Des faits prouvant que l'évolution vous a laissé avec quelques bizarreries étranges

Sympa

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Transcript

00:00:00Imagine this, if someone managed to unroll all the DNA contained in the human body,

00:00:06it would extend over about 16 billion kilometers.

00:00:09Do the math, it's twice the distance from Earth to Pluto,

00:00:13and it's not the only incredible thing our body is capable of.

00:00:17Trillions of nerve connections constantly feed your memory.

00:00:21According to some studies, after watching 2,500 images for only 3 seconds,

00:00:26most people will remember these images with an accuracy rate of 92%.

00:00:31Incredible.

00:00:33Your body shines, emitting tiny amounts of barely visible light.

00:00:37This glow is the product of biochemical reactions that have their home in your body.

00:00:42The light increases and decreases throughout the day.

00:00:45Although it is not visible, you cannot detect it with the naked eye.

00:00:49Bacteria represent between 0.5 and 2.7 kilos of your total body weight.

00:00:55And between 100 million and 1 billion bacteria can live on a single tooth.

00:01:00It is impossible to perceive the flavor of food without saliva.

00:01:04Indeed, the chemical substances contained in food must be dissolved in the saliva

00:01:08before being detected by the taste buds.

00:01:11It may sound like a myth, but eating too many carrots can actually make your skin orange.

00:01:17Carrots contain large amounts of beta-carotene.

00:01:20This compound can cause what is called carotenemia.

00:01:24If you have too much of it in your blood, it sticks to the parts of your body where the skin is thickest.

00:01:29On the plant of the feet, on the knees, elbows, palms, and even on certain areas around the nose.

00:01:35But do not worry, it is not dangerous.

00:01:38You can easily reverse this phenomenon by reducing your consumption of food rich in beta-carotene.

00:01:44The muscles of the chin, whose scientific name is chin muscle, have a rather bizarre aspect.

00:01:50We don't really know what to think about it.

00:01:52Look at these strange little tentacles.

00:01:56Yet, they allow us all kinds of expressions, making the lips, chin and cheeks play.

00:02:01And yes, it is they who are at the origin of these wrinkles and these bizarre folds that appear on your chin.

00:02:08And this is because these muscles pull directly on the skin.

00:02:13We can live without some of our organs and lead a normal life.

00:02:17The human body is made up of simple organs and working organs in pairs.

00:02:21And when you have two, one is actually enough for you to survive.

00:02:25Your intestinal wall is actually not that small.

00:02:28It is even bigger than you.

00:02:30It measures about 7 meters.

00:02:32The cornea, the transparent part of your eyes, is not irrigated by blood.

00:02:37It is the air that directly provides it with the oxygen it needs.

00:02:41Humans develop their unique digital footprints very early in their lives, at the embryonic stage,

00:02:46only three months after conception.

00:02:48Moreover, even if we seriously damage these digital footprints,

00:02:51they grow back naturally and find their original design.

00:02:55Everyone is born with an immersion reflex.

00:02:58This reflex is activated and interrupts bodily functions in case of drowning or prolonged immersion.

00:03:03The human brain is not smooth at all.

00:03:06But if you decide to flatten all the ridges that cover it,

00:03:09your brain will be the size of a pillowcase.

00:03:12Not so useful, however.

00:03:14Newborns blink only once or twice a minute.

00:03:17As a comparison, an adult person blinks at least 10 times during the same period of time.

00:03:23Our lungs are the only organs capable of floating on water.

00:03:26The reason is that they are made up of about 300 million alveoli,

00:03:29small balloon-shaped structures.

00:03:32In addition, even if we are in perfect health,

00:03:34our lungs are never totally free of germs or sterile.

00:03:38Your nose is a superhero.

00:03:40It is both a heating, a filter and a humidifier.

00:03:43All this thanks to its corneae, three pairs of bone-wrapped blades.

00:03:47They contain blood vessels capable of heating the air

00:03:50and caliciform cells used to humidify it.

00:03:53In addition, the air you breathe is filtered through your nose

00:03:57before being sent to your lungs.

00:03:59Every time you eat something,

00:04:01your oesophageus, the organ through which food passes to reach your stomach,

00:04:05performs a series of undulating contractions that push food.

00:04:09This is what is called peristaltism.

00:04:12There is a link between your digestive system and your brain,

00:04:15the brain-intestinal axis.

00:04:17This is why stress or brain problems can affect

00:04:20the way your body digests food.

00:04:22Even if hockey is generally harmless

00:04:25and stops by itself after a few minutes,

00:04:27it is not really pleasant.

00:04:29You must therefore know that it can occur

00:04:31as a result of a temperature change.

00:04:34The density of your brain increases throughout your life.

00:04:37All this because new neural connections appear.

00:04:40They also appear because the structure of the brain does not stop changing.

00:04:45If you do not want to peristalsis, pinch the skin of the ridge of your nose.

00:04:49Your brain then receives an alarm signal.

00:04:52Very quickly, it slows down all other processes,

00:04:55including the reflex to peristalsis.

00:04:57Moreover, studies have shown that peristalsis

00:05:00is a way for your nose to re-initialize.

00:05:03Peristalsis re-initializes cells called cells

00:05:06that cover your nasal cavity.

00:05:08The part of the brain responsible for the vision

00:05:10is located at the back of the head.

00:05:12It is interesting to note that the right side of your brain

00:05:15controls the vision on the left side, and vice versa.

00:05:19If you are in a noisy place,

00:05:21in a nightclub or at a concert,

00:05:23cover your ears and you will hear your friends better.

00:05:26Push on the tragus, the rounded, skin-covered ridge,

00:05:29which is just in front of the auditory tract,

00:05:31so that it penetrates your ear.

00:05:33Then turn this ear to your friend.

00:05:35When a person snores,

00:05:37the noise usually does not exceed 60 decibels.

00:05:40It is about the volume of a normal conversation.

00:05:43But the sound level can sometimes reach 80 decibels.

00:05:46It is the noise made by a mixer in motion.

00:05:49Like salamanders that push their tails back,

00:05:52we would be able to regenerate our cartilage,

00:05:55the rubbery material that envelops our joints.

00:05:58Scientists have recently discovered

00:06:00that the cartilage could repair itself.

00:06:03This process is apparently effective at the level of the ankle,

00:06:06less effective at the level of the knee

00:06:08and even less effective at the level of the hip.

00:06:11If a person suffers from anosmia,

00:06:13also called olfactory cystitis,

00:06:15it can neither detect nor distinguish odors.

00:06:19Your eyes do not stop moving when you look at something.

00:06:22Without that, you could not see the whole image.

00:06:25This movement escapes you,

00:06:27because your brain is an excellent video editor.

00:06:30It stabilizes the images and all these fragments

00:06:33in a homogeneous visual flow.

00:06:36The liver is the only human organ

00:06:38able to regenerate completely.

00:06:40Even if it must regenerate up to 25% of its initial weight,

00:06:44the organ will find its original size.

00:06:47Your mouth itches when you nibble on the pineapple,

00:06:50because while you eat this fruit,

00:06:52it eats you too, finally, in a way.

00:06:55Pineapple would be the only food to contain bromelain.

00:06:58It is an enzyme that breaks down proteins.

00:07:01Fortunately, our gastric acid knows how to deal with this nasty enzyme.

00:07:06Bacteria capable of producing electricity live in our intestines.

00:07:10These bacteria emit electrons,

00:07:12which creates tiny electric currents.

00:07:15This may be the way bacteria produce energy.

00:07:19The impression of déjà vu could actually result

00:07:21from a shift in the processing of information by the brain.

00:07:25This shift would occur

00:07:27when our brain transfers information between different areas.

00:07:32If there is any delay,

00:07:34your brain will receive the same information twice.

00:07:37As a result, it will consider it as an event that has already occurred.

00:07:41The mutation of the DECTU gene

00:07:43allows some people to sleep only a few hours

00:07:46while feeling in good shape.

00:07:48They are not tired and never do the morning fat.

00:07:51On average, these people wake up at 4 or 5 a.m.

00:07:555% of the world's population has this feature.

00:08:00It happens that your ears open

00:08:02or hurt you when you travel by plane.

00:08:04You can solve this problem by chewing a chewing gum.

00:08:07It allows you to open the stache tube,

00:08:09a narrow duct that connects your throat to your middle ear.

00:08:12The opening of this duct

00:08:14balances the pressure inside the ear

00:08:16and puts an end to this unpleasant phenomenon.

00:08:19Chewing also allows you to open the stache tube.

00:08:22It is possible that your feet get bigger with age,

00:08:25just like your nose and ears.

00:08:27As we age, our feet weaken at the level of ligaments and tendons.

00:08:31The plantar vault flattens.

00:08:33The feet become wider and longer.

00:08:38It may seem that there is nothing exciting in human bones,

00:08:41unless you find them in your closet.

00:08:44But normally, they are hidden under multiple layers of cells and tissue.

00:08:49They are dense, hard and unpretentious.

00:08:51But are they really?

00:08:54Your bones not only protect your internal organs and help you move,

00:08:57but they also store fats and minerals.

00:09:00Your blood cells are produced there.

00:09:02Most bone tissues are not even solid.

00:09:05Why not take a trip through your bones to see it with your own eyes?

00:09:09But you will first have to go through several layers of other tissues.

00:09:13To begin with, you have to go through the skin,

00:09:16your largest organ.

00:09:18Be careful, it is a labyrinth of pillar follicles,

00:09:20glands, nervous endings and blood vessels

00:09:24where you can easily get lost.

00:09:26Directly under the skin, there is a layer of fat.

00:09:29Its main objective is to keep your body warm.

00:09:32This layer is made up of tiny plastic bags,

00:09:35each containing a drop of fat,

00:09:37and they can kill you hard to navigate around these bubbles.

00:09:41After going through this test, you find yourself inside your muscles.

00:09:45Your fibrous and long cells are always ready to take action,

00:09:48helping you transport your body where you need it.

00:09:51Moving through this layer of tissue is delicate

00:09:54because these cells form vessels,

00:09:56and that's what makes your muscles so strong.

00:09:58Imagine that you take a bunch of elastics and stretch them.

00:10:01Is it difficult?

00:10:02Your muscle tissue is as hard as that.

00:10:05You finally arrive at your destination,

00:10:07and you see a thin and dense membrane.

00:10:09This is the outer surface of a bone.

00:10:11This layer is mainly made up of conjunctive tissues

00:10:14made up of proteins.

00:10:16You also spot many blood vessels.

00:10:19Their tiny perpendicular branches

00:10:21go deeper into the bone to feed the bone cells.

00:10:24You notice that these branches are in tiny channels.

00:10:28The interior of the superficial layer is filled with stem cells.

00:10:31They are the most active during childhood,

00:10:33and become less and less as a person grows up.

00:10:36But if a bone is damaged,

00:10:38they take action and start repairing it.

00:10:41Fortunately, all your bones are intact.

00:10:43But if there was a fracture,

00:10:45you would see the neighboring vessels bleed

00:10:47and form a thick mass around the wound.

00:10:50In about two days,

00:10:51the area would be surrounded by countless bone-producing cells.

00:10:54They would begin to change,

00:10:56transforming into different types of cells

00:10:58and forming a new bone

00:10:59between the ends of the fractured one.

00:11:02Anyway,

00:11:03it's time to move on to the hardest part of the bone,

00:11:06the outer layer, which is smooth and solid.

00:11:08Because of its density,

00:11:09it is also called a compact bone.

00:11:11This type of bone is the reason

00:11:13why X-rays,

00:11:14which can normally go through almost everything,

00:11:16including the soft tissues of your body,

00:11:18can hardly go through your bones.

00:11:20This part is 80% of your total bone mass.

00:11:25It is incredibly difficult to go through the compact bone

00:11:28because it is made up of many microscopic columns.

00:11:30Inside these cylinders,

00:11:32there are even more bone-producing cells.

00:11:35And in the middle,

00:11:36there is a central channel

00:11:37that contains the nerve fibers

00:11:39and the blood vessels of the bone.

00:11:41The cylinders stretch the bone

00:11:42and prevent it from bending

00:11:44or fracturing.

00:11:45Once you have gone through this super hard layer,

00:11:48the image around it changes radically.

00:11:50You are in a spongy bone.

00:11:52As its name suggests,

00:11:53it looks like a sponge

00:11:54or a ray of a bee hive

00:11:56made up of tiny needles.

00:11:58This bone tissue is much less dense than the compact bone,

00:12:01more flexible

00:12:02and also much lighter.

00:12:05You notice that the spongy tissue

00:12:07is only near the ends of the bone you are exploring.

00:12:10This means that you are inside one of the long bones,

00:12:13whose structure is a bit different from the others.

00:12:16In the middle,

00:12:17there is what looks a bit like a tunnel.

00:12:19It is made up of a compact bone

00:12:20that surrounds a cavity

00:12:21filled with a special substance.

00:12:23This is what is called

00:12:24the yellow soft bone

00:12:25and it is rich in fat.

00:12:27But it is time to return to the spongy bone.

00:12:29It is mainly found at the end of the long bones,

00:12:32inside the vertebrae

00:12:33and near the joints.

00:12:35This spongy tissue

00:12:36has open spaces.

00:12:38They are filled with red soft bones

00:12:40that produce blood cells.

00:12:43While exploring the human skeleton,

00:12:44we discover that it is made up of 5 types of bones.

00:12:48The long bones.

00:12:49They are much longer than the wide ones.

00:12:51For example, the thigh bones,

00:12:52the arms, the toes and the fingers.

00:12:55The flat bones.

00:12:56They are thin and slightly curved.

00:12:58These bones are like a cake with several layers.

00:13:00A spongy bone

00:13:01made up of a sandwich

00:13:02between two parallel layers of compact bones.

00:13:05Your ribs and most of the bones in your skull

00:13:07are flat bones.

00:13:09The short bones.

00:13:10In the shape of a cube,

00:13:11they consist of a thin layer of compact water

00:13:13around the spongy interior.

00:13:16The short bones are found

00:13:17in your wrists and ankles.

00:13:19The sesamoid bones.

00:13:21These are bones surrounded by tendons

00:13:23and their main function

00:13:24is to keep the tendons

00:13:25away from the joints.

00:13:27There are many bones in the feet,

00:13:29hands and knees,

00:13:30including the kneecap.

00:13:31These bones have received this name

00:13:33because they look like sesame seeds.

00:13:36Irregular bones.

00:13:37They do not fall into any category

00:13:39because their shape is too complicated.

00:13:41They are most of the bones in your face

00:13:43and part of your skull.

00:13:45The skeleton of an adult

00:13:46is made up of 206 bones.

00:13:48And each one has its own function.

00:13:50It is interesting to note

00:13:51that people are born

00:13:52with almost twice as much water.

00:13:54But as they grow up,

00:13:55these small bones merge

00:13:56and form larger bones

00:13:57as they age.

00:14:00If a bone is broken,

00:14:01those around it

00:14:02cannot function properly either.

00:14:04It usually takes

00:14:05about 12 weeks

00:14:06for a bone to heal.

00:14:08The smallest bone in your body

00:14:10is dozens of times smaller

00:14:11than a piece of a centimeter.

00:14:13This bone is called the calf

00:14:14and is found in your middle ear.

00:14:16It weighs as much as

00:14:17two sesame seeds.

00:14:18You have a new skeleton

00:14:19every 10 years

00:14:20because every year

00:14:2110% of the mineral content

00:14:22of your bones

00:14:23is renewed.

00:14:25On average,

00:14:26a person makes

00:14:271 to 3 million steps a year.

00:14:28This is why the bones

00:14:29must be so resistant

00:14:30otherwise they will not

00:14:31withstand the pressure.

00:14:33Your longest

00:14:34and strongest bone

00:14:35is in your leg.

00:14:36The femur,

00:14:37as it is called,

00:14:38goes from your hip

00:14:39to your knee.

00:14:40Even if your teeth

00:14:41are part of the skeletal system,

00:14:42they do not count as bones.

00:14:45More than half of the bones

00:14:46in your body

00:14:47are in your hands

00:14:48and your feet.

00:14:49The only bone in your body

00:14:50that is not connected

00:14:51to another

00:14:52is the bone of the tongue.

00:14:53This is a V-shaped bone

00:14:54located at the base of the tongue

00:14:56that holds it in place.

00:14:581% of people

00:14:59are born with a 13th rib.

00:15:02Your bones are not white.

00:15:03Their color

00:15:04is rather yellow

00:15:05or pink on the outside

00:15:06and dark red on the inside.

00:15:08This is because of the blood vessels

00:15:09that surround them.

00:15:11If you fracture a bone,

00:15:12ouch,

00:15:13it will heal by itself

00:15:14by producing

00:15:15new bone cells.

00:15:16A plaster

00:15:17will only help it heal.

00:15:19People have known for a long time

00:15:20how to treat broken bones.

00:15:22In ancient Egypt,

00:15:23around 1600 BC,

00:15:25broken bones were re-aligned

00:15:26and bandaged with linen.

00:15:29You cannot control your bones.

00:15:30You can only communicate

00:15:31to your muscles

00:15:32attached to your bones

00:15:33where they must move.

00:15:34Your bones reach

00:15:35their maximum density

00:15:36at the age of 30.

00:15:38Only 10% of animals in the world,

00:15:40including humans,

00:15:41have vertebrae,

00:15:42that is,

00:15:43they have a skeletal system.

00:15:45A special tissue coating

00:15:47called cartilage

00:15:48covers a bone

00:15:49and prevents it

00:15:50from rubbing directly

00:15:51against another.

00:15:53The enamel that covers your teeth

00:15:54is even more resistant

00:15:55than your bones.

00:15:56It protects the delicate tissues

00:15:57and nerves

00:15:58that are below.

00:16:00The largest joint

00:16:01of your body

00:16:02is actually your knee.

00:16:03It must be wide

00:16:04to connect three bones

00:16:05of the same size.

00:16:06The femur,

00:16:07which goes from the hip to the knee,

00:16:08the rotule

00:16:09and the tibia.

00:16:12Some joints

00:16:13barely move

00:16:14or do not move at all.

00:16:15These are those

00:16:16located between the teeth,

00:16:17inside the skull

00:16:18and between the first pair of ribs.

00:16:22The bones store minerals,

00:16:23for example,

00:16:24calcium and phosphate.

00:16:25They can be released

00:16:26in the blood if necessary.

00:16:29And finally,

00:16:30the super sensitive part

00:16:31of your elbow,

00:16:32which is called

00:16:33funny bone in English,

00:16:34is not a bone at all.

00:16:36It is a nerve

00:16:37that runs inside your elbow.

00:16:38When you hit it,

00:16:39you feel a sharp and piercing pain.

00:16:41The bone of the arm

00:16:42that the nerve crosses

00:16:43is called the humerus.

00:16:44No,

00:16:45this pain has absolutely

00:16:46nothing humorous.

00:16:47But it can be funny

00:16:48when it happens

00:16:49to someone else.

00:16:52Hey, listen to this.

00:16:53You know,

00:16:54your bones are designed

00:16:55to be extremely

00:16:56sought after on a daily basis.

00:16:57Some of them

00:16:58can absorb

00:16:59the force of two

00:17:00or even three times

00:17:01the weight of your body.

00:17:02It's impressive,

00:17:03but your teeth

00:17:04are even stronger.

00:17:05When you bite something,

00:17:06they can withstand

00:17:07an incredible pressure,

00:17:08up to 90.5 kg.

00:17:10Besides,

00:17:11the enamel is considered

00:17:12to be part of your skeleton.

00:17:14Every time

00:17:15you pivot your hand,

00:17:16the bones of your forearm

00:17:17cross.

00:17:18Grab your arm

00:17:19and turn the apple

00:17:20of your hand

00:17:21up and down.

00:17:22You will see that it is true.

00:17:23Not only is your body

00:17:24composed of 60% water,

00:17:25but your bones

00:17:26also contain liquid

00:17:27water.

00:17:28About 25%

00:17:29of the human bone mass

00:17:30is composed of water.

00:17:31The human eye

00:17:32has something in common

00:17:33with the engine

00:17:34of a car.

00:17:35Both can't work

00:17:36properly without

00:17:37various liquids.

00:17:38The eye needs tears

00:17:39as much as the engine

00:17:40needs oil.

00:17:41Tears must be

00:17:42evenly distributed

00:17:43on the surface

00:17:44of the eye.

00:17:45That's why you blink

00:17:46your eyes up to

00:17:4720,000 times a day.

00:17:48And your eyelid

00:17:49acts as

00:17:50an icebreaker.

00:17:51The only part

00:17:52of the human body

00:17:53that doesn't receive

00:17:54nutrients from blood

00:17:55is the nose.

00:17:56The nose

00:17:57is the surface

00:17:58of the eye

00:17:59before it covers

00:18:00the eye.

00:18:01It is fed

00:18:02by tears

00:18:03outside

00:18:04and by special

00:18:05fluids inside.

00:18:06When you blush,

00:18:07it means that

00:18:08the blood flow

00:18:09in your body

00:18:10increases.

00:18:11So,

00:18:12it's not just

00:18:13your cheeks

00:18:14but also

00:18:15the wall

00:18:16of your stomach

00:18:17that turns red.

00:18:18It's because

00:18:19there are a lot

00:18:20of blood vessels.

00:18:21When there is

00:18:22more blood

00:18:23than usual

00:18:24in these vessels,

00:18:25you can't really

00:18:26say that

00:18:27you're well.

00:18:28But usually,

00:18:29it's because

00:18:30you have

00:18:31a lot

00:18:32of food

00:18:33inside.

00:18:34It's because

00:18:35you don't eat

00:18:36as much

00:18:37as you should

00:18:38or as much

00:18:39as you should

00:18:40and because

00:18:41you don't

00:18:42need

00:18:43enough

00:18:44water

00:18:45to feed

00:18:46your stomach

00:18:47enough

00:18:48and your

00:18:49hair

00:18:50enough

00:18:51to grow

00:18:52plentiful

00:18:53hair

00:18:54Muuuuh!

00:18:55The stomach is the most important protector of the immune system.

00:18:59It contains chloride acid.

00:19:01This acid eliminates the dangerous food toxins,

00:19:04viruses and bacteria that accompany the food you eat.

00:19:07The stomach itself would be digested by this powerful acid

00:19:10if its mucous membrane did not protect it.

00:19:13You have two really fast muscles.

00:19:15They control the closure of your eyelids.

00:19:17They are the fastest of your body.

00:19:19Your eyes are fragile and need to be protected.

00:19:21When a particular reflex is triggered, for example

00:19:24when something suddenly touches your eye,

00:19:26these muscles only need a tenth of a second

00:19:28to close the eyelids and protect your eye.

00:19:31Women usually blink more often than men.

00:19:34And the older you get, the more often you do it.

00:19:36Besides, when you watch a movie with a friend,

00:19:39you probably both blink at the same time.

00:19:42Do you think you owe your firm hand to your muscle exercises?

00:19:45Nope.

00:19:46It's thanks to your little finger.

00:19:47I'm kidding.

00:19:48And yet, the ear is the strongest finger there is.

00:19:51It is responsible for 50% of the strength of the hand.

00:19:54But the most used finger is the thumb.

00:19:57If a person loses it, his hand becomes 40% less agile.

00:20:00Oh, and the thumb has its own skin,

00:20:02thanks to the artery that runs through it.

00:20:04Your big toes carry more than 40% of your weight,

00:20:07more than all the other toes combined.

00:20:09In fact, all your toes are very important.

00:20:12They provide support and balance when you walk.

00:20:14And when you run, they help you be faster.

00:20:17Not more than 2% of people have natural brown hair.

00:20:20They are followed by blondes, about 3%,

00:20:22and by all kinds of shades of brown, about 11%.

00:20:25But the most common hair colors in the world

00:20:27are black and French brown.

00:20:29Hair is almost indestructible.

00:20:32It can be burned or affected by strong acids,

00:20:34but that's about all you can do to destroy them.

00:20:37Your hair usually ceases to grow to a certain length.

00:20:40And since a hair lives from 2 to 7 years,

00:20:43its length normally does not exceed 106 cm.

00:20:46Tell this lady, Xi Jinping from China,

00:20:49who broke the Guinness World Record

00:20:51with the longest hair of all time.

00:20:53In 2004, they were 5 meters long.

00:20:55Wow!

00:20:56Nails can also become super long.

00:20:58Some of the longest nails in the world

00:21:00belonged to an Indian, Shridhar Shillal.

00:21:03Their total length was 9 meters,

00:21:05which is almost as long as a two-story red bus in London.

00:21:08The man cut them in 2018.

00:21:10Nails help us catch small objects

00:21:12and take off stickers.

00:21:14But that's not all.

00:21:16If you don't have a rigid structure

00:21:18against which to lean,

00:21:19you won't be able to understand

00:21:21how firmly you should hold things.

00:21:23Not only your hair and nails can grow,

00:21:25but also your liver.

00:21:27It is the largest internal organ in terms of mass.

00:21:29The liver can regenerate completely,

00:21:31going from only 51% of its initial mass

00:21:33to its maximum size.

00:21:35And at the same time,

00:21:36constant damage to the liver

00:21:38leads to scars.

00:21:40The most important organ of your body is the skin.

00:21:42It represents more than 15% of your total weight.

00:21:45People lose 30,000 to 40,000 skin cells

00:21:47every minute.

00:21:49This represents up to 4 kg of skin cells per year.

00:21:52You know this dust in your house?

00:21:54Well, now you know where some of it comes from.

00:21:57The tongue is not the only organ

00:21:59that helps you recognize your taste.

00:22:00Your nose also plays a crucial role in this process.

00:22:03It is often said that the nose is responsible

00:22:05for 75 to 95% of the perception of taste.

00:22:08Try to pinch your nose the next time you eat.

00:22:10It is not that you won't taste anything,

00:22:12but it will be a lot more dull.

00:22:14Your taste buds won't work properly

00:22:16if your mouth is too dry.

00:22:18You won't taste as much as long as

00:22:20your food is not covered in saliva.

00:22:22It contains enzymes,

00:22:24which are complex protein molecules.

00:22:26They begin to break down your food

00:22:28as soon as it enters your mouth.

00:22:30A recent study has shown that people

00:22:32can distinguish more than a billion smells.

00:22:34You tend to remember smells better

00:22:36than sounds or images.

00:22:38This is why smells can evoke distant memories.

00:22:40When you sleep, you don't smell anything.

00:22:42Basically, your sense of smell

00:22:44is deactivated at night.

00:22:46Even if there is a terrible stench in your room,

00:22:48you won't notice it.

00:22:50I'm sure my dog is relieved to hear that.

00:22:52The color of your dreams seems to be affected

00:22:54by the television you watched

00:22:56when you were a child.

00:22:58If it was black and white most of the time,

00:23:00you will have monochrome dreams.

00:23:02If you are used to colored television,

00:23:04your dreams will probably be colored.

00:23:06What kind of dreams did people

00:23:08have in the Middle Ages?

00:23:10Your heart can betray you when you lie,

00:23:12starting to beat faster.

00:23:14Women's hearts are usually smaller than men's.

00:23:16That's why they have to work harder

00:23:18and beat more.

00:23:20Otherwise, they won't be able

00:23:22to pump enough blood.

00:23:24Even if you brush your teeth twice a day

00:23:26and never forget to wash your mouth,

00:23:28your mouth remains one of the dirtiest parts

00:23:30of your body.

00:23:32Millions of bacteria live there.

00:23:34It's where the bad bacteria and viruses live.

00:23:36The second dirtiest part is your navel.

00:23:38You don't really use it after you're born.

00:23:40This neglected area accumulates

00:23:42all kinds of germs, sweat and dirt.

00:23:44The navel has more than

00:23:462,300 bacterial species

00:23:48and requires special attention.

00:23:50They say that the eyes don't grow

00:23:52with the rest of the body,

00:23:54but that's not 100% true

00:23:56because the eyes are not fully developed

00:23:58before the age of 21.

00:24:00But the absolute champions of growth here

00:24:02are the eyes and the nose.

00:24:04They don't stop growing.

00:24:06Wow, what was that thing with the elephants?

00:24:08Ah, that must have been another video.

00:24:10If all the blood vessels were spread

00:24:12over a single line,

00:24:14you'd be in trouble.

00:24:16On the other hand,

00:24:18you'd have to go around the Earth

00:24:20four times.

00:24:22You can't do squats,

00:24:24no matter how hard you try.

00:24:26You just checked and you failed,

00:24:28didn't you?

00:24:30Why do you fall asleep after breakfast?

00:24:32One of the reasons is the circadian rhythm

00:24:34that works according to a 24-hour cycle.

00:24:36It requires you to take a nap

00:24:38seven hours after you wake up,

00:24:40and the food only adds to this effect.

00:24:42It's as simple as that.

00:24:44Oops, sorry, it's time.

00:24:50Look at this.

00:24:52There are people who can fold their little finger

00:24:54without folding their ring finger,

00:24:56but most find it difficult,

00:24:58and it's impossible to achieve.

00:25:00When they move their middle finger

00:25:02or little finger,

00:25:04they tend to slightly bend their ring finger as well.

00:25:06Yes, it's the same for me.

00:25:08The luxation of the ocular globe

00:25:10is an extremely rare condition

00:25:12that allows some people

00:25:14to take their eyes out of their orbits.

00:25:16Unfortunately,

00:25:18this ability has disadvantages.

00:25:20It can lead to many eye problems.

00:25:22Some indigenous peoples,

00:25:24like the Tibetans,

00:25:26have a much higher oxygen level

00:25:28than those of Mount Everest.

00:25:30This rare ability

00:25:32is very likely to have appeared

00:25:34after years of evolution.

00:25:36The ancestors of the modern Tibetans

00:25:38lived in high regions

00:25:40for thousands of years,

00:25:42and their red blood cells

00:25:44have adapted as a result,

00:25:46making it possible to survive

00:25:48with dangerously low oxygen levels.

00:25:50The Bajau are nomads

00:25:52of the sea living in Southeast Asia.

00:25:54Thanks to this,

00:25:56they can easily spend 5 to 10 minutes

00:25:58fishing underwater

00:26:00without going back to the surface

00:26:02to breathe,

00:26:04if only once.

00:26:06About 14% of the population

00:26:08has long-palmar muscles.

00:26:10Poor old man.

00:26:12It's actually a rudimentary part of the body

00:26:14whose need has disappeared

00:26:16during our evolutionary process.

00:26:18So, if you don't have this muscle,

00:26:20don't worry.

00:26:22It doesn't affect the functioning

00:26:24of your forearm in any way.

00:26:26About 5 to 37% of people

00:26:28have no wisdom teeth

00:26:30since their birth.

00:26:32These teeth are no longer

00:26:34really necessary today.

00:26:36They were important for our ancestors

00:26:38because they helped them chew

00:26:40hard foods like nuts,

00:26:42roots and raw meat.

00:26:44And the caramels,

00:26:46soft with the salt of Guérande.

00:26:48No, I'm making it up.

00:26:50The wisdom teeth

00:26:52are no longer just a simple atavism.

00:26:54Most people have only one spiral

00:26:56of hair implantation

00:26:58that goes in the direction of needles and a watch.

00:27:00But 5 people out of 100

00:27:02have a double crown.

00:27:04And if both spirals are directed

00:27:06in the opposite direction of needles and a watch,

00:27:08it makes the person even more unique.

00:27:10Some scientists think

00:27:12there is a genetic link

00:27:14between the direction of this spiral

00:27:16and our right hand.

00:27:18The brain of the man ages faster

00:27:20than that of the woman.

00:27:22With age, men begin to complain

00:27:24more and more often

00:27:26of memory problems

00:27:28and lack of concentration.

00:27:30At the same time,

00:27:32women do not have

00:27:34such serious problems

00:27:36with their memory,

00:27:38but they feel more often depressed.

00:27:40Which one would you choose?

00:27:42When a person dies,

00:27:44the brain of the man

00:27:46When a person lies,

00:27:48his own nose betrays him.

00:27:50Psychologists at the University of Grenada

00:27:52discovered that when a person

00:27:54told a lie,

00:27:56the temperature around his nose

00:27:58and in the inner corners of his eyes increased.

00:28:00This phenomenon was called,

00:28:02surprise surprise,

00:28:04the Pinocchio effect.

00:28:06Japanese people have specific bacteria,

00:28:08plebeius bacteroides,

00:28:10in their intestines.

00:28:12These bacteria help them digest sushi.

00:28:14Japanese people have been eating

00:28:16raw algae for centuries.

00:28:18The microorganisms present

00:28:20at the surface of these algae

00:28:22have entered their bodies

00:28:24and have actively developed.

00:28:26Today, these bacteria help

00:28:28Japanese people to digest raw food

00:28:30and prevent various problems

00:28:32related to their diet.

00:28:34Humans would have as many hairs

00:28:36on their bodies as chimpanzees.

00:28:38The number of hairs

00:28:40of an individual and a chimpanzee

00:28:42is so small and so thin

00:28:44that it is almost impossible to distinguish.

00:28:46Humans do not have more genes

00:28:48than other species.

00:28:50In fact, people have even less genes

00:28:52than an ostrich.

00:28:54Tomatoes also have a lot more genes

00:28:56than you and me.

00:28:58But we are so complex creatures.

00:29:00Well, recently, scientists have concluded

00:29:02that the number of genes contained

00:29:04in a genome was not closely related

00:29:06to the complexity of a living being.

00:29:08Let's take a break to breathe a little.

00:29:10Here, your left lung

00:29:12is made up of two lobes,

00:29:14while your right lung

00:29:16is divided into three parts.

00:29:18In addition, the left lung

00:29:20is a little smaller

00:29:22because it must leave room

00:29:24for your heart.

00:29:26Your lungs also contain

00:29:28about 2,400 km of respiratory tract.

00:29:30It is more than half the distance

00:29:32between New York and Los Angeles.

00:29:34There are also more than 300 million

00:29:36alveoli in your lungs,

00:29:38and these people have five senses

00:29:40among the most obvious.

00:29:42The sight, the smell, the touch,

00:29:44the hearing and the taste.

00:29:46But that's not all.

00:29:48What about thermosensation,

00:29:50the sense of heat,

00:29:52or nociception,

00:29:54the perception of pain,

00:29:56or even the consciousness

00:29:58of one's own body,

00:30:00proprioception?

00:30:02To understand what it is about,

00:30:04close your eyes and touch your nose.

00:30:06This list can be much longer.

00:30:08Some experts claim

00:30:10that people have 21 to 53 senses.

00:30:12Your fingers become all shriveled

00:30:14after spending too much time

00:30:16in the water.

00:30:18The shriveled fingers are caused

00:30:20by the shrinking of your blood vessels.

00:30:22When you stay in the water for a long time,

00:30:24your nervous system

00:30:26retracts your capillaries.

00:30:28Your body removes the blood from this area,

00:30:30and this loss of blood

00:30:32makes your vessels narrower.

00:30:34This process is called

00:30:36thermosensation.

00:30:38Scientists believe

00:30:40that this process

00:30:42helps us feel better

00:30:44when our hands and feet

00:30:46are wet.

00:30:48There are three kinds of cones

00:30:50in the eyes of an ordinary person.

00:30:52These cones help to recognize

00:30:54the colors in the blue,

00:30:56red and green spectrums.

00:30:58Thanks to them,

00:31:00most people can distinguish

00:31:02between colors.

00:31:04This characteristic allows them

00:31:06to see up to 100 million different colors.

00:31:08This vision anomaly is extremely rare,

00:31:10and it is much more common

00:31:12in women than in men.

00:31:14Interestingly,

00:31:16most people with tetrachromatism

00:31:18do not even realize

00:31:20that they see a brighter world

00:31:22than others.

00:31:24Not all people have round pupils.

00:31:26Two out of 10,000 people

00:31:28have unusual-shaped pupils.

00:31:30This eye disorder

00:31:32is called colobome.

00:31:34It should be noted that some people

00:31:36with this condition

00:31:38have no vision problems.

00:31:40Only 3 to 22% of people

00:31:42in the world have a morton's toe

00:31:44or Greek foot.

00:31:46It is a structure of the foot

00:31:48where the second toe is longer than the first.

00:31:50Michelangelo's David

00:31:52and the Statue of Liberty

00:31:54both have this unusual

00:31:56body characteristic.

00:31:58Some people

00:32:00accumulate saliva

00:32:02in a gland under their tongue.

00:32:04It can then be propelled

00:32:06by a jet when the person presses

00:32:08on this gland.

00:32:10If the mouth is open at this time,

00:32:12the jet can reach several meters.

00:32:14This process,

00:32:16the glavitator,

00:32:18can occur spontaneously.

00:32:20A person accidentally presses

00:32:22his tongue against the gland

00:32:24while eating,

00:32:26up to 35% of people

00:32:28could do it, but only 1%

00:32:30can do it on command.

00:32:32I had a friend at the university

00:32:34who did that. Yes, it was weird.

00:32:36About 18 to 35%

00:32:38of people have an interesting reaction

00:32:40to the sunlight.

00:32:42They blink.

00:32:44This phenomenon has its own name,

00:32:46the photosternitatory reflex.

00:32:48In Greek, it means

00:32:50solar blink.

00:32:52Just like salamanders

00:32:54can't move their tails,

00:32:56humans could be able to regenerate

00:32:58their cartilage.

00:33:00It's this rubbery matter

00:33:02around your joints.

00:33:04Recently, scientists have discovered

00:33:06that the cartilage could be able

00:33:08to repair itself.

00:33:10In the most effective way,

00:33:12on the ankle, not very well on the knees

00:33:14and less effectively on the hip.

00:33:16The human brain is composed of

00:33:1873% water, just like your heart.

00:33:20That's why if your brain loses

00:33:22water, you start to feel

00:33:24exhausted. It also affects

00:33:26your memory, reduces your

00:33:28attention capacity and has a negative

00:33:30impact on your mood.

00:33:32So, have a drink.

00:33:34Your brain constantly processes

00:33:36tons of visual information,

00:33:38about 600 million bits per minute.

00:33:40Everything starts when

00:33:42the light goes through the cornea.

00:33:44The protective outer layer

00:33:46is transparent to your eye.

00:33:48Then, the light turns into

00:33:50electrical signals.

00:33:52It moves to your brain

00:33:54and interprets them as images you see.

00:33:56This complex process

00:33:58takes place in a few milliseconds.

00:34:00People who live up to 110 years

00:34:02or more, known as

00:34:04supercentenarians, could have a secret.

00:34:06Researchers have discovered

00:34:08that their immune cells,

00:34:10called T-Auxiliary Lymphocytes,

00:34:12could change

00:34:14and adapt to the last stage

00:34:16of aging.

00:34:18These cells are likely to protect them

00:34:20from viruses and other health problems.

00:34:22We have become

00:34:24multitasking workers thanks to technology.

00:34:26Or rather, it seems

00:34:28only to be so.

00:34:30The human brain cannot concentrate

00:34:32on two things at the same time.

00:34:34What it can do is quickly switch

00:34:36from one task to another.

00:34:38But this reduces your attention capacity

00:34:40and damages your short-term memory

00:34:42as well as your learning capacity.

00:34:44So, put this phone down.

00:34:48When a woman is pregnant,

00:34:50her brain undergoes many changes

00:34:52that prepare her for childbirth.

00:34:54And the part of her brain

00:34:56responsible for the social signals decreases.

00:34:58This makes the brain more efficient

00:35:00to take care of the baby.

00:35:02But don't worry,

00:35:04it doesn't stay that way.

00:35:06It returns to its standard size

00:35:08after pregnancy.

00:35:10In one day, your body produces

00:35:12one liter of saliva.

00:35:14This represents about

00:35:16And in one life,

00:35:18you can fill two Olympic swimming pools

00:35:20with saliva.

00:35:22Imagine swimming in it.

00:35:24It's both disturbing and disgusting.

00:35:26Humans have a secret superpower

00:35:28hidden in our stomachs.

00:35:30Our gastric acid.

00:35:32It has a pH of about 1

00:35:34and it is one of the most acidic substances

00:35:36in the world.

00:35:38It is so powerful that it can dissolve metals.

00:35:40And the stomach must develop

00:35:42a special protective mucus

00:35:44to prevent your body from dissolving.

00:35:46But don't try to eat metals.

00:35:48They can be toxic.

00:35:50If you take a deep breath,

00:35:52your left lung

00:35:54will be filled with much less air

00:35:56than your right lung because it is smaller.

00:35:58Your heart takes up a lot of space,

00:36:00so the left lung must make room for it.

00:36:02The lungs are divided into lobes.

00:36:04The right has three

00:36:06and the left lung has only two lobes.

00:36:08Your lungs are not the only organs

00:36:10that are not proportional in size.

00:36:12Your kidneys are also a little different.

00:36:14The left kidney is generally a little bigger

00:36:16than the right kidney.

00:36:18If you have ever wondered what their size is,

00:36:20your kidneys are the size of a fist.

00:36:22Everyone knows that sharks

00:36:24have strong teeth,

00:36:26but the outer layer of our teeth,

00:36:28called enamel, is as strong

00:36:30as the one that covers the shark's teeth.

00:36:32Enamel is also the strongest

00:36:34substance in the body.

00:36:36It protects our teeth from all kinds of damage

00:36:38so that you can eat

00:36:40your favorite food in peace.

00:36:44Toothpicks grow twice as slowly

00:36:46as fingernails.

00:36:48And if there was an Olympic sport

00:36:50that determined which nail grew the fastest,

00:36:52your little finger nail

00:36:54would always come last

00:36:56because it is the nail that grows

00:36:58the slowest of all.

00:37:00The reason is that some fingers

00:37:02are not used as much as others

00:37:04and do not have as much blood supply.

00:37:06There are strange animals

00:37:08and crabs that lose their skeleton

00:37:10in order to grow.

00:37:12Do not be shocked to learn that we do the same thing.

00:37:14We do not literally leave our skeleton,

00:37:16of course,

00:37:18but we regenerate slowly again every 10 years.

00:37:20Thus, throughout our life,

00:37:22we will change our skeleton about 8 times.

00:37:24Many years ago,

00:37:26we were like reptiles,

00:37:28like Spider-Man's evil lizard.

00:37:30Fortunately, we have evolved

00:37:32and lost almost all our reptilian characteristics,

00:37:34with the exception of the third vestigial eyelid,

00:37:36which is partially visible

00:37:38at the end of your eye,

00:37:40near your nose.

00:37:42Reptiles always have it.

00:37:44It is used to protect and clean the eye.

00:37:46If you have a polychorea,

00:37:48your eye can develop more than one pupil.

00:37:50Unfortunately, this will not improve your vision.

00:37:52In fact, it can worsen it,

00:37:54but in most cases,

00:37:56it will not affect your vision much.

00:37:58This condition is extremely rare

00:38:00and generally begins in childhood,

00:38:02but it can also develop later in life.

00:38:04Dermatography is a generally harmless condition

00:38:06that allows you to write

00:38:08almost literally on your skin.

00:38:10People who have this condition

00:38:12do not need a notebook to take notes.

00:38:14If you have this condition

00:38:16and you scratch your skin slightly,

00:38:18the redness can last half an hour.

00:38:20This could be useful for your next exam,

00:38:22if you see what I mean.

00:38:24Another unique condition

00:38:26that some people have is

00:38:28syndactyly, or palmed toes.

00:38:30It's when your toes are fused together.

00:38:32No one knows what causes this,

00:38:34but it's nothing serious.

00:38:38Did you know that your tongue

00:38:40is as unique as your fingerprints?

00:38:42Me neither.

00:38:44The tongue has special shapes

00:38:46and geometric figures,

00:38:48like fingerprints,

00:38:50which differ from person to person.

00:38:52Who knows, maybe we'll unlock

00:38:54our phones by licking them in the future.

00:38:56An adult is made up of about

00:38:587 octillions of atoms.

00:39:00This number is so large

00:39:02that I can't even say it in one breath.

00:39:04It's 7 followed by 27 zeros.

00:39:08The earwax looks like wax,

00:39:10has the texture of wax

00:39:12and tastes like...

00:39:14Of course, I have no idea what it tastes like

00:39:16and I beg you not to try to discover it.

00:39:18My point is that it's not really wax.

00:39:20It's a combination of fat,

00:39:22skin cells, dirt and sweat.

00:39:24It's important for the health of the ears

00:39:26because it keeps them clean.

00:39:30Book by book,

00:39:32bones are much more solid than steel.

00:39:34The same bone density

00:39:36will almost always outweigh steel.

00:39:38But if you compare the same

00:39:40bone and steel volume,

00:39:42the bone will break before steel.

00:39:44Bones are made to be light and solid.

00:39:46If they were made of steel,

00:39:48we would be much heavier

00:39:50and would need a lot more energy to move.

00:39:52When you were born,

00:39:54you had more water than now

00:39:56because most of them merged.

00:39:58An adult person has 206 bones

00:40:00while babies have 300 bones.

00:40:02Some of these bones

00:40:04are made of cartilage

00:40:06which is flexible and soft.

00:40:08The strongest, heaviest

00:40:10and longest bone is the femur.

00:40:12This bone is the most difficult to break.

00:40:14It can support up to 30 times

00:40:16the weight of your body,

00:40:18or about 2721 kg.

00:40:20Technically, you could balance

00:40:22two small cars on your femur

00:40:24and remain indifferent.

00:40:26Bioluminescence is a talent

00:40:28that some animals have,

00:40:30such as the angelfish,

00:40:32lice, lanternfish and humans.

00:40:34And yes, you really shine in the dark.

00:40:36Scientists have discovered

00:40:38that we shine,

00:40:40but the sparkle is a thousand times

00:40:42weaker than what our eyes can detect.

00:40:44You can see your own light

00:40:46if you have an ultra-sensitive camera.

00:40:48The amount of melanin

00:40:50in your eyes determines their color.

00:40:52Brown eyes contain

00:40:54a lot of melanin,

00:40:56while blue eyes have much less.

00:40:58However, people with heterochromia

00:41:00can have different eye colors.

00:41:02One eye can be blue,

00:41:04and the other brown,

00:41:06or any other color,

00:41:08which is cool.

00:41:10Sometimes, only half of the eye

00:41:12can be of a different color.

00:41:14When you blink,

00:41:16the air coming out of your nose

00:41:18and your mouth

00:41:20can reach

00:41:22the sky.

00:41:24Have you ever heard

00:41:26that your eyes can leave their orbit

00:41:28if you blink without closing them?

00:41:30It's a lie.

00:41:32Nothing will happen.

00:41:34The heart is the only muscle

00:41:36that works 24 hours a day,

00:41:387 days out of 7.

00:41:40It beats more than 3 billion times

00:41:42in a person's life

00:41:44and pumps about 9500 liters

00:41:46of vital fluid every day.

00:41:48So you should take care of it

00:41:50when you hit it,

00:41:52you have the impression that a thousand ants

00:41:54crawl under your skin.

00:41:56This nerve is quite long.

00:41:58It starts in the spine

00:42:00and ends in your ear and your ring finger.

00:42:02Almost all of us have heard

00:42:04that our noses and ears

00:42:06never stop growing.

00:42:08Well, it's not really true.

00:42:10Our noses and ears stop growing

00:42:12when we become teenagers,

00:42:14but they grow older

00:42:16because gravity attracts them.

00:42:18When you don't sleep enough,

00:42:20the brain can really

00:42:22start devouring itself.

00:42:2413 protected neurons are destroyed

00:42:26when you don't get a good night's sleep.

00:42:28It's a lot of brain power to lose.

00:42:30Instead of finishing this episode

00:42:32of your favorite series,

00:42:34go to bed.

00:42:36It's not worth it.

00:42:38When you are well rested

00:42:40and you have slept enough,

00:42:42your brain can generate electricity

00:42:44to power a light bulb

00:42:46or a computer.

00:42:48It moves at a speed

00:42:50of about 241 km per hour

00:42:52and the signals transported

00:42:54by your motor neurons

00:42:56can move twice as fast.

00:42:58Unlike our other primate cousins,

00:43:00most people have plantar vaults.

00:43:02They help us move.

00:43:04This plantar vault acts

00:43:06like an integrated shock absorber

00:43:08for our feet.

00:43:10This is what allows us to bounce.

00:43:12But there is another one.

00:43:14You can see it as a bridge

00:43:16that helps keep your foot in shape.

00:43:18Research shows that this arch

00:43:20is also important

00:43:22because it is responsible

00:43:24for about 40% of the stiffness of the foot.

00:43:26In other words, it is the scaffolding

00:43:28that keeps the foot in place.

00:43:30When medical researchers dissected

00:43:32this transverse arch,

00:43:34the foot lost a lot of its firmness.

00:43:36However, when they incised

00:43:38the lower part of the vault,

00:43:40the loss was not as spectacular.

00:43:42Is this a modern phenomenon?

00:43:44No, these arches do not date from yesterday.

00:43:46The transverse arch has existed

00:43:48for nearly 3 million years

00:43:50and the medial arch appeared

00:43:52about 1.8 million years ago.

00:43:54Let's focus on another element

00:43:56of our feet before moving on.

00:43:58The little toe is, too,

00:44:00more important than it seems.

00:44:02Whether you were born with it

00:44:04or lost it by accident,

00:44:06you can still walk.

00:44:08But these little fingers

00:44:10ensure balance.

00:44:12Inside your foot,

00:44:14there are 26 bones

00:44:16that join to prevent you from tilting.

00:44:18The little toe is part

00:44:20of this work of balance.

00:44:22Our ancestors, the great apes,

00:44:24needed their toes to climb,

00:44:26climb and swing on trees.

00:44:28Today, we have traded our climbing skills

00:44:30for comfortable sofas

00:44:32and TV series.

00:44:34Well, let's look a little higher

00:44:36and talk about the appendix.

00:44:38The appendix is a special organ

00:44:40that is useless.

00:44:42But no, when a human being

00:44:44is in his mother's womb,

00:44:46this organ is already starting

00:44:48its work.

00:44:50Towards the 11th week of development,

00:44:52it begins to produce special cells

00:44:54that release hormones

00:44:56and useful compounds.

00:44:58The appendix contributes

00:45:00to the training of the disorders

00:45:02of our immune system,

00:45:04ensuring that it forms

00:45:06over time.

00:45:08As food regimes evolve,

00:45:10this piece shrinks like a

00:45:12deflating bubble.

00:45:14Unlike most other vestigial structures,

00:45:16the appendix is not always harmless.

00:45:18It can turn into a real calvary.

00:45:20By the way,

00:45:22vestigial organs are those

00:45:24that have lost their main

00:45:26ancestral function.

00:45:28Most of the time,

00:45:30these structures are no longer

00:45:32of apparent use.

00:45:34And we have had problems

00:45:36since the Enlightenment.

00:45:38Yet, almost 95% of us do not.

00:45:40And 90% of us

00:45:42may even be confronted

00:45:44one day or the other

00:45:46with the discomfort

00:45:48of an included wisdom tooth.

00:45:50If you don't have any,

00:45:52you can consider yourself happy.

00:45:54And here's another interesting fact

00:45:56about wisdom teeth.

00:45:58Even if your teeth are covered

00:46:00with a mineral

00:46:02that is similar in hardness

00:46:04to those of a human wisdom tooth,

00:46:06this is explained by the fact

00:46:08that their surfaces are made of

00:46:10mineral crystals held together

00:46:12by proteins.

00:46:14These prevent them from breaking

00:46:16easily in the event of an impact.

00:46:18The difference between the use

00:46:20we make of our teeth

00:46:22and that of sharks

00:46:24therefore depends on their design

00:46:26and not on their hardness.

00:46:28Anthropologists have examined

00:46:30teeth that are as hard as roots

00:46:32and raw meat.

00:46:34At the time, these additional teeth

00:46:36were very useful.

00:46:38But we discovered the kitchen

00:46:40and, suddenly, our food

00:46:42became more tender

00:46:44and our jaws more reduced.

00:46:46Geneticists have their own point of view

00:46:48on the matter.

00:46:50It is a gene called MIH16

00:46:52which seems to play a role

00:46:54both in the size of the brain

00:46:56and in the characteristics of the jaw.

00:46:58The history of our evolution

00:47:00remains a bit mysterious.

00:47:02Now, another useless thing

00:47:04is our eyelid.

00:47:06Finally, not the normal eyelid.

00:47:08We are talking about this little pink thing

00:47:10that hides at the corner of the eye.

00:47:12Birds and other furry animals

00:47:14use it to repel dust and debris

00:47:16that could damage their eyes.

00:47:18But in us, humans,

00:47:20it is mostly vestigial.

00:47:22Here is the long-palmar muscle.

00:47:24About 85% of us still wear it

00:47:26and you too.

00:47:28You can test it by placing your hand

00:47:30on a flat surface and touching

00:47:32your ear and thumb.

00:47:34If you see a small group of tendons

00:47:36that make pirouettes in the middle of your wrist,

00:47:38you know you found it.

00:47:40It was used to grab objects

00:47:42and swing like Tarzan.

00:47:44Let's continue with the apprehension trick.

00:47:46Even before being born,

00:47:48around the 16th week of your stay

00:47:50in your mother's womb,

00:47:52you are already training to catch a cold.

00:47:54When you finally arrive in the world,

00:47:56this reflex helps you to hang on.

00:47:58Funny fact.

00:48:00Little monkeys can hang on one hand

00:48:02during lullabies thanks to a similar trick.

00:48:04On the other hand,

00:48:06we, humans,

00:48:08lose this apprehension

00:48:10around the age of 3 months.

00:48:12When you are still in gestation,

00:48:14you also have a mini tail.

00:48:16But as you grow up,

00:48:18it disappears and these tiny vertebrae

00:48:20become your coccyx.

00:48:22Our ears also have vestigial muscles.

00:48:24They allow animals

00:48:26to hear better

00:48:28and express certain feelings.

00:48:30But in humans,

00:48:32these ear muscles are not very useful.

00:48:34We have found other ways

00:48:36to listen and show our emotions.

00:48:38However, some of us can still

00:48:40move their ears with a little training.

00:48:42It is surprising to note

00:48:44that the nails of the toes

00:48:46are also part of the vestigial elements.

00:48:48They are the first line of defense

00:48:50because they protect the body

00:48:52against harmful microorganisms.

00:48:54During our evolution,

00:48:56we have used the nails of our hands

00:48:58and feet to defend ourselves,

00:49:00dig and climb.

00:49:02In the modern world,

00:49:04nails still help us

00:49:06either to peel a fruit

00:49:08or for the sweet sensation

00:49:10of scratching a snack.

00:49:12On the other hand,

00:49:14the nails of the feet

00:49:16have retired.

00:49:18In 1798,

00:49:20an anatomist examined

00:49:22a single bird

00:49:24unable to fly

00:49:26and gave his observations.

00:49:28This aviary species

00:49:30was none other than the ostrich.

00:49:32Ostriches and cassowaries

00:49:34are just a few examples

00:49:36of birds

00:49:38with vestigial wings.

00:49:40From an anatomical point of view,

00:49:42these are rudimentary wings

00:49:44unable to allow

00:49:46these corpulent creatures to fly.

00:49:48However,

00:49:50they are not totally devoid of function.

00:49:52They serve to maintain the balance

00:49:54during fast races.

00:49:56In addition, they allow to elaborate

00:49:58nuptial parades,

00:50:00helping these birds to attract potential partners.

00:50:02Now, when it comes to animals,

00:50:04many of them shine too.

00:50:06About 76% of marine animals,

00:50:08including jellyfish,

00:50:10worms, sharks

00:50:12and starfish, are bioluminescent.

00:50:14They present a molecule

00:50:16called luciferin,

00:50:18which reacts with oxygen

00:50:20to create light.

00:50:22For them, this light is used

00:50:24to confuse predators,

00:50:26attract prey

00:50:28or warn others of a danger.

00:50:30We humans can also shine.

00:50:32Unfortunately, this light is very weak

00:50:34and our eyes cannot see it.

00:50:36Our body emits light,

00:50:38but it is about a thousand times

00:50:40weaker than what our eyes can detect.

00:50:42Our face has changed throughout the day.

00:50:44It is the weakest in the morning

00:50:46and the brightest in the afternoon.

00:50:48Our face shines more than the rest of our body.

00:50:50We think this is due to the fact

00:50:52that our face is more exposed

00:50:54to the sun and that it contains

00:50:56melanin, whose components

00:50:58can stimulate the production of light.

00:51:00Some unique faculties

00:51:02distinguish us from the rest of the animal kingdom.

00:51:04Did you know, for example,

00:51:06that man was the only animal capable of reddening?

00:51:08It would seem that we have

00:51:10no sensitivity to this pink-cheeked phenomenon.

00:51:12When we find ourselves

00:51:14in an embarrassing situation,

00:51:16our blood vessels dilate

00:51:18and that's what makes us blush.

00:51:20Embarrassment is a rather complex emotion.

00:51:22It is about understanding what others think of us

00:51:24and it may be too complex

00:51:26for other animals.

00:51:28It is interesting to note that

00:51:30bald wacaris are also able to blush,

00:51:32but without giving it the same meaning.

00:51:34For them,

00:51:36it is a sign of good health.

00:51:38We must pay tribute to our bowels.

00:51:40These include the stomach,

00:51:42the liver and many other things.

00:51:44They are often called

00:51:46our second brain.

00:51:48It has its own nervous system,

00:51:50strong with a hundred million messengers

00:51:52sending information

00:51:54to the rest of your body.

00:51:56Even if the connection between the brain and the intestine

00:51:58is cut off,

00:52:00they continue to operate.

00:52:02They thus ensure the autonomous functioning

00:52:04of your digestive system.

00:52:06The human body is a perfectly

00:52:08balanced machine, isn't it?

00:52:10Well, not really in my case.

00:52:12Normally, all these parts

00:52:14work perfectly together to allow us

00:52:16to prosper and, of course,

00:52:18to stay alive.

00:52:20Each of our organs is essential

00:52:22to our daily activities,

00:52:24whether it is breathing, walking,

00:52:26talking or finding brilliant ideas

00:52:28that advance humanity.

00:52:30But are they really essential?

00:52:32Do we really need all these parts of the body?

00:52:34Or are some of them

00:52:36just old relics

00:52:38that fell on us during this strange game?

00:52:40What an evolution!

00:52:42The wisdom teeth, for example.

00:52:44Well, it's been a long time since they were removed.

00:52:46And yes, these are these pairs of teeth

00:52:48stuck at the bottom of the mouth

00:52:50for which you often have to go to the dentist.

00:52:52They are also called the third molar.

00:52:54And although they can be used

00:52:56to chew food,

00:52:58many people think

00:53:00they are simply useless.

00:53:02Just so you know,

00:53:04about 22% of people in the world

00:53:06do not even have these four molars.

00:53:08When they grow,

00:53:10they are likely to be included,

00:53:12which means they remain stuck

00:53:14in the bone of the jaw

00:53:16and cannot come out correctly

00:53:18from the gums.

00:53:20All this because our jaws

00:53:22are often too small

00:53:24to accommodate them.

00:53:26Some scientists think

00:53:28that this is because we have evolved

00:53:30and that what we eat

00:53:32when we are children

00:53:34could also be the cause,

00:53:36but it is difficult to be sure.

00:53:38Apparently, consuming

00:53:40difficult foods to chew,

00:53:42such as raw vegetables and nuts,

00:53:44can stimulate the growth of the jaws,

00:53:46while consuming soft

00:53:48and transformed food

00:53:50can somehow slow it down.

00:53:52This leaves little room

00:53:54for the teeth at the bottom

00:53:56to develop.

00:53:58We will have to wait

00:54:00to see what they estimate.

00:54:02Now let's talk about the vomeronasal organ,

00:54:04or, as I like to call it,

00:54:06the secret instrument of the nose.

00:54:08You see, rodents and other mammals

00:54:10have this formidable ability

00:54:12to communicate with each other

00:54:14thanks to chemical signals

00:54:16called pheromones.

00:54:18And guess what?

00:54:20They have a special organ,

00:54:22the vomeronasal organ,

00:54:24which helps them detect these pheromones.

00:54:26While most adult human beings

00:54:28have something that looks like

00:54:30an ovary in their nose,

00:54:32it turns out that it is essentially

00:54:34a useless vestige.

00:54:36Neuroscientists even claim

00:54:38that if we examine the anatomy of this organ,

00:54:40we do not distinguish any cell

00:54:42resembling that of similar organs

00:54:44in other mammals.

00:54:46In addition, in humans, this organ

00:54:48does not seem to communicate with the brain either.

00:54:50There is not only bad news, however.

00:54:52Even if the human ovary has little interest,

00:54:54it seems that it can still react

00:54:56to certain pheromones.

00:54:58Will man keep this organ

00:55:00on his list of evolutionary projects in progress?

00:55:02For the moment,

00:55:04let's put it in the pile of maybes.

00:55:06And now, here's a little story.

00:55:08Animals with a tail

00:55:10need this structure for many reasons.

00:55:12Some need it for their balance,

00:55:14others to move,

00:55:16others to attract potential partners.

00:55:18But did you know that when we are

00:55:20a few weeks old in our mother's belly,

00:55:22we also have a tail?

00:55:24That's right.

00:55:26We have a complete little tail

00:55:28with its own vertebrae.

00:55:30As we develop,

00:55:32this tail disappears like magic

00:55:34and all we have left is our faithful coccyx.

00:55:36Humans and great apes

00:55:38have the peculiarity of not having a tail,

00:55:40unlike other primates.

00:55:42The reason why great apes

00:55:44have lost their tails remains a mystery.

00:55:46But we all agree

00:55:48that it distinguishes us from baboons

00:55:50and other macaques.

00:55:52However, from time to time,

00:55:54a human is born with a small vestigial tail.

00:55:56It's cute, isn't it?

00:55:58But don't get too excited

00:56:00because these tails have no vertebrae

00:56:02and can sometimes be associated

00:56:04with a pathology of the spine.

00:56:06Anyway,

00:56:08these tails are generally harmless

00:56:10and can be easily removed

00:56:12by a quick surgical intervention.

00:56:14And let's be honest,

00:56:16it's not as if we were going to miss it.

00:56:18Who needs a tail

00:56:20when we have arms and legs to move around?

00:56:22And then, can you only imagine

00:56:24trying to find pants your size

00:56:26with a tail that protrudes in the back?

00:56:28It's not very aesthetic.

00:56:30There is little chance

00:56:32that man will need a tail in the future.

00:56:34So I guess future generations

00:56:36can already say goodbye to these tail bones.

00:56:38Humans also have a funny

00:56:40small fold of the membrane

00:56:42in the inner corner of the eyes

00:56:44called the semilunar fold of the conjunctive.

00:56:46In fact, it is these

00:56:48that remain of a third eyelid

00:56:50that we still find in some animals

00:56:52like gorillas

00:56:54and other primates.

00:56:56But the most curious thing is that

00:56:58even our close relatives, chimpanzees,

00:57:00have this small fold that seems useless.

00:57:02So we are not the only ones

00:57:04to have this bizarre ocular rice.

00:57:06Speaking of unusual membranes,

00:57:08they fulfill various functions

00:57:10in different animals,

00:57:12such as eye protection against dirt and moisture

00:57:14or the concealment of iris against predators.

00:57:16Some species

00:57:18can even see through their transparent membrane

00:57:20when they are underwater or underground.

00:57:22Now, the reason

00:57:24why we humans

00:57:26have lost our third eyelid

00:57:28remains a bit mysterious.

00:57:30Maybe the evolution of our habitat

00:57:32and the physiology of our eyes

00:57:34made it useless.

00:57:36Or maybe we have become too cool

00:57:38to have a third eyelid.

00:57:40Who knows?

00:57:42Without vestigial organs,

00:57:44it is interesting to imagine

00:57:46what humans could look like in the future.

00:57:48Many organs have become obsolete

00:57:50due to the evolution of our way of life.

00:57:52Would you like to take a look

00:57:54at what we could look like

00:57:56in the future?

00:57:58And in the same vein, or artery,

00:58:00have you ever heard of the concept

00:58:02of the texto grip?

00:58:04It is when you spend so much time

00:58:06typing on your phone or your laptop

00:58:08that your hand begins to have cramps

00:58:10and this is one of the physical changes

00:58:12that could happen to us

00:58:14if we do not take care of our body

00:58:16in this world dominated by technology.

00:58:18But our hands are not the only ones concerned.

00:58:20We could end up

00:58:22with elbows at 90 degrees

00:58:24by constantly holding our devices

00:58:26at this angle.

00:58:28And even a smaller brain

00:58:30because of all the distractions

00:58:32and overload of information.

00:58:34Well, I know what you're thinking.

00:58:36We're not going to give up technology

00:58:38and go back to the Stone Age.

00:58:40And you're probably right,

00:58:42we don't have to get there.

00:58:44But we have to be aware

00:58:46of the potential negative effects

00:58:48and take measures to reduce them.

00:58:50This is why a team of designers

00:58:52has put together these creative efforts

00:58:54to present Mindy to us.

00:58:56A human of the future whose body

00:58:58would have changed physically

00:59:00depending on the constant and endless use

00:59:02of smartphones, laptops

00:59:04and other types of chronophage devices.

00:59:06While Mindy's body may not represent

00:59:08our near future,

00:59:10the concerns that surround it are very real.

00:59:12So what can we do?

00:59:14One suggestion would be

00:59:16to regularly move away from our screens

00:59:18and to stretch our legs a little.

00:59:20Maybe even encourage yoga in the office

00:59:22or dance parties to circulate blood.

00:59:24It is not necessary to completely

00:59:26give up technology,

00:59:28but we have to be aware of

00:59:30its effects on our body and mind.

00:59:32In several years,

00:59:34we will become smaller.

00:59:36A scientist estimates that if we were smaller,

00:59:38our body would need less energy,

00:59:40which would be very useful

00:59:42on our increasingly overpopulated planet.

00:59:44It is amusing to think

00:59:46how different our lives are today

00:59:48from that of hunter-gatherers.

00:59:50At the time, we had to interact

00:59:52only with a handful of people every day.

00:59:54Today, remembering everyone's names

00:59:56is a very important feature

00:59:58and it could even be that

01:00:00we are led to improve it.

01:00:02But know that technology could

01:00:04actually play a role in our evolution.

01:00:06Some researchers think that one day

01:00:08we could have implants in our brain

01:00:10that would help us remember people's names.

01:00:12It is as if you had a biological ring

01:00:14directly in your body.

01:00:16Wouldn't that be practical?

01:00:18And who knows, maybe in the future

01:00:20we will even have a visible technology

01:00:22that will be part of our appearance.

01:00:24Imagine an artificial eye capable

01:00:26of perceiving different colors and images.

01:00:28And I'm not even talking about what

01:00:30would happen if we colonized Mars.

01:00:32Due to its low gravity,

01:00:34our body could change in all kinds of ways.

01:00:36We could have arms and legs

01:00:38that are longer or even hair

01:00:40as long as our ancestors of Neanderthal.

01:00:42It is difficult to determine

01:00:44what we could look like in the future

01:00:46without having very precise data

01:00:48to test these projections.

01:00:50But we can say that these changes

01:00:52will be at least interesting.

01:00:54As for me, the least we can say

01:00:56is that it is too late.

01:00:58It's time to say goodbye.

01:01:00See you later.

01:01:02Try it, you'll see.

01:01:04Pinch your elbow as hard as you can.

01:01:06You can barely feel the pain.

01:01:08How does it look?

01:01:10Nervous endings are different

01:01:12depending on the regions of the body.

01:01:14The latter is indeed more sensitive

01:01:16to pain in the most fragile and risky areas.

01:01:18These areas have more nervous endings

01:01:20so that we react faster

01:01:22to protect ourselves.

01:01:24And thick skin, like the elbows,

01:01:26has less pain detectors.

01:01:28But I'm not talking about this tingling

01:01:30and sudden pain that you can feel

01:01:32when you pinch your elbow.

01:01:34It's a bit like if your arm

01:01:36had been electrocuted.

01:01:38I wouldn't say that this sensation

01:01:40is funny, even if English speakers

01:01:42talk about a funny bone that would be the cause.

01:01:44Although it's not a bone,

01:01:46it's a nerve that starts from your spine,

01:01:48goes through your neck, crosses your elbow

01:01:50and ends up in your fingers.

01:01:52Its real name is the ulnar nerve.

01:01:54It's one of the three main nerves of your arm.

01:01:56And it transmits the sensations

01:01:58at the tip of your fingers.

01:02:00Your ulnar nerve is well protected

01:02:02by muscles, fat and bones.

01:02:04But there is a place in your elbow

01:02:06where this nerve is exposed.

01:02:08And this place is exactly where you pinch yourself.

01:02:10A different version,

01:02:12but real, of Achilles' heel.

01:02:14Now you know why it's so funny

01:02:16when you pinch your elbow

01:02:18and why you feel nothing when you pinch your skin.

01:02:20The next phenomenon

01:02:22also concerns our most embarrassing movements.

01:02:24But not only.

01:02:26It can also happen

01:02:28when you see the person you love.

01:02:30I'm talking about blushing.

01:02:32There are no butterflies in your stomach

01:02:34when you're in love.

01:02:36But I'm sure of this.

01:02:38When you blush,

01:02:40the wall of your stomach blushes too.

01:02:42Yes, I looked carefully.

01:02:44The mucous membrane of the stomach

01:02:46protects the walls of this organ

01:02:48When you blush,

01:02:50it blushes too.

01:02:52Because blushing occurs when our blood

01:02:54rises to the surface of our skin.

01:02:56And it also affects the stomach.

01:02:58It's a natural process,

01:03:00a physiological response to a change of emotion.

01:03:02And since we're talking about the stomach,

01:03:04know that the gastric liquid

01:03:06has the ability to melt

01:03:08a table in steel.

01:03:10This means that this acid

01:03:12would be able to digest

01:03:14your internal organs.

01:03:16So the wall of your stomach

01:03:18prevents this from happening.

01:03:20Now we're going to talk about

01:03:22the fact that you shine in the dark.

01:03:24Don't turn off the lights yet.

01:03:26You can't see that with the naked eye.

01:03:28These images of sparkling human bodies

01:03:30come from ultra-sensitive cameras.

01:03:32Japanese scientists

01:03:34were the first to immortalize

01:03:36human bioluminescence.

01:03:38Only these ultra-sensitive cameras

01:03:40can detect the tiny amounts of light

01:03:42that our body emits.

01:03:44Apparently, all living creatures

01:03:46produce a small amount of light

01:03:48due to chemical reactions

01:03:50in their cells.

01:03:52And humans are no exception.

01:03:54Researchers photographed

01:03:56a group of volunteers

01:03:58for several days.

01:04:00And their results show

01:04:02that the light emitted

01:04:04follows a 24-hour cycle.

01:04:06The light is at its maximum

01:04:08in the late afternoon

01:04:10and its minimum late at night.

01:04:12The light is emitted by the cheeks,

01:04:14the forehead, and the neck.

01:04:16But these areas don't correspond

01:04:18to the brightest areas

01:04:20that appear on thermal cameras.

01:04:22Did you know that you are

01:04:24a little taller in the morning

01:04:26than you are later in the day?

01:04:28Yes, I measured you.

01:04:30Joking aside, this difference in size

01:04:32is related to gravity.

01:04:34Its force compresses the cartilage

01:04:36of your spine and your knees

01:04:38when you get up or sit.

01:04:40That's why, when you wake up,

01:04:42after a long night's sleep,

01:04:44you are taller.

01:04:46But this difference in size

01:04:48is quite negligible.

01:04:50No need to organize a contest

01:04:52and open bets.

01:04:54A funny detail,

01:04:56astronauts are taller

01:04:58than they were

01:05:00when they left Earth.

01:05:02It's because of the absence

01:05:04of gravity on the ISS.

01:05:06But they don't keep

01:05:09Now let's get back to this organ

01:05:11we talked about earlier, the skin.

01:05:13Yes, the skin is an organ.

01:05:15In fact, it's the largest organ

01:05:17in your body.

01:05:19It represents about 15%

01:05:21of your body weight.

01:05:23And what does this organ do

01:05:25in addition to covering your body?

01:05:27It fulfills vital functions.

01:05:29For example, it protects you

01:05:31from external physical and biological damage.

01:05:33And it avoids excessive water loss.

01:05:35I can't help but wonder

01:05:37what other surprises the human body

01:05:39has in store for us.

01:05:41But for now, let's move on

01:05:43to the animal world.

01:05:45The owls don't have eyeglasses.

01:05:47Instead, they have eye tubes.

01:05:49Their eye-shaped rods

01:05:51don't move in their orbits

01:05:53like our eyes do.

01:05:55So they would have to move

01:05:57their entire body

01:05:59to look around them.

01:06:01But that would make too much noise.

01:06:03And other animals would hear them.

01:06:05Their eyes would rotate

01:06:07about 270 degrees

01:06:09without making any noise.

01:06:11But what's the point?

01:06:13Well, night vision

01:06:15requires large corneas

01:06:17to capture as much light as possible.

01:06:19That's why most nocturnal animals

01:06:21like the loris or the tarsier

01:06:23have big eyes.

01:06:25For the owls, it's a little different.

01:06:27Since they have small heads,

01:06:29they can't have such big eyes.

01:06:31And although they don't have eyeglasses,

01:06:33they can have one to blink,

01:06:35one to sleep,

01:06:37and one to clean their eye tubes.

01:06:39Do owls think it's cool?

01:06:41Of course!

01:06:43Now we're going to talk

01:06:45about a so-called twilight animal.

01:06:47Meow!

01:06:49Cats have a special organ

01:06:51that lets them smell in the air.

01:06:53It's called the Jacobson organ

01:06:55or the vemeronasal organ.

01:06:57The Jacobson organ is located

01:06:59inside the cat's nasal cavity

01:07:01and opens on the palate,

01:07:03in the mouth.

01:07:05It detects specific chemical substances

01:07:07through nerves that lead

01:07:09directly to the brain.

01:07:11And they're not ordinary substances.

01:07:13The Jacobson organ's receptors

01:07:15have a very special function.

01:07:17They capture substances

01:07:19that don't smell at all.

01:07:21In other words,

01:07:23cats can detect undetectable smells.

01:07:25And that's not all.

01:07:27The Jacobson organ increases their odour.

01:07:29Imagine two mother cats

01:07:31and four kittens.

01:07:33The kittens can tell

01:07:35their mother from the other cat

01:07:37thanks to their odour.

01:07:39When you meet someone,

01:07:41you analyze their body language.

01:07:43Cats can analyze themselves

01:07:45by sniffing the head of their fellow cat.

01:07:47They emit pheromones,

01:07:49and this substance usually lasts

01:07:51a long time on an individual.

01:07:53For example, what the feline likes to eat

01:07:55or if it's in good health.

01:07:57Or if it's in a bad mood.

01:07:59All thanks to the Jacobson organ.

01:08:01Here's another fact about cats.

01:08:03Their muzzles have nerves

01:08:05that form a kind of pattern.

01:08:07We have digital prints,

01:08:09and cats have nasal prints.

01:08:11They can be used to identify them.

01:08:13So, Mr. Cat,

01:08:15did you break this vase?

01:08:17We found your prints on the crime scene,

01:08:19but we can make a deal.

01:08:21Tell us what you know about this dog

01:08:23and this DVD.

01:08:25Maybe you prefer dogs.

01:08:27Here's a myth you probably know.

01:08:29Dogs are daltonians.

01:08:31But that's not the case.

01:08:33It's true that the range of colors

01:08:35they can detect is limited

01:08:37compared to the spectrum available to humans.

01:08:39They mainly see yellow,

01:08:41blue and purple tones.

01:08:43And they don't see our red,

01:08:45our green and our orange.

01:08:47And finally, the turtles.

01:08:49These creatures can't leave their shell

01:08:51and come back when they want to.

01:08:53In fact, they are completely attached

01:08:55to their shell.

01:08:57This one grows with it, like the human skin.

01:08:59The turtle's shell

01:09:01is made up of 50 bones.

01:09:03It includes a skeleton with a vertebral column

01:09:05and a thoracic cage.

01:09:07So they go on vacation with it.

01:09:09It's a bit like your RV

01:09:11if you had to live in it all your life.

01:09:13Hey, can you speak louder?

01:09:15I just ate a whole pizza.

01:09:17It's because after eating a big meal,

01:09:19our hearing tends to be a little less fine.

01:09:21During digestion,

01:09:23most of our blood flow

01:09:25is directed to the stomach,

01:09:27which deprives a little of all the other organs.

01:09:29So the next time you want to listen

01:09:31to your favorite band during a concert,

01:09:33make sure you eat a lighter meal

01:09:35so that your hearing is optimal.

01:09:37In addition to our stomach and our left kidney,

01:09:39we have a magic organ

01:09:41that can grow back

01:09:43if we remove a part of it.

01:09:45Our liver can regenerate

01:09:47by making new cells called hepatocytes.

01:09:49They begin to multiply

01:09:51as soon as the liver has been damaged.

01:09:53The gravity of the lesion determines

01:09:55if the liver can regenerate completely

01:09:57and how long it will take to do so.

01:09:59Have you ever wondered

01:10:01what is the worst thing for your body?

01:10:03Not sleeping or not eating?

01:10:05It turns out that lack of sleep is more dangerous.

01:10:07Indeed, if you don't rest,

01:10:09your body is exposed to much more risk.

01:10:11After 24 hours without sleep,

01:10:13you can start to have memory problems

01:10:15and have trouble concentrating.

01:10:17After only 17 hours without sleep,

01:10:19you start to feel tired

01:10:21and dizzy, irritable,

01:10:23tense and more emotional.

01:10:25Ok, I need a nap.

01:10:27Your pain receptors

01:10:29also become more sensitive,

01:10:31which means that everything hurts you

01:10:33a little more than normal.

01:10:35Oh, and it also affects your hearing.

01:10:37What?

01:10:39On the other hand, you can have

01:10:41your first 24-hour period without food

01:10:43before your body realizes

01:10:45that you have stopped eating.

01:10:47During the first 8 hours,

01:10:49you continue to digest the last meals you took.

01:10:51After these first hours,

01:10:53you start using the stored fats

01:10:55as a source of energy.

01:10:57If you don't eat for more than 24 hours,

01:10:59your body will start eating

01:11:01its own proteins,

01:11:03which means that you will literally

01:11:05start losing muscle.

01:11:07Rainwater is not always drinkable.

01:11:09It can sometimes contain dangerous bacteria

01:11:11and viruses.

01:11:13Some communities

01:11:15only use rainwater

01:11:17as their main source of hydration.

01:11:19But does rainwater

01:11:21have health benefits?

01:11:23Not really,

01:11:25according to current studies.

01:11:27Some of these dangerous substances

01:11:29can be eliminated from rainwater

01:11:31if you boil it.

01:11:33But it is preferable to be careful

01:11:35and to drink only water

01:11:37that comes from sources

01:11:39without any risk to human consumption.

01:11:41Rainwater can be used

01:11:43as a body lotion

01:11:45and to add a little moisture,

01:11:47like the one we need

01:11:49in the palm of our hands

01:11:51to have a better grip.

01:11:53But sweat doesn't just appear

01:11:55on our skin.

01:11:57It comes out of about

01:11:595 million pores on our body.

01:12:01We literally walk on

01:12:03a quarter of our bones every day.

01:12:05Our body has a little over 200 bones,

01:12:07but about a quarter of them

01:12:09are in our eyes.

01:12:11Our eyes produce tears

01:12:13for many reasons,

01:12:15like to protect ourselves from infections

01:12:17or to eliminate debris

01:12:19such as smoke and dust.

01:12:21Or when your baby

01:12:23makes you miserable.

01:12:25But the amount of tears

01:12:27we produce is quite surprising,

01:12:29up to 113 liters per year.

01:12:31It's almost enough

01:12:33to fill a bathtub.

01:12:35Wow, it's overwhelming!

01:12:37Our hormones, like adrenaline

01:12:39and noradrenaline,

01:12:41help us boost the energy

01:12:43we need in the morning.

01:12:45But they also increase our blood pressure,

01:12:47which is generally higher

01:12:49between 6 a.m. and noon.

01:12:51During the night,

01:12:53as we should technically sleep

01:12:55and do no physical activity,

01:12:57our blood pressure drops to 20%.

01:12:59Speaking of vital fluids,

01:13:01our blood represents about 10%

01:13:03of the total weight of our body.

01:13:05You may think that our body weight

01:13:07is mainly made up of muscles,

01:13:09fat reserves and bones,

01:13:11but there is much more than that.

01:13:13In an adult person in good health,

01:13:15bones represent 15%

01:13:17of the total weight of the body.

01:13:19Muscles represent about 40% to 45%.

01:13:21Fat deposits, about 15%.

01:13:23And the rest is composed

01:13:25of elements such as skin,

01:13:27tendons, hair

01:13:29and other nice little things.

01:13:31Let's see, it gives ...

01:13:33Yeah, 100%!

01:13:35Your lungs are not twins,

01:13:37they are brothers and sisters.

01:13:39Indeed, they are not the same size

01:13:41or the same shape.

01:13:43Your right lung is bigger

01:13:45and tends to weigh more.

01:13:47And it is your heart that is responsible

01:13:49since your heart is tilted a little to the left.

01:13:51This creates a small cavity

01:13:53in the left lung called the heart.

01:13:55The right lung may be bigger,

01:13:57but it is a little shorter

01:13:59since it must make room for the liver.

01:14:01Many measurements of your body

01:14:03are quite symmetrical in a surprising way.

01:14:05If you try two arms,

01:14:07your size and that you measure them,

01:14:09you should see how tall you are.

01:14:11Based on these similar measurements,

01:14:13specialists can even elaborate

01:14:15theories on the appearance of ancient humans.

01:14:17It would seem that we have evolved

01:14:19to become more and more symmetrical

01:14:21in order to appear more attractive

01:14:23and in better health to attract partners.

01:14:25Hmm ...

01:14:27In addition, as we have evolved

01:14:29on two legs, our symmetrical characteristics

01:14:31help us to move

01:14:33with as little energy as possible

01:14:35because they create a balance.

01:14:37Humans are not natural champions

01:14:39in terms of odors, that's for sure.

01:14:41But our nose can capture

01:14:43about a trillion different smells.

01:14:45Scientists continue to do research

01:14:47on this subject and think that this figure

01:14:49could be even higher.

01:14:51Some dog breeds are able to perceive

01:14:53odors between 10,000 and 100,000 times

01:14:55higher than ours.

01:14:57But it turns out that the best nose

01:14:59of the animal kingdom could come back to the elephant

01:15:01due to the quantity and

01:15:03the stupefying number of olfactory

01:15:05receptor genes it has.

01:15:07More than 10,000, while humans

01:15:09and chimpanzees have less than 400.

01:15:11We tend to consider

01:15:13our little fingers as our most delicate fingers.

01:15:15But they have more power than we think.

01:15:17It turns out that in case of loss

01:15:19or failure of the ear,

01:15:21the overall strength of our grip

01:15:23can decrease up to 33%.

01:15:25The liquid contained

01:15:27in our stomach, composed of

01:15:29hydrochloric acid, potassium chloride

01:15:31and sodium chloride,

01:15:33is much more powerful than any

01:15:35acidic food you can think of,

01:15:37like lemons, pineapples

01:15:39or tomatoes.

01:15:41The pH of the healthy gastric acid

01:15:43must be between 1 and 3,

01:15:45just below that of the acid of a battery.

01:15:47The strands of our hair

01:15:49are also very resistant,

01:15:51so resistant that research

01:15:53has been carried out on them

01:15:55to reproduce their strength on

01:15:57human-made materials.

01:15:59Healthy hair should be able

01:16:01to withstand a weight of 12 tons.

01:16:03This is due to a small protein

01:16:05contained in the strands of hair,

01:16:07keratin, which is also found

01:16:09in nails and skin.

01:16:11Only one third of humans have a perfect vision.

01:16:13Glasses and contact lenses

01:16:15are much more numerous than we think,

01:16:17as they represent about

01:16:1966% of the population.

01:16:21Due to our large ocular affections,

01:16:23our vision also deteriorates with age.

01:16:25When we are born,

01:16:27our head represents a quarter of our total length.

01:16:29When we reach 25 years of age,

01:16:31our head no longer represents

01:16:33an eighth of this length.

01:16:35This is explained by the fact that

01:16:37the size of our head does not change much

01:16:39as we age, unlike the rest of our body,

01:16:41mainly in terms of

01:16:43legs and torso.

01:16:45Our brain is a very powerful computer,

01:16:47and a single cell in the human brain

01:16:49can contain five times more information

01:16:51than the Britannica encyclopedia.

01:16:53You may remember.

01:16:55We have not yet determined the exact amount

01:16:57of data it can support,

01:16:59but in terms of electronics,

01:17:01the brain's storage capacity

01:17:03is about 2,500 Teraoctets.

01:17:05For comparison,

01:17:07the National Archives of Great Britain,

01:17:09which has more than 900 years of history,

01:17:11only take 70 Teraoctets.

01:17:13This is probably the reason

01:17:15why our brain needs

01:17:17more oxygen than other organs.

01:17:19About 20% of the total oxygen

01:17:21enters the bloodstream.

01:17:23However,

01:17:25it only represents 2% of our body mass.

01:17:27Our normal activities

01:17:29and the effect of gravity

01:17:31cause the cartilage of our ankles,

01:17:33knees, hips, back and neck

01:17:35to compress slowly.

01:17:37Once you have rested during the night,

01:17:39the cartilage returns to normal.

01:17:41On average, you are about

01:17:43one centimeter taller in the morning

01:17:45than you are in the night.

01:17:47This is why we sleep in a so-called

01:17:49lying position.

01:17:51You are as bald as a monkey.

01:17:53No, it's not an insult.

01:17:55Your fingerprints are not unique.

01:17:57You can hear better if you cover your ears.

01:17:59Are these statements true

01:18:01or are they legends?

01:18:03When a person lies,

01:18:05you can unmask it with your nose.

01:18:07Is that true?

01:18:15Yep!

01:18:17Researchers at the University of Grenoble

01:18:19have discovered that

01:18:21when a person lies,

01:18:23the temperature around the nose

01:18:25and in the corner of the eyes increases.

01:18:27This phenomenon is called

01:18:29the Pinocchio effect.

01:18:31So what?

01:18:33Humans have the same amount of hair

01:18:35as chimpanzees.

01:18:37Do you believe it?

01:18:39It's surprising,

01:18:41but it's still true.

01:18:43The number of hairs

01:18:45on a human body

01:18:47and on the body of a chimpanzee

01:18:49or any other monkey

01:18:51of the same size as us

01:18:53is almost equal.

01:18:55The only difference

01:18:57is that human hairs

01:18:59are often thin and colorless.

01:19:01It's hard to count them.

01:19:03Your two lungs are identical.

01:19:05It's likely,

01:19:07but it's not true.

01:19:13It's a legend.

01:19:15Your left lung

01:19:17is composed of two lobes

01:19:19while your right lung

01:19:21is divided into three parts.

01:19:23In addition,

01:19:25the left lung

01:19:27is a little smaller

01:19:29to leave room for the heart.

01:19:31Moreover,

01:19:33the lungs contain

01:19:35more than 300 million alveoli,

01:19:37small air bags

01:19:39in the shape of balloons.

01:19:41You've probably heard that

01:19:43eating carrots is good for your sight.

01:19:53Unfortunately, it's not true.

01:19:55And it's not true

01:19:57that eating carrots

01:19:59makes you see better at night.

01:20:01These are vegetables

01:20:03that are good for your eyes.

01:20:05But if you need glasses,

01:20:07you'll have to wear them

01:20:09even if you eat a lot of carrots.

01:20:11Some people blink

01:20:13when they look at the sun.

01:20:15Is that possible?

01:20:19Yes,

01:20:21about 25% of the population

01:20:23react by blinking

01:20:25when they look at the sun.

01:20:27This phenomenon even has a name.

01:20:29The photosternitatory reflex.

01:20:31This shaving

01:20:33strengthens the hair

01:20:35and makes them darker.

01:20:37Is that true?

01:20:41Don't worry,

01:20:43it's a legend.

01:20:45You may feel

01:20:47that your hair is thicker,

01:20:49grows faster,

01:20:51or changes color

01:20:53after shaving.

01:20:55But it's just an illusion.

01:20:57Shaving cuts the follicle

01:20:59and makes it darker.

01:21:01But if the hair grows back,

01:21:03it'll be the same as before.

01:21:05Fingerprints are unique.

01:21:07That's obviously true, isn't it?

01:21:15The problem with this statement

01:21:17is that researchers can't prove

01:21:19that fingerprints are unique.

01:21:21It's apparently true,

01:21:23but impossible to verify.

01:21:25And even if it's improbable,

01:21:27it's possible to find

01:21:29two people with the same fingerprint.

01:21:31Humans have more than 5 senses.

01:21:33Is that a legend

01:21:35or a reality?

01:21:41We have 5 main senses.

01:21:43Sight, smell, touch,

01:21:45hearing and taste.

01:21:47But what about thermoperception,

01:21:49the perception of heat,

01:21:51nausea, the perception of pain,

01:21:53or the perception of your body,

01:21:55the proprioception?

01:21:57Close your eyes and touch your nose.

01:21:59That's it!

01:22:01It's a perfect example of proprioception.

01:22:03The list is still long.

01:22:05Some experts estimate

01:22:07that humans have between 21 and 53 senses.

01:22:09Fingers are tingling

01:22:11when you spend too much time in the water.

01:22:13It's for your safety.

01:22:15Is it true?

01:22:17What do you think?

01:22:19Researchers think it's true.

01:22:21But let's start from the beginning.

01:22:23Fingers are tingling

01:22:25when blood vessels shrink.

01:22:27It's the nervous system

01:22:29that makes blood vessels shrink

01:22:31when you spend too much time in the water.

01:22:33Your body removes blood from your fingers.

01:22:35Blood vessels are thinner

01:22:37and the skin adapts to their new shape.

01:22:39That's why it's funny.

01:22:41Researchers are not 100% sure,

01:22:43but they think this mechanism

01:22:45triggers to allow you

01:22:47to have a better grip

01:22:49with wet hands and feet.

01:22:51Humans use only 10%

01:22:53of their brain capacity.

01:22:55I hope it's a legend.

01:23:01Yes, it is.

01:23:03Apparently, we use 100%

01:23:05of our brain capacity every day.

01:23:07This organ is still active

01:23:09even when we sleep.

01:23:11When you snore,

01:23:13the frontal lobe,

01:23:15and the areas that allow you

01:23:17to perceive your environment

01:23:19are still active.

01:23:21Some people see with

01:23:23brighter colors.

01:23:25How is it done?

01:23:33It's true.

01:23:35There are three types of photoreceptors

01:23:37in the eyes of a normal person

01:23:39that distinguish the colors

01:23:41of blue, red and green spectra.

01:23:43In the eyes of these photoreceptors,

01:23:45most people distinguish

01:23:47about a million different shades.

01:23:49But people with tetrachromatism

01:23:51have four photoreceptors in their eyes.

01:23:53They can distinguish about 100 million

01:23:55different shades.

01:23:57It's an extremely rare anomaly

01:23:59that affects women more often

01:24:01than men.

01:24:03But what's funny is that

01:24:05most people with tetrachromatism

01:24:07don't know they see the world

01:24:09with brighter colors.

01:24:11Close your ears.

01:24:13It's a bit counterintuitive,

01:24:15but is it true?

01:24:23Yes, if you are in a noisy place,

01:24:25for example in a club or at a concert,

01:24:27you should cover your ears

01:24:29to better hear your friends.

01:24:31Press on your tragus.

01:24:33It's this little part of the cartilage

01:24:35at the entrance of your auditory tract.

01:24:37Lean your ear towards your friend

01:24:39and that's it!

01:24:41You can avoid dizziness.

01:24:43Ah, that would be so convenient!

01:24:45But is it a legend?

01:24:53No, it's true!

01:24:55All you have to do is pinch

01:24:57the root of your nose.

01:24:59In doing so,

01:25:01the brain receives an alarm signal

01:25:03and slows down all processes

01:25:05including dizziness.

01:25:07Ok, you are still watching

01:25:095 episodes of your favorite TV show.

01:25:11You will sleep more tomorrow to recover.

01:25:13But is it possible?

01:25:21Unfortunately, no.

01:25:23You can always try to recover

01:25:25the hours of sleep lost with

01:25:27naps or fat mornings on the weekend.

01:25:29But it won't change anything.

01:25:31If you didn't sleep enough

01:25:33the night before

01:25:35or if you went to bed late

01:25:37the fat mornings until noon

01:25:39won't change anything.

01:25:41Even worse, you may feel dizzy

01:25:43if you sleep too much.

01:25:45Some people have more ribs than others.

01:25:47Is it true or not?

01:25:53It's true!

01:25:55Most people have 12 pairs of ribs,

01:25:5724 in total.

01:25:59But out of 200 people,

01:26:01one has a 25th rib.

01:26:03It's a cervical rib

01:26:05that is formed at the base of the neck

01:26:07above the clavicle.

01:26:09It can be formed on the right or left

01:26:11and even on both sides of the body.

01:26:13Those who have this extra rib

01:26:15probably don't know it.

01:26:17Indeed, it is rare that it is fully formed

01:26:19and can simply look like

01:26:21body tissue.

01:26:23In this case, it is not even visible

01:26:25to the X-ray.

01:26:27You have to wait at least half an hour

01:26:29before going to bathe after eating.

01:26:31I bet you have heard this phrase before.

01:26:33Is it true?

01:26:37It's a legend!

01:26:39We think that after a meal

01:26:41at the pool,

01:26:43blood moves to the stomach

01:26:45to help with digestion.

01:26:47Your muscles would not receive

01:26:49enough blood,

01:26:51which would cause cramps.

01:26:53But in reality,

01:26:55there is no risk if you take a bath

01:26:57after eating.

01:26:59You would still have enough blood in your muscles.

01:27:03Some people's snoring

01:27:05is louder than a kitchen robot.

01:27:07What do you think?

01:27:15On average, when someone snores,

01:27:17the noise does not exceed 60 decibels,

01:27:19which corresponds to the volume

01:27:21of a normal conversation.

01:27:23But sometimes, snoring can reach

01:27:2580 decibels,

01:27:27according to the noise of a mixer.

01:27:29Everyone does not have round pupils.

01:27:31Is it possible?

01:27:39Yes!

01:27:41Out of 10,000 people,

01:27:43two have strange-shaped pupils.

01:27:45In general, they look like

01:27:47lock holes.

01:27:49This anomaly is called colobome.

01:27:51Surprisingly, some people

01:27:53with this characteristic

01:27:55are born with it.

01:27:59It is possible that you have

01:28:01this physical characteristic

01:28:03without knowing it,

01:28:05since sometimes even radiographs

01:28:07miss it.

01:28:09We have for the most part

01:28:1112 pairs of ribs,

01:28:13namely 24 ribs in all.

01:28:15However, some people

01:28:17have 25.

01:28:19One in 200 people

01:28:21is born with this little plus.

01:28:23This little plus is generally

01:28:25above the first ribs,

01:28:27at the base of the neck

01:28:29and just above the clavicles.

01:28:31This is nothing alarming.

01:28:33Most of the time,

01:28:35the cervical ribs go unnoticed

01:28:37and if they ever cause pain,

01:28:39they are easy to remove.

01:28:41Do you see the huskies?

01:28:43Have you noticed that their eyes

01:28:45are sometimes two different colors?

01:28:47Some humans also have

01:28:49this characteristic.

01:28:51It is called chroma,

01:28:53which means color.

01:28:55There are cases of total,

01:28:57central or partial heterochromia.

01:28:59When a person's eyes

01:29:01are two completely different colors,

01:29:03let's say a brown eye

01:29:05and a green eye,

01:29:07we talk about total heterochromia.

01:29:09When the outline of the pupil

01:29:11is a different color

01:29:13from the rest of the iris,

01:29:15we talk about central heterochromia.

01:29:17And when one part of the eye

01:29:19is a different color

01:29:21from the rest of the iris,

01:29:23we talk about total heterochromia.

01:29:25Some people have this characteristic

01:29:27but it can also appear

01:29:29at a specific time,

01:29:31such as after an accident.

01:29:33It is still very rare.

01:29:35In the United States,

01:29:37people with this characteristic

01:29:39are less than 200,000.

01:29:41Let's say it's pretty cool anyway.

01:29:43Speaking of the color of the eyes,

01:29:45do you know what the rarest color is?

01:29:47The percentage of people with blue eyes

01:29:49is estimated between 8 and 17%

01:29:51in the world.

01:29:53As for gray eyes,

01:29:55they are even less common.

01:29:57Less than 1% of the population

01:29:59has eyes of this color.

01:30:01This very rare characteristic

01:30:03is due to a low level of melanin

01:30:05in the layers of the iris.

01:30:07You are more likely to meet

01:30:09someone with gray eyes

01:30:11in Eastern and Northern Europe.

01:30:13There are even rarer colors of eyes,

01:30:15such as blue,

01:30:17red,

01:30:19yellow,

01:30:21green,

01:30:23blue,

01:30:25red,

01:30:27blue,

01:30:29red,

01:30:31red,

01:30:33red,

01:30:35red,

01:30:37red,

01:30:39red,

01:30:41red,

01:30:43red,

01:30:45red,

01:30:47red,

01:30:49red,

01:30:51red,

01:30:53red,

01:30:55red,

01:30:57red,

01:30:59western

01:31:05Italian

01:31:07our

01:31:09placement

01:31:11It's great to have a good time in the evening.

01:31:15Joking aside, people with biphidia can have problems eating, drinking and speaking.

01:31:22They can also have digestion problems and have a strange speech.

01:31:27But it depends on the size of the spout.

01:31:31Here is a feature that is not ideal to enjoy your holidays.

01:31:35But people who are provided with it are more effective with less hours of sleep.

01:31:39It is said that Nikola Tesla, Margaret Thatcher and Winston Churchill

01:31:43presented this super rare feature.

01:31:46This gene, called DEC2, helps regulate circadian rhythms.

01:31:52These are our natural biological clocks

01:31:55that tell us when to go to sleep and eat,

01:31:58making us feel tired or hungry.

01:32:01A person with this rare mutation has a shorter sleep cycle than the average.

01:32:07She will feel rested even after having slept only 4 or 5 hours.

01:32:11I would love to have the same superpower!

01:32:14What would you say about a genetic mutation that allows you to have superhero bones?

01:32:19The bones become practically unbreakable and the skin is less prone to aging.

01:32:24It really looks like with this mutation,

01:32:27you can get out of any accident and resist as long as it goes.

01:32:31Some people have a very attractive feature

01:32:34that can go unnoticed at first sight.

01:32:37It presents what is called dystichiasis,

01:32:40that is, a second row of eyelashes.

01:32:43If you ever wanted to know more about the medical aspect of this feature,

01:32:47it is the result of a genetic mutation of the FOXC2 gene.

01:32:51It may be very nice to see,

01:32:53but people affected by dystichiasis may feel discomfort in the eyes.

01:32:58And in some cases, they may have vision problems.

01:33:03You may never have heard of the hair loss syndrome,

01:33:07but you may have it.

01:33:09I know, the name says it all,

01:33:12but just for your information, it makes your hair dry and messy.

01:33:16They become so unmanageable that you can't comb them.

01:33:20They also tend to grow in all directions.

01:33:24As for the color, hair is generally light blue or silver.

01:33:29We generally have cylindrical hair.

01:33:32People affected by this syndrome have triangular hair,

01:33:36heart-shaped or simply flat.

01:33:39It is an extremely rare syndrome.

01:33:41There are only 100 confirmed cases, and it fades with age.

01:33:45Most humans have evolved by developing traits

01:33:48according to the geographic area where they live.

01:33:51But there are some individuals,

01:33:53especially those who live at altitude,

01:33:56who have developed rather cool traits.

01:33:59Let me explain.

01:34:00There is less oxygen at altitude.

01:34:03Not only have these individuals adapted to it,

01:34:06but they behave very well in this type of environment.

01:34:09For example, the inhabitants of the Andes in South America

01:34:13have red blood cells that carry much more oxygen than the average.

01:34:17Their circulatory system is much more efficient.

01:34:21In other similar environments,

01:34:23individuals have adapted to their way.

01:34:26They have the ability to breathe more

01:34:29to meet the needs of their body in oxygen.

01:34:32This is a trait that has an aesthetic interest,

01:34:36but that has almost no impact on health.

01:34:42People with this trait have little melanocytes,

01:34:45the cells that produce hair pigments in certain parts of the hair.

01:34:50Decolorated hair is generally located at the front of the scalp.

01:34:54It can also be eyebrows or eyelashes.

01:34:57This is a trait that exists from birth

01:35:00and that persists throughout life.

01:35:03If you want to get rid of it, you can always dye your hair.

01:35:06But personally, I think it looks super cool.

01:35:09We all know that coriander doesn't like everyone.

01:35:12I don't know what you think, but for me it tastes like soap.

01:35:16It's not really a matter of taste, but rather of genetics.

01:35:20A study conducted on 30,000 individuals

01:35:23showed that people who consider that coriander tastes like soap

01:35:27have a particular gene that reacts more to the smell than to the taste of the plant itself.

01:35:32If you are one of these people, but you want to give coriander a chance,

01:35:36you can try this little trick

01:35:39or ask the people who cook at your house to do it.

01:35:42Fold the leaves before using them.

01:35:45Why?

01:35:47Because by crushing the leaves,

01:35:49the components responsible for this taste of soap

01:35:52decompose and thus disturb much less.

01:35:56No one really knows what the appendix is for,

01:35:59but it is always at the end of a book.

01:36:02Oh no, it's not the right appendix.

01:36:04Some researchers consider that the human appendix

01:36:07helped our ancestors to digest the bark of trees

01:36:10and the other foods they ate at the time.

01:36:13Now the appendix is balanced,

01:36:15and our appendix could disappear without any consequences.

01:36:19Wisdom teeth also have no use.

01:36:22Yes, they were useful before the invention of the dentist,

01:36:25but we can do without them now.

01:36:29Your brain grows by about 2% if you venture into space.

01:36:33With terrestrial gravity,

01:36:35we think that the fluids in the brain flow down

01:36:38when we stand up.

01:36:40Terrestrial gravity prevents this process from occurring,

01:36:43and the fluids accumulate in the brain and in the skull.

01:36:47As you age, the size of your brain gradually decreases.

01:36:51At 75, the brain is smaller than at 30,

01:36:54and it starts to shrink at the age of 40.

01:36:57It happens to everyone,

01:36:59so you just have to accept it and always train your brain.

01:37:03If you look closely at your eyes in a mirror,

01:37:06you will notice a small pink circle in the corner of the eye.

01:37:09This is your third eyelid.

01:37:11Useless for humans, it is very useful for animals,

01:37:14especially for birds.

01:37:16It protects the eyes from dust.

01:37:18If you've ever heard of natural selection,

01:37:20you know what I'm talking about.

01:37:22Natural selection maintains some parts of the body

01:37:25through generations, but some are harmful.

01:37:28So if an element is dangerous or useless,

01:37:30it disappears the next generation,

01:37:32like the third eyelid, for example.

01:37:34It's not just our brain that shrinks over time.

01:37:37So our bones become more fragile

01:37:39and the spine compresses.

01:37:41Conversely, when you sleep and you relax,

01:37:44your bones also relax and you wake up bigger than the day before.

01:37:50Our ears help us maintain balance.

01:37:52They are not just used to hear.

01:37:54Our inner ear contains our vestibular system.

01:37:57The channels of the inner ear contain fluids

01:38:00and small sensors that look like hairs

01:38:02and that allow you to maintain balance.

01:38:05As far as hairs are concerned,

01:38:07only a few parts of the body are not covered.

01:38:09These are the palms of the hands,

01:38:11the plants of the feet and the lips.

01:38:13There are even hairs in the navel

01:38:15that protect it from impurities.

01:38:17Mine do their job very well.

01:38:19And not just impurities.

01:38:21Our navels host a varied fauna.

01:38:23There are more than 70 different bacteria.

01:38:26Some of these bacteria are also present

01:38:29in the ground in Japan

01:38:31and others in the ice caps.

01:38:33You see, there is a real navel operation going on in your navel

01:38:36and you did not know it.

01:38:38There is only 43% of yourself that is really there.

01:38:42You are composed of 50% of small creatures

01:38:45that live mostly in your intestine

01:38:47and in other parts of the body.

01:38:49Although the number of your cells

01:38:51is less than the number of bacterial cells,

01:38:53you still have 100 trillion.

01:38:56Knowing this,

01:38:58your genes finally correspond to less than half of what constitutes you.

01:39:01If we consider all the microbes

01:39:03that live in your body

01:39:05and that we count their genes,

01:39:07we will talk about 2 to 20 million genes

01:39:09and their combinations.

01:39:11When you sleep,

01:39:13it is not certain that your whole body also sleeps.

01:39:15Sometimes the brain works even harder

01:39:17when you are asleep.

01:39:19It has to process tons of information

01:39:21and the calculations take time.

01:39:25One thing that really rests

01:39:27when you sleep is your nose.

01:39:29It is impossible to smell when you sleep.

01:39:32The smell goes away at night.

01:39:35If it smells really bad in your room,

01:39:37you will not even realize it.

01:39:40Scientists thought that humans could

01:39:42distinguish about 10,000 smells.

01:39:44But no! Recent research has shown

01:39:46that humans could distinguish

01:39:48about 1 trillion smells

01:39:50and that they are well embedded in our memory.

01:39:53They can also send us back to old memories.

01:39:56By the way, our most intense memories

01:39:58are often made up.

01:40:01The central memory works like this.

01:40:03It gives us the certainty

01:40:05that our memories are real,

01:40:07even if some details are a little far from the truth.

01:40:10No problem if I call you a mammal, right?

01:40:14We are the only mammals

01:40:16to be able to walk on two limbs

01:40:18and maintain this posture all our lives.

01:40:21You will tell me that kangaroos and gorillas

01:40:23move in the same way.

01:40:25But kangaroos use their tails as a third leg

01:40:27and gorillas use their arms

01:40:29to maintain balance.

01:40:32Your bones play a role in your metabolism.

01:40:35Since they are mainly made up of calcium,

01:40:38the bones begin to relax

01:40:40if there is not enough in your body.

01:40:43On the contrary, when there is too much calcium

01:40:45in your blood, it is stored in the bones.

01:40:50Our size, the shape of our body

01:40:52and our skin color

01:40:54depend on where our ancestors lived.

01:40:57But we can also adapt to new conditions

01:40:59throughout our life.

01:41:01For example, if you move from the plain

01:41:03to the mountains,

01:41:05you will produce more red blood cells

01:41:07to compensate for the lack of oxygen.

01:41:09And of course, if you move

01:41:11from a cold climate to a warmer climate,

01:41:13your skin will slightly change

01:41:15its pigmentation to adapt.

01:41:18Our lifespan is programmed in our cells.

01:41:20They renew and divide constantly,

01:41:22but they have an internal countdown

01:41:24that stops at some point.

01:41:26Some cells also stop reproducing

01:41:28before others.

01:41:30On average, cells stop dividing

01:41:32when they reach 100 years.

01:41:34If we could find a way

01:41:36to set the countdown to zero,

01:41:38we could potentially live forever.

01:41:41But we would have a lot of wrinkles.

01:41:45Fat is used as an insulator,

01:41:47energy reserve and bumper.

01:41:50Your body accumulates most of the fat

01:41:52around the waist,

01:41:54since this is where the internal organs are located.

01:41:56If something happens to you,

01:41:58this layer of fat can protect your organs

01:42:00from major damage.

01:42:02Your skull is not made up of a single bone.

01:42:04It is made up of 22 different bones,

01:42:06most of which are glued

01:42:08to protect your brain.

01:42:10The mandible, in other words the lower jaw,

01:42:12is the only bone in the skull

01:42:14that is attached to your head

01:42:16by conjunctive tissues and muscles.

01:42:18You can move it in all directions.

01:42:20And the smallest bone in the body

01:42:22is located in the ear.

01:42:24It is called the calf

01:42:26and it is not bigger than a grain of rice.

01:42:28The most powerful muscles of your body

01:42:30are not only in your legs and arms.

01:42:32There are some in your head.

01:42:34This is the masseter,

01:42:36the chewing muscle.

01:42:38It needs to be powerful enough

01:42:40to ensure chewing.

01:42:42And you see the muscles that allow you

01:42:44to move your ears?

01:42:46These are temporal muscles

01:42:48and they are located above the temples.

01:42:50They also help you chew your food.

01:42:52We have two really fast muscles,

01:42:54the muscles that control the tilting of the eyelids.

01:42:56These are the fastest muscles of our body.

01:42:58Our eyes are fragile

01:43:00and they must be protected.

01:43:02When necessary,

01:43:04these muscles close the eyes

01:43:06in less than a tenth of a second.

01:43:08We can only distinguish

01:43:10the colors purple-blue,

01:43:12green-yellow and yellow-red.

01:43:14It is impossible to calculate

01:43:16the number of color combinations

01:43:18visible by the human eye

01:43:20since each person sees things

01:43:22in a slightly different way.

01:43:24It is still a million combinations on average.

01:43:26Your stomach has an incredible

01:43:28container, up to 1.5 liters of liquid.

01:43:30It is the equivalent of a large

01:43:32bottle of coca.

01:43:34It is difficult to evaluate

01:43:36the amount of solid food

01:43:38that can be stored there

01:43:40since the food is grinded by the teeth

01:43:42and there is not enough room

01:43:44for a whole turkey.

01:43:46But who knows,

01:43:48a good chicken could fit in there.

01:43:50As my grandmother used to say,

01:43:52there is always room for ice.

01:43:54Show me where this stomach

01:43:56is full of coca, chicken and ice.

01:43:58If you indicate your stomach,

01:44:00it is wrong.

01:44:02The stomach is between your ribs.

01:44:04Your stomach is full of intestines.

01:44:06Let's see if you or your friends

01:44:08had some of these rare physical characteristics.

01:44:10Elf ears are very rare.

01:44:12They are pointed on the outside.

01:44:14They have an additional cartilage fold

01:44:16in the middle of the area

01:44:18called the pavilion.

01:44:22Most humans are right-handed.

01:44:24There are only 10% left-handed.

01:44:26But there are also people

01:44:28who can use their right hand

01:44:30as well as their left,

01:44:32without particular preference.

01:44:34They can play the guitar,

01:44:36use scissors, write, etc.

01:44:38They are called ambidextrous

01:44:40and they represent only 1% of humans.

01:44:42If you can speak with both sides

01:44:44of your mouth,

01:44:46you can be a future in politics.

01:44:48Only a third of the population

01:44:50has spread their nostrils on command.

01:44:52The muscle responsible for this movement

01:44:54is very little developed

01:44:56because it is not used for much.

01:44:58This is why this movement

01:45:00is not common.

01:45:02The inhabitants of Nepal and Tibet

01:45:04have a special gene

01:45:06that allows them to breathe

01:45:08at extreme altitudes.

01:45:10Most people do not feel well

01:45:12in such conditions.

01:45:14But not the locals.

01:45:16They manage to breathe normally.

01:45:18It is a super athlete gene.

01:45:20It is found in the Denisovans,

01:45:22a tribe that populated

01:45:24the mountainous areas of Asia

01:45:26about 40,000 years ago.

01:45:28This gene allows them to have

01:45:30more hemoglobin carrying oxygen.

01:45:32Their body can distribute oxygen

01:45:34between them.

01:45:36They do not feel the lack of oxygen

01:45:38by being active at such altitudes.

01:45:40The gerontoxin is also

01:45:42a rather rare feature.

01:45:44It is a white or gray arc

01:45:46located above and under the outside

01:45:48of the cornea,

01:45:50namely the transparent striping

01:45:52that covers the front part of the eye.

01:45:54It is quite common among the elderly.

01:45:56It can turn into a complete ring

01:45:58around the iris,

01:46:00the colored part of the eye.

01:46:02Some people do not need

01:46:04a lot of sleep.

01:46:06Most of us cannot spend

01:46:08two sleepless nights

01:46:10without having to suffer the consequences.

01:46:12But a small percentage of people

01:46:14have a special gene

01:46:16that allows them to sleep

01:46:18only 6 hours or less,

01:46:20which corresponds to 2 hours

01:46:22less than the average.

01:46:24Only 1 to 3% of the population

01:46:26have this gene.

01:46:28They are generally more productive

01:46:30than short-sighted people.

01:46:32Leonardo da Vinci, Thomas Jefferson

01:46:34and other well-known figures

01:46:36would have been among these people.

01:46:38We have, for the most part,

01:46:40three types of photoreceptor cones

01:46:42in the eyes, which allows us

01:46:44to perceive a wide spectrum of colors.

01:46:46But some people have a fourth type of cone.

01:46:48These are tetrachromats,

01:46:50and thanks to this particularity

01:46:52they perceive up to 100 million colors.

01:46:54On average, a person perceives

01:46:56about 1 million colors.

01:46:58These are rare characteristics

01:47:00that are mainly found in women.

01:47:02Have you ever heard of heterochromia?

01:47:04It is a color difference

01:47:06between the iris of both eyes.

01:47:10Sometimes the color difference

01:47:12can be found on other parts of the body,

01:47:14such as hair or skin.

01:47:16It is sometimes simply a difference

01:47:18in shades between the two irises.

01:47:20Heterochromia is a genetic origin.

01:47:22People with this characteristic

01:47:24do not have a homogenous level of melanin

01:47:26in the body.

01:47:28This characteristic is only present

01:47:30in 1% of the population.

01:47:32Chimerism is a rare genetic phenomenon.

01:47:34A person affected by chimerism

01:47:36presents two different sets

01:47:38of genetic material,

01:47:40called genomes, in the body.

01:47:42A certain genome is dominant

01:47:44in an organ or in a part of the body,

01:47:46and another is dominant

01:47:48in other tissues and other organs.

01:47:50This is a phenomenon

01:47:52that also exists in animals.

01:47:54People and animals

01:47:56with this characteristic

01:47:58may have two blood groups simultaneously.

01:48:00It is probably

01:48:02the same amount of each group.

01:48:04It would be cool

01:48:06to have indestructible bones.

01:48:08This is the case of some people

01:48:10who present a mutation

01:48:12of the LRP5 gene.

01:48:14People with this characteristic

01:48:16have bones 8 times more resistant

01:48:18than the average.

01:48:20When someone tells you

01:48:22that you have a bone,

01:48:24you can imagine

01:48:26small particles of blood

01:48:28circulating in the veins.

01:48:30But it does not really happen like this,

01:48:32and the blood is not golden.

01:48:34It is an extremely rare blood group

01:48:36that has been found

01:48:38only in 40 people in the world.

01:48:40These people do not have

01:48:42all the antigen cells

01:48:44of the rhesus system.

01:48:46In short,

01:48:48it means that all those

01:48:50people with this characteristic

01:48:52do not have all the genes

01:48:54of the rhesus system.

01:48:56So,

01:48:58if you have a bone,

01:49:00it means that

01:49:02you do not have

01:49:04all the genes

01:49:06of the rhesus system.

01:49:08But if you have a bone,

01:49:10it means that

01:49:12you do not have

01:49:14all the genes

01:49:16of the rhesus system.

01:49:18So,

01:49:20if you have a bone,

01:49:22it means that

01:49:24you do not have

01:49:26all the genes

01:49:28of the rhesus system.

01:49:30But if you have a bone,

01:49:32it means that

01:49:34you do not have

01:49:36all the genes

01:49:38of the rhesus system.

01:49:40So,

01:49:42if you have a bone,

01:49:44it means that

01:49:46you do not have

01:49:48all the genes

01:49:50of the rhesus system.

01:49:52And if you have a bone,

01:49:54it means that

01:49:56you do not have

01:49:58all the genes

01:50:00of the rhesus system.

01:50:02So,

01:50:04finally,

01:50:06if you have a bone,

01:50:08it means that

01:50:10you do not have

01:50:12all the genes

01:50:14are even rarer, less than 2% of the population.

01:50:1811% of the population has naturally curly hair.

01:50:22We all learned at school that the heart is slightly to the left of the chest.

01:50:27But the heart of some people is slightly to the right.

01:50:30There are not necessarily negative consequences, but it can affect other organs.

01:50:3522% of humans have a Morton's toe.

01:50:38And suddenly, Morton has no toe anymore.

01:50:42Ah, I'm kidding.

01:50:44Morton's toe is when the second toe is longer than the big toe.

01:50:48If you pay attention, you will notice that the Statue of Liberty has Morton's toe.

01:50:55Some people have a cartilaginous rupture above the ear,

01:50:59called Darwin's tubercle.

01:51:02It is said that these people have a better ability to perceive the tone of the voice.

01:51:08There are only 16% of people on Earth who can produce a rustle in their head.

01:51:14They use a small muscle of the jaw, which can prevent them from hearing certain noises, such as chewing.

01:51:21But if these people flex this muscle, they hear a rustle in their head.

01:51:26Only a third of the population knows how to play the piano,

01:51:30and only 1% of them know how to do it on command.

01:51:34Not very useful, but very rare.

01:51:374% of the population has Reynaud's syndrome.

01:51:41It is the part of the body, usually the fingers and toes, that turns white at low temperatures.

01:51:47It is a physical reaction to cold or stress.

01:51:52So look at your fingers.

01:51:54They are in a loop, in a spiral or in an arc.

01:51:57The first two types are the most common,

01:51:59but only 5% of the population has fingerprints in an arc.

01:52:03Only 10% of the population has birthmarks.

01:52:06In most cases, these marks are oval and brown.

01:52:12Faucets are rarer than we think.

01:52:14Only a quarter of the population has this characteristic.

01:52:17You can have one or two faucets and inherit them.

01:52:21So if your parents have one, well, that's it.

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