Jaw-Dropping Body Facts You'll Never Believe Without Proof

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Transcript

00:00:00It may seem there's nothing exciting about human bones, unless you find them in your

00:00:05closet.

00:00:07But normally, they're hidden under multiple layers of cells and tissues.

00:00:11They're dense, hard, and unassuming.

00:00:14But are they?

00:00:16Your bones not only protect your internal organs and help you move, but also store fat

00:00:21and minerals.

00:00:23Your blood cells are produced there.

00:00:25Most of the bone tissue isn't even solid.

00:00:27How about going on a journey through your bones to see it with your own eyes?

00:00:32But you'll need to get through several layers of other tissues first.

00:00:35To start with, you'll have to squeeze through the skin, your largest organ.

00:00:40Be careful, it's a labyrinth of hair follicles, sweat glands, nerve endings, and blood vessels

00:00:45where you can easily get lost.

00:00:48Right under the skin, there's a layer of fat.

00:00:50Its main purpose is to keep your body warm.

00:00:53This layer consists of tiny plastic bags, each with a drop of fat, and you may have

00:00:58a tough time navigating around these bubbles.

00:01:01After passing this obstacle course, you're inside your muscles.

00:01:05Their cells, fibrous and long, are always ready to spring into action, helping you transport

00:01:11your body wherever you need.

00:01:13Moving through this layer of tissue is tricky because such cells form bundles, and that's

00:01:18what makes your muscles so strong.

00:01:21Imagine taking a bunch of rubber bands and stretching them.

00:01:24Hard?

00:01:25Your muscle tissue's tough like that.

00:01:27Finally, you reach your destination and see a thin, dense membrane.

00:01:32It's the outer surface of a bone.

00:01:34This layer consists mostly of connective tissue made up of proteins.

00:01:38You also spot numerous blood vessels.

00:01:41Their tiny perpendicular branches sneak deeper into the bone to feed bone cells.

00:01:46You notice that these branches lie in minuscule channels.

00:01:50The inside of the surface layer is filled with stem cells.

00:01:53They're the busiest in childhood and become less active when a person grows up.

00:01:58But if a bone is damaged, they jump back into action and get down to repairing it.

00:02:04Luckily, all your bones are intact.

00:02:06But if there was a fracture, you'd see nearby vessels bleeding and forming a thick lump

00:02:12around the injury.

00:02:13In about 2 days, the area would be surrounded by countless bone-producing cells.

00:02:18They would begin to change, turning into different kinds of cells and forming new bone between

00:02:23the ends of the fractured one.

00:02:25Anyway, it's time to move further toward your bone's hardest part – the outer layer,

00:02:31which is smooth and solid.

00:02:33Because of its density, it's also called compact bone.

00:02:37This kind of bone is the reason why X-rays, which can normally pass through nearly anything

00:02:42including your body's soft tissues, can hardly get through your bones.

00:02:46This part makes up 80% of your total bone mass.

00:02:50It's incredibly hard to squeeze through the compact bone because it consists of numerous

00:02:54microscopic columns.

00:02:57Inside these cylinders, there are even more bone-producing cells.

00:03:01And in the middle, there's a central canal that connects the bone's nerve fibers and

00:03:05blood vessels.

00:03:06The cylinders go along the bone and help to prevent it from bending or fracturing.

00:03:11Once you get through this super-hard layer, the picture around changes dramatically.

00:03:16You're in spongy bone!

00:03:19True to its name, it looks like a sponge or a honeycomb that consists of tiny needles.

00:03:24This bone tissue is way less dense than the compact bone, more flexible, and also much

00:03:30lighter.

00:03:31You notice that the spongy tissue is only near the ends of the bone you're exploring.

00:03:36It means you're inside one of the long bones, whose structure is a bit different from others.

00:03:41In the middle, it has what looks like a tunnel to you.

00:03:44It's made of compact bone that surrounds a cavity filled with a special substance.

00:03:49It's called yellow bone marrow, and it's rich in fat.

00:03:53But it's time to return to the spongy bone.

00:03:56It's mostly found at the ends of long bones, inside vertebrae, and near joints.

00:04:01This sponge-like tissue has open spaces in it.

00:04:04They're filled with red bone marrow, which produces blood cells.

00:04:09While traveling further through the human skeleton, you discover that it consists of

00:04:13five types of bones.

00:04:15Long.

00:04:16They're much longer than they are wide.

00:04:18For example, your thigh or upper arm bones, and your toes and fingers.

00:04:23Flat.

00:04:24They're thin and slightly curved.

00:04:26These bones are like a layered cake.

00:04:28Spongy bone sandwiched between two parallel layers of compact bone.

00:04:33Your ribs and most of the bones in your skull are flat bones.

00:04:37Short bones.

00:04:38Shape-like cubes.

00:04:39They consist of a thin layer of compact bone around spongy insides.

00:04:43Short bones can be found in your wrists and ankles.

00:04:47Sesamoid.

00:04:48These are bones surrounded by tendons, and their main purpose is to hold tendons away

00:04:52from joints.

00:04:53There are numerous bones in your feet, hands, and knees, including the kneecap.

00:04:58These bones got such a name because they look like grains of wheat.

00:05:02Irregular bones.

00:05:04These don't fit into any category because their shape is too complicated.

00:05:08Those are most of the bones of your face and some of your skull.

00:05:12An adult skeleton's made up of 206 bones, and each of them has its own function.

00:05:18Interestingly, people are born with nearly twice as many bones, but as you grow up, these

00:05:23small bones fuse together and form larger ones as a person matures.

00:05:29If one bone's broken, those around it can't work properly either.

00:05:34It usually takes about 12 weeks for a bone to heal.

00:05:39The smallest bone in your body is dozens of times smaller than a penny.

00:05:43This bone's called the stapes and is located in your middle ear.

00:05:47The tiny thing weighs as much as 2 sesame seeds.

00:05:52You get a new skeleton every 10 years, because every year, 10% of your bone's mineral content

00:05:58gets renewed.

00:06:00The average person walks 1 to 3 million steps per year.

00:06:04That's why bones have to be so resilient, otherwise they wouldn't cope with the pressure.

00:06:10Your longest and strongest bone is in your leg.

00:06:13The femur, that's how it's called, runs from your hip to your knee.

00:06:18Even though your teeth are part of the skeletal system, they don't count as bones.

00:06:24More than half of all the bones in your body are in your hands and feet.

00:06:29The only bone in your body that's not connected to another is the tongue bone.

00:06:33It's a V-shaped bone at the base of your tongue that holds it in place.

00:06:39One percent of people are born with a 13th rib.

00:06:43Your bones aren't white, their color's rather yellow or pinkish from the outside

00:06:47and deep red inside.

00:06:49That's because of the blood vessels in and around them.

00:06:53If you fracture a bone, it'll heal on its own by producing new bone cells.

00:06:58A cast will only help it heal straight.

00:07:02People have known how to deal with broken bones for ages.

00:07:06In ancient Egypt, around 1600 BCE, they realigned fractured bones and bandaged them with linen.

00:07:15You can't control your bones, you can only tell your muscles attached to your bones where

00:07:19to move.

00:07:21Your bones reach their maximum density at the age of 30.

00:07:26Only 10% of the world's animals, including humans, are vertebrates, meaning they have

00:07:31a skeletal system.

00:07:33A coating of special tissue called cartilage covers a bone and prevents it from rubbing

00:07:38directly against another one.

00:07:41The enamel covering your teeth is even stronger than your bones.

00:07:45It protects the delicate tissue and nerves underneath.

00:07:49The biggest joint in your body is actually your knee.

00:07:53It has to be large to connect three equally big bones – the femur, going from your hip

00:07:57to your knee, the kneecap, and the shinbone.

00:08:02Some joints hardly move or don't move whatsoever.

00:08:06Those are between your teeth, inside the skull, and between the first pair of ribs.

00:08:12Bones store minerals, for example, calcium and phosphate.

00:08:16They can be released in your bloodstream when necessary.

00:08:19And finally, the so-called funny bone isn't a bone at all.

00:08:23It's a nerve that runs inside your elbow.

00:08:26When you hit it, you feel sharp, piercing pain.

00:08:30The upper arm bone the nerve runs by is called the humerus.

00:08:34But the pain is clearly not humerus.

00:08:37It can be funny when it happens to someone else though.

00:08:42Almost all of our body is covered with hairs, even if we don't notice them.

00:08:46They grow even in the belly button.

00:08:48Their purpose is to catch lint.

00:08:50Check it out, see?

00:08:52A single human hair can support 3.5 ounces of weight.

00:08:57That's how much two candy bars weigh.

00:09:00Our hair color is easily explained by genes.

00:09:03There's not more than 2% of people with natural red hair.

00:09:08They're followed by blondes and by all the varieties of brown shades.

00:09:13The vast majority goes to black hair, including very dark brown.

00:09:17Yeah, your hair can stop growing at a certain length.

00:09:21A hair usually grows from 2 to 7, so usually it doesn't exceed 42 inches.

00:09:26Well, tell that to this gal from China, who broke all the hair records with the longest

00:09:31hair ever.

00:09:32In 2004, her hair was 18 feet, 5.5 inches long.

00:09:38With age, your hair loses its natural color.

00:09:41It happens because keratin receives less pigment.

00:09:44As people grow older, the pigment cells in their hair follicles gradually vanish, and

00:09:50hair becomes gray.

00:09:51Some time passes and no pigment is produced at all.

00:09:55That's when hair turns white.

00:09:57The only part of the human body that doesn't get any nutrients from blood is the cornea

00:10:01of the eye.

00:10:03Instead, it's fed by tears and fluid in front of your eyes.

00:10:07A human eye has some resemblances to a car engine.

00:10:11They both need various liquids to perform properly.

00:10:15An engine needs gasoline, and an eye needs tears.

00:10:18In order to work well, the tears should be thoroughly distributed all over the eye.

00:10:23That's why we blink up to 20,000 times a day.

00:10:27So a lid is a bit of a windshield washer.

00:10:31We've got two really fast muscles.

00:10:34They control the eyelid closing.

00:10:36They're the fastest muscles in our body.

00:10:39Eyes are fragile and need protection.

00:10:41That's why when the reflex is triggered, these muscles shut the eyes within about 100 milliseconds.

00:10:47No more than 0.1 seconds.

00:10:50We recognize only purple-blue, green-yellow, and yellow-red colors.

00:10:56Everything else is a combination of these three.

00:10:59It's impossible to calculate how many of these combinations the human eye sees because

00:11:03every single person has slight vision differences.

00:11:07But it's about one millionth combinations on average.

00:11:11You see?

00:11:12The inability to distinguish colors, also known as color blindness, affects around 8%

00:11:17of males and 0.5% of females.

00:11:22But colors themselves aren't as stable and objective as they might seem.

00:11:27Several tests have shown that people experience colors differently, depending on many factors

00:11:31such as geographical location, language, and gender, to name a few.

00:11:37It means that you can enjoy the same sunset with your friend and see completely different

00:11:41colors without even knowing it.

00:11:45Just like fingerprints, your eye color is unique.

00:11:47It can even affect the way you perceive light and make your vision one of a kind.

00:11:52To understand how this is possible, you gotta figure out how the eye color is formed.

00:11:57This is the iris, the colored part of the eyeball.

00:12:00The iris contains pigmentation, and its content determines what eye color you have.

00:12:06Every human has a slightly different amount of pigmentation, that's why you won't find

00:12:11two people with identical eye colors.

00:12:15Three specific genes in your body are responsible for melanin levels and determine pigmentation.

00:12:21Blue and green-eyed people have less melanin in their iris, and those who have more melanin

00:12:27have darker eye colors, like brown and hazel.

00:12:31Some rare people have beautiful deep black eyes, but this is only an optical illusion

00:12:36caused by the abundance of melanin.

00:12:39Pure black iris doesn't exist in nature.

00:12:42Although these eyes look very dark, they're actually dark brown.

00:12:47Studies have proved that eye pigmentation impacts your vision.

00:12:51No matter how dark or light your eye color is, people with lighter eye colors are more

00:12:55sensitive to light, which may cause them to feel uncomfortable on sunny days.

00:13:01If you have a light eye color and have to squint when you go outside, don't forget to

00:13:06put on sunglasses.

00:13:08Your irises contain less pigment that serves as protection from the sun's rays.

00:13:13But since melanin acts like natural sunglasses, you have better night vision compared to dark-eyed people.

00:13:19On the contrary, if you have a darker eye color, your eyes can cope with bright light

00:13:24better during the daytime.

00:13:26Dark-eyed people should feel more confident while driving at night, because they don't

00:13:31get blinded by car headlights that much.

00:13:35Your peripheral vision is almost completely black and white.

00:13:39It's because you have more color-detecting cones in the center of your retina than at

00:13:43the sides.

00:13:46Women can distinguish more colors than men because they have two X chromosomes, and men

00:13:51only have one.

00:13:53Even if something is wrong with one of the chromosomes, a woman can still see colors

00:13:58correctly.

00:13:59That's why women are rarely colorblind.

00:14:02There must be at least some photos where you have red eyes.

00:14:07When the camera flash goes off, your eyes aren't prepared for such an influx of light.

00:14:11Your pupils remain dilated, which is why the light gets reflected off the red blood

00:14:16cells of the choroid.

00:14:18This is a layer of tissue at the back of your eye that nourishes your retina.

00:14:24The weird-looking flies you see right in front of your eyes every now and then are eye floaters.

00:14:29You see them because of tiny structural imperfections in one particular part of the eye that gets

00:14:34in the way of light.

00:14:36They get worse with age.

00:14:39You spend 10% of the time when you're awake with your eyes closed.

00:14:43It's all those times you're blinking.

00:14:46Humans are capable of using echolocation like bats and dolphins.

00:14:51With some training, you can find your way in complete darkness analyzing the surroundings

00:14:55by sounds bouncing off objects.

00:14:58Don't need to practice that.

00:15:01About 6% of people can vibrate and rapidly shake their eyeballs back and forth.

00:15:07That doesn't mean something's not right with their eyes.

00:15:10It's just a unique trick they can perform.

00:15:13The main purpose of eyelashes is to shield your eyes and protect them from sand, moisture,

00:15:18dust, and debris in the air.

00:15:21Your eyelashes sense when something comes up too close to your eyes, like an insect

00:15:25flying towards you, and trigger your blink reflex.

00:15:30Blinking also helps when you need to flush out some tiny particles or debris stuck in

00:15:35your puncta.

00:15:36Those are small openings you have in your eyelids.

00:15:39That's where the tears get pumped out.

00:15:41Your eyebrows stop sweat from running directly into your eyes.

00:15:45Your skin there and the shape of your bones also work together to direct the sweat towards

00:15:50the sides of your face.

00:15:53Onions produce a special chemical irritant.

00:15:56It stimulates special glands in your eyes, causing them to release tears.

00:16:01The nose is probably one of the most underappreciated parts of the body.

00:16:05You wouldn't even be able to enjoy eating without it.

00:16:09About 80% of the taste of any food is thanks to the nose and its ability to recognize odors.

00:16:15If you hold your nose while eating, you will taste almost nothing.

00:16:19With no sense of smell, you're likely to recognize food mostly by texture, so an onion

00:16:24might seem no different than a big, refreshing apple.

00:16:28Scientists used to believe we could distinguish about 10,000 smells, but they were wrong.

00:16:35Recent research showed that people are actually able to distinguish between more than a trillion

00:16:40smells.

00:16:41We also remember them better than anything else, and smells can even evoke some distant

00:16:46memories.

00:16:48Your nose doesn't just help you breathe and catch odors.

00:16:51It filters the air for sensitive throats and lungs.

00:16:55If we inhale dry air, the nose moistens it, cools it, and heats it if necessary.

00:17:00Also, the nose cleans the air of dirt.

00:17:04Your nostrils don't work with the same efficiency all the time.

00:17:08When you breathe, one nostril does most of the work, and they switch every couple of

00:17:12hours.

00:17:1318% of people can move both ears at the same time, while 22% can move one ear at a time.

00:17:21People who can do it use weak vestigial muscles we got from our ancestor humans, who had this

00:17:26trait in common with cats.

00:17:30Some people can produce a roaring noise in their heads.

00:17:33All they have to do is tense their ears or jaws.

00:17:37There's a small muscle in the ear.

00:17:39It dampens loud sounds, like when you're chewing.

00:17:42But some people can flex that muscle, and that creates an audible rumble.

00:17:46Your teeth are the only part of your body that cannot heal itself.

00:17:52So you're positive that your body is all perfectly symmetrical.

00:17:56Surprise, surprise.

00:17:58And some paired body organs still don't work equally and compete for dominance all the

00:18:03time.

00:18:04Your face, for example.

00:18:05You probably already know your best side.

00:18:08But if not, you can use special apps that will take a picture of your face and split

00:18:12the image into the left and the right section.

00:18:15Then it will mirror the images to create two separate symmetrical faces.

00:18:19One face will show you what you'd look like if the right side of your face were the dominant

00:18:24one.

00:18:25And the other will show the left side option.

00:18:27Usually these two pictures don't look a lot like your actual face.

00:18:31But one of these faces reminds you a little more than the other.

00:18:35That's the one based on your dominant side.

00:18:38Some of the app developers analyzed the images and suggested that the left side of the face

00:18:42of most humans expresses emotions more intensively.

00:18:46That's why it seems more aesthetically pleasing to other people.

00:18:50But no worries.

00:18:51There are plenty of natural massage techniques and exercises to make your face look more

00:18:56symmetrical.

00:18:57For example, puckering your lips into a tight O will help balance facial muscles.

00:19:03Or you can open your eyes as widely as possible, stick out your tongue, and raise your eyebrows.

00:19:09This exercise also helps release muscle cramps from excessive talking and improper chewing.

00:19:15Want to make your jawline more defined and improve the tone of your vocal cords?

00:19:19Yogis have an exercise for that.

00:19:21They call it Jiva Mudra, or Lion's Pose.

00:19:24Open your mouth wide, lift your tongue, and roll it and press it against the hard palate.

00:19:30Look at the tip of your nose while you're widening your mouth.

00:19:34Try to breathe only through your nose during this exercise.

00:19:37Try gradually inhaling deeper and holding the air for longer with each time.

00:19:43Eyes don't work in perfect symmetry either.

00:19:45Your brain has a preference for which one of them takes the most information.

00:19:49Let's find out your dominant eye right now.

00:19:52Keep your spine and head straight, stick your arms out at eye level, and make a triangle

00:19:57in the air in front of you with your hands.

00:20:00Focus it on an object in the distance, a clock for example.

00:20:04Close your left eye.

00:20:06If you can still see the object in the center of the triangle, your right eye is your dominant eye.

00:20:11If the object isn't there, your dominant eye is your left eye.

00:20:16If the object isn't centered, no matter what eye you close, you might have mixed ocular dominance.

00:20:22How's that fun?

00:20:24Here's another test for you.

00:20:25Extend your arm and form a circle with your thumb and index finger.

00:20:30Pick an object on a wall.

00:20:32Keep both eyes open and center this object inside the circle.

00:20:36If one eye is dominant, the object will move outside the circle.

00:20:40So, if for example the object seemed to move when you closed your right eye, then you have

00:20:45right eye dominance, and vice versa.

00:20:48The next test will help you quickly find out your dominant eyebrow.

00:20:52Stand in front of a mirror.

00:20:53Try to lift only one eyebrow, and then try to lift the opposite eyebrow.

00:20:59You probably have better control over one of them, but don't worry if you don't have

00:21:03control over either of them.

00:21:05You can develop this skill if you practice in front of a mirror.

00:21:09As for your hands, you probably already know your dominant one.

00:21:13There's no country or population on this planet where left-handed people are the majority.

00:21:19Most people in the world, about 85 to 90 percent, are right-handed.

00:21:23That's why most tools, like scissors or knives, and even books, are designed with right-handed

00:21:28customers in mind.

00:21:30Studies found your dominant brain side defines which ear you use for your cell phone.

00:21:35Among the right-handed participants of the survey, 68 percent claimed they held their

00:21:39phones to their right ear, while 25 percent of polled people used the left ear, and only

00:21:457 percent had no preference.

00:21:48The result was different for those who are left-handed.

00:21:5072 percent of polled people used their left ear while talking on their cell phones, 23

00:21:57percent used their right ear, and 5 percent used both ears.

00:22:01It's all clear with hand dominance, but did you know you also have your dominant leg or

00:22:07foot?

00:22:08This information can be useful to you if you're engaged in sports, like snowboarding or dancing.

00:22:14Or you just do stretching to sit on a front split.

00:22:16Usually, if one is right-handed, then one must be right-leg dominant, but of course,

00:22:22there are exceptions.

00:22:24You can check which of your feet is dominant.

00:22:26Squeeze a pen between your right big toe and the second toe and try to write your name

00:22:30on a piece of paper.

00:22:32Or if it's too hard, just try to draw a circle, then try the same thing with your left foot.

00:22:37Now compare the two pictures.

00:22:40One of them probably looks better than the other, so your dominant foot is the one that

00:22:44writes better.

00:22:46Around one lucky percent of folks have equally dominant hands and feet and can use them equally

00:22:51well.

00:22:52The name of this rare condition is ambidexterity.

00:22:58You can try to develop this skill by special training techniques.

00:23:02Your dominant nostril is the nose hole you're breathing through the most.

00:23:05It changes several times during the day, depending on your brain activity.

00:23:10You might not notice when exactly your nostrils take turns in the lead role, but you can find

00:23:15out the current dominant nostril with this simple test.

00:23:19Place your finger on the right nostril and pinch it, then inhale and exhale slowly through

00:23:25your left nostril only.

00:23:27And now, do the same thing with your left nostril.

00:23:30If it's easier to breathe through your right nostril, it means that it's more active at

00:23:34the moment.

00:23:35Of course, this test should only be done when you blow your nose and you're healthy.

00:23:40Otherwise, mucus can distort the result.

00:23:43Your body flexibility can also develop asymmetrically, especially if you don't do stretching exercises

00:23:49regularly.

00:23:50Can you grasp your left hand with your right hand behind your back?

00:23:54And what about the opposite position, when your left hand is reaching from above and

00:23:58the right one from below?

00:24:00If you find these two tasks equally easy, congrats, you're probably a superhero!

00:24:05To balance the flexibility in your left and right body sides, you can quit the habit of

00:24:10sitting or standing in asymmetrical poses for too long.

00:24:15Try to sit with an even spine and feel the pleasant vibe throughout your back.

00:24:20Avoid leaning on your right or left elbow, or you can do that grasping exercise regularly

00:24:25to stretch more.

00:24:27If you prefer to sleep on the side, you probably have a favorite one.

00:24:31Your muscle memory forces your body to return to the sleeping position that was recorded

00:24:35as the most repeatable.

00:24:37So, if you ever decide to retrain yourself to sleep on your back, get ready to spend

00:24:42a few nights feeling uncomfortable.

00:24:44But if fetal position is your thing and you don't want to get rid of it, experts recommend

00:24:49putting some pillows between your knees and arms to minimize tension.

00:24:53Now what about your ears?

00:24:55Do you think they hear equally well?

00:24:57Well, it depends on many factors.

00:24:59The left and right ears process sound a little differently.

00:25:03The right ear responds more to speech and logic.

00:25:06While the left ear is more focused on emotional perception and music.

00:25:12Scientists believe it's because the left hemisphere of the brain processes primarily speech, while

00:25:17the right hemisphere processes creative and emotional signals like music and other arts.

00:25:23When a male hears a female voice, the auditory section of his brain gets activated.

00:25:29This means that female speech sounds more like music for the male brain.

00:25:34But when the same male brain hears a male voice, it will use the brain part responsible

00:25:39for speech processing.

00:25:41One of the explanations of this phenomenon is that the female voice is just more complex

00:25:45than the male voice.

00:25:47The vocal cords and larynx of women and men have different sizes and shapes.

00:25:52Also, females tend to have a greater melody in their voices, causing a more rich range

00:25:57of sound frequencies.

00:26:00If you don't have special equipment, but want to check if it's true, try tracking

00:26:04your overall sensation in the ears and the brain while listening to music.

00:26:08Then listen to some male's voice and feel the difference in sensations.

00:26:13Memorize or write down this difference, and then listen to some melodic female voices.

00:26:19Try to understand if it feels more like listening to music or speech.

00:26:23And finally, your heart is a dominant body organ, 24-7.

00:26:28It's the only muscle that never gets tired.

00:26:31So it makes sense to always treat it gently.

00:26:35Ok, look at yourself in the mirror.

00:26:39Yeah, right in the eye.

00:26:41See that little fold of tissue in the inner corner of both of your eyes?

00:26:45Well, get ready for this.

00:26:47It was actually once a third eyelid, or nictitating membrane.

00:26:52You can see it today in snakes or lizards, for example.

00:26:55The third eyelid was used for the same purpose as the other two, although it's unclear

00:27:00whether humans ever even had it fully grown.

00:27:03This membrane wasn't as thick as the two eyelids we have, and it could moisten the

00:27:08eye without obstructing the view.

00:27:10Right now, all we have left of it is this tiny fold in the corner of the eye, and most

00:27:15likely in the future we will lose it altogether.

00:27:19And maybe we'll finally stop waking up with that yucky crust that forms in our eyes overnight.

00:27:25Now, while you're still in front of the mirror, look lower.

00:27:29Lower, and lower still.

00:27:31Yeah, those are your toes!

00:27:33Say hello, and goodbye.

00:27:36Scientists believe that, in some more or less distant future, we'll get rid of our toes

00:27:41completely.

00:27:42Our ancestors, the ancient primates, needed toes to climb trees more efficiently.

00:27:48They used both their hands and feet to grab tree branches.

00:27:51You can see it today in most monkeys and apes.

00:27:54They have longer and more flexible toes, along with flappier feet that allow them to

00:27:58get a hang on branches.

00:28:00Their feet mobility also lets them grab objects from the ground if necessary.

00:28:05For us humans, even lifting a pin we dropped on the floor with our toes is a complex task,

00:28:11but not for our primate relatives.

00:28:14Humans have evolved along a different route.

00:28:16We started walking upright and climbed down from trees, making rigid feet and shorter

00:28:21toes more of a necessity over time.

00:28:24Today, we still use our toes for balance when rolling from the balls of our feet to the

00:28:30tips of the toes, but our balance is now much more centered.

00:28:34It first moved towards our inner feet, which resulted in our pinky toes becoming so tiny,

00:28:40and the big toes, well, so big.

00:28:43As the balance moves away from the toes entirely, though, they're more likely to get fused

00:28:48together in the future.

00:28:50Now turn around and look at your gorgeous behind!

00:28:54If you've ever fallen off a skateboard or slipped on an icy patch, you must remember

00:28:58what a terrible thing it is to hit that tailbone on a hard surface.

00:29:03Luckily for us, scientists predict it's going to go away pretty soon in the course

00:29:07of evolution.

00:29:09A tailbone is a feature that was left to us by our primate ancestors too.

00:29:14But yet again, they needed their tails to achieve more mobility among tree branches,

00:29:20using them to fling themselves from tree to tree.

00:29:23It's hard to say when humans dropped the tail to never pick it back up, but facts are

00:29:28facts, the only thing we have reminding us of those glorious tree-jumping days is the

00:29:33pretty useless bone at the lower end of our backs.

00:29:37Okay, back to the face now.

00:29:39Open your mouth and say, ah!

00:29:42If you're a lucky individual to have no wisdom teeth, then you can be proud knowing

00:29:47that you're a product of evolution going strong.

00:29:51As you might know, teeth are the only part of the human body that doesn't repair itself.

00:29:56So if you lost all your teeth back in the dark times with no dentists around, the only

00:30:02choice you had was to eat liquid food.

00:30:05Not cool.

00:30:07Dentists believe that nature gave us wisdom teeth as a replacement for old worn-out teeth

00:30:12we've had since childhood.

00:30:14That's why they grow so late in our lives.

00:30:17Today though, with all the progress dentistry has gone through, we tend to keep all or most

00:30:22of our teeth intact until a very old age.

00:30:26And even if we lose some, we can always replace them with new ones.

00:30:30That makes wisdom teeth a vestigial thing.

00:30:33And they seem to understand that, since more and more people never have to go through the

00:30:37ordeal of teething as grown-ups.

00:30:40Speaking of teeth, our entire jaw has been changing for the past 10,000 years, and is

00:30:46predicted to change even more quite soon.

00:30:50In fact, it's been the fastest changer of all our body parts.

00:30:55Back in the day, when early humans survived by hunting and gathering, they needed massive

00:31:00powerful jaws and bigger teeth to chew through raw meat and grind plants.

00:31:06As they came to cooking and then farming, their food became less tough, and so their

00:31:11jaws became smaller to fit the current needs.

00:31:14As time went by, our jaws shrank more and more, and they're likely to continue doing

00:31:19so in the future.

00:31:21With lots of processed foods that don't need much chewing, humans of the future are probably

00:31:26going to have more delicate facial features with thin jaw lines and smooth cheekbones.

00:31:33Some body parts are not going away, but making a comeback instead.

00:31:38A hundred years ago, Fabella, a tiny bone in the back of the knee, was only present

00:31:43in around 11% of people, and scientists thought it would disappear entirely pretty soon.

00:31:49But against all odds, the brave little bone has made it into the knees of a whopping 39%

00:31:56of modern people.

00:31:58It's still unknown why exactly the Fabella returned.

00:32:01But the most popular opinion is that we've grown taller and heavier than our ancestors.

00:32:07That much is true.

00:32:09As our diet became better and more nutritious, we learned to live longer and grow taller.

00:32:14We're now probably at the peak of our evolutionary height.

00:32:19And the Fabella might've appeared in our bodies to provide a smooth surface for the

00:32:23tendon behind the knee to slide on, reducing friction and lowering the chances of damage

00:32:29because of wear and tear.

00:32:31Speaking of becoming bigger, let's get you back to that mirror, shall we?

00:32:36Flux a little bit.

00:32:38Nice biceps there.

00:32:40But unfortunately, not as nice as your ancient ancestors were.

00:32:45Not everything about evolution is 100% good for us.

00:32:48It's just a set of features that adapt at best.

00:32:52And that's the case with our muscles.

00:32:55They've grown smaller and weaker with time, especially in our upper bodies.

00:33:00In ancient times, humans needed big and strong muscles to do a lot of handiwork.

00:33:05From hunting and schlepping their catch home to crafting tools and building shelters.

00:33:10Later, it didn't grow easier.

00:33:12Much the opposite, in fact, plowing fields and building complex structures required a

00:33:17lot of physical strength and endurance.

00:33:21As the technological progress started booming, physical capabilities gave way to brain power.

00:33:27And machines began doing a lot of work for us, most of it even better than us.

00:33:33We shifted more towards sedentary lifestyle, spending more and more time in front of computers.

00:33:39And our muscles have been growing steadily smaller, because we simply don't need them

00:33:44as much anymore.

00:33:46It's highly likely that, as the progress goes further, we'll become much slenderer

00:33:51and have more trouble gaining muscle mass.

00:33:55Our brain is of particular interest because it's been changing in a kind of strange pattern.

00:34:01Our distant ancestors had a rather small brain at first, but the close relatives of humans,

00:34:07the Neanderthals, obtained a larger brain than the average modern human has.

00:34:12In the course of evolution, human brain grew larger.

00:34:16But in the more recent centuries, it started shrinking, and no one knows exactly why.

00:34:23Some experts say it might have to do with the change of our lifestyle and social connections.

00:34:28Early humans, especially hunter-gatherers, had to remember every plant and animal they

00:34:33saw, their properties, and how to use this or that thing.

00:34:37They were more generalists, having to learn everything their parents knew and find out

00:34:42more on their own.

00:34:44The modern human is more specialized in a certain area, delving deeper into some narrow

00:34:49subject while relying on their peers for the rest.

00:34:53Where ancient humans worked in groups in which anyone could potentially replace anyone else,

00:34:59we gather in teams, where each member has their own specific task and is irreplaceable.

00:35:05Still, brain size doesn't seem to matter that much, because orcas and elephants, for

00:35:10example, have bigger brains than us, which doesn't make them more intelligent.

00:35:15Happier?

00:35:16I'm guessing yes.

00:35:19And if we venture further into the unknown, meaning millennia from today, we might even

00:35:24develop some pretty unbelievable traits.

00:35:27Some go as far as to say that, if the tendency for the sea levels to rise persists, humans

00:35:33might adapt to living in water.

00:35:36We might evolve to have webbed hands and feet to swim better, and develop gills to

00:35:41be able to breathe underwater.

00:35:44Or if we go into space and start colonizing other planets, we will inevitably have to

00:35:49adapt to their conditions.

00:35:51Mars, for instance, has lower gravity and a much colder climate.

00:35:56It will probably make humans taller and lighter, but also may cause them to grow much more

00:36:01body hair to keep warm.

00:36:04Other planets with stronger gravity and higher temperatures will, on the contrary, turn humans

00:36:10into stocky, sturdy, and likely hairless creatures.

00:36:13The possibilities are endless.

00:36:16Eh, maybe due to social media, we'll just turn into little blobs with big eyes and thumbs

00:36:21and not much else.

00:36:23So much better for texting.

00:36:25Hope not.

00:36:27Your body actually glows!

00:36:29It emits a super-faint light that's at its strongest at around 3-4 PM.

00:36:34The sad news is that this glowing is 1,000 times less intense than what your eyes can

00:36:39see.

00:36:41Humans are the only animals that have chins.

00:36:44Even our closest genetic relatives, gorillas and chimps, lack this small piece of bone

00:36:48that extends forward from the jaw.

00:36:51Their lower jaws slant down and back from their front teeth.

00:36:55Scientists still haven't figured out this mystery.

00:36:57The opinions about why people are made this way differ.

00:37:01Some researchers think chins help us chew our food.

00:37:04Others are sure they have something to do with speaking.

00:37:06A few of us think it's simply a special place to grow a goatee.

00:37:11The most abundant element in the human body is oxygen at 65%.

00:37:16But it also contains lithium, cobalt, gold, and uranium.

00:37:21The rarest one of all is radium.

00:37:24On average, humans yawn 20 times a day.

00:37:27Partially spontaneously, for example, when you're tired, but sometimes when someone yawns

00:37:32near you.

00:37:34Scientists think it could be a thing called social mirroring.

00:37:37Usually, when animals mimic each other, they recognize some action as useful, so they decide

00:37:43to do it too.

00:37:44With humans, it happens when someone crosses legs, laughs, smiles at you, or...

00:37:52Your stomach acid breaks down the foods you eat and turns them into easy-to-digest particles.

00:37:57It also stops nasty pathogens and microbes that could make you sick.

00:38:01In fact, your stomach acid is so strong that it can even dissolve bone and metal.

00:38:07Don't start munching down on your soda cans, though.

00:38:10That's probably not going to end well.

00:38:12Your brain has more than 86 billion nerve cells.

00:38:16They're all joined together by 100 trillion connections.

00:38:19That's even more than the number of stars in the Milky Way galaxy.

00:38:23There's a good chance you can guess someone's name based on how they look.

00:38:28Researchers showed portrait photos to a group of people with four names written below.

00:38:33They were asked to choose the right name for this or that person.

00:38:36The law of chance says you'll guess it 25% of the time.

00:38:40But in this research, people got the names correct at a rate of 25 to 40%.

00:38:46And there were more than 94,000 faces shown.

00:38:49Let's say a man is called Bob.

00:38:52People will expect for him to have a rounder face than Tim.

00:38:55They expect Bob to be more jolly and ready to hang out with people.

00:39:00It has to affect his facial appearance in some way.

00:39:03A woman called Catherine can be considered more serious, studious, and concentrated.

00:39:08That could eventually influence her facial muscles as well.

00:39:12When ancient Romans flexed their biceps, they thought their muscles looked like mice.

00:39:18That's why the word muscle translates as little mouse in Latin.

00:39:22Your left lung is smaller than the right one because it shares space with your heart.

00:39:28Experts used to think that we can only distinguish 10,000 smells.

00:39:32In fact, a recent study found human beings can recognize 1 trillion smells.

00:39:38Millennials, or people born between 1981 and 1996, are more forgetful than older people.

00:39:45The main cause of their forgetfulness comes from higher levels of stress.

00:39:49So come on, dude, chill out, okay?

00:39:51Some scientists think that the purpose of fingerprints is a better grip.

00:39:56But others believe they're there to help wick water off them and allow the skin to stretch

00:40:00when needed to protect it from damage.

00:40:03There's also a theory saying that fingerprints improve the sense of touch.

00:40:08Hot coffee can taste better than cold coffee.

00:40:11Your taste bud receptors are most sensitive when your food is at or a little bit above

00:40:15room temperature.

00:40:17Hot coffee can then seem less bitter because taste buds that detect bitterness are more

00:40:21sensitive when the coffee is cold.

00:40:24The biggest molecule in the human body is the chromosome 1.

00:40:28A human cell has 23 chromosome pairs, and each chromosome 1 is made of 10 billion atoms.

00:40:35You inhale 25 sextillion molecules in just one breath.

00:40:40That's 25 followed by 21 zeros.

00:40:44When you're walking faster, at some point, you'll feel the natural urge to start jogging.

00:40:49Your body wants to have a stable state, whether you're running or walking.

00:40:54So if you're walking fast, it will unconsciously force you to start running.

00:40:58One theory is, we use more energy when walking faster than running.

00:41:02So that's one of the ways the body saves energy.

00:41:06Your pinky is a powerful little thing.

00:41:09Without it, your hand would lose a significant part of its power.

00:41:12Your index and middle fingers cooperate with your thumb to grab and pinch.

00:41:17And your pinky, together with your ring finger, provides grip strength.

00:41:22The fattiest organ in your body is your brain.

00:41:25Fat makes up at least 60% of its dry weight.

00:41:28This quality got the brain to the Guinness World Records.

00:41:32The organ contains around 25% of your body's cholesterol, which is vital for the brain's

00:41:36well-being.

00:41:38Your bones are four times harder than concrete.

00:41:41The strongest bone in your body is the femur.

00:41:44They can support up to 30 times the weight of a grown-up person.

00:41:48Even crazier is that our bones are made up of composite material, meaning they're both

00:41:53hard and elastic at the same time.

00:41:56Your fingernails grow twice as fast as your toenails.

00:41:59It would take 15 and a half months for your toenails to grow one inch, but only seven

00:42:04months for your fingernails to get this long.

00:42:07The outer layer of your skin is thicker on your feet than on other parts of your body.

00:42:12The heart has its own electrical system and can continue beating even when it's disconnected

00:42:16from the body.

00:42:18The vessels in your body are long enough to circle the earth twice or more.

00:42:23The idea that we use only 10% of our brains is a myth.

00:42:27At any given time, you use almost 100%.

00:42:30Otherwise, you wouldn't be able to perform simple tasks like drink a cup of coffee.

00:42:35More than 70% of your brain consists of water, and it needs 20% of your body's oxygen supply.

00:42:43The average lifespan of one eyebrow hair is four months.

00:42:47The body of a 110-pound person contains 40 tablespoons of salt.

00:42:53If you ironed out all the wrinkles in your brain and laid it flat, it would be the size

00:42:58of a pillowcase.

00:42:59The brain wrinkles as there's not a lot of room in the skull, so it folds over itself

00:43:04as it grows.

00:43:05By the way, don't do that pillowcase thing with your brain.

00:43:08Trust me on this one.

00:43:10We spend 40% of our life with our eyes closed.

00:43:14Most of that time is when we're asleep.

00:43:16But don't forget to count blinking, too.

00:43:19Or while driving.

00:43:20You produce around 85,000 pints of spit in your lifetime.

00:43:25That's enough saliva to fill around 500 bathtubs.

00:43:29Nuff said.

00:43:30The highest blood flow isn't actually in your heart, and it's not in your brain, either.

00:43:35It's in your kidneys.

00:43:36It's super hard for us to grasp just how small an atom is.

00:43:40But think of it this way.

00:43:42Your body is made up of a staggering seven octillion atoms.

00:43:46Yeah, doesn't that look like a seven being chased by a whole mob of zeros?

00:43:51For adults, the blood makes up 7-8% of the total body weight.

00:43:56About 55% of your blood is liquid plasma.

00:43:59The rest is red and white blood cells and platelets.

00:44:03They form clots and prevent bleeding.

00:44:06You can't swallow and breathe at the same time.

00:44:09The food you swallow and the air you breathe go down the same part of your throat at first.

00:44:14Only a bit deeper does the passage split into the esophagus, for food and liquid, and the

00:44:19trachea, for air.

00:44:21When you swallow, your airway gets automatically closed off.

00:44:25This prevents you from accidentally inhaling food.

00:44:28But occasionally, it still happens.

00:44:31There's a name for the growling sound that your stomach makes when you're hungry.

00:44:35It's called borborygmy.

00:44:38It takes 6-8 hours for food to travel through your stomach and small intestine.

00:44:43That's because your body is trying to absorb all its nutrients.

00:44:47The idea that the tongue has flavor zones is a myth.

00:44:51All taste buds can detect five tastes.

00:44:53But some receptors are more responsive than others.

00:44:57Human beings are the only animals that willingly delay sleep.

00:45:01Just make sure you get enough.

00:45:04Some people even see colors as letters and numbers, or hear them.

00:45:08Those who live closer to the Arctic Circle can name different shades of snow, because

00:45:12that's what they see all the time.

00:45:15To others, it's just white.

00:45:17Some languages only have general names for colors.

00:45:21For example, dark stands for cool hues like black, blue, and green.

00:45:26Colors like white, red, orange, and yellow are all called warm.

00:45:31Your eye processes more variations of warmer colors than cooler ones.

00:45:38There's a tribe in Australia who describes texture, the function of an object, and how

00:45:42it feels instead of its color.

00:45:45They don't have any names for colors at all.

00:45:49The Kandoshi, who live on the banks of the Amazon River in Peru, don't have a word that

00:45:54would describe the very concept of color.

00:45:56Instead, the name of some yellow bird will be used to describe the yellow color.

00:46:01Any ripe fruit will stand for red, and unripe fruit for dark green.

00:46:08A lot of people lose their ability to perceive some colors as they get older.

00:46:13By around the age of 70, their eye lens has become yellowish.

00:46:17This natural yellow filter they look through doesn't let them tell blue from purple and

00:46:21yellow from green.

00:46:24Half of your brain is hardwired to process visual information.

00:46:29A much smaller part is left to perceive flavor.

00:46:33That's why the color of food or drink can boost or curb your appetite.

00:46:37You'll always choose the reddest apple because your brain perceives it as the sweetest and

00:46:41ripest.

00:46:43There are no naturally blue foods, so you're least attracted to them and can even fear

00:46:48them.

00:46:49That's why installing a blue light in your fridge or eating from blue plates is a great

00:46:53way to eat less.

00:46:55You'll always choose brighter foods and vegetables because they're associated with

00:47:00a richer flavor.

00:47:02Eating them makes you feel healthier and happier.

00:47:05Yellow can boost your appetite as you associate it with energy and excitement.

00:47:09White can trick you into eating more and paying less attention to what you're munching on.

00:47:14That's because white food seems more harmless in terms of calories.

00:47:18If you eat from a white plate, you're more likely to overeat as it makes your food look

00:47:22brighter.

00:47:24Your brain also remembers the color of food wrapping.

00:47:27If you put salt and vinegar chips into a cheese and onion package, you might not even notice

00:47:32the difference in flavor while snacking on them.

00:47:36Food companies know that you'll eat more of whatever they're selling when it comes in

00:47:39different colors and flavors.

00:47:43Red gives you courage and strength for physical work.

00:47:46Yellow makes you happier and more productive and confident.

00:47:50Green brings balance and harmony to the office environment.

00:47:53Your eyes also love this color.

00:47:55They don't need time to adjust to it.

00:47:58Orange gives you a sense of comfort and warmth, so it's perfect for an office lounge.

00:48:02Birds, fish, and many mammals see the entire color spectrum in all its glory, just like

00:48:09humans.

00:48:10For some animals, good color vision is crucial.

00:48:13Without it, they won't tell ripe fruit from unripe green fruit.

00:48:19Whenever we yawn, we use the muscles in our mouth and tongue, and the contact can squeeze

00:48:24some of the saliva-producing glands.

00:48:27As a result, we might squirt a tiny stream of saliva without even noticing it.

00:48:32I had a friend in college who could do it at will.

00:48:34It was impressive.

00:48:36It turns out that saliva is basically filtered blood.

00:48:39Blood is processed thanks to special glands, and special cells absorb its properties.

00:48:44After that, the blood becomes saliva.

00:48:48People with red-colored hair are 1% of all people.

00:48:512% are natural blondes.

00:48:53Yeah, most people you see with these hair colors have dyed hair.

00:48:56Black is the most common hair color in the world.

00:49:01Your memory is affected by your body position.

00:49:04For example, you're much more likely to recall a situation where you waved to someone if

00:49:09you stand and wave again.

00:49:12Most scientists agree that tears that appear out of emotion are a unique human feature.

00:49:18No other animal is capable of crying because of sadness or joy.

00:49:23The pupils narrow and expand in order to control the incoming light.

00:49:28If there's a lot of light, they narrow the passage for light so as not to harm the vision.

00:49:33In the dark, the pupils expand to capture as much light as possible.

00:49:38The tongue has a lot of muscles, and some of them can strain only when you're learning

00:49:42a new language.

00:49:44A human bite almost always becomes infected because of all the bacteria that live in our

00:49:49mouth.

00:49:50In this sense, we're quite close to hyenas.

00:49:53Your bones are designed to be used a lot daily, and some of them can absorb two or even three

00:49:58times your body weight.

00:50:00That's impressive, but your teeth are even stronger.

00:50:05Even if you brush your teeth twice a day and never forget about mouthwash, your mouth

00:50:10still stays one of the dirtiest parts of the human body.

00:50:15Millions of bacteria live inside it.

00:50:17The good news is that most of these bacteria are good for the body and protect it from

00:50:21bad bacteria and viruses.

00:50:24In the morning, you're taller than in the evening.

00:50:27While sleeping, you're no longer affected by the force of gravity, and your spine stretches.

00:50:32Too bad you become shorter by daytime, though.

00:50:35A rollercoaster actually tosses your organs around, so you feel like your stomach's falling

00:50:39down.

00:50:40It's actually flipping inside your body.

00:50:43You think your fingerprints are the only unique thing in your body?

00:50:46Well, they're not.

00:50:48Your tongue print and your smell are also one of a kind.

00:50:51If anyone sniffs you, it's reason enough to get suspicious.

00:50:56If all your blood vessels were stretched into a single line, boy, that would hurt, but it

00:51:00would go around the Earth more than twice.

00:51:03An impressive feat that you wouldn't see because, well, you can't live without your

00:51:06blood vessels.

00:51:09Toothache and headache are linked together thanks to the trigeminal nerve.

00:51:13It goes through the jaw right to the head, so that when you feel tooth pain, it usually

00:51:18goes hand-in-hand with that in your head.

00:51:21You lose calories doing literally anything.

00:51:24A healthy eight-hour sleep, for example, makes you lose up to 800 calories.

00:51:28And yes, you spend energy even while eating.

00:51:32A person can go without food for more than 20 days.

00:51:35However, if you don't sleep for 10 days, your body will simply stop functioning.

00:51:40Talking about sleep, the average person forgets 90% of their dreams.

00:51:45And maybe that's a good thing.

00:51:46Otherwise, imagine how crazy the world would have been.

00:51:50The color of your dreams is affected by the TV you watched as a kid.

00:51:54If you're of an older generation that watched black-and-white TV, you'll see monochrome

00:51:58dreams more often than not.

00:52:00If you're used to color television, your dreams will also be colorful.

00:52:07Out of every 10,000 people on Earth, one person has their organs mirrored or reversed from

00:52:12their usual and customary positions.

00:52:15That is, their liver would be larger on the left side and the kidney would be a bit superior

00:52:19to the left one.

00:52:22People with light-colored eyes, blue or green, are better at tolerating pain than those with

00:52:26dark eyes.

00:52:28You'd think it might be related to melanin that affects the color of the eyes.

00:52:32The length of your foot is similar to that of your forearm.

00:52:35Don't believe me?

00:52:36Go check.

00:52:37I'll wait right here.

00:52:39Nah.

00:52:41We have seven major holes in our bodies.

00:52:43Our mouths, our ears, nose, eyes, and our, you know, down under.

00:52:48Hey, we're Australian.

00:52:50G'day mate.

00:52:51We're also a Taurus, if you dig geometry.

00:52:55A human ring, a donut, a life buoy, or even a bagel.

00:52:59Mmm, bagel.

00:53:01Don't forget the schmear.

00:53:03Seriously, counting the pores in your skin and the rest, there'd be millions of holes

00:53:07though.

00:53:08Trillions more likely.

00:53:09Holy cow, we're holy.

00:53:13Bodies throw thermal radiation off as a tiny amount of light.

00:53:16This light is 1,000 times less visible than normal light, so you're not a torch yet.

00:53:22Breathe in deep through your nose.

00:53:24Air only goes up one nostril at a time, and our nostrils take turns at it.

00:53:29Sharing is caring.

00:53:31Our brains tell us when our bodies hurt, but they can't feel pain themselves.

00:53:35There are no pain receptors in the brain.

00:53:39That feeling of your stomach rising is what actually happens.

00:53:42Hold on.

00:53:43Every human has a unique smell except for identical twins.

00:53:47They share the same DNA and the same smell.

00:53:50Our fingerprints aren't just for identifying us to the police if we've done something wrong.

00:53:55The ridges allow our skin to stretch to prevent damage and improve our sense of touch.

00:54:02When you're scared, you can become a lot stronger than you were before.

00:54:06Maybe not lift a car strong, but you won't feel pain or fatigue as quickly.

00:54:12You know what?

00:54:13In 10 years from now, you'll be a completely different person.

00:54:16Well, at least your skeleton will be.

00:54:19To reach its adult size, your skeleton went through a process called modeling, which means

00:54:24the development of growth and formation.

00:54:27Turns out it regenerates completely once every 10 years or so.

00:54:31This entire process ensures you always have healthy bone cells, which can support you

00:54:36and provide calcium to your body.

00:54:38And speaking of ways the body regenerates, every second you make 25 million new cells.

00:54:44I'll do the math for you.

00:54:46Okay, that means in about 15 seconds, you'll have made more cells than there are people

00:54:51in the United States.

00:54:52Think about that the next time you feel you haven't been productive enough.

00:54:58Some animals have eyes that need to adapt to hot climates.

00:55:01Like camels, for example.

00:55:03Their eyes feature a third eyelid, but these sweep across from the corner of each eye.

00:55:09Because their environment is filled with small particles, they need to clean their eyes more

00:55:13frequently than other species.

00:55:15Now, see that little pink thing in the corner of your eye?

00:55:19It's also a third eyelid.

00:55:21Well, a vestige at least.

00:55:23In humans, the third eyelid is unnecessary because it no longer serves its original purpose.

00:55:30Next time you're tuning in to your favorite song, try to pay some attention to your heartbeat.

00:55:36If you listen closely, you'll notice that sometimes your heartbeat may synchronize with

00:55:41the rhythm of the song.

00:55:42Now, not all genres of music have this special ability, but some tunes trigger the release

00:55:48of dopamine, or the happy hormone.

00:55:51This effect may give you a lower heart rate, breathing rate, and blood pressure.

00:55:57And speaking of that healthy ticker of yours, just in case you're wondering, it beats on

00:56:01average about 75 times per minute.

00:56:05This means each year, a human heart can pump enough blood to fill an Olympic-sized pool,

00:56:10if that were a thing.

00:56:12What's even more fascinating is that if you were to connect all your blood vessels end-to-end,

00:56:17it would be able to circle the Earth two and a half times.

00:56:21But that's not good for your own health, so don't do that.

00:56:25Your heart can also continue to beat even if it's removed from the body.

00:56:29That's because it has its own internal battery, which allows it to beat as long as it receives

00:56:34oxygen.

00:56:36If you regularly have your nails done at a salon, you've probably noticed you need more

00:56:41appointments for your fingers than your toes.

00:56:44That's because fingernails do grow faster.

00:56:46The definitive scientific answer is still up for debate, but many specialists think

00:56:51it's because fingernails used to be claws, somewhere back in our ancient history.

00:56:56These days, they're flatter and have widened a bit, and it all happened when primates started

00:57:01using tools in their day-to-day lives, like stones and branches, so there was less use

00:57:06for claws.

00:57:08Once they got flatter, it meant nails wouldn't have gotten in the way if primates wanted

00:57:12to use the palms of their hands.

00:57:15As for why fingernails grow faster than toenails, the short answer may be the fact that we use

00:57:21our hands more than your feet.

00:57:23As such, our fingernails are more exposed, and we may have evolved to grow them faster.

00:57:28The more you use a certain part of your body, the more it becomes exposed to damage.

00:57:34So for me, I'm in danger of my mouth falling off.

00:57:38Oh boy…

00:57:40Getting back to our hands, it's about time we give a nice shout-out to our humble pinkies.

00:57:45We don't see them as being really that important, since we don't use them for holding objects,

00:57:50eating, or writing.

00:57:52But recent studies have shown that losing the pinky on our dominant hands would have

00:57:56a devastating effect.

00:57:59Specialists haven't gathered enough data to supply specific numbers, but from what

00:58:03they've learned so far, losing our pinky would weaken our grip strength considerably,

00:58:08even if it's the lesser-used finger.

00:58:11Adding the ring finger to that, and the effect would be worse for our grip strength.

00:58:16Another recent study done in the UK has shown that only about 40% of people are happy with

00:58:22how their nose looks.

00:58:25Regardless of how you feel about it, the human nose is a real-life superhero.

00:58:30That's because it acts as a heater, filter, and humidifier all at once.

00:58:35Inside each nostril, there are small, shelf-like bones that feature blood vessels.

00:58:40They heat the air up before it reaches other parts of our respiratory system.

00:58:44The mucus that's inside there handles making the air more humid.

00:58:49As for the filtering part, that's why we have nose hairs.

00:58:53Small particles get stuck on these small hairs, which helps prevent pollen, spores, viruses,

00:58:58or bacteria from reaching our lungs.

00:59:01Now, when watching cartoons, we're led to believe that the sound our heart makes is

00:59:06because it's touching its environment while beating.

00:59:09Well, it turns out that sound is actually made by the opening and closing of the heart

00:59:14valves.

00:59:15They're like small doors inside our hearts that open and close to pump blood correctly

00:59:20from one side of the heart to the other.

00:59:22For our bodies to work, blood needs to move at the right time and in the right direction.

00:59:28Now, let's talk teeth.

00:59:32Throughout your entire life, you'll probably spend up to 40 days total just brushing your

00:59:37teeth.

00:59:38And in case you're still wondering, teeth are not in fact bones, even though they do

00:59:42have a lot in common.

00:59:44One of the primary differences between bones and teeth is that our bones can regenerate

00:59:49– they are living tissue.

00:59:51Our teeth are not, and they remain permanently damaged once broken.

00:59:56Here's another shocker.

00:59:58We are the only species on this planet to have a chin.

01:00:02There's still some debate about this subject in the scientific community, but one of the

01:00:06reasons why seems to be to make our jaws stronger.

01:00:10As humans have continued to evolve, their teeth and the muscles in their jaws got smaller

01:00:15and smaller, so they needed something to help with increased jaw resistance.

01:00:22Most of us have developed some specific traits depending on the area of the globe in which

01:00:27we live.

01:00:28But there is a group of people, specifically those who live in higher altitudes, that develop

01:00:33some pretty cool traits.

01:00:35That's because high-altitude environments come with less oxygen.

01:00:39Not only do these people survive in these locations, but they've adapted so well that

01:00:44they actually thrive.

01:00:46In the Andes Mountains of South America, people have evolved red blood cells that can carry

01:00:51much more oxygen.

01:00:53It makes their overall circulatory system much more efficient.

01:00:57People living in Tibet have to endure similar conditions, but, surprisingly, they have adapted

01:01:02differently.

01:01:03In Tibet, they can take more breaths so that they can properly oxygenate their bodies.

01:01:10You've probably heard the myth about dreams only lasting a couple of seconds in reality.

01:01:15Turns out that yes, some of them do, but not all dreams are the same.

01:01:20There are a lot of things we don't understand yet about how we dream.

01:01:24What we do know is that they mainly happen during the rapid eye movement, or REM, stage

01:01:29of sleep.

01:01:30During this time, your brain is more active, about as active as it is when you're awake.

01:01:35And it's named REM because, during the sleep stage, your eyes tend to move a lot.

01:01:41Dreams can happen during the other stages of sleep too, but you're less likely to remember

01:01:45them.

01:01:47As for the length of each dream, they can go from a few seconds to even 20-30 minutes.

01:01:53Also, you're more likely to remember a dream if you've woken during the REM stage.

01:01:58Most people have 3-5 dreams per night, but some people can have up to 7.

01:02:03I know, seems unlikely, but remember, you immediately forget most of what you dream.

01:02:09Just like we have unique fingerprints, we also develop unique tongue prints.

01:02:15Research has shown that those approximately 10,000 taste buds on our tongues are laid

01:02:20out in a one-of-a-kind pattern.

01:02:22Truth is, about 80% of what you believe is taste is actually smell.

01:02:27That combination of taste and smell that we perceive is what we come to know as flavor.

01:02:33That's probably because our sense of smell is around 10,000 times more sensitive than

01:02:37our sense of taste.

01:02:40Our mouths have also another cool superpower called mouth feel.

01:02:44With the help of the somatosensory system, it allows us to sense the texture of our food.

01:02:50The system is activated by physical touches, such as pressure, touch, or vibrations.

01:02:55It's even sensitive to pain and temperature.

01:02:59We also use our tongues to identify the size, form, and texture of food, which is crucial

01:03:04for proper chewing and digestion.

01:03:07A. Tongues are also good for wagging, sticking out at certain people, and trumpet playing.

01:03:16A. Not to freak you out or anything, but every second, your body creates 25 million new cells.

01:03:22I'll do the math for you.

01:03:24That means that in about 15 seconds, you'll have produced more cells than there are people

01:03:29in the United States.

01:03:30Think about that next time you feel you haven't been productive enough.

01:03:35It may account for only 2% of our body mass, but our brains actually take up 20% of our

01:03:40blood supply and oxygen.

01:03:42Our brains can also produce enough energy to supply a lightbulb.

01:03:46That is, when we're awake.

01:03:48Ever thought about what the largest human organ is?

01:03:51It's your skin, and it's thickest on the palms of your hands and soles of your feet.

01:03:56I know, I know, I hate dusting too, but you are particularly responsible for that layer

01:04:02of fluff on your TV screen, you know.

01:04:05Every human being sheds about 600,000 particles of skin every hour, and most of the dust around

01:04:11your house is actually composed of that.

01:04:13So yes, we're all rather flaky.

01:04:17These days, it's considered more of a beauty mark, but the reason why people are born with

01:04:21a Cupid's bow is actually quite intriguing.

01:04:24As our features start to develop before we're even born, it appears that the Cupid's bow

01:04:29is actually the place where our face, well, zips up.

01:04:33The right side of the face and the left side of the face, that is.

01:04:36While in humans, it may not be that obvious.

01:04:39If you look at your dog's nose, you'll see it has a straight vertical line just under

01:04:43the nostrils.

01:04:44That's right, dogs have this zip too.

01:04:48Did you know you were born with more bones than you have today?

01:04:51At birth, we have somewhere around 300 bones, but as we age, some of them fuse together.

01:04:58That's why in adulthood, we end up having about 200 bones.

01:05:02Although your teeth are technically part of your skeletal system, they're not actually

01:05:06bones.

01:05:07They do look sort of similar and do share some characteristics, like being the hardest

01:05:11elements in your body.

01:05:13Why the misconception though?

01:05:14Well, it's mostly because both teeth and bones contain calcium.

01:05:19To be a bit more specific, about 99% of the body's calcium is in your bones and teeth.

01:05:24The remaining calcium is in your bloodstream.

01:05:27So what makes them different, you might ask?

01:05:29It's in how the bones and teeth heal and how you should take care of them.

01:05:34While bones can repair and heal themselves, your teeth aren't able to do that.

01:05:38That's why we have dentists.

01:05:40We don't only have unique fingerprints, our tongues are one of a kind as well.

01:05:45Research has shown that those approximately 10,000 taste buds on our tongues are laid

01:05:50out in a unique pattern, specific for each one of us.

01:05:54About 80% of what you believe is taste is actually smell.

01:05:58The combination of taste and smell that we perceive is what we come to know as flavor.

01:06:03That's probably because our sense of smell is around 10,000 times stronger than our sense

01:06:08of taste.

01:06:10So the next time you're tuning in your favorite song, try to pay some attention to your heartbeat.

01:06:16Do you hear that?

01:06:17Yep, that's right.

01:06:18While listening to some music, your heartbeat will sync with the rhythm of the song.

01:06:23Speaking of that healthy ticker of yours, just in case you're wondering, it beats on

01:06:27average about 75 times per minute.

01:06:30This means that in any given year, a human heart can pump enough blood to fill an Olympic-sized

01:06:36pool.

01:06:37What's even more fascinating is that if you were to connect all your blood vessels end-to-end,

01:06:41you'd be able to circle the Earth four times.

01:06:44But that would really hurt, so don't try that.

01:06:47We are the only species on this planet to have a chin.

01:06:51There's still some debate around this subject in the scientific community, but one of the

01:06:55reasons seems to be to make our jaws stronger.

01:06:58As humans have continued to evolve, their teeth and the muscles in their jaws got smaller

01:07:03and smaller, so they needed something to help with increased jaw resistance.

01:07:09That transparent part of your eye is called the cornea, and it helps the light go through.

01:07:14It's also the only part of your body that isn't connected to any blood supply.

01:07:18Why?

01:07:19Because it's especially designed to get its oxygen straight from the surrounding atmosphere.

01:07:24If you took out all the fat found in a healthy human body, it would be enough to make 7 bars

01:07:30of soap.

01:07:31We also produce enough saliva in our lifetimes to fill two swimming pools.

01:07:35Great expectorations!

01:07:38Ever wondered how much we actually eat during our whole lifetimes?

01:07:41I'll spare you the math.

01:07:43An average-sized person eats nearly 66,000 pounds of food throughout the whole course

01:07:48of their lifetime.

01:07:49How much is that for scale?

01:07:51About 6 elephants.

01:07:53And that ain't peanuts.

01:07:55Each of us carries around 4 pounds of bacteria on average at any given time in our bodies.

01:08:01But hey, don't go running to the doctor just yet.

01:08:04Most of that bacteria is actually good and have specific functions in the human body,

01:08:09like digestion and our immune systems.

01:08:12If you want to have an accurate depiction of your height, make sure you measure yourself

01:08:17in the morning.

01:08:18That's because you're about 0.4 inches taller right when you wake up.

01:08:23Trust me, it isn't magic.

01:08:24It's merely because, throughout the day, the soft cartilage between your spinal bones

01:08:29gets squashed down and compressed, making you seem shorter by the time you go to bed.

01:08:35We know that we have some sort of energy moving around our bodies, so we actually do emit

01:08:40a tiny amount of light.

01:08:42It's too weak for our own eyes to see, though, but if you think about it, you're

01:08:46actually glowing as we speak.

01:08:49The humorist and author Mark Twain once said,

01:08:52Man is the only animal that blushes, or needs to.

01:08:56How true.

01:08:57But not all humans can blush, and those that do blush to different degrees.

01:09:02Is there some sort of evolutionary reason for why we blush?

01:09:06It seems so.

01:09:07Blushing is a way for us to communicate without using any words, just like dogs wag their

01:09:12tails when they're happy or excited.

01:09:14So basically, blushing can be translated to, I'm embarrassed, similar to how we

01:09:19shiver when we're cold.

01:09:21If the human eye was a camera, it would have about 576 megapixels.

01:09:26Our vision of the world changes throughout our lives.

01:09:29As soon as we're born, we see the world upside down for a bit.

01:09:33Our brain is programmed to show the inverted image formed on our retina by the convict's

01:09:37eye lens, but that doesn't kick in immediately after birth.

01:09:42Hey, I'm sure you enjoy that weekly cardio and weightlifting, but the strongest muscle

01:09:46in the human body is definitely not the one you've been working on.

01:09:50It's actually in your jaws.

01:09:52Your jaws are designed similarly to a nutcracker.

01:09:55Why?

01:09:56So you can get powerful bites with as little energy as possible.

01:10:01The fastest muscle is located in your eyes.

01:10:03That's probably how we came up with the expression, in the blink of an eye, for when

01:10:08something happens really quickly.

01:10:10Did you know that your nose comes with a built-in reset feature?

01:10:14It happens when you sneeze.

01:10:16Sneezing is basically your nose's way of getting rid of all the bad particles it has

01:10:20inhaled up to a certain point.

01:10:22If you think that's bad, it's not.

01:10:25Did you also think your pinky finger is something weak and pretty much useless?

01:10:30Well, it actually packs up to 50% of the strength in your hand.

01:10:34We still haven't figured out precisely why people yawn.

01:10:38We aren't the only creatures to do it.

01:10:40Baboons, guinea pigs, and the Siamese fighting fish yawn to warn other animals to stay away.

01:10:46Penguins seem to yawn during courtship rituals, and snakes yawn at times after a good meal.

01:10:51Boy, there's a happy snake!

01:10:53Some theories suggest it helps us get more oxygen in, while others indicate that it helps

01:10:58with regulating our body temperatures.

01:11:00Either way, we still don't know for sure.

01:11:03Our ears and noses are the only organs that continue to grow throughout our lifetimes.

01:11:09Our eyes stay more or less the same size as we grow up.

01:11:12By the time we're 3 months old, our corneas should technically reach their full size.

01:11:19People with a single palmar crease have just one line running across their palm, while

01:11:25the majority of the world's population has two.

01:11:29Also called the simian crease, this feature is found only in 1.5% of the world's population.

01:11:36Men are more likely to have a single palmar crease than women.

01:11:39In most cases, it runs in families.

01:11:43Less than 50 people have ever had the Rh-Null blood type, dubbed Golden Blood.

01:11:48For the first time, this blood type was discovered in an Australian Aboriginal woman.

01:11:54This unique blood type is universal and can be accepted by anyone, even those with rare

01:11:59blood types within the Rh system.

01:12:023% of people all over the planet have lines creating the letter X on both their hands.

01:12:08This is a rare phenomenon, and in many cultures, this feature is believed to be a sign of a

01:12:14strong character.

01:12:16About 25% of people have an interesting reaction to sunlight – they sneeze.

01:12:21This phenomenon even has its own name – the photic sneeze reflex.

01:12:26In the Greek language, it's called sun sneezing.

01:12:30In some people, saliva accumulates in a gland under their tongue.

01:12:34Then it can get propelled out in the stream when a person presses on this gland.

01:12:39If the mouth is open at the moment, a jet can reach several feet.

01:12:43This process, called gleeking, can occur spontaneously.

01:12:47A person accidentally pushes their tongue against the gland while eating, yawning, talking,

01:12:52or cleaning their teeth, and voila!

01:12:55Up to 35% of people can gleek, but just 1% can do it on command.

01:13:01Less than 1% of the world's population has dextrocardia.

01:13:04That's a rare condition when the heart points toward the right side of the chest, rather

01:13:09than the left side.

01:13:10Sometimes people with this unique feature have all their internal organs on the mirror

01:13:14image side of the body.

01:13:18Ocular albinism affects only a person's eyes.

01:13:21Their hair and skin are usually a bit lighter than that of their family members, but the

01:13:25difference isn't that dramatic.

01:13:28Albinism is a rare feature to have, but if it's ocular, that's even more unique.

01:13:33Experts don't have exact numbers, but they think between 1 person in 20,000 to 1 person

01:13:39in 50,000 have ocular albinism.

01:13:43You may have a tiny hole at the top of your ear where it meets the temple.

01:13:48If so, you're among 10% of the world's population.

01:13:51This hole is most commonly found on the right side, but some people have it on both of their

01:13:56ears.

01:13:57These holes may go all the way through, or they can be dimples, dents, or even small

01:14:02lumps.

01:14:04Around 65% of the world's population have loop-shaped fingerprints.

01:14:09In 30% of people, fingerprints are whorl-shaped.

01:14:13And only 5% of people have arch-shaped fingerprints.

01:14:17All these types are divided into smaller groups.

01:14:19For example, there might be plain or tinted arches, accidental whorls, or a peacock's

01:14:25eye, and so on.

01:14:29Most people have 12 pairs of ribs, which makes 24 in total.

01:14:33But 1 in 200 people has an additional 25th rib.

01:14:38Called cervical, it forms at the base of the neck above the collarbone.

01:14:42It can grow on the left, right, or even both sides.

01:14:46Those with extra ribs most likely know nothing about this modification.

01:14:50That's because an extra rib rarely forms completely and can look like a thin strand

01:14:54of tissue.

01:14:55In this case, you won't even see it on an X-ray.

01:14:59If you have a circular hair whorl on your head, it's likely to be clockwise.

01:15:04Some scientists think there's a genetic link between hair whorl direction and handedness.

01:15:09A bit more than 8% of right-handed people have counterclockwise hair whorls.

01:15:14But in the left-handed, this number grows up to 45%.

01:15:19When you're asked to clasp your hands, which finger do you put on top?

01:15:23If it's the right thumb above the left one, you're among 50% of the world's population.

01:15:2949% of people position their left thumb above the right.

01:15:33And a mere 1% place their thumbs next to each other.

01:15:37Red hair occurs naturally in a mere 1-2% of the world's population.

01:15:43Most often, redheads have Northern or Northwestern European origin.

01:15:47This color is caused by a genetic mutation.

01:15:50The hue can vary from bright copper and auburn to red-orange and strawberry blonde.

01:15:57Only 3-22% of people in the world have Morton's toe.

01:16:02It's a foot structure when the second toe is longer than the first one.

01:16:06Michelangelo's David and the Statue of Liberty both have this unusual body feature.

01:16:12And they aren't even alive.

01:16:13Oops, spoiler, sorry.

01:16:16Only 2 people out of every 10,000 have an unusually shaped pupil.

01:16:20Most commonly, it resembles a keyhole.

01:16:23This eye disorder is called coloboma.

01:16:26Luckily, people with this condition don't usually have any problems with their vision.

01:16:31You know, on second thought, it's not so rare.

01:16:33All of my teachers thought I was an unusual pupil.

01:16:39Having different colored eyes, heterochromia is a rare body feature that occurs in less

01:16:43than 1% of people.

01:16:45It can be complete, then a person has eyes of two different colors, for example, one

01:16:50brown and one blue.

01:16:52A person can also have a differently colored ring around the pupil.

01:16:56It's central heterochromia.

01:16:58And partial heterochromia is when a part of one iris has a different color from the

01:17:03rest of it.

01:17:05People with dystichiasis have one more row of eyelashes.

01:17:09This phenomenon is a genetic mutation.

01:17:12It's not harmful in any way, but can cause some discomfort.

01:17:16A hair can grow where an oil gland is supposed to be on the wet part of the eyelid.

01:17:21Then it causes irritation and tearing.

01:17:24There are people who don't have to stress over how much calcium they consume.

01:17:28They have a rare mutation in the LRP5 gene.

01:17:32It gives them mega-dense bones almost unable to break.

01:17:36One of the few drawbacks of this condition, such people have difficulty staying afloat

01:17:41while swimming.

01:17:43Some women have super-color vision, tetrachromacy, thanks to special cells in their eyes.

01:17:49These cells are called cones, and a regular person has three types of them.

01:17:54Tetrachromats have four cones.

01:17:57It allows them to see 100 million different colors.

01:18:01The TEC2 gene lets people work more and sleep less.

01:18:05Nicholas Tesla, Winston Churchill, and Margaret Thatcher all had this unusual feature.

01:18:11The gene basically allows a person to go through their sleep cycle in less time than regular

01:18:16people need.

01:18:18Another gene mutation helps people keep their bad cholesterol levels extremely low.

01:18:23The gene gives your body instructions for producing a protein that controls the amount

01:18:28of cholesterol in your blood.

01:18:30Unfortunately, only 2-3% of people have this useful feature.

01:18:35Only 4% of people have an outie belly button.

01:18:39Several factors, like the fat distribution around your waistline or genetics, determine

01:18:44which kind of belly button you'll end up with.

01:18:47Genetics play a crucial role even in your taste buds.

01:18:50Up to 25% of the population are supertasters.

01:18:54They have more visible taste papillae – those are tiny dots littering your tongue – than

01:18:59regular tasters.

01:19:01This extra option makes them more sensitive to certain foods.

01:19:04For example, sweet, bitter, or salty.

01:19:08Supertasters also have more pain receptors on their tongue.

01:19:10That's why they shy away from spicy food.

01:19:14When wisdom teeth try to break through the gums, they often run out of space and have

01:19:19to be taken out.

01:19:21Around 5 million people go through such surgery every year.

01:19:25But 35% of the world's population don't have to worry about pain and inconvenience.

01:19:30They lack wisdom teeth altogether.

01:19:34Long palm muscles helped our ancestors to climb trees.

01:19:38Even though most of us don't need this option anymore, some people are still born this way.

01:19:43You can check whether you have these muscles by putting your palm on a flat surface and

01:19:48touching your thumb to your pinky.

01:19:50If they do exist, they'll pop out of your wrist.

01:19:54Scientists claim Tibetans are genetically mutated to be able to live at such high altitudes.

01:20:00One of their genes is responsible for fast adapting to falling oxygen levels.

01:20:04The same gene is also linked with improved endurance in athletes.

01:20:08By the way, it was one of the fastest evolutionary mutations ever recorded in people.

01:20:14It developed in less than 3,000 years.

01:20:17Gray eyes are an incredibly rare body feature.

01:20:21Only 1% of the human population are born with gray eyes.

01:20:25Such people have low levels of melanin in the front part of their irises.

01:20:30Blue eyes are also not as common as you might think.

01:20:33Just 8-17% of people have them.

01:20:35An even rarer thing is a combination of red hair and blue eyes.

01:20:40If a person is born like this, it means both their parents carried these genes for a child

01:20:45to have.

01:20:48You may have this rare body feature already and not know about it since sometimes even

01:20:53an x-ray can't spot it.

01:20:55Most of us have 12 pairs of rib bones, which means we were born with 24 ribs.

01:21:01There are some folks, though, that actually have 25 ribs.

01:21:05Only 1 in 200 people have this rare extra feature, and it's called a cervical rib.

01:21:11It generally appears above the first rib right at the base of the neck and above the

01:21:15collarbone.

01:21:16It's nothing to worry about, though.

01:21:19Most of the time, they're unnoticeable, and if ever painful, they can be safely removed.

01:21:25Do you know how huskies can sometimes have their eyes in different colors?

01:21:29Some people come equipped with this rare feature, too.

01:21:32The medical term for it is heterochromia.

01:21:35The name comes from the ancient Greek word heteros, which translates to different, and

01:21:41chroma, which means color.

01:21:43People with this condition can either have complete, central, or partial heterochromia.

01:21:49The complete type means that the person has two completely different colored eyes, say

01:21:54one brown and one green.

01:21:56Two different colors in the same eye are what specialists call central heterochromia.

01:22:02A person with a partial heterochromia has just a portion of their eye of a different

01:22:06color.

01:22:07You can either be born with this condition or get it, say, after an injury.

01:22:12Still, it's extremely rare.

01:22:14Less than 200,000 people are diagnosed with it in the US.

01:22:19Either way, let's face it, it does look pretty cool!

01:22:24Speaking of eye color, wanna try guessing what the rarest one is?

01:22:28I'll spare you the Google search.

01:22:29It's gray.

01:22:30Blue eyes may have been your first thought, and they are indeed already pretty rare.

01:22:36Only around 8-17% of the world's population have this eye color.

01:22:41When it comes to gray eyes, though, they're even more special.

01:22:44Less than 1% of people have them.

01:22:48This rare body feature is caused by a lower level of melanin in the eye's layers.

01:22:53If you're interested in meeting someone with gray eyes, your best chance is in Eastern

01:22:57and Northern Europe.

01:22:59Some rarer eye colors are red or violet, but these can sometimes be the result of different

01:23:04health conditions.

01:23:06There are people out there who have the superpower of seeing 100 million different colors without

01:23:12the help of any fancy gadgets.

01:23:14We see colors thanks to some cells in our eyes named cones.

01:23:19Most of us have three types of cones to help translate what we see into the colors that

01:23:23our brain is able to understand.

01:23:26However, specialists think that there's a small group of people called tetrachromats

01:23:31who have four types of these cones.

01:23:34So far, researchers have only been able to identify women with this condition.

01:23:40That little teardrop-shaped ball hanging in the back of your neck, you know, the one that

01:23:44helps with swallowing your food, is called a uvula.

01:23:48The name comes from Latin and translates to little grape.

01:23:52Surprisingly enough, around 2% of people are born with a bifid uvula, which means that

01:23:57this indispensable organ in them is either split or forked.

01:24:02You sure can surprise others with this cool feature of yours at parties.

01:24:06Joking aside though, people with this bifid uvula may sometimes have trouble eating, drinking,

01:24:11and speaking.

01:24:13They might also have issues with digesting food.

01:24:16Their speech may also sound a bit unusual, but this depends on how much the uvula is

01:24:20split.

01:24:22This particular body feature might not be the perfect trait when going on vacation,

01:24:26but it does allow people to do more with less sleep.

01:24:30They say that famous people like Nikola Tesla, Margaret Thatcher, and Winston Churchill had

01:24:35this super rare feature.

01:24:37This gene, called the DEC2 gene, helps with regulating our circadian rhythms.

01:24:43Those are the natural biological clocks that let us know when we should be sleeping or

01:24:48eating by making us sleepy or hungry.

01:24:51A person with this rare mutation can basically go through a normal sleep cycle in less time.

01:24:58They can feel rested even if they slept for only 4-5 hours.

01:25:02That's one superpower I'd definitely want to have!

01:25:05How about a gene mutation that gives you superhero-like bones?

01:25:10They're basically unbreakable.

01:25:12It also makes your skin less prone to aging.

01:25:14Yep, looks like with this feature you can walk away from accidents unharmed and even

01:25:19withstand the flow of time.

01:25:22Some other people out there come with a very attractive feature, but it can go unnoticed,

01:25:26at least at first glance.

01:25:28They have a little something called distichiasis, which basically means an extra row of eyelashes.

01:25:35Just in case you're wondering about the medical aspects too, it results from a genetic mutation

01:25:40of a certain gene.

01:25:42As beautiful as it may sound, people with that extra eyelash layer can experience some

01:25:47pretty unpleasant sensations in their eyes and, in some cases, even have problems with

01:25:52their vision.

01:25:54If spun glass hair doesn't ring a bell, know that it is, in fact, a condition you might

01:26:00have.

01:26:01I know it's pretty self-explanatory, but just FYI, it causes frizzy and dry hair.

01:26:08It's basically so unmanageable that you literally can't comb it.

01:26:12It also tends to grow out from the scalp in all directions.

01:26:16As for coloring, it comes in either bright blonde or silver.

01:26:20Most of us have hair strands that are cylindrical.

01:26:23People with this condition have triangular or heart-shaped strands or even flat altogether.

01:26:29It's extremely rare, with only 100 confirmed cases, but it does become more manageable

01:26:35with age.

01:26:36Most of us humans have evolved to have some specific traits depending on the area of the

01:26:41globe that we live in, but there is a group of people, specifically those that live in

01:26:46higher altitudes, that develop some pretty cool traits.

01:26:50Let me explain.

01:26:51High-altitude environments come with less oxygen.

01:26:54Not only do these people survive in these locations, but they've adapted to actually

01:26:58thrive out there.

01:27:00For example, those living in the Andes Mountains of South America have red blood cells that

01:27:05can carry much more oxygen.

01:27:08It makes their overall circulatory system a lot more efficient.

01:27:12People living in similar conditions in other parts of the world have also adapted in their

01:27:17own way.

01:27:18They're able to take more breaths, so that they can properly supply their bodies with

01:27:22oxygen.

01:27:25This one is very important when it comes to looks, but means little in terms of a person's

01:27:30overall health.

01:27:31I'm talking about Poggeboldism.

01:27:34Those who have it lack melanocytes.

01:27:37Those cells that produce hair pigment in some parts of their hair.

01:27:41It's most common above the forehead, in front of their hairline, but it can also appear

01:27:45on the eyebrows or eyelashes.

01:27:49Folks who have it are born with this condition and carry it throughout their entire lifetime.

01:27:54If you really want to get rid of it, there's always hair dye available, but I personally

01:27:58think it looks super cool.

01:28:01We all know cilantro really isn't everyone's cup of tea.

01:28:05I don't know about you, but it tastes like soap to me.

01:28:08It turns out it's not actually a preference, but rather a gene that causes the plant to

01:28:12have this vile taste instead.

01:28:15A study performed on a group of about 30,000 people revealed that you can find a particular

01:28:21gene variant in people who say that cilantro tastes soapy.

01:28:25This gene has more to do with the odor of the plant than the taste itself.

01:28:30If you're one of those people but really want to give cilantro a chance, either way, there's

01:28:34a small trick you can try.

01:28:36Or ask the people that cook the meals in your household.

01:28:40You can always crush the herb before using it in dishes.

01:28:43Why does that help?

01:28:44Well, because with crushing, the chemicals that are responsible for the soapy taste are

01:28:48broken down and are less likely to taste unpleasant.

01:28:52Now, nobody really knows why we need the appendix, but it's always at the back of the book.

01:28:59Wait, wrong appendix.

01:29:01Some researchers claim the human appendix helped our ancestors process the tree bark

01:29:06and whatever they were eating at that time.

01:29:09As we have a way more balanced diet now, the appendix can disappear from our bodies without

01:29:14any consequences.

01:29:16Another purposeless thing in our bodies is the wisdom teeth.

01:29:19Yeah, they used to come in handy when dentists didn't exist, but now we can ideally make

01:29:24do without them.

01:29:26Your brain will grow by roughly 2% if you venture into space.

01:29:31Under normal gravity, it's thought that fluid in the brain naturally moves downwards

01:29:35when we stand upright, but there is evidence that microgravity prevents this, resulting

01:29:41in fluid accumulation in the brain and skull.

01:29:44When you age, your brain is gradually reducing in size.

01:29:48By age 75, it's much smaller than at age 30, and it starts shrinking at 40.

01:29:54It happens to everyone, so you just have to go with it and keep your brain busy and nimble.

01:30:00If you stare into your eyes in the mirror, you'll see a small pink circle settled in

01:30:04the corner of your eye.

01:30:06This is your third eyelid.

01:30:08Useless for us, but valuable for animals, like birds, to keep dust and scattered debris

01:30:12from getting into their eyes.

01:30:15This might sound familiar to you if you've heard of natural selection.

01:30:18In short, natural selection keeps body parts throughout generations, but some of them are

01:30:23harmful so they're phased out in the next generation and others that aren't staying,

01:30:28just like the third eyelid.

01:30:31Not only your brain shrinks as you get older, you too shrink dramatically.

01:30:35The bones get more brittle, the backbone gets compressed.

01:30:38It works vice versa too.

01:30:40When you rest at night, your bones kinda relax too, so you wake up taller than when you went

01:30:45to bed last night.

01:30:47Our ears help us keep the balance, so hearing isn't their only duty.

01:30:52Our vestibular system occupies the inner ear.

01:30:55Canals in your inner ear contain fluid and tiny sensors that look somewhat like hairs,

01:31:00helping you keep your balance.

01:31:02As for hairs, only a few body parts aren't covered with them.

01:31:06These are palms, the soles of the feet, and lips.

01:31:10Hairs grow even in the belly button.

01:31:12Their purpose is to catch lint.

01:31:14Mine does a great job!

01:31:16And not only lint, our belly buttons have an entire animal encyclopedia in them, with

01:31:21a range of about 70 different bacteria.

01:31:24Some of them can also be found in soil in Japan, and even some bacteria typical for

01:31:29polar ice caps.

01:31:31See, you have a whole naval expedition going on and didn't even know it!

01:31:36Only about 43% of you is you.

01:31:39You're over 50% tiny little creatures that mainly live in your gut and other body parts

01:31:45without ever leaving it.

01:31:46Still, even though your cells are fewer than microbial ones, there are, on average, about

01:31:52100 trillion of them in you.

01:31:55With this in mind, your genes are less than half of what you consist of.

01:31:59If you take all the microbes dwelling within your body and count their genes, it'll be

01:32:03anywhere from 2 to 20 million genes and their combinations.

01:32:08If you sleep, and I recommend that you do, it doesn't mean all of your body sleeps.

01:32:13In fact, sometimes your brain has to work even harder when you're asleep.

01:32:18It needs to process tons of information, and reports usually take time.

01:32:23One thing that indeed rests while you're sleeping is your nose.

01:32:27You won't smell anything nasty in your sleep.

01:32:29The thing is that your sense of smell deactivates at night.

01:32:33If there's some terrible smell in your bedroom, you won't even be bothered.

01:32:38Scientists used to believe we could distinguish around 10,000 smells.

01:32:42Nope.

01:32:43Recent research showed that people could indicate more than a trillion smells.

01:32:47We also remember them better than anything else, and odors can even evoke some distant

01:32:53memories.

01:32:54Meanwhile, our strongest and most emotional memories are usually fake.

01:32:58It's the way the central memory works.

01:33:00It gives us the confidence to believe everything we remember is real, even though we should

01:33:05be confident about fewer details.

01:33:08You don't mind if I call you a mammal, do you?

01:33:11Well, among us mammals, only humans can always walk on two hind limbs and keep that posture

01:33:17for their entire lives.

01:33:19You may want to say that kangaroos or gorillas move in the same way.

01:33:22But kangaroos use their tail as a third leg, and gorillas use the help of their long arms

01:33:28to keep balance.

01:33:30Your bones take part in metabolism too.

01:33:32Since they mainly consist of calcium, when there's not enough of this element in your

01:33:36blood, bones start shedding it into the bloodstream, balancing your body.

01:33:41And vice versa, when there's too much calcium in your blood, it goes into the bones to be

01:33:45stored for later.

01:33:48Our height, shape of our body, and skin color depend a lot on where our ancestors used to

01:33:53live.

01:33:54But we can adapt to new conditions even within our lifespan.

01:33:58For example, if you move from the plains to the mountains, you'll eventually develop

01:34:03more red blood cells to compensate for the lack of oxygen.

01:34:07And naturally, if you drive from a colder climate to a hotter and sunnier one, your

01:34:11skin will change pigmentation slightly to adapt.

01:34:15Our lifespan is programmed within our cells.

01:34:18They constantly renew and divide, but they have a sort of internal timer that stops at

01:34:23some point.

01:34:24Some cells also stop reproducing sooner than others.

01:34:27On average, cells cease dividing when we reach the age of 100.

01:34:32If we find a way to trick ourselves into turning off the timer, we could potentially live forever.

01:34:38But we'd be a huge mass of wrinkles by then.

01:34:42Body fat acts as insulation material, energy reserve, and shock absorber.

01:34:47Your body sends the most fat into your waist region because that's where your internal

01:34:52organs are.

01:34:53If something happens to you, this layer of fat might as well protect those organs from

01:34:57serious damage.

01:34:59Your skull isn't a single bone.

01:35:01It consists of 22 different bones, many of which are fused to protect your brain.

01:35:07The mandible, or the lower jaw, is the only skull bone that's only attached to your head

01:35:12with connective tissues and muscles.

01:35:14This is what makes it so mobile – you can move it in any direction you like.

01:35:18And the smallest bone in your whole body is inside your ear.

01:35:22It's called the stapes, and it's no larger than a grain of rice.

01:35:27Some of the strongest muscles in your body aren't in your arms or legs – they're

01:35:31in your head.

01:35:32The masseter is the primary muscle responsible for chewing, and it needs to be the strongest

01:35:38for you to eat normally.

01:35:39But you know those muscles that allow you to move your ears?

01:35:42Those are temporalis, located above your temples.

01:35:46They also help you to chew your food.

01:35:48We've got two really fast muscles – they control the eyelids' opening.

01:35:52In fact, they're the fastest muscles in our body.

01:35:56Eyes are fragile and need protection.

01:35:58So when the reflex is triggered, these muscles shut the eyes within less than a tenth of

01:36:02a second.

01:36:04We recognize only purple-blue, green-yellow, and yellow-red colors.

01:36:09Everything else is a combination of these three.

01:36:11It's impossible to calculate how many of these combinations the human eye sees because

01:36:16every single person has slight vision differences, but it's about one million combinations

01:36:22on average.

01:36:24Your stomach has an impressive capacity, holding up to a half a gallon of liquids – a whole

01:36:29large bottle of Coke!

01:36:30It's pretty hard to estimate how much hard food you can squeeze into your stomach, since

01:36:35the food is processed with your teeth before it gets down there.

01:36:39There's not enough room for a whole turkey, but who knows, probably a good-sized chicken

01:36:44might fit it.

01:36:45And hey, like my grandmother said, there's always room for ice cream.

01:36:50Now show me where your stomach with all that cola, chicken, and ice cream is.

01:36:55If you're pointing at your tummy, nope, it's up there, hidden in between your ribs.

01:37:00Your tummy is full of intestines.

01:37:03Now if you were asked where your stomach was, you'd probably point to your tummy.

01:37:07Sorry, but that's wrong.

01:37:09It's actually up here, hidden behind your ribs.

01:37:13Your stomach has a pretty incredible capacity, being able to hold up to a half a gallon of

01:37:17liquids – that's a whole large bottle of Coke!

01:37:21It's pretty hard to estimate how much hard food you can eat, because it's processed

01:37:25with your teeth before it ever gets to your stomach.

01:37:27There's definitely not enough room for a turkey, but a good-sized chicken would probably

01:37:32fit it in.

01:37:34Speaking of organs, scientists believe that the appendix will disappear eventually.

01:37:39Nobody really knows why we need it, but some researchers claim it might've existed to

01:37:43help our ancestors digest tree bark.

01:37:47Because it's no longer a part of our daily diet, the appendix isn't necessary and can

01:37:51disappear from our bodies without any consequences.

01:37:55Now the appendix isn't the only obsolete part of our body.

01:37:58Wisdom teeth aren't that useful either.

01:38:01Yeah, they used to come in handy when our ancestors lost some of their teeth.

01:38:05But the only thing they help us lose now is the money we spend extracting them.

01:38:10In fact, you can easily survive without your appendix, stomach, one kidney, or one lung.

01:38:16Nice to know we have spare parts!

01:38:18If you never knew you had a personal bodyguard, look deeper.

01:38:22Your liver is your security guard, protecting you from toxins and many other things you

01:38:26don't want to have.

01:38:28It's also pretty indestructible and can even regenerate.

01:38:32Your liver is a very important organ that works a lot and is responsible for 500 individual

01:38:37functions.

01:38:38Up to 10% of it is made of fat.

01:38:41The liver can grow back.

01:38:43Yep, even if you only have half of your liver left, it can still regenerate to its original

01:38:49size.

01:38:51On average, the heart is as big as your fist.

01:38:54It beats 115,000 times and pumps around 2,000 gallons of blood each day.

01:39:00The right lung is bigger than the left one because your body needs to make some room

01:39:04for the heart.

01:39:06You inhale a lot of different types of debris, including 7,000 of your very own skin flakes,

01:39:12and that's only in a day.

01:39:14The stomach is the most important defender of the immune system.

01:39:18Hydrochloric acid in our stomach kills dangerous food toxins, viruses, and bacteria that get

01:39:24in there with the food you eat.

01:39:26This acid can digest even the stomach itself, but the mucous membrane protects it.

01:39:32You can burn calories when you take a hot bath as many as you would if you took a half-hour

01:39:37walk.

01:39:38You burn somewhere between 100 and 200 calories per hour while standing.

01:39:43Sitting burns 60 to 130, depending on your height, weight, gender, and age.

01:39:49Your own body makes mosquito bites swell and itch.

01:39:52A mosquito breaks your skin.

01:39:54Your immune system perceives the insect's saliva as a foreign substance, so it starts

01:39:59a special reaction to flush the intruder out of your body.

01:40:02A compound produced by the immune system, called histamine, makes the blood flow faster

01:40:07around the bitten area, and it causes swelling.

01:40:10The histamine also sends a signal to the nearest nerves, which makes the bite itch.

01:40:15Meanwhile, the food on the plane is likely to taste different than on the ground.

01:40:21That's because you lose up to 30% of your tastebud's sensitivity due to the dryness

01:40:25and pressure in the cabin.

01:40:27It's especially true about salty and sweet foods.

01:40:30Now, you wouldn't be able to taste food without saliva.

01:40:33Your taste buds have chemoreceptors that recognize different flavors, but they need some liquid

01:40:38for those flavors to bind into their molecules.

01:40:41Also, you can't taste things saliva doesn't dissolve.

01:40:45You can always squeeze in some dessert, no matter how much salad, soup, or meat you've

01:40:49eaten before.

01:40:50Your body gets bored of savory tastes.

01:40:53But when you see and smell something sweet, like ice cream, cakes, or chocolate, your

01:40:58brain gets excited.

01:40:59It overrides all fullness signals for pleasure.

01:41:02Plus, your stomach is a flexible organ, and sugar helps it relax and physically make room

01:41:07for dessert.

01:41:08Hey, I rely on that information!

01:41:11The tongue is one of the strongest muscles in your body.

01:41:15This organ contains more than 10,000 taste buds, and each bud is filled with microscopic

01:41:20hairs.

01:41:21Their job is to sense your food, distinguish tastes, and send information to your brain

01:41:26to initiate the appropriate digestion process.

01:41:29During your life, all those tiny bumps and ridges on your tongue create a special individual

01:41:34pattern.

01:41:35That's why experts say that tongue prints are as unique as fingerprints.

01:41:39Your tongue doesn't have separate bitter, sweet, sour, or salty sections for tasting.

01:41:44Each of the 8,000 taste buds you have on the tongue, the roof of the mouth, and even

01:41:48in the throat can detect all the tastes.

01:41:52For some people, cilantro may taste similar to soap because the plant contains a chemical

01:41:57used in soap making.

01:41:58But only 4-14% of the world's population have special genes that can detect it.

01:42:04The masseter is the strongest muscle you have based on its weight.

01:42:08Together with the rest of the jaw muscles, it can close your teeth with a force of 200

01:42:13pounds on the molars and 55 pounds on the incisors.

01:42:17Your spine has a great memory.

01:42:19It remembers your posture, making it so difficult to change it for the better.

01:42:24You owe goosebumps to your ancestors from many, many, many years ago.

01:42:29Their hair used to stand up to make them look bigger and scarier to foes.

01:42:33Cats hiss and arch their backs for the same reason.

01:42:37Only about 43% of you is actually you.

01:42:41Over 50% of the cells in your body belong to tiny little creatures that mainly live

01:42:46in your gut.

01:42:47Still, even though your own cells are fewer than the microbial ones, there are, on average,

01:42:52about 100 trillion of them in you.

01:42:55See, you're not alone!

01:42:57With this in mind, your own genes are less than half of what you really consist of.

01:43:02If you take all the microbes dwelling within your body and count their genes, you'll

01:43:07find between 2-20 million.

01:43:10Our height, the shape of our body, and skin color depend a lot on where our ancestors

01:43:15used to live.

01:43:16But we can adapt to new conditions even within our own lifespan.

01:43:20For example, if you move from the plains to the mountains, you'll eventually develop

01:43:24more red blood cells to compensate for the lack of oxygen.

01:43:28And naturally, if you move from a colder climate to a hotter and sunnier one, your skin will

01:43:33get darker to adapt.

01:43:35Our lifespan is programmed within our cells.

01:43:38They constantly review and divide, but they have a sort of internal timer that stops at

01:43:43some point.

01:43:44Some cells also stop reproducing sooner than others.

01:43:47On average, cells cease dividing when we reach the age of 100, if we're that lucky.

01:43:53That means that if we could find a way to trick our cells into turning off the timer,

01:43:58we could potentially live forever.

01:44:00And move in with our grandchildren.

01:44:03A human mouth is pretty unique.

01:44:05You won't find two identical sets of teeth even among identical twins.

01:44:10That's because the shape depends on how each person is using their jaw.

01:44:15Even the tiniest habits you used to have many years ago, such as lip-biting, affect the

01:44:20formation of your teeth and the uniqueness of your dental impression.

01:44:24You've probably noticed that lipstick prints on a napkin or a mirror are always slightly

01:44:29different depending on who left them.

01:44:31Alright, who left the lip prints?

01:44:34Studies of both females and males revealed that lip print patterns for each individual

01:44:38are unique.

01:44:39They didn't reveal any special traits based on the gender factor.

01:44:43The mandible, or the lower jaw, is the only skull bone that isn't fixed to the bone around

01:44:48it.

01:44:49It's attached with connective tissues and muscles.

01:44:52This is what makes it so mobile.

01:44:54You can move it in any direction you like.

01:44:56There are clusters of sensory cells in your tongue.

01:44:59The buds that are closer to the surface are more short-lived.

01:45:02That's the reason you don't have to wait for too long to be able to taste again after

01:45:06burning your tongue.

01:45:08Your fingertips are sensitive, but hundreds of times less so than your lips.

01:45:13Aha, the lips again!

01:45:22Now I've tried this one myself too.

01:45:24Pinch your elbow as hard as you can.

01:45:27You barely feel pain.

01:45:28How come?

01:45:30Well, different areas of your skin have different nerve endings.

01:45:33Our bodies are designed to be more sensitive to pain in places that are at higher risk

01:45:38of getting damaged.

01:45:39Those important parts have more nerve endings so that we're more alert and able to protect

01:45:44ourselves.

01:45:45And thick skin, like that on elbows, has fewer pain detectors.

01:45:49Now I'm not talking about the tingling, jolting pain you can feel when you hit your elbow

01:45:54against something.

01:45:55Oh, that feels almost like your entire arm has been electrocuted!

01:46:00It's not a feeling I would consider funny.

01:46:01But it comes from the funny bone.

01:46:04Now the funny bone isn't actually a bone.

01:46:06It's a nerve that starts in your spine, goes through your neck, through your elbow, and

01:46:11through your fingers.

01:46:12Its real name is the ulnar nerve.

01:46:15It's one of the three primary nerves in your arm, and it provides sensation to the fingertips.

01:46:20Your ulnar nerve is well-protected by muscle, fat, and bone.

01:46:24But there's one spot at your elbow where this nerve is exposed, and that spot is, yeah,

01:46:30the funny bone.

01:46:31A different but real version of Achilles' story, huh?

01:46:35Okay, so now you know why it hits so different when you bump your funny bone and why you

01:46:40feel nothing when you pinch your elbow.

01:46:43Now the next phenomenon is related to socially awkward moments.

01:46:46Okay, maybe not entirely.

01:46:48It might happen when your crush gives you a compliment.

01:46:51I'm talking about blushing.

01:46:53Now I'm not sure those butterflies in your stomach exist when you're in love.

01:46:58But I'm sure of this, when you blush, your stomach lining also turns red.

01:47:03Yeah, I've looked.

01:47:05The stomach lining is the tissue that protects your stomach walls from the acid inside.

01:47:10When you blush, it also turns red because blushing happens when the blood rises to the

01:47:14surface of the skin.

01:47:16This affects the stomach too.

01:47:18Now this is a natural process, a physiological response to the change in your emotions.

01:47:23Now since we're talking about the stomach, it might be a good time to mention that the

01:47:27stomach fluid has the ability to melt a steel table.

01:47:32Yup.

01:47:33This means the acid would be able to digest your internal organs.

01:47:36Luckily, the stomach lining prevents this from happening.

01:47:40Number 3 is about letting you know that you can glow in the dark.

01:47:43Now don't turn off the lights just yet, you can't see it with the unaided eye.

01:47:48These visuals of glittering human bodies come from ultra-sensitive cameras.

01:47:53Japanese scientists were the first to capture the images of human bioluminescence.

01:47:58Only ultra-sensitive cameras can reveal that our bodies emit tiny amounts of light because

01:48:03this light is a thousand times weaker than the human eye can detect.

01:48:07Apparently, all living creatures produce a small amount of light thanks to the chemical

01:48:12reactions in their cells.

01:48:14Humans are newly added to this list.

01:48:16The researchers had been photographing the upper bodies of the volunteers for several

01:48:20days.

01:48:21The results showed that the amount of emitted light followed a 24-hour cycle.

01:48:26The glow is at its highest in late afternoon and lowest late at night.

01:48:31Plus, the brightest light is emitted from the cheeks, forehead, and neck.

01:48:35Interestingly, this does not correspond with the brightest areas caught by thermal cameras.

01:48:41Did you know you're a little bit taller in the morning than you are later at night?

01:48:45Yes, I've been measuring you.

01:48:47Seriously.

01:48:48This height difference is related to gravity.

01:48:51Its force compresses the cartilage in your spine and knees when you stand up or sit down

01:48:56throughout the day.

01:48:57But when you're lying down, your spine decompresses and relaxes.

01:49:02That's why when you wake up in the morning after resting in bed all night, you're taller.

01:49:06The increase in height is not even above an inch, so don't bet on who is taller after

01:49:11hearing this information.

01:49:13In fact, astronauts returning from a mission are a few inches taller than they usually

01:49:18are on Earth.

01:49:19It's because of the lack of gravity on the International Space Station.

01:49:22They don't remain that tall forever, though.

01:49:25When they're on the Earth again, gravity gradually squeezes them back down to their

01:49:29usual height.

01:49:30Now, let's get back to the organ we've already spoken about – the skin.

01:49:35Yes, the skin is an organ.

01:49:37In fact, it's the largest organ in your body.

01:49:40It contributes to about 15% of your body weight.

01:49:43What else does this organ do, besides covering your body?

01:49:46It performs vital functions.

01:49:49For instance, it protects your body from external physical and biological harm.

01:49:53Plus, it prevents excessive water loss.

01:49:55Now, I can't help wondering what other surprises the human body has in store for us.

01:50:01But right now, let's move on to the animal planet.

01:50:05Owls don't have eyeballs.

01:50:06Instead, they have something called eye tubes.

01:50:09Their rod-shaped eyes do not move in their sockets as our eyeballs do.

01:50:13That's why owls would have to move their entire bodies to look around.

01:50:18But moving their torsos would make some noise, and other animals would hear it.

01:50:22So owls have evolved to have necks that can twist to around 270 degrees, and they move

01:50:28super silently.

01:50:30But why the concern?

01:50:31Well, night vision requires large corneas to get as much light as possible.

01:50:36This is the main reason why most nocturnal animals, such as the slow loris or tarsier,

01:50:42have big eyes.

01:50:43For owls, it works a little differently.

01:50:45Since they have small heads, such large eyes wouldn't be able to fit inside.

01:50:50Now, even though these creatures don't have eyeballs, they have three sets of eyelids.

01:50:55One set is for blinking, one is for sleeping, and the last one is for keeping their eye

01:50:59tubes clean.

01:51:00So do the owls give a hoot about that?

01:51:03Yes, yes they do.

01:51:05Moving on from nocturnal animals to the ones you're more familiar with – meow!

01:51:10Cats have an extra organ that allows them to taste scents in the air.

01:51:14This organ is called Jacobson's organ, or the vomeronasal organ.

01:51:18Jacobson's organ is located inside the cat's nasal cavity and opens into the roof of the

01:51:23mouth.

01:51:24This organ can detect specific chemicals by using nerves that lead directly to the brain.

01:51:29That's not a regular sniffing, though.

01:51:32The odor receptors of Jacobson's organ aren't designed to catch ordinary smells.

01:51:36They detect chemicals that have no odor at all.

01:51:39In other words, cats can detect undetectable smells.

01:51:43It's not just this – Jacobson's organ increases the sense of smell.

01:51:48For instance, when kittens need to find their mother's milk, imagine there are two mother

01:51:52cats and four kittens.

01:51:55Kittens can distinguish their mother from the other grown-up cat with the help of their

01:51:58sense of smell.

01:52:00Now when two people meet, they assess each other's body language.

01:52:04Cats can usually do this by sniffing each other's heads.

01:52:07This greeting releases pheromones that can tell a lot about one cat to the other.

01:52:12Like what the other feline likes to eat, or if they are healthy or not.

01:52:15They can even evaluate whether the other cat is happy or moody – all thanks to Jacobson's

01:52:21organ.

01:52:22Now another fact about cats – their nose has distinct ridges that look like a pattern.

01:52:28Similar to our fingerprints, every cat has a unique nose print.

01:52:32It can be used as a form of identification.

01:52:34Okay, cat, we can nail you for breaking the vase.

01:52:37We have your nose prints all over it.

01:52:39Now do you want to cut a deal?

01:52:41Just tell us what you know about the dog and that chewed-up DVD.

01:52:46Dog lovers, no, I didn't forget about you.

01:52:48Here's a myth you've probably heard – dogs are colorblind.

01:52:52But they aren't!

01:52:53However, it is true that the color range they can detect is limited compared to the spectrum

01:52:58humans can see.

01:53:00Their color palette consists mostly of yellows, blues, and violets.

01:53:04Our reds, greens, and oranges are not noticeable to them.

01:53:08This one is about turtles.

01:53:10These animals cannot leave their shells and get back whenever they want.

01:53:13In fact, they are completely attached to their shells.

01:53:17These shells grow with turtles, similar to the human skin.

01:53:20A turtle's shell consists of 50 bones.

01:53:23It also includes a skeleton with the spine and ribcage.

01:53:27So they go on vacation with it.

01:53:29It's kind of like an RV that you can't get rid of.

01:53:32Hey, can you speak up?

01:53:34I just ate an entire pizza!

01:53:37That's because after eating a hearty meal, our hearing tends to be a bit less sharp.

01:53:42During digestion, most of our bloodstream is directed toward the stomach, which takes

01:53:46away a bit from all the other organs.

01:53:49So next time you want to go listen to your favorite band at a live concert, make sure

01:53:54to eat a lighter meal to keep your ears pitch perfect.

01:53:58On top of our stomach and left kidney, we have a magical organ that can grow back if

01:54:03we remove a part of it.

01:54:05Our liver can regenerate itself by making new cells called heptocytes.

01:54:10They begin to multiply once the liver is damaged.

01:54:13The seriousness of that damage defines if it can regenerate completely and the amount

01:54:18of time it takes to do so.

01:54:21Ever wondered what's worse for your body – no sleep or no food?

01:54:25Turns out the lack of sleep is more dangerous.

01:54:28That's because if you don't rest, your body becomes exposed to a lot more risks.

01:54:34After 24 hours without any shut-eye, you can start to have memory problems and find it

01:54:39difficult to concentrate.

01:54:41At just 17 hours without sleep, you start to feel tired and groggy, irritable, tense,

01:54:48and more emotional!

01:54:49I need a nap.

01:54:50Your pain receptors also become more sensitive, which means everything hurts a bit more than

01:54:55it should.

01:54:56Oh, and it also affects your hearing too.

01:55:00On the other hand, you can be well into your 24-hour period with no food before your body

01:55:06realizes you've stopped eating.

01:55:09In the first 8 hours, you just keep digesting the last meals you had.

01:55:13After those first hours, you start to use stored fats for energy.

01:55:17Not eating for more than 24 hours means that your body will start eating away at its own

01:55:22protein, which means you literally start to lose muscle.

01:55:28Rainwater isn't always safe to drink.

01:55:30It can sometimes hold harmful bacteria and viruses.

01:55:34Also in heavily polluted locations, it may even meet other harmful materials.

01:55:39Some communities out there do depend solely on rainwater as their primary source of hydration.

01:55:46Does rainwater have any other health benefits?

01:55:49Not really, according to current studies.

01:55:51Some of those risky substances may be removed from rainwater if you boil it, but it's

01:55:56best to stick to the safer side and only drink water from sources that are 100% safe for

01:56:02human consumption.

01:56:05We produce sweat mostly to regulate our body temperature and for some added moisture, like

01:56:10the one we need in the palms of our hands for a better grip.

01:56:14But sweat doesn't just show up on our skin.

01:56:17It comes out of around 5 million pores on our bodies.

01:56:20We're literally stepping on a quarter of our bones each day.

01:56:24We have just over 200 bones in our body, but about a quarter of those are in a very small

01:56:30surprising area – our feet.

01:56:33Since we have 26 bones in each foot, we end up with literally 52 in both.

01:56:40Our eyes produce tears for many reasons, like protecting themselves from infection

01:56:44or clearing up debris such as smoke and dust, or when your baby done you wrong.

01:56:50But the number of tears we produce is quite surprising – up to 30 gallons per year!

01:56:55That's almost enough to fill a bathtub!

01:56:57Wow, that is heartbreaking!

01:57:00Our blood pressure wakes up hours before we do.

01:57:03That's because in the morning, the body produces a bunch of hormones like adrenaline

01:57:08and noradrenaline.

01:57:10They help give us the energy boost we need during our morning hours, but they also increase

01:57:14our blood pressure, which is usually higher between 6 a.m. and noon.

01:57:19During the night, since we should technically sleep and perform no physical activity, our

01:57:24blood pressure drops down by up to 20%.

01:57:28Speaking of our vital fluid, our blood accounts for about 10% of our total body weight.

01:57:34We tend to think of our body weight as being mostly made up of muscles, fat stores, and

01:57:39fat.

01:57:40But there's a lot more to it.

01:57:41In a fit adult person, bones make up 15% of the total body weight, about 40-45% is left

01:57:48to muscles, about 15% to fat deposits, and the rest are stuff like skin, tendons, hair,

01:57:55and other yucky things.

01:57:56Let's see, that adds up to… yep, 100%.

01:58:02Your lungs aren't twins – they're siblings.

01:58:04That's because they aren't the same size or shape.

01:58:08Your right lung is bigger and tends to weigh more, and your heart is to blame for it since

01:58:12your ticker tilts to the left a little bit.

01:58:15This creates a small indentation in the left lung called the cardiac impression, which

01:58:21is also what funny heart doctors do at comedy clubs.

01:58:25The right lung may be bigger, but it's a bit shorter since it needs to make room for

01:58:29the liver.

01:58:30Doesn't your house have a liver room?

01:58:33Many of your body measurements are quite symmetrical in surprising ways.

01:58:38If you were to stretch out both of your arms, your wingspan, and measure it, it should show

01:58:43how tall you are.

01:58:45Based on these similar measurements, specialists can even produce theories about what ancient

01:58:49humans used to look like.

01:58:51Looks like we've evolved to be increasingly symmetrical to appear more attractive and

01:58:56healthier to attract mates.

01:59:00Since we've evolved to also walk on two legs, our symmetrical features help us to

01:59:04move around with the least amount of energy because it creates balance.

01:59:10Humans aren't natural champions when it comes to the scent of smell, that's for sure.

01:59:15But our noses can pick up about 1 trillion different scents.

01:59:20Scientists are still performing research on this subject and believe the number may be

01:59:24even higher.

01:59:25Some dog breeds may be able to notice scents somewhere between 10,000 and 100,000 times

01:59:31better than we do, but turns out the best nose in the animal kingdom may be attributed

01:59:36to the elephant because of its staggering number and type of olfactory receptor genes

01:59:42over 10,000 while humans and chimpanzees have less than 400.

01:59:49We tend to look at our pinkies as our most delicate fingers, but we do have more power

01:59:54in them than we think.

01:59:56Turns out that should our pinky finger be lost or affected, the overall strength of

02:00:00our grip may decrease by up to 33%.

02:00:06The liquid in our stomach, made of hydrochloric acid, potassium chloride, and sodium chloride,

02:00:12is way more powerful than any acidic food you can think of, like lemons, pineapples,

02:00:17or tomatoes.

02:00:18The pH of healthy stomach acid should be between 1 and 3, so if you think about it,

02:00:24it's just below that of battery acid.

02:00:28Our hair strands are strong too, so strong that research has performed on them to duplicate

02:00:33their resistance into human-made materials.

02:00:36A healthy head of hair should be able to withstand up to 26,000 pounds.

02:00:41It's due to a little protein in the hair strand called keratin, which you can also

02:00:46find in your nails and skin.

02:00:50Only about one-third of us humans have perfect vision.

02:00:53There are a lot more glasses and contacts out there than you'd think, making up about

02:00:5766%.

02:00:59Apart from different eye conditions, our vision also gets worse with age.

02:01:04When we're born, our heads amount to one-quarter of our total length.

02:01:09By the time we reach 25, our head will only be one-eighth of it.

02:01:13That's because our heads won't change their size a lot as we grow older, as opposed to

02:01:18the rest of our body, mostly when it comes to the legs and torso.

02:01:22Our brains are these super-powerful computers, and a single human brain cell can hold 5 times

02:01:28as much information as the entire Encyclopedia Britannica.

02:01:33Maybe you remember that!

02:01:35We've yet to pinpoint the exact amount of data it can support, but in electronic terms,

02:01:40the storage capacity of the brain is around 2,500 terabytes.

02:01:45For comparison, the National Archives of Britain, which keeps over 900 years of history, only

02:01:51takes up 70 terabytes.

02:01:54It's probably the reason our brains need the most amount of oxygen compared to other organs

02:01:59– about 20% of the total oxygen that enters the bloodstream.

02:02:04And that's despite the fact that it makes up only 2% of our body mass.

02:02:09Our normal activities, plus the effect of gravity, make the cartilage in our ankles,

02:02:14knees, hips, back, and neck slowly compress.

02:02:18Once you rest overnight, the cartilage goes back to normal.

02:02:22On average, you are somewhere around 0.4 inches taller in the morning than you are later at

02:02:27night.

02:02:29And that's why they call me Stretch.

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