your brain

00:55:06loses even 2% of liquid, you start to feel tired. It also makes your memory worse,

00:55:12shortens your attention span, and puts a dampener on your mood.

00:55:17By the way, your brain makes sure you don't drink too little or too much water. After you

00:55:22swallow some liquid, your mouth and throat start to fire signals to your brain, telling it to stop

00:55:28drinking. Otherwise, you'd be gulping down water for the entire 10-60 minutes it takes the liquid

00:55:34to get to your cells. Your eyes can see something for a mere 13 milliseconds, and your brain will

00:55:41process this image. For comparison, the average blink lasts from 100 to 400 milliseconds.

00:55:48Even though the tongue isn't the strongest muscle in your body,

00:55:52it never gets tired. That's because of the way it's built. It's made up of 8 interwoven muscles.

00:55:58But unlike other muscles in your body, these aren't situated around a supporting bone.

00:56:04The tongue's structure is similar to an elephant's trunk or an octopus' tentacles.

00:56:11Your body emits visible light. That's why they call me sunny.

00:56:17You're the brightest at 4 PM, and your glow is the least visible at 10 AM.

00:56:22Unfortunately, this glowing is a thousand times less intense than what your eyes can see.

00:56:28Sweat is mostly water mixed with proteins, sugars, ammonia, and a lot of other stuff. It even

00:56:34contains tiny amounts of trace metals, like copper, zinc, nickel, iron, and so on. What

00:56:40makes sweat taste salty is the sodium it contains. Plus, the more salt you eat, the saltier your

00:56:47sweat is. Your body's trying to get rid of the excess, and the fastest way is to sweat it out.

00:56:54In an adult, the blood makes up 7-8% of the total body weight. About 55% of your blood is

00:57:01liquid plasma. The rest is red and white blood cells and platelets. They form clots and prevent

00:57:07bleeding. You can't swallow and breathe at the same time. The food you swallow and the air you

00:57:13breathe go down the same part of your throat at first. Only a bit deeper, the passage splits

00:57:19into the esophagus for food and liquid, and trachea for air. When you swallow, your airway

00:57:25gets automatically closed off. This prevents you from accidentally inhaling food. But occasionally,

00:57:32it still happens. Your brain sometimes generates more than 48

00:57:37thoughts in just one minute. That's almost 3,000 thoughts per hour and 69,000 per day!

00:57:44Fingernails grow faster on the dominant hand. If you use your right hand more, you'll have to trim

00:57:50nails on it more often. Fingernails also grow more quickly in the summer and during the day.

00:57:56You might keep in memory up to 10,000 different faces. Sure, it varies from person to person,

00:58:02and the average number is 5,000. It doesn't mean you can put a name to each of these faces.

00:58:08It's only about recognizing the features. You might try to hide the truth, but your nose

00:58:14will always give you away. When a person tells a lie, the temperature around their nose

00:58:20and in the inner corners of their eyes goes up. This phenomenon is known as the Pinocchio effect.

00:58:28Women have more taste buds on the surface of their tongues than men do.

00:58:32That's one of the reasons why 35% of ladies and only 15% of guys are supertasters. Those are

00:58:39people who feel flavors more strongly than others. Your teeth are the only part of your body that

00:58:45can't repair itself. But the enamel they're covered with is one of the toughest things in

00:58:50the human body. Your heartbeat often syncs with the music you're listening to. If a piece has a

00:58:56continuous increase in volume or tempo, like rock, it can make your heart rate faster. Some classic

00:59:03music lowers heart rate and blood pressure. This phenomenon affects everyone from professional

00:59:09musicians to amateurs and music lovers. There are 2 to 5 million sweat glands on your body.

00:59:16The sweat they produce is of two different kinds – stress sweat and regular sweat. Hey,

00:59:21don't sweat the small stuff, huh? The sweat caused by stress has fatty acids and proteins in it.

00:59:28And the regular sweat is mostly made up of water, salt, and a tiny bit of other substances.

00:59:34It's actually possible to brush your teeth too thoroughly and hard.

00:59:38This can wear down the enamel and make your teeth super sensitive to cold and hot foods.

00:59:44If you walked in the same direction for 12 hours a day, you would need around 800 days to travel

00:59:50around the globe. And don't forget your rubber boots for the ocean parts. If your stomach acid

00:59:56made contact with your skin, it would most likely eat a hole in it – all because of hydrochloric

01:00:03acid. This type of acid is incredibly potent. It can easily dissolve some metals, for example,

01:00:09magnesium or zinc. Hydrochloric acid is the main component of the gastric acid your stomach

01:00:16produces. It protects your immune system and gets rid of viruses and bacteria in the food you eat.

01:00:22This acid also helps your body break down, digest, and absorb all kinds of nutrients,

01:00:28including proteins. Your lips look red because there is a great

01:00:32concentration of miniature blood capillaries right below the skin.

01:00:37Your pinky is a powerful little thing. Without it, your hand would lose a significant part of

01:00:43its power. Your index and middle fingers cooperate with your thumb to grab and pinch.

01:00:48And your pinky, together with your ring finger, provides grip strength.

01:00:534. The fattest organ in your body is your brain. Fat makes up at least 60% of its dry weight.

01:01:01This quality got the brain to the Guinness World Records. The organ contains around 25%

01:01:06of your body's cholesterol, which is vital for the brain's well-being.

01:01:11So is that where the term fat head comes from?

01:01:15Your skeletal cells never stop regenerating. That's why you get a new skeleton every 10 years

01:01:21or so. This process slows down with age, and the regeneration takes longer. That's one of

01:01:27the main reasons why bones become thinner. And there's a newly discovered type of brain

01:01:33cells crucial for visual search. They're called target cells. Without their help,

01:01:38you wouldn't be able to spot an acquaintance in a crowd or your dog in the park.

01:01:43Interestingly, target cells don't care what the thing you're searching for looks like.

01:01:48All they want to know is whether an object is your target or not. Hey, it's not picky!

01:01:56Wow, humans can distinguish between more than 1 trillion scents, and each person has a unique

01:02:03odor. Tell me about it. Just kidding, this ain't smell-o-vision. But have you ever wondered how

01:02:10this sense is possible? Well, let's sniff around and find out.

01:02:16Imagine you're eating a freshly baked cookie. Mmm, not only does it smell good, but it tastes

01:02:23delicious. As it crumbles in your mouth, it starts to release little molecules. These travel through

01:02:31the back of your throat, while some of them make their way into your nose. Now picture yourself

01:02:38walking into a room with a vanilla-scented candle. You identify the musky smell through

01:02:45a process called diffusion. Air and odor molecules spread freely in all directions

01:02:51until they reach your nose. Let me shrink myself down to the size of an odor molecule,

01:02:58and I'll show you how it works. As you take a deep breath, I'll enter through your nose,

01:03:04the first organ of your respiratory system. Careful, don't trip on the boogers!

01:03:10Can you see those thick little hairs inside your nostrils? Those act as security guards,

01:03:15and they're as thick as the follicles on your head. Their job is to stop dust, debris, germs,

01:03:21and other particles from getting into your lungs. The shiny stuff on the edges of the hairs is

01:03:27mucus. No, it's not. Yes, it is. It traps the unwelcome particles that show up in your nose.

01:03:36It also keeps the lining of your nose moist because the skin there is very sensitive

01:03:41and needs constant hydration. Uh-oh, watch out! Sometimes I have to dodge these big,

01:03:49fleshy things that occasionally invade here. But not to worry, these are called fingers,

01:03:55and they're only interested in mining for the boogers.

01:04:00Further in, there are some tiny hairs called the cilia, but you can only see them through

01:04:05a microscope. They're another defense mechanism in your system. You've also got these in your ears

01:04:10and other parts of your body. When unwelcome visitors get trapped, the cilia move back and

01:04:17forth to push the mucus out of the way. They send it to either the back of your throat or to the

01:04:23front of your nose. Finally, we have some room. This huge chamber is the nasal cavity.

01:04:31It goes all the way to the upper back of your throat.

01:04:35Its job is to filter, moisturize, and warm up the air you inhale.

01:04:41Can you see those three extended pieces on the wall of your nasal cavity that look like small

01:04:47hot dogs? Those are the turbinate, and you've got three in each nostril. The first turbinate is

01:04:53the first tissue to meet the outside air. Oxygen molecules will go down that slide that leads to

01:04:59your lungs. But we're heading the other way. Some odor molecules go into your lungs too,

01:05:05but they come right out when you exhale. Look up at that thin layer of mucus,

01:05:12that's where we're heading. Right underneath the mucus, you've got more cilia, and then there's the

01:05:17olfactory epithelium. This is a very special tissue lying on the roof of your nasal chamber.

01:05:25Think of it as a block of soft, squishy sponges that contains a lot of important things,

01:05:31like the smell detectors leading to your brain. Oh, look! There are some teeny tiny things

01:05:38branching out like little plant roots. Those are the dendrite, and they're extensions of your

01:05:44nerve cells. You've got around 8 million neurons in each nostril. Let's squeeze through and see

01:05:51what's going on further in. Ah, here we are! These round little guys that look like small

01:05:57cherry seeds are your smell receptors. And they're supported by other cells, like a bunch of pillows

01:06:03placed between glass spheres to keep them in place. Let me just shrink even further and wake

01:06:10up one of those smell receptors. Here. Each of them is sensitive to a group of smells.

01:06:16I'll bind myself to one that's sensitive to my smell, just like a piece of puzzle fitting into

01:06:21place. The moment the receptor cell picks me up, it triggers a series of events. The receptor is

01:06:29now firing an electric signal through a thin tube called the axon. Let's follow it and see where it

01:06:36goes. We're now passing through a connective tissue that has olfactory glands. These are

01:06:42responsible for producing the mucus in your nose that we just swam through. Knock knock! That feels

01:06:50like a hard shell. It's called the cribriform plate, and it separates your brain from your nasal cavity.

01:06:57It's got little holes in it to allow the nerves that pick up smells to go through.

01:07:02As we move upwards, the nerves are starting to connect into bundles.

01:07:07Squeezing through one of the holes in the plate, we see a bunch of them going further in.

01:07:14Oh wow, look at that! Those bundles of nerve connect to a little ball. That's the glomerulus.

01:07:21It received the input from the little receptor cells, and it will process it further.

01:07:26Even though it receives smell data from one receptor, it can detect multiple smells. You've

01:07:32got around 1,800 of those spheres extending above each nostril, and they're all located on top of

01:07:38the bony plate we've just squeezed through. Now we're in the outward extension of the brain that

01:07:44sits right above your nasal cavity. It looks like a bulb, which is why it's called the olfactory bulb.

01:07:52We've got a long road ahead of us. The little processing spheres are now extending to something

01:07:58called the mitral cells. These are neurons, and they look like little spiders with very long legs

01:08:04extending on each side. Let's move further into the bulb, to the olfactory tract, and then inside

01:08:12the brain. The bulb is part of the limbic system. This is a large network of structures close to the

01:08:18middle of the brain that connects to the central nervous system. Brain cells carry the information

01:08:24to a small area in your brain called the amygdala. That's where you process your emotions.

01:08:32Stop it! Okay. It's also the area that activates your fight-or-flight response. Then the signals

01:08:39go to the hippocampus, the place where you make memories, process emotions, and learn stuff.

01:08:45Next stop, the thalamus, which sends some of the smell information to the orbital frontal cortex

01:08:50to connect it with your taste information. Smell is the only sensation that travels directly to

01:08:57the emotional part of your head. Other senses, such as sight and sound, first go to the thalamus.

01:09:04This acts as a relay center in the middle of the cerebral hemisphere,

01:09:08and it sends the data to other regions of the brain.

01:09:12But our sense of smell works in mysterious ways. When you haven't eaten for some time,

01:09:18your body produces a hormone called ghrelin. That hormone sends a signal to your brain,

01:09:24hey, you need energy, buddy, I can't find anything in your stomach.

01:09:28Your brain responds by making you hungry. The same hormone activates some receptors,

01:09:34which trigger the little smell bulb we traveled through earlier.

01:09:37This gives you a heightened sense of smell to improve your chances of finding food.

01:09:43Now, imagine you're in a store, and someone sprays some perfume on a piece of paper.

01:09:48You lean in to sniff it and close your eyes. That action works like an elimination process,

01:09:54where you remove one of your senses to heighten the other ones.

01:09:59It's like when people turn down the radio in their cars when they're lost or trying to

01:10:03concentrate. When you have a cold, you lose your sense of smell. That's called anosmia,

01:10:10or smell blindness. And because the roof of your throat connects to your nose,

01:10:14when you chew on food, aromas are released and activate your smell receptors.

01:10:20With a stuffed nose, the smell molecules from the food can't reach the sensory cells.

01:10:25They can't make their way to the thalamus to connect to your sense of taste.

01:10:29This is why everything seems tasteless. Everyone smells the world using different receptors,

01:10:34and some scientists believe that every individual has at least one odor that they can't detect.

01:10:40It could be vanilla, garlic, menthol, coffee, or even certain kinds of fruit.

01:10:47Have you ever sniffed some spicy peppers that made you cough?

01:10:51A few years ago, scientists discovered that the lungs have some odor receptors too.

01:10:57But instead of sending the spicy scent to your brain, they give you a signal to cough.

01:11:02Quite amazing, isn't it? Who else knows what the nose knows?

01:11:06Your toes? Well, maybe on some future video. Bye-bye!

01:11:12The cornea is the only part of your body with living cells that doesn't have blood vessels.

01:11:18It gets nutrients and oxygen directly from the tear fluid on the outside.

01:11:23And the thick watery substance you have between the cornea on the inside.

01:11:28And also from the nerve fibers connected to the cornea.

01:11:31That's why contact lenses used to be a potential issue.

01:11:35The older ones were reducing oxygen supply, since the cornea mostly gets oxygen from the outside.

01:11:42This problem was solved, or at least reduced, when silicone hydrogel lenses came to the market.

01:11:48Some other parts of your body with no blood vessels are your nails,

01:11:52hair, outer skin layers, and tooth enamel.

01:11:57Did you notice your sweat sometimes smells of onions after your workout?

01:12:01You have nothing to worry about. There are two types of sweat glands in your skin.

01:12:07The first kind of glands are located on certain areas of your body,

01:12:10like the groin region and the armpits.

01:12:13They produce a specific oily fluid, which is a response to certain emotional experiences.

01:12:20Another type of sweat gland is way more common.

01:12:23They're distributed all over your body,

01:12:25and are responsible for the specific sweat you get after the workout.

01:12:29The sweat cools your body down as it evaporates from your skin.

01:12:33It's 99% water, so it's practically odorless.

01:12:38Well, at least when it first leaves the pores and comes to the surface of your skin.

01:12:43But there are many types of bacteria on the human skin,

01:12:46and they feed on the nutrients in that sweat.

01:12:49Together with skin flakes.

01:12:50One of the byproducts of this is specific chemicals,

01:12:53and their smell can sometimes strongly remind you of onion.

01:12:58You may have noticed you produce more saliva when you go for a run,

01:13:02especially if it's a short jog in cold weather.

01:13:06But if you're running a marathon, and it's a nice warm day outside,

01:13:10you'll produce less saliva.

01:13:13It's your body trying to offset the drying effect,

01:13:16since you breathe through your mouth way more.

01:13:20But your body becomes more dehydrated over longer periods,

01:13:24which is why it's trying to conserve water by reducing saliva production.

01:13:28Every training you do, no matter how intensive it is,

01:13:32also makes you secrete more of a specific type of protein.

01:13:36It makes the saliva more viscous and sticky,

01:13:39which is why you may feel like your mouth is dry way more after your workout.

01:13:45Humans see the world 15 seconds out of date,

01:13:48which means your brain constantly keeps you a little bit in the past.

01:13:52This way, it helps you stabilize your vision of the world around you.

01:13:57Your eyes receive a huge amount of visual information.

01:14:00Yep, literally millions of colors, shapes,

01:14:03and ever-changing motion wherever you turn.

01:14:06It's not an easy task for your brain to process all that.

01:14:10The visual world alters all the time

01:14:12because of changes in viewpoint, light, and the rest of the outer factors.

01:14:17Your visual input changes because you need to blink.

01:14:21Plus, your head, eyes, and your entire body are always in some sort of motion.

01:14:27Your brain has to establish a mechanism that can create illusory stability.

01:14:33It automatically smooths your visual input.

01:14:35It doesn't analyze every little visual snapshot.

01:14:39It's like a time machine.

01:14:41You actually perceive an average of things you saw in the past 15 seconds

01:14:46at any given moment.

01:14:48The brain pulls together objects so they appear more similar to each other.

01:14:52That's why it tricks you into believing you're in stable surroundings.

01:14:56If your brain kept you updated in real time,

01:14:58the world would feel like a very, very chaotic place

01:15:02with constant changes in movement, light, and shadow,

01:15:05which would probably feel like you were hallucinating all the time.

01:15:10Your bones are really strong, but your teeth,

01:15:13which we also consider as part of the skeletal system, are even stronger.

01:15:18That's because of the enamel, the hard outer layer of your tooth.

01:15:23The enamel keeps the tissue and the delicate nerves inside your teeth safe.

01:15:29You're basically burning calories while you're thinking.

01:15:32When you rest and don't engage in any particular activity except for the basics,

01:15:36which includes digesting, breathing, and keeping yourself warm,

01:15:41it's the stage where your brain uses up to 20 to 25% of the total energy of your body.

01:15:47That means your body will burn around 350 to 450 calories per day

01:15:52while pretty much doing nothing.

01:15:55We're not the only ones in the animal kingdom with such a mechanism.

01:15:59Some small mammals like the minuscule pygmy marmoset and the tiny tree shrew

01:16:04devote the same percentage of their total body energy to their brain.

01:16:08Most of the energy the brain burns is to help its cells,

01:16:12the neurons, to communicate with each other.

01:16:14They do it via chemical signals the brain transmits across synapses,

01:16:19those special cell structures.

01:16:21So the brain directs a lot of energy towards synapses in order to make them work.

01:16:26Your brain never really rests.

01:16:29Even when you're sleeping, certain parts are active.

01:16:32So your brain needs its fuel to work,

01:16:36and you're basically burning calories in your sleep.

01:16:40The more demanding mental tasks you take throughout the day,

01:16:43the more calories you burn.

01:16:45So if you skip today's workout, solve some sudoku.

01:16:50Do you like to rush with your ice cream?

01:16:52Sometimes it pays off, but if you do it often,

01:16:55you must know the feeling of brain freeze pretty well.

01:17:00It's a pretty intense and uncomfortable feeling

01:17:03that comes from the front or sides of your head

01:17:05right after you drink or eat something cold,

01:17:08such as a slushy drink, ice cream, or an ice pop.

01:17:12Some people even go through a similar sensation

01:17:15whenever they're exposed to cold air.

01:17:17Scientists are still not sure exactly why this happens,

01:17:21but one of the theories is the cold substance

01:17:23stimulates a cluster of nerves located at the back of the palate.

01:17:28Another theory says the blood vessels in the roof of the mouth and sinuses

01:17:32quickly constrict because the temperature in your mouth drops

01:17:36before they dilate again.

01:17:38Brain freeze is not something dangerous

01:17:40that you should be seriously worried about.

01:17:42And no, hanging over the table, groaning,

01:17:45or clasping your head in your hands won't help much.

01:17:50Some people like to sleep a lot.

01:17:52Hey, guilty as charged.

01:17:54But some have a certain condition called familiar natural short sleepers,

01:17:59which means they're kind of immune to sleep deprivation.

01:18:03About 1% of our population has it.

01:18:06They can fall short on sleep and feel pretty good about it.

01:18:10They're fine with sleeping for six hours per night.

01:18:12This amount would wreck the majority of people after a couple of nights.

01:18:17The human eye normally has three cones.

01:18:20That means we can recognize approximately a million different shades

01:18:24in the green, red, and blue spectrums of colors.

01:18:27But there are some people with a rare condition,

01:18:30so-called tetrachromats, that have four cones in their eyes.

01:18:34This allows them to see ultraviolet shades,

01:18:37which means they can distinguish 100 million distinct colors.

01:18:43Did you know your skeleton is all wet?

01:18:45I mean, your entire body mostly consists of water, up to 60%.

01:18:50That fluid is not only in your organs, muscles, and skin.

01:18:53It's in your skeleton, too.

01:18:55Your bone mass is almost one-third water.

01:18:59There's this amazing hidden network a human body holds inside.

01:19:03Blood vessels are really small.

01:19:04But if you could line them all up, you'd get something huge.

01:19:08Your entire body boasts a network of 60,000 miles of blood vessels.

01:19:14One of the ways to keep your network healthy is by eating right.

01:19:18Have you ever wondered why our distant relatives,

01:19:20the primates, are so much stronger than us?

01:19:24In many ways, our bodies are very similar.

01:19:26Look at the chimp's muscle structure, for example.

01:19:29But our closest primate relatives are approximately 1.35 times stronger than us.

01:19:35The human body developed more slow-twitch muscle fibers

01:19:39compared to the rest of the primates.

01:19:41This type of muscle fiber is a less powerful one,

01:19:44but it lets us endure more than other primates

01:19:47and do things like foraging and hunting,

01:19:50activities that helped our distant ancestors to survive.

01:19:53That's also the reason why we can run a marathon.

01:19:56A monkey could never do it.

01:19:58But we'd still lose in a strength competition.

01:20:02Laughter is contagious.

01:20:04It's not just a metaphor.

01:20:06Researchers have found that strong emotions

01:20:08can make the brain activity of different people sink.

01:20:12Laughter is something science usually links with social creatures.

01:20:17People are almost 30 times more likely to laugh when in some social situation.

01:20:21Hanging out with their friends or people they feel relaxed with.

01:20:25One of the theories says that you're probably going to join

01:20:28when you see your friend laughing because humans are empathetic beings.

01:20:32Your brain will release endorphins when you're laughing.

01:20:35These are special chemicals that make you feel safe and at ease.

01:20:39So, we're not sure why exactly our laughter is contagious,

01:20:42but it feels really good, so...

01:20:44Join us on the bright side of life and laugh away.

01:21:14Full of nerve endings.

01:21:16That's why it hurts so bad when we get a foot injury.

01:21:19Yet, they aren't as delicate as we think.

01:21:22It's incredible how our feet are put together.

01:21:24They consist of 26 bones, 33 joints, and over 100 muscles, tendons, and ligaments.

01:21:31These are working together like a machine to let us move around.

01:21:36When we run, our feet work like springs.

01:21:40They must handle up to seven times our body weight every time they hit the ground.

01:21:44Thanks to the clever arrangement of ligaments, tendons, and muscles,

01:21:49our feet store and return much of that force to the ground.

01:21:53By the way, they can also give us hints about our overall health.

01:22:00And every pair of feet is unique.

01:22:04No two pairs are exactly the same.

01:22:07They come in different sizes, shapes, flexibility, strength, and walking patterns.

01:22:13It's like our feet have their own personalities.

01:22:17But how have our feet come to this point?

01:22:20Researchers have been trying to figure out when and how early humans started walking upright.

01:22:26Well, they've been looking at feet.

01:22:29Toes, to be exact.

01:22:31Bipedalism, which means walking on two legs, was a major step in human evolution.

01:22:37It influenced a bunch of other changes in our lineage,

01:22:40like how we behave socially and develop our material culture.

01:22:44So, these scientists have been digging into the details of foot evolution

01:22:48to piece together the story of our species.

01:22:55The team has been checking out these special joints called metatarsophalangeal joints,

01:23:00which are placed between the long bones of the foot and the toe bones.

01:23:04In 2015, they found that, unlike in other primates,

01:23:08this type of joint in humans faces upwards,

01:23:11allowing us to extend it, which is perfect for walking on two legs.

01:23:15But apes and other primates have downward-facing joints,

01:23:19giving their feet a hand-like grasp.

01:23:25In their latest study, the researchers looked at fossils of primates and hominins,

01:23:29a human group, to see when this upward-facing joint first appeared.

01:23:34It turned out it had shown up about 4.4 million years ago

01:23:38in the lateral toes closest to the outside edge of the foot.

01:23:42Yet the big toe kept its downward-facing joint until much later, about 2.2 million years ago.

01:23:51So, it seems like early feet might have still kept some grasping ability

01:23:55while people were adapting to walking on two legs.

01:23:59The fully bipedal adapted big toe evolved relatively recently.

01:24:03But weirdly, our feet didn't leave much of a trace in the fossil record until recently.

01:24:11It's frustrating because understanding how our feet evolved

01:24:14is crucial to unraveling the story of human evolution,

01:24:18especially when it comes to walking on two legs.

01:24:21Our modern human foot evolved separately to suit different needs.

01:24:25The chimpanzee foot is more flexible, suitable for climbing trees,

01:24:29while the human foot is stiffer, perfect for bipedal walking.

01:24:33So, we might as well talk about the benefits of walking barefoot.

01:24:42It can actually bring us closer to our natural walking pattern or our gait.

01:24:47That's a good thing because it allows our body to move the way it's meant to.

01:24:52Shoes can make you feel like you are walking on clouds,

01:24:55but they can sometimes hinder certain muscle groups from doing their job and strengthening our bodies.

01:25:01But when you go barefoot, for starters,

01:25:04you have better control over how your foot lands on the ground.

01:25:08This helps with balance, body awareness, and even pain relief.

01:25:13Plus, it can improve your foot mechanics,

01:25:15which can positively affect your hips, knees, and core.

01:25:19It keeps your foot and ankle joints flexible and strong,

01:25:22thanks to the proper range of motion and muscle stability.

01:25:26And let's not forget about those uncomfortable shoes that don't fit right.

01:25:30Walking barefoot can relieve issues like bunions or hammer toes caused by improper footwear.

01:25:37Have I mentioned stronger leg muscles?

01:25:39Yep, going barefoot can give your legs a nice workout,

01:25:42which is excellent for supporting your lower back.

01:25:45So, kick off those shoes and let your feet breathe

01:25:48the next time you find yourself on soft grass or sandy shores.

01:25:52Not just our feet have evolved over time,

01:25:54our ancestors had bigger brains too.

01:25:57It means our brains have shrunk.

01:26:00Researchers looked at cranial fossils and discovered that our brains started downsizing

01:26:04about 3,000 years ago.

01:26:07Agriculture took the stage around 10,000 to 5,000 years ago,

01:26:11and civilizations sprouted like mushrooms after a rainstorm.

01:26:16But it's not just our feet that have evolved over time.

01:26:18There were sprawling cities, architectural wonders,

01:26:25and even some fancy writing thrown into the mix.

01:26:31The connection between brain size and IQ isn't as straightforward as it seems.

01:26:36Many critters rock brains that make ours look dumb.

01:26:39A massive study with thousands of brain scans and IQ tests

01:26:43revealed that brain size and IQ are like two friends at a party.

01:26:47Sometimes they dance together, and sometimes they go solo with no strict correlation.

01:26:52It turns out some ant societies are like a mirror to our own,

01:26:56complete with their own version of farming and teamwork.

01:27:00And ants with bigger societies have bigger brains,

01:27:03except when they get into the whole farming gig.

01:27:06But smaller brains might be a cooler choice when teamwork gets super complex.

01:27:12Maybe the invention of writing around 2,000 years ago also played its role.

01:27:16It's like the ultimate external brain.

01:27:19You write stuff down, and boom, you have ideas at your fingertips.

01:27:23It's like your brain is outsourcing its memory power.

01:27:29Here is a recent thing you might want to consider, especially if you are a gamer.

01:27:34Some streamers have made an unexpected discovery after spending countless hours wearing headphones.

01:27:41There's a headphone-shaped groove on top of their heads.

01:27:44Let's bring in science before we all start imagining our skulls reshaping like Play-Doh.

01:27:50It's highly unlikely that headphones are engaged in skull remodeling.

01:27:54According to experts, giving a human skull a makeover takes 297 pounds of pressure.

01:28:01So what's really happening here?

01:28:04The headset is just giving a friendly nudge to our softer bits and pieces,

01:28:08causing a temporary dent that can be smoothed away.

01:28:11Another thing is about your phone holding style.

01:28:14Do you use your pinky to prop up the weight of your device,

01:28:17forming a sort of locked-in position?

01:28:20Ever wondered if this way of gripping might be causing some issues to your hand's well-being?

01:28:28Now, as smartphones keep getting bigger and better, a funny thing is happening.

01:28:33More and more people start noticing this smartphone-pinky issue.

01:28:38You might have noticed a tiny groove forming on your pinky from being a loyal phone holder.

01:28:44Let's set the record straight once and for all.

01:28:46Holding your phone this way for long periods can actually bring some trouble.

01:28:51A common issue here is a trigger finger.

01:28:54Basically, bending your small finger to cradle the phone can cause it to get stuck in a flexed

01:28:59position, especially if you've got a trigger finger lurking beneath the surface.

01:29:03It's like a tiny finger traffic jam.

01:29:06Treatment often involves injections or minor procedures to release the tendon tangles.

01:29:11Your wrist might also decide to join the hand-hurting parade.

01:29:15This one causes numbness and tingling in your thumb and other digits.

01:29:19Plus, when your elbow is flexed, like when you're holding your phone to your ear,

01:29:24it can put pressure on the ulnar nerve,

01:29:26leading again to numbness and tingling in your ring and little fingers.

01:29:30Interestingly, apart from a tiny muscle called the erector pili,

01:29:35our fingers don't have muscles.

01:29:37So how in the world do we wiggle them?

01:29:41The muscles in our forearms are like puppeteers pulling the strings behind the scenes.

01:29:45These muscle maestros initiate finger movements.

01:29:49And here's where the real magic happens.

01:29:52Those movements are like secret messages zipping down to our fingers through tendons.

01:29:57Think of tendons as those trusty messengers delivering commands straight to our fingertips.

01:30:02How's that for finger wizardry?

01:30:12We, I mean, human beings, have been evolving for 6 million years.

01:30:16But we're still not perfect.

01:30:18Turns out that our bodies have a bunch of design flaws.

01:30:23First of all, we're not perfect.

01:30:26First of all, human eyes have tiny blind spots.

01:30:29Never mind the philosophical ones.

01:30:31Such a spot is about the size of a pinhead.

01:30:34It's located at the point where the optic nerve

01:30:36passes through the surface of the retina at the back of the eye.

01:30:40Your optic nerves connect your eyes to the brain.

01:30:43They carry images for your brain to process.

01:30:45This is how you see.

01:30:47In the spot where these nerves leave your eye, though,

01:30:49there's a lack of something called photoreceptors.

01:30:52These receptors detect light and are the reason you can see.

01:30:56Without them, your eyes wouldn't be able to send

01:30:58any signals to your brain to describe what you're looking at.

01:31:01But because there are no photoreceptors there,

01:31:04you've got a tiny blind spot in each of your eyes.

01:31:09If people were designed perfectly without this flaw,

01:31:12they'd have eyes just like octopuses.

01:31:14It may sound weird, but the eyes of these creatures are eerily similar to humans.

01:31:19But their optic nerves run behind the retina.

01:31:22This means that the nerves don't have to leave the eye at any point,

01:31:25so there's no gap that causes the blind spot in human eyes.

01:31:30What else?

01:31:31Around 65 million Americans complained about having issues with their back,

01:31:35and this is because of evolution.

01:31:37Just like dogs, humans used to walk on all fours.

01:31:40When people were walking on their hands and knees,

01:31:43the curve of their spine was pretty much perfect,

01:31:46and all their organs felt comfortable.

01:31:48Because of this, there was never any pressure on their backs.

01:31:51Well, we evolved to start walking on two legs to save energy.

01:31:55The search for food took longer and longer,

01:31:57and when walking on two legs, people saved 25% of energy.

01:32:03But this was bad news for people's backs.

01:32:05Because this way, their spines were basically forced to turn into a column

01:32:09to support all the weight and make space for other organs.

01:32:13But if your spine was completely straight, you wouldn't be able to walk on two legs.

01:32:17So it evolved to become curved.

01:32:19But this puts a big amount of pressure on your lower back.

01:32:23So basically, to get rid of our pesky back problems,

01:32:26you should start walking on all fours again.

01:32:28That'll work.

01:32:31Make no bones about it, people have too many bones in their feet.

01:32:34We have all these bones because our ape-like ancestors

01:32:37needed them to grab onto tree branches.

01:32:39Now people aren't swinging from trees anymore,

01:32:42but we still have all those bones, which makes us prone to damaging them.

01:32:46And this can be extremely uncomfortable.

01:32:49Think about how many times you've stubbed your toes.

01:32:53If we were designed perfectly, our feet would look like those of an ostrich.

01:32:57These birds have way fewer bones.

01:32:59And the parts that look like knees turned backwards are actually their ankle joints.

01:33:04This makes ostriches less prone to injuries and also helps them run fast.

01:33:08Wow, if people were designed this way, it would make the Olympics way more interesting.

01:33:12I'd sure watch.

01:33:15Now, chew on this one.

01:33:17Human teeth are also far from perfect.

01:33:19People spend so much money on preserving them.

01:33:22At the same time, no other animal has to visit a dentist as we do.

01:33:26Also, once our teeth are permanently damaged or fall out, we can't grow new ones.

01:33:32Sharks are the opposite.

01:33:34They have an endless supply of teeth.

01:33:36In some shark species, a new set of teeth develops every two weeks.

01:33:40Kangaroos also have way better teeth than people do.

01:33:43If we were designed perfectly, we'd probably have the same teeth as our bouncing buddies.

01:33:48Once their teeth wear down, they fall out.

01:33:51And their rear teeth migrate forward.

01:33:55That's not the only issue we have with our teeth.

01:33:57Our mouths are way too crowded.

01:33:59Hey, I normally have a foot in mine.

01:34:02In the process of evolution, the human brain grew dramatically.

01:34:05And our jaws had to become wider and shorter to make room for it.

01:34:09But this left almost no room for our wisdom teeth.

01:34:13In the past, wisdom teeth were helpful when people needed to break down food.

01:34:18But as we learned to cook and process food, these teeth weren't needed anymore.

01:34:22So, in short, people should just get rid of them completely.

01:34:25And this may actually be happening.

01:34:28Around 25% of people, mostly Eskimos, are now born without some or all of their four wisdom teeth.

01:34:36Now it happens that our knees are quite impractical too.

01:34:39It's the most complex joint in the body.

01:34:41It's sandwiched between two massive levers, which is already pretty risky.

01:34:46The knee only moves forward or backward, which doesn't make it a very secure construction.

01:34:51That's why there's a bunch of rules in many kinds of sports, like soccer or rugby,

01:34:56that forbid hitting an opponent's knee from the side.

01:34:59To make people better suited to their new sporty lifestyle,

01:35:02the hinge-like mechanism of the knee could be replaced with a ball and socket.

01:35:07This would be like the structure you have in your shoulders and hips.

01:35:12Friends, Romans, countrymen, waggle your ears!

01:35:15Yep, like dogs and cats, some humans can waggle their ears.

01:35:19These lucky ones can move their ears independently thanks to special muscles called

01:35:23extrinsic ear muscles.

01:35:25But those serve literally no purpose, apart from providing a cool party trick.

01:35:30Speaking of design flaws, human voice boxes are in the completely wrong place.

01:35:35Your windpipe, thanks to which you can breathe, and your food pipe,

01:35:39which is, you guessed it, where the food goes, open into the same space.

01:35:43This space extends from your nose and mouth down to your voice box.

01:35:48You have a little leaf-shaped flap that covers the opening to your voice box whenever you swallow.

01:35:53It prevents food from going into your windpipe.

01:35:56But this mechanism isn't always fast enough.

01:35:59If you're talking while eating, it's incredibly easy for the food to slip down and

01:36:03accidentally go into your airway. And you definitely don't want that.

01:36:08The whale's voice box is designed much more wisely.

01:36:11It's located in its blowhole, away from its mouth.

01:36:14If people could move their voice box into their nose,

01:36:17they would have two separate tubes, and there would be no risk of choking.

01:36:22But there would be a downside – we wouldn't be able to talk.

01:36:25But we could communicate through singing instead, like our whale friends.

01:36:29We'd be able to do this by producing vibrations in our noses,

01:36:32kinda like this. Don't I sound better?

01:36:35Hey, leave me a comment below!

01:36:39You like ribs? I love em! But we're not talking about those kinds of ribs.

01:36:44Some of us humans have an extra 13th set of ribs.

01:36:47Between 1 and 3% of the world's population have these ribs,

01:36:51called cervical, and they serve absolutely no purpose.

01:36:55Some people have just one of such ribs, on the left side or the right side of their body.

01:37:00And others have cervical ribs on both sides.

01:37:03Appendix

01:37:04Now, you don't really need your appendix. It may contain some useful bacteria to help

01:37:08when you have stomach issues, but apart from that, it's not really necessary.

01:37:13The worst thing is that the appendix can get easily inflamed.

01:37:16The appendix was originally designed to help people digest cellulose,

01:37:20which is found in most green plants. This was back when people's diet mainly consisted of plants

01:37:25and almost no animal food. So, I say, let's get rid of it!

01:37:30Blood

01:37:31Moving on, blood is delivered from your heart to all the tissues of your body

01:37:35through thin pipes called arteries. The blood flows into each of your arms and legs through

01:37:40one large artery. For your arms, this artery is located at the biceps, and for your legs,

01:37:45it's in the front of the thigh. But your back needs blood too. And still, instead of having a

01:37:51large artery at the back of your body, you have smaller ones branching out and bundling around

01:37:56your bones and nerves. This is really impractical and makes people pretty susceptible to glitches,

01:38:02which is why you often get numb arms or legs. Bummer!

01:38:07How about something humorous? Take a look at your elbow. There, a branch of the artery

01:38:12meets up with something called the ulnar nerve. Thanks to this, you can move your pinky fingers.

01:38:17This is also why when you bang your funny or humorous bone, your arm goes all numb and tingly.

01:38:26To fix this, we really need one more large artery in the back of our body near the shoulder blades.

01:38:31This extra pipe would provide the blood with a more direct route. This would also stop your

01:38:36arms and legs from going numb when you bump them in the wrong place.

01:38:40Finally, there's this tail. People still have a tailbone, even though there's no tail in sight.

01:38:46For our ape-like ancestors, the tail was incredibly helpful.

01:38:50They used it to balance themselves while jumping from one high branch to another.

01:38:56Now that we live in actual houses, most of us don't swing through trees anymore.

01:39:00The tailbone, whose official name is the coccyx, is easily fractured, so currently,

01:39:06it's just a design flaw. Researchers also claim that removing it would improve posture issues too.

01:39:13Ay-yi-yi, about 6% of people can vibrate and rapidly shake their eyeballs back and forth.

01:39:19It doesn't mean something's not right with their eyes, it's just a unique trick they can perform.

01:39:24Good at parties, I suppose. Your bones are designed to be used a lot daily,

01:39:29and some of them can absorb 2 or even 3 times your body weight. That's impressive,

01:39:34but your teeth are even stronger. When you bite something, the teeth can exert incredible

01:39:39pressure – up to 200 pounds! By the way, the enamel is considered to be part of your skeletal

01:39:45system. Your stomach has a pretty incredible capacity, being able to hold up to half a gallon

01:39:51of liquid – a whole large bottle of Coke. It's pretty hard to estimate how much hard food you can

01:39:56squeeze into your stomach, since the food is processed with your teeth before it gets inside.

01:40:01There's definitely not enough room for a turkey, but a good-sized chicken will probably fit it.

01:40:06Whenever you rotate your hand, the bones inside it actually intersect.

01:40:11Grab your hand and verify it. Yeah, not very useful.

01:40:15Now, show me where your stomach is. If you're pointing at your tummy,

01:40:18sorry, but it's wrong. It's up here, hidden between your ribs.

01:40:23Fun fact about bones. You know that your body is about 60% water, right? What's new here is that

01:40:29your bones are in this too. About 25% of the human bone mass is made up of water.

01:40:35Scientists believe that the appendix isn't here to stay. Nobody really knows why we need it,

01:40:41but some researchers claim it helped our ancestors process the tree bark they were eating.

01:40:46As it's no longer part of our daily diet, the appendix can disappear from our bodies

01:40:50without any consequences. A human eye has some resemblance to a car engine.

01:40:55They both need various liquids to perform properly. An engine needs gasoline, and an eye

01:41:00needs tears. In order to work well, the tears should be thoroughly distributed all over the eye.

01:41:06That's why we blink up to 20,000 times a day. So, a lid is a bit of a windshield washer.

01:41:12Almost all of our body is covered with hairs, even if we don't notice them.

01:41:16They grow even in the belly button. Their purpose is to catch lint. The only part of

01:41:22the human body that doesn't get any nutrients from blood is the cornea of the eye. Instead,

01:41:27it's fed by tears and fluid in the front of your eyes. If you never knew you had a personal body

01:41:33guard, look deeper. Your liver is your security guard, protecting you from toxins and many other

01:41:39things you don't want to have. It's also pretty indestructible and can even regenerate.

01:41:44When you blush, it means there's an increased blood flow in your body.

01:41:48Not only do your cheeks get somewhat red, but your stomach lining too. It's because it has

01:41:53plenty of blood vessels, and when there's more blood than usual, it turns red.

01:41:58Only about 43% of you is actually you. You're over 50% tiny little creatures that mainly live

01:42:05in your gut and other body parts without ever leaving it. Still, even though your own cells

01:42:10are fewer than microbial ones, there are, on average, about 100 trillion of them in you.

01:42:16Let's count them. You start. Your stomach has a lining replaced every 3-4 days. That's done to

01:42:23stop it from eating itself. The digestive acids we've got can be pretty damaging. One thing that

01:42:29surely rests while you're sleeping is your nose. You just won't smell anything nasty in your sleep.

01:42:35The thing is that your sense of smell basically deactivates at night. If there's some really

01:42:40terrible smell in your bedroom, you won't even be bothered. We can accidentally digest small

01:42:45objects, such as plastic items, glass, coins, and many other small objects. They pass their way

01:42:51through the digestive tract within 48 hours. Really, just trust me on this one. You have

01:42:56better things to do. Scientists used to believe we could distinguish about 10,000 smells. Nope.

01:43:02Recent research showed that people were able to distinguish more than a trillion smells.

01:43:07We also remember them better than anything else, and smells can even evoke some distant memories.

01:43:13We can digest tiny quantities of plastic, but the human digestive system can't really bear

01:43:19grass. Grazing animals have special teeth and several stomachs to process raw leaves and grass,

01:43:25while we have none of that stuff. But don't feel bad. Among mammals,

01:43:29only humans can always walk on two hind limbs and keep that posture for their entire lives.

01:43:35You might object that kangaroos or gorillas move in the same way, but the roos use their

01:43:40tail as a third leg, and gorillas use the help of their long arms to keep balance.

01:43:45The stomach is the most important defender of the immune system. Hydrochloric acid in our stomach

01:43:51kills dangerous food toxins, viruses, and bacteria that get in there with the food you eat. This

01:43:56acid can digest even the stomach itself, but the mucous membrane protects it.

01:44:01Body fat isn't just a nuisance. It acts as insulation material, energy reserve, and shock

01:44:07absorber. Your body sends the most fat into your waist region because that's where your internal

01:44:12organs are. If something happens to you, this layer of fat might as well protect your vitals

01:44:17from irreparable damage. We've got two really fast muscles. They control the eyelid closely.

01:44:23These are the fastest muscles in our body. Eyes are fragile and need protection. That's why,

01:44:28when the reflex is triggered, these muscles shut the eyes within about 100 milliseconds.

01:44:34That's not more than 0.1 second! We recognize only purple-blue,

01:44:39green-yellow, and yellow-red colors. Everything else is a combination of these three. It's

01:44:44impossible to calculate how many of these combinations the human eye sees because

01:44:48every person has slight visual differences. But it's about 1 million combinations on average.

01:44:54Now, even if you brush your teeth twice a day and never forget about mouthwash,

01:44:59your mouth still stays one of the dirtiest parts of the human body. Ew. Millions of bacteria live

01:45:05inside it. The good news is that most of these bacteria are good for the body and protected from

01:45:10bad bacteria and viruses. The second dirtiest place is the belly button, and it's probably

01:45:17because it's the first ignored place. The thing is, we don't really use them after we're born,

01:45:22so this forlorn area accumulates all kinds of germs, sweat, and dirt. The belly button has

01:45:28over 2,300 bacterial species, and it does need extra attention. You think you owe your strong

01:45:35handshake to all your strength workouts? Well, you're more likely to owe it to your pinky.

01:45:40Just kidding. Anyway, a pinky is the strongest finger out there. This humble finger is

01:45:46responsible for 50% of your hand strength. Still, the most used finger is the thumb. It takes to

01:45:53itself 40% of the hand's action. Well, it probably makes it the most important finger too. Two more

01:45:59humble helpers are your toes that carry about 40% of your weight. If you've ever heard that humans

01:46:05don't really need their toes, don't believe it. They're also the main pushers when you walk.

01:46:10Tomatoes have more genes than humans. This shouldn't concern you, though, because it's not

01:46:15the number of genes that matters, but the complexity of their connections.

01:46:20Nails don't only help us catch random objects and peel the stickers off. If you didn't have

01:46:25a rigid structure against which to press, you wouldn't be able to judge how firmly to hold

01:46:29anything. Our hair color is easily explained by genes. There are not more than 2% of people with

01:46:36naturally red hair. They're followed by blondes, about 3%. And all the varieties of brown shades,

01:46:42only about 11%. The vast majority goes to black hair, including very dark brown.

01:46:49Yeah, your hair can stop growing at a certain length. A hair usually grows from 2 to 7 years,

01:46:55so usually it doesn't exceed 42 inches. Well, tell that to this gal from China who broke all

01:47:02the hair records with the longest hair ever. In 2004, her hair was 18 feet 5.5 inches long.

01:47:09Rapunzel, where have you been, girl? When we laugh, think, look at something, dream, move,

01:47:15or do some other activity with our body, small electrical and chemical signals run between

01:47:21neurons along those connections. Our brain is always active, sometimes even more when we're

01:47:26sleeping than when we're awake. And by that, neurons make and send more information than all

01:47:31the phones in the whole world. You're sitting somewhere outside, and an insect lands on your

01:47:37leg. Your skin has sensory neurons, and they quickly send the message to your brain at an

01:47:42impressive speed, 150 miles per hour. The brain sends back the message to your leg to shake the

01:47:48insect off very fast, and the speed that information travels is even bigger, 200 miles per hour.

01:47:56Toenails grow around 4 times slower than your fingernails. This happens because we do more

01:48:01things with our hands compared to feet, which is why we cause more trauma to our fingernails.

01:48:06There's a high possibility your right hand has different types of microbes than the left one.

01:48:11This happens because they cover our skin from head to toe, and their variety depends on our

01:48:17skin thickness, humidity, temperature, texture, and chemistry, which can change as we use our

01:48:22right and left hands in different ways. Our nails and hair are made of keratin,

01:48:27which is a material we find in certain body parts of some other animals as well. For instance,

01:48:33claws, hooves, horns, wool, fur, feathers, beaks, turtle shells, and porcupine quills.

01:48:40Our body is made of stardust. Really. The more complex elements in our body can only come about

01:48:46through supernovas. The first stars were just gassy lumps that were drawn together and,

01:48:52at some point, started the process of combustion. This finally led to a nuclear reaction in its

01:48:58center. Stars that were there right after the Big Bang were over 50 times bigger than our Sun is

01:49:03now. Inside of them, there was a constant process of making the elements, and those large stars were

01:49:09burning their fuel faster. Most of the elements in the human body were formed in those stars over

01:49:14billions of years, so you could realistically say that part of you is immortal. Cool, huh?

01:49:212. Humans have tails. Okay, that sounds weird, I know, but it's true! While our bodies are still

01:49:29forming in the womb, at around day 31-35, you can really start to see it. Right now, you have a tail.

01:49:36It's inside you. It's part of your coccyx, to be more precise. If you were to have an x-ray right

01:49:41now and ask the doctor to show you your tail, you'd see some small bony segments at the bottom

01:49:46of your spine. We lost our tails over many millennia of evolution. Imagine if we still

01:49:52had our tails. They'd have to redesign pants. Maybe they'd have a special hole or even a tail

01:49:57pocket. Sitting might be a bit uncomfortable too, to say the least. Our ancestors also had fur we

01:50:03lost at about 1.2 million years ago. You might be thinking that we still have fur in the form of our

01:50:09body here, but that's nothing compared to what we used to have. We were thickly furred like

01:50:14chimpanzees and gorillas are now because we needed it to stay warm. You might be annoyed

01:50:19that we lost it if you live somewhere freezing cold like Alaska. Still, you could look at it

01:50:24the other way. Losing our fur lets us enjoy the warm weather a bit more. Living in larger groups

01:50:30meant we shared stuff, and not all of it was positive. It's possible that humans with less

01:50:34hair or fur would get sick less often because they didn't have as many parasites on them,

01:50:39like lice or ticks. This might be the reason why we evolved to lose our fur and become what you

01:50:45see today. Although, I have to admit, more body warmth would come in very handy right now. I

01:50:51wouldn't need to keep this blanket on my legs anymore. Oh, not again. Let me just grab a cup

01:50:57of water to make these hiccups go away. Ah, much better. Okay, in reality, it's not that easy to

01:51:04stop hiccuping. But why is it so hard to stop them? Well, it could be because of a strange feature of

01:51:09a past evolution. One theory is that hiccups have no real use anymore, and that we actually only do

01:51:15it because we come from amphibians. They had both lungs and gills at the same time. When they went

01:51:21underwater, the entryway or glottis to their lungs would close. Fast forward to today, and we still

01:51:27have that mechanism of closing the glottis, but it's useless because we don't live in the water.

01:51:32Wow, how unfair. If we have to get frustrated by hiccups, we should at least be able to get some

01:51:38use out of it. Picture this, you start getting the hiccups, and it's like a superpower. You

01:51:43stop breathing through your lungs and start using some gills. That'd be something else,

01:51:47especially for anyone who really likes swimming. Most of our teeth fit pretty much perfectly in

01:51:52our mouth, but there are 4 of them who arrive late to the party and ruin everything. I'm talking

01:51:57about wisdom teeth. They serve no real purpose, but humans and a few primates have them. However,

01:52:04lucky species like the tamarins don't have to worry about them. About 35% of people don't

01:52:09even have wisdom teeth. We might be on our way to losing them altogether, once and for all.

01:52:14No more going to the dentist on a mission to remove them. No more headaches from them either.

01:52:19In Ireland, there are a lot of people with red hair. Like, really a lot. Upwards of 30%. That's

01:52:25a lot of redheads out there. This is a result of genetic drift. Genetic drift is when a feature

01:52:31is passed on from your ancestors without really having any purpose. This is exactly why some

01:52:36people have red hair. So, if you have red hair, there's no real reason for it. It's just your

01:52:41ancestors from a past age who passed it on to another member of your family, and eventually

01:52:47you. And I think red hair is incredibly fun and attractive. Inside our mother's womb 16 weeks in,

01:52:53we get a powerful urge to grasp the umbilical, and so we do. Monkeys do this too, and there's

01:52:59a reason for it. It's because, when they're out in the wild, they need to hold on to their

01:53:04parents' fur. Humans used to do this, but since we lost all of our fur, there's no reason for

01:53:09us to develop this involuntary grasping, called the Palmar Grasp Reflex. Open wide and say,

01:53:15ah, good, I can see your tonsils now. But what are they even used for? If we take a good look at it,

01:53:21they actually cause more problems than benefits. Tonsils appeared as a way to protect us from

01:53:26germs and other nasty stuff when we eat food. Still, more often than not, all they do is give

01:53:32us a horrible sore throat. Because of this, it's really common for people to get rid of them.

01:53:37Picture a little pouch. We have one of these inside our body. Not exactly like this, but an

01:53:43organ that sort of resembles a pouch – our appendix. Scientists used to think it was completely

01:53:49useless, but recently found that it might actually have some use. Still, like tonsils, it often

01:53:55causes more problems than benefits. People commonly have their appendix removed and face

01:54:00no real consequences, so it can't be that important. It might've helped our ancestors in the

01:54:05past, but issues with the appendix can be a real big stomachache. Okay, you know how some people

01:54:11can weirdly move their ears? Like this. I can't do it. You might be able to, though. Try it for

01:54:17yourself. Some of us can do this because, like other animals, we have a muscle called the Auricular

01:54:23Muscle, but it's useless for us. Cats, on the other hand, control their ears pretty well. If only

01:54:29we could learn from them. They look forwards and listen out for a noise behind them without moving

01:54:34their heads – just their ears. That's a pretty cool skill if you ask me. Stretch your arm as far

01:54:40as you can. Your hand, too. Now connect your thumb with your pinky finger. You might see a line appear

01:54:45on your wrist. What you're seeing is called the Palmus Longus, and about 90% of the world's

01:54:51population has it. Statistically speaking, it's likely that you have it, too. Back then,

01:54:56our ancestors needed every bit of help they could get to climb trees and grasp things.

01:55:01But when we started walking, it made these muscles completely useless. Monkeys, on the other hand,

01:55:07still climb trees easily. They have a muscle in their feet called the Plantaris Muscle,

01:55:11also known as the Monkey Muscle. We have this, too, except we don't really need it because we

01:55:17don't go around doing any monkey business. Like the Palmaris Longus, about 10% of people are born

01:55:23with it. Chances are, if monkeys are hanging from a branch, that's the muscle they're using.

01:55:28If you're getting that late-night urge for food at 3am, it's because of hunger. You probably

01:55:34already knew that, but what you don't know is that hunger evolved as a trigger to drive us to

01:55:39search for more food. So, if you still got a few extra pounds you're trying to get rid of,

01:55:44you know what to do. Blame it on evolution! Our hungriest ancestors would've tried harder to

01:55:50look for food and survived to pass that trait on to us. Our love of sugary snacks like delicious

01:55:56chocolate cookies and milk is because of evolution, too. Our taste buds evolved just as hunger did

01:56:02to help us find food that's beneficial to us. You're out for a walk and get hit with a chilly

01:56:08breeze. You're only wearing a t-shirt, so you decide to go back home. You get into your house

01:56:13with chattering teeth and realize that you've got goosebumps, too. We get this from our furry

01:56:18ancestors. When it was cold, they would get goosebumps and their fur would stand on end.

01:56:23This would trap air and insulate their bodies like a nice fluffy coat. We don't have fur anymore,

01:56:29so it doesn't do much. Evolution also explains why you might get goosebumps when you're scared.

01:56:35Picture this, you're a caveman out in the wild when suddenly a tiger jumps out at you. It starts

01:56:41growling at you. No worries, your hair stands on end and you look giant. The big pointy fur

01:56:47intimidates the tiger so it runs off. Or you have the alternative ending where the tiger doesn't

01:56:52care and eats you anyway. Maybe that's why we lost the fur, because it didn't work all the time.

01:56:59We don't actually need five toes. You're doing the laundry and your hands are full.

01:57:03Oh, you dropped a towel. What do you do? You pick it up with your feet, of course.

01:57:07This is possible because of our fifth toe, but we could do without it.

01:57:11Since we walk upright and we don't need to go around jumping from branch to branch,

01:57:16this toe is mostly useless. We can walk and even run just fine with four toes,

01:57:21maybe even less. So who knows, maybe in the future, humans will only have four toes on each foot.

01:57:28Not even twins have tongue prints that are alike. The tongue is a movable and strong set of muscles

01:57:34that almost never gets tired. It contains anywhere from 5,000 to 10,000 taste buds.

01:57:41Those little white and pink bumps on your tongue aren't taste buds, but each of them does have a

01:57:46bunch of them inside its surface tissue. Evolution gave us taste buds so that we can stay alive.

01:57:52For instance, sour and bitter flavors can be a sign that you may be eating rotten food or

01:57:58poisonous plants. The back of the tongue is more sensitive when it comes to bitter flavors,

01:58:04which is why we can spit out bad food before we swallow it.

01:58:07Salty and sweet tastes tell us if foods are rich in nutrients.

01:58:12By the time they're 60, the majority of people lose half their taste buds.

01:58:17Yes, your tongue is pretty cool, and its prints can be used for biometric authentication,

01:58:22just like fingerprints. Each of us have a different and unique tongue print.

01:58:26So if you don't want to reveal your secret identity, keep your tongue hidden.

01:58:31That would be funny. Why do we even have fingerprints? Scientists had a lot of

01:58:36different theories, but they now believe it's because having them allows skin to stretch more

01:58:41easily. That prevents blisters, protects the skin from damage, and may improve our sense of touch.

01:58:48Humans are not the only ones with unique fingerprints. Koalas have them too.

01:58:53Only around 7% of people are left-handed. Left-handed people mostly chew food on the

01:58:59left side of their mouth, while right-handed people do so on the right.

01:59:03We lose almost 9 pounds of skin cells every year. Don't worry, we replace them quickly.

01:59:09We produce more cells than there are people living in the United States, every 15 seconds.

01:59:15Our body is always regenerating, and we replace our skin hundreds of times during one lifetime.

01:59:21Yep, our body regenerates, except for our teeth.

01:59:25They're the only part of the body that can't heal itself.

01:59:29We have teeth that are similar to a shark's. Their teeth also have a thing called dentin

01:59:34inside of them, and theirs are just as strong as ours. Of course, theirs are sharper and bigger,

01:59:40but still. Teeth are part of the human skeleton, but they're not considered bones.

01:59:46You'll spend approximately 38 days of your life brushing your teeth. And guess what,

01:59:51it's possible to brush them too much. That can make them more sensitive,

01:59:56because it wears down the natural enamel. Your left and right lungs are not the same size.

02:00:02The right one is bigger, because the left shares its real estate with your heart.

02:00:07Hiccups are something almost all mammals go through from time to time, not just humans.

02:00:13The record was set by a man named Charles Osborne. He couldn't stop hiccuping for 68 years.

02:00:19Guess no one told him about the whole eating sugar trip.

02:00:22There's only one part of your body that doesn't get a regular delivery of blood,

02:00:26your corneas. They get oxygen directly from the air.

02:00:30Our eyes can differentiate between 10 million different colors.

02:00:34The muscles that help our eyes focus on something make around 100,000 movements a day.

02:00:40If you wanted to make your leg muscles do the same amount of work,

02:00:44you'd need to take a long walk, at least 50 miles.

02:00:48We can't all see infrared light or ultraviolet radiation.

02:00:52Only 1% of us can do that. And if you can see one of those,

02:00:56it doesn't necessarily mean you can see the other.

02:00:59Research says blue-eyed people all over the world may be related,

02:01:03or at least share a very distant ancestor. Scientists looked at blue-eyed individuals

02:01:09from Turkey, India, Jordan, and Scandinavia. They all had the same eye color gene sequences.

02:01:16They believe this trait comes from one blue-eyed person

02:01:19whose genes mutated around 10,000 years ago.

02:01:23Before that, people's eyes were just all different shades of brown.

02:01:27People with blue eyes are generally a bit more sensitive to pain

02:01:31than individuals with other eye colors. We blink about 20 times in one minute,

02:01:36which means we do it more than 10 million times a year.

02:01:40That thing about being similar to sharks, well, that goes for our eyes, too.

02:01:45If part of your eye gets damaged, you can replace it with a shark's.

02:01:50We can't sneeze with our eyes open. Try it. It's really hard to override

02:01:55your built-in reflexes. Eyelashes have their own life, too.

02:01:59One single lash lives for about 150 days before falling out.

02:02:04We all get goosebumps when we hear Good News, our favorite song,

02:02:08or when it's ridiculously cold in the frozen food aisle.

02:02:12It's a reflex we got from our ancestors. It happens when you release adrenaline.

02:02:17It makes your hair stand on end and helps you look more imposing.

02:02:22Scary, huh? The human brain has 100 billion neurons

02:02:26and a memory capacity that's equal to more than 4 terabytes, which is a lot.

02:02:32Your brain uses more than a quarter of all the oxygen your lungs take in,

02:02:36and it's mostly water, more than 75%. Stay hydrated, people.

02:02:41It's not true that humans use only 10% of their brain.

02:02:45We use much more than that, even when we're asleep.

02:02:48Most of our brain is constantly active. We just don't use all parts of it at the same time.

02:02:54Out of all the species out there, humans are the only ones who can blush.

02:02:59It comes from a rush of adrenaline. When you see your face turn red,

02:03:03know that your stomach is turning red, too. How weird is that?

02:03:07When you crack your knuckles, the sound you're hearing is tiny gas bubbles being released.

02:03:13There are pockets of gas trapped between your joints,

02:03:16so when you stretch them, they make a popping noise.

02:03:19Ugh, so satisfying.

02:03:23We use 43 muscles when we frown, but only 17 when we smile.

02:03:27No, scientists are still arguing over this one.

02:03:30Say cheese!

02:03:32An average person eats around 33 tons of food over a lifetime.

02:03:36That's 6 elephants worth!

02:03:40We breathe in approximately 2,900 gallons of air on a daily basis,

02:03:45but we can't swallow and breathe at the same time.

02:03:48Most people need about 7 minutes to fall asleep,

02:03:51and we're just about the only living creatures that sleep on our backs.

02:03:56Randy Gardner decided to set the record for the longest period without sleep.

02:04:00The year was 1964, and he stayed awake for 11 days.

02:04:05That's 264 hours.

02:04:07Guess he had pretty noisy neighbors.

02:04:09Amongst all animals, humans are the only ones with chins.

02:04:14When you're thirsty, it means the water loss you're experiencing

02:04:17is equal to 1% of your total body weight.

02:04:20If it goes past 5%, you might even faint.

02:04:24During your lifespan, your body goes from having 300 bones to 206.

02:04:30Over half of all your bones are in your feet, your ankles, hands, and wrists.

02:04:35The biggest human bone is the thigh bone,

02:04:37and the smallest one is called the stirrup bone.

02:04:40It's inside your eardrum.

02:04:42Your nose can recognize a trillion different scents and remember 50,000 of them.

02:04:48Also, women are better smellers than men,

02:04:51and our sense of smell is 10,000 times more sensitive than our sense of taste.

02:04:56Our lungs have a surface area that's almost equal to the area of an entire tennis court.

02:05:02So what's up with that feeling you get when you're going over a crest on a roller coaster,

02:05:06and your stomach jumps up into your throat?

02:05:09Well, the seatbelt keeps your body in place,

02:05:11but your stomach, intestines, and smaller internal organs get a little airtime.

02:05:17It doesn't do you any harm, but your nerves can't figure out what's going on.

02:05:21They really think your stomach has jumped all the way into your throat.

02:05:25We're all taller in the morning because throughout the day,

02:05:29the cartilage between our bones gets compressed.

02:05:32That makes us around one fingernail shorter by the end of each day.

02:05:36Nose and ears, parts of our body that never stop growing.

02:05:40It's mostly thanks to gravity.

02:05:42The veins and arteries inside your body are long enough to make two trips around the world.

02:05:48Blood makes up about 8% of your body weight.

02:05:51When you listen to music, your heartbeat syncs with the general vibe of the song.

02:05:55So choose wisely.

02:05:57Your skin is the biggest organ you have.

02:06:00It counts for about 15% of your total weight.

02:06:03Get this, you can burn more calories during sleep than when watching TV.

02:06:08Hmm, then what about sleeping while the TV's still on?

02:06:13That's it for today.

02:06:14So hey, if you pacified your curiosity, then give the video a like and share it with your friends.

02:06:19Or if you want more, just click on these videos and stay on the Bright Side!

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