Des faits surprenants sur le corps humain qui pourraient dérouter un professeur de biologie

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Transcript

00:00:00Look at yourself in the mirror.

00:00:03Yes, right in the eyes.

00:00:05Do you see this little fold of skin in the inner corner of the eye?

00:00:09Well, in the past, it was a kind of third eyelid, or nictitating membrane.

00:00:15We can observe it nowadays in snakes or lizards, for example.

00:00:19This one had a priori the same function as the other two,

00:00:22but we don't really know if it reached a full development stage in humans.

00:00:27The membrane that made it up was not as thick as our current eyelids,

00:00:31and it could moisten the eye without obstructing the view.

00:00:34All that is left of it today is this tiny fold in the corner of the eye,

00:00:39and it is very likely that in the future, it will completely disappear.

00:00:42And maybe on this occasion, we will stop waking up

00:00:45with this little not-so-aesthetic crust that forms in this place during the night.

00:00:50As long as you are still in front of your mirror, look lower.

00:00:53Even lower.

00:00:54All the way down, actually.

00:00:55Yes, these are your toes.

00:00:57Say hello to them, and goodbye.

00:00:59Indeed, scientists think that in the relatively distant future,

00:01:03we will completely get rid of our toes.

00:01:06Our ancestors, the ancient primates,

00:01:08needed toes to climb trees more efficiently.

00:01:11They used both their hands and their feet to grab the branches of trees.

00:01:15This is clearly visible today in most monkeys.

00:01:18They have longer and more flexible toes,

00:01:20as well as more slender feet that allow them to cling to the branches.

00:01:24The mobility of their feet also allows them to catch objects on the ground if necessary.

00:01:29For most of us, picking up a pen lying on the ground with our toes

00:01:33remains a rather complex task,

00:01:35unlike our primate cousins.

00:01:37Humans have evolved on a different path.

00:01:40We started walking standing up and down trees,

00:01:43which made our feet stiff and our toes shorter over time.

00:01:48Today, we still use our toes to balance ourselves

00:01:51by moving our weight from our heels to the tip of our feet,

00:01:55but our balance point is now much more centered.

00:01:58It first moved towards the inside of our feet,

00:02:01which made our small toes so small,

00:02:04and our big toes so big.

00:02:06If this balance point had just been centered outward,

00:02:10our toes would be more likely to merge in the future.

00:02:13Now, turn around and look at your magnificent tomb behind you.

00:02:17If you've ever fallen off a skateboard or slipped on an ice sheet,

00:02:21you probably remember how painful it is

00:02:24to hit a hard surface directly on the coccyx.

00:02:27Fortunately for us, scientists predict that this bone growth

00:02:31will soon disappear as we evolve.

00:02:33The coccyx is another feature of our primate ancestors.

00:02:37And yet again, they needed their tails to be more mobile

00:02:41among the branches of the trees,

00:02:43to swing from one tree to the other.

00:02:46It's hard to say when humans dropped their tails

00:02:49to never use them again,

00:02:51but the facts are what they are.

00:02:53The only thing that reminds us of those glorious days

00:02:56where we easily jumped from tree to tree

00:02:58and this little useless piece of bone at the bottom of our back.

00:03:01Let's go back to the face now.

00:03:03Open your mouth and say,

00:03:06If you are lucky enough not to have wisdom teeth,

00:03:10then you can be proud to know that you are a pure product of evolution.

00:03:15As you may know, teeth are the only part of the human body

00:03:18that does not repair itself on its own.

00:03:21If you lost all your teeth at this dark time

00:03:23when there were no dentists,

00:03:25your only option was to consume only liquid food.

00:03:31Scientists think that nature gave us wisdom teeth

00:03:34to replace the older and worn teeth we have since childhood.

00:03:38That's why they grow so late in our lives.

00:03:41But today, with all the progress made by dental surgery,

00:03:44we tend to keep almost all our teeth intact

00:03:47until an advanced age.

00:03:49And even if we lose them,

00:03:51we can still replace them.

00:03:53This makes wisdom teeth a slightly outdated legacy,

00:03:56which it seems to understand by itself,

00:03:58since fewer and fewer people

00:04:00need to undergo the ordeal

00:04:02that their adult extraction represents.

00:04:04Speaking of teeth,

00:04:06our entire jaw has evolved over the last 10,000 years.

00:04:10And it is expected that it will change even more in the future.

00:04:13In fact, of all the parts of our body,

00:04:16it is the one that has transformed the fastest.

00:04:19When the first humans survived

00:04:21thanks to hunting and gathering,

00:04:23they needed massive and powerful jaws

00:04:25as well as larger teeth

00:04:27to be able to chew raw meat and grind plants.

00:04:30When they started to cook,

00:04:32then to cultivate,

00:04:34their food became less hard

00:04:36and their jaws adapted accordingly.

00:04:39Over time, they shrunk more and more,

00:04:41and it is likely that they will continue to do so.

00:04:44With a lot of transformed food

00:04:46that does not require a lot of chewing,

00:04:49future humans will probably have

00:04:51more delicate facial features,

00:04:53thin jaws, and smooth jaws.

00:04:56Some parts of the body do not disappear,

00:04:59but, on the contrary, return to strength.

00:05:02100 years ago, the fabella,

00:05:04a tiny bone located at the back of the knee,

00:05:07was found in about 11% of people,

00:05:09and scientists thought it would

00:05:11disappear entirely and quickly.

00:05:13But against all odds,

00:05:15this brave little bone managed to

00:05:17end up in the knees of 39% of humans today.

00:05:21We still do not know exactly

00:05:23why the fabella came back,

00:05:25but the most plausible hypothesis

00:05:27is that we have become bigger

00:05:29and heavier than our ancestors.

00:05:31As our food has become

00:05:33of better quality and more nutritious,

00:05:35our size and our life expectancy have increased.

00:05:38Today, we are probably at the peak

00:05:40of our evolutionary size,

00:05:42and the fabella may have appeared

00:05:44in our body to provide a smooth surface

00:05:46to the tendon behind the knee

00:05:48so that it can slide better,

00:05:50thus reducing the friction

00:05:52and the risk of damage due to wear.

00:05:54Speaking of size,

00:05:56let's go back to our mirror.

00:05:59Stretch out your arms a little,

00:06:01look at those pretty biceps.

00:06:03Unfortunately, they are probably

00:06:05not as developed as those of your ancestors.

00:06:07Everything that comes from evolution

00:06:09is not always what we consider

00:06:11to be the best for us.

00:06:13It is above all a set of characteristics

00:06:15in principle the best adapted to our lifestyles.

00:06:17And this is also the case with our muscles.

00:06:19They have become smaller and stronger

00:06:21over time, especially in the upper part of our body.

00:06:23In the past, humans needed

00:06:25a great muscular power

00:06:27that they mobilized to perform

00:06:29all kinds of essential manual work,

00:06:31such as hunting and transportation of prey,

00:06:33as well as the manufacture of tools

00:06:35and the construction of shelters.

00:06:37Then, it did not become easier.

00:06:39On the contrary, ploughing the fields

00:06:41and building complex structures

00:06:43required a lot of physical strength and endurance.

00:06:45But with the rise of technological progress,

00:06:47physical abilities have left more and more

00:06:49energy dedicated to brain functions,

00:06:51allowing us to invent machines

00:06:53that work in our place

00:06:55sometimes more efficiently.

00:06:57We are oriented towards a sedentary lifestyle,

00:06:59spending more and more time

00:07:01sitting in front of screens.

00:07:03In general, our musculature

00:07:05has not ceased to decrease,

00:07:07because it is less and less necessary.

00:07:09It is very likely that

00:07:11as progress progresses,

00:07:13we will see our strength diminish

00:07:15and we will have more difficulty

00:07:17gaining muscle mass.

00:07:19Our brain is particularly interesting

00:07:21because it has evolved

00:07:23in a rather strange way.

00:07:25At first, our distant ancestors

00:07:27had a rather small brain.

00:07:29But the close relatives of the Homo sapiens,

00:07:31the Neanderthals,

00:07:33had a brain larger than that of the average modern man.

00:07:35As evolution progressed,

00:07:37the human brain grew larger.

00:07:39But in the most recent centuries,

00:07:41it began to shrink

00:07:43and no one knows exactly why.

00:07:45Some experts claim

00:07:47that this may have something to do

00:07:49with the change of our lifestyles

00:07:51and our socialization.

00:07:53The first humans, especially the hunter-gatherers,

00:07:55began to remember each plant and animal

00:07:57they saw, their properties

00:07:59and how to use this or that thing.

00:08:01They had more general knowledge,

00:08:03learning everything their parents knew

00:08:05and discovering even more by themselves.

00:08:07Modern humans have a more specialized

00:08:09knowledge in a certain field,

00:08:11deepening a specific subject

00:08:13while relying on their peers for the rest.

00:08:15While our ancestors worked

00:08:17mostly in groups

00:08:19in which everyone knew more or less everything

00:08:21and could replace each other,

00:08:23we tend more to form teams

00:08:25where each member has a specific task

00:08:27and is replaceable.

00:08:29After all, the size of the brain

00:08:31does not seem to have such a major importance.

00:08:33Orcs and elephants, for example,

00:08:35have a brain much larger than ours,

00:08:37which does not necessarily make them smarter.

00:08:39Happier?

00:08:41Maybe.

00:08:43And if we look even further into the unknown,

00:08:45that is, in the millennia,

00:08:47we could develop incredible characteristics.

00:08:49Some even say

00:08:51that if the sea level continues to rise,

00:08:53humans could adapt

00:08:55to underwater life.

00:08:57We could have palmed hands and feet

00:08:59to swim better

00:09:01and even develop branches to breathe underwater.

00:09:03Another scenario,

00:09:05if we go into space and begin to colonize

00:09:07other planets, we will inevitably

00:09:09have to adapt to their conditions.

00:09:11Mars, for example,

00:09:13has a lower gravity and a much colder climate.

00:09:15This would probably make humans

00:09:17bigger and lighter,

00:09:19but it could also lead them to develop their

00:09:21hairiness to keep warm.

00:09:23Planets with a stronger gravity

00:09:25and higher temperatures would transform,

00:09:27on the contrary, humans into

00:09:29hairy, robust creatures

00:09:31and probably bald.

00:09:33The possibilities are endless.

00:09:35Maybe because of social networks,

00:09:37we will simply become small blurry shapes

00:09:39with big eyes and thumbs and not much else.

00:09:41It will be so much more convenient to send messages

00:09:43and likes. What a charming perspective!

00:09:45But what's going on?

00:09:47You were so tired.

00:09:49You were eager to put your head

00:09:51on this scented pillow.

00:09:53You could barely stand up at 9 p.m.

00:09:55And now you turn in your bed,

00:09:57you change position,

00:09:59everything is suddenly so long and boring.

00:10:01Should you cover your feet

00:10:03or leave them uncovered?

00:10:05Sleep on the back, the front,

00:10:07on the left or right side?

00:10:09Ah!

00:10:11There is a moonlight passing through the window.

00:10:13So you take a look

00:10:15at the other bed in the corner.

00:10:17Your friend there is sleeping so deeply.

00:10:19He fell asleep after a minute.

00:10:21It's not fair!

00:10:23You spend the night here because tomorrow

00:10:25you will both go on a little excursion

00:10:27in a neighboring city.

00:10:29Of course, you will have to get up at 5 a.m.

00:10:31Yeah!

00:10:33Oh, and look at the time now.

00:10:35Why can't you fall asleep?

00:10:37Why? Why?

00:10:39Last week, you went camping

00:10:41in the woods with some friends

00:10:43and you had the same difficulties.

00:10:45You were very tired after a long day

00:10:47spent carrying all your stuff,

00:10:49walking, preparing food,

00:10:51talking for hours near the campfire.

00:10:53Your eyes were half closed,

00:10:55you thought you would fall asleep in a few seconds.

00:10:57But then, nothing.

00:10:59Big open eyes,

00:11:01every little thing bothered you

00:11:03and no sleeping position was good.

00:11:05So here's the question I ask you,

00:11:07why?

00:11:09That's how we call it

00:11:11when we have trouble sleeping in a new place.

00:11:13Sleep is a wonderful thing,

00:11:15but evolution has made it a little

00:11:17inappropriate for us at times.

00:11:19During sleep,

00:11:21the brain stops for a few hours.

00:11:23So you're not really protected.

00:11:25You can't detect a potential danger

00:11:27or defend yourself if something happens.

00:11:35Some animals, like dolphins and whales,

00:11:37have developed a sleeping system

00:11:39where only a part of their brain

00:11:41rests at the same time.

00:11:43The other part is awake and ready to work.

00:11:45It's kind of the same thing

00:11:47that happens in our heads.

00:11:49Not that there are dangers

00:11:51in your friend's room.

00:11:53Although, when you think of all this dust under the bed,

00:11:55who knows what's hiding underneath?

00:11:57We have certain instincts

00:11:59that have manifested a long time ago.

00:12:01At the time when our ancestors

00:12:03lived in caves and knew

00:12:05that if they slept as if there was no tomorrow,

00:12:07they might not have any.

00:12:09That's also why they knew

00:12:11it was not wise to sleep outside their cave.

00:12:13This is largely

00:12:15the reason for the effect of the first night.

00:12:17If you sleep in your own bed,

00:12:19in a room where you feel good,

00:12:21your brain thinks,

00:12:23OK, you're safe now.

00:12:25But if you go to a new place,

00:12:27nothing happens.

00:12:29Not even a comfortable bed,

00:12:31a soft pillow,

00:12:33nothing.

00:12:35Your brain knows you're far from your cave.

00:12:37So it can't relax

00:12:39and let you sleep completely.

00:12:41It's a bit like dolphins.

00:12:43Part of your brain rests,

00:12:45but the other listens carefully

00:12:47in case something unpredictable happens.

00:12:49Your brain won't bother you forever

00:12:51with this story of half the brain sleeping

00:12:53and half not sleeping.

00:12:55When you spend two nights in a row

00:12:57in the same place,

00:12:59your brain is more likely to say,

00:13:01Even if this pile of dust

00:13:03still worries me a little.

00:13:05And it will probably let you fall asleep.

00:13:07The effect of the first night

00:13:09is not so serious

00:13:11if it only happens occasionally.

00:13:13But if you change places often,

00:13:15you could spend most of your time

00:13:17tired, unproductive

00:13:19or faced with other problems.

00:13:21Our brain has habits

00:13:23that evolution has given it.

00:13:25But fortunately,

00:13:27it is also quite flexible.

00:13:29Your brain is frightened

00:13:31by the fact that you are

00:13:33in an unknown space.

00:13:35You can familiarize the place

00:13:37and show it that everything is fine.

00:13:39You can bring something

00:13:41that you like with you.

00:13:43Maybe your favorite pajamas,

00:13:45your pillow,

00:13:47this soft blanket

00:13:49that you would not change for anything in the world.

00:13:51Do you have the habit of drinking hot milk

00:13:53before going to bed?

00:13:55Do the same in your new place.

00:13:57Go to bed at the time you usually go to bed.

00:13:59Do you have exercise rituals

00:14:01before going to bed?

00:14:03Yes, me neither.

00:14:05But whatever routine you use

00:14:07before going to bed,

00:14:09do the same in your new home.

00:14:11If you book a hotel room,

00:14:13try to find a bed similar

00:14:15to the one you have at home.

00:14:17If you usually sleep in a double bed,

00:14:19you could feel weird

00:14:21lying in a king-size bed.

00:14:23Or just bring your favorite pajamas,

00:14:25depending on what you do is not guaranteed.

00:14:27But it's worth a try.

00:14:29By the way,

00:14:31don't you get bored of meeting someone

00:14:33who can sleep anywhere?

00:14:35It's really, really great to lie down,

00:14:37to slip under a pile of warm blankets

00:14:39and...

00:14:41Oops, sorry.

00:14:43Anyway, sleep is important.

00:14:45We literally need it to survive,

00:14:47just like we need food

00:14:49or water.

00:14:51We spend about a third of our life sleeping.

00:14:53Scientists don't yet know

00:14:55all the reasons why we sleep.

00:14:57But here's what they know for now.

00:14:59We sleep to store energy.

00:15:01Eight hours of good sleep

00:15:03can produce enough energy

00:15:05to allow us to spend

00:15:07an energetic and productive day.

00:15:09Our body needs to restore itself

00:15:11during sleep.

00:15:13Hair and nails grow, muscles repair.

00:15:15All this and much more

00:15:17happens while you sleep effortlessly.

00:15:19Then there's the brain function.

00:15:21If you put a book under your pillow

00:15:23during the night, hoping

00:15:25your brain will read it one way or another

00:15:27and be ready for the final exam the next day,

00:15:29it won't happen.

00:15:31But if you study a lot and assume

00:15:33a lot of facts, a good night's sleep

00:15:35can certainly help you remember everything.

00:15:37A brown bat sleeps about 20 hours a day,

00:15:39while a giraffe

00:15:41only sleeps very little,

00:15:43usually every five-minute nap.

00:15:45This poor giraffe doesn't know what it's missing.

00:15:47Cats certainly know

00:15:49how to enjoy life.

00:15:51They spend two-thirds of their lives sleeping.

00:15:53Randy Gardner set the record

00:15:55for the longest sleepless period

00:15:57in 1964.

00:15:59He was 17 when he

00:16:01stayed awake for 11 days,

00:16:03or 264 hours.

00:16:05Be careful, don't try this at home.

00:16:07Or elsewhere.

00:16:09Peter Powers decided to set the reverse record

00:16:11and stayed asleep for

00:16:13eight days in a row.

00:16:15How come he didn't need to

00:16:17get up to go to the bathroom?

00:16:19If you lie down in your bed and

00:16:21fall asleep almost immediately,

00:16:23it means you're really, really tired

00:16:25and you lack sleep.

00:16:27Ideally, you need about 10 to 15 minutes

00:16:29to fall asleep.

00:16:31There are two specific times of the day

00:16:33when we feel very tired,

00:16:352 a.m. and 2 p.m.

00:16:37That's why we want to take a nap

00:16:39after lunch instead of continuing to work.

00:16:41Show this video to your boss

00:16:43the next time you're surprised

00:16:45by the amount of sleep we get

00:16:47after lunch.

00:16:49We are the only mammals that

00:16:51deliberately delay their sleep.

00:16:53And of course,

00:16:55the least cool mammals in the world.

00:16:57At the time, only 15% of people

00:16:59dreamed in color.

00:17:01Now, 75% of us do.

00:17:03Some think it's because our TVs

00:17:05are currently in color.

00:17:07Speaking of which, we spend about

00:17:09two hours in the land of dreams every night.

00:17:11But if you want to remember your dreams,

00:17:13you can write them down right after you wake up.

00:17:15If you wait too long,

00:17:17you will forget all the superpowers you had.

00:17:19During the average night,

00:17:21you can change your sleeping position

00:17:23about 20 times.

00:17:25The position you prefer

00:17:27can say a lot about your character.

00:17:29The position lying on your back,

00:17:31arms in the air towards your pillow

00:17:33is called starfish.

00:17:35This type of sleeper tends to be listening

00:17:37and to be an altruistic person

00:17:39who likes to help others.

00:17:41He likes to let his guard down more easily.

00:17:43Then there is the free-fall position,

00:17:45in which you are on your stomach,

00:17:47hands on your pillow

00:17:49and head turned to the side.

00:17:51Some say that these sleepers

00:17:53do not stand criticism

00:17:55and tend to be quite direct.

00:17:57Finally, the affection request position

00:17:59consists of lying on your side

00:18:01with both arms outstretched in front of you.

00:18:03This type of sleeper is a bit complex,

00:18:05but also very open-minded.

00:18:07They are slow to make a decision,

00:18:09even if they are taken.

00:18:11The type and style of pyjamas you wear in bed

00:18:13are also very revealing.

00:18:15But we will keep this question

00:18:17for another video.

00:18:19Did you know?

00:18:21A single hair can withstand

00:18:23a traction of about 85 grams.

00:18:25On average, a person has about 150,000 hair.

00:18:27And when your hair is put together,

00:18:29they can withstand a traction

00:18:31of about 13 tons,

00:18:33the weight of two elephants,

00:18:35not to mention peanuts.

00:18:37It would be enough for your brain

00:18:39to light a small bulb,

00:18:41if only you knew how to do it.

00:18:43If you are not bad when you cut

00:18:45your nails or your hair,

00:18:47it is because the only living part

00:18:49of these is under your skin.

00:18:51Also, our nails grow faster

00:18:53in summer than in winter,

00:18:55even in places where there is

00:18:57not much difference between seasons.

00:18:59And your nails grow faster

00:19:01on your right hand,

00:19:03probably because you use it more often.

00:19:05You can control 50% of the strength

00:19:07of your hand.

00:19:09It usually works with your ring

00:19:11to give you power.

00:19:13The other three are more suitable

00:19:15to catch things.

00:19:17Just like the tip of your fingers,

00:19:19your tongue has a unique footprint,

00:19:21but you can't use it to unlock

00:19:23your phone, at least not yet.

00:19:25In addition, your tongue is full of fat.

00:19:27If you gain weight, your tongue

00:19:29also gains weight.

00:19:31There is acid in your stomach

00:19:33and a lot of wood.

00:19:35The total length of all adult blood vessels

00:19:37is about 160,000 km,

00:19:39which is four times the circumference of the equator.

00:19:41During your life, you will produce

00:19:43enough saliva to fill two pools.

00:19:45Our ancestors needed chicken

00:19:47to straighten the hair of their bodies

00:19:49and frighten their enemies.

00:19:51We no longer need it,

00:19:53but we still have chicken.

00:19:55One day, our evolution

00:19:57will make us lose this feature.

00:19:59You probably never noticed it,

00:20:01but the brain only breathes through one nostril at a time.

00:20:03Every few hours, your nostrils connect.

00:20:05That's why only one of your nostrils moves

00:20:07when you have a cold.

00:20:09Most people think they have five senses,

00:20:11but it's not true.

00:20:13Scientists are not sure yet,

00:20:15but they think there are more than 20.

00:20:17There is sight, hearing, touch, smell and taste,

00:20:19and other senses like time,

00:20:21hunger and thirst.

00:20:23And then there is proprioception,

00:20:25the sense of the position of your body in space.

00:20:27The brain does not always differentiate

00:20:29between good and bad.

00:20:31It understands that you feel a very strong emotion,

00:20:33but it is sometimes a little confused.

00:20:35That's why you can cry when you are very happy.

00:20:37Your eyes remain about the same size

00:20:39all your life, but your nose and ears

00:20:41never stop growing.

00:20:43The opposite would be really weird.

00:20:45In the past, all humans had brown eyes.

00:20:47Other colors developed

00:20:49as a result of a fortuitous mutation.

00:20:51Scientists think that if the first humans

00:20:53appeared on Earth about 6 million years ago,

00:20:55the first person with blue eyes

00:20:57was probably

00:20:59the same ancestor.

00:21:01Uncle Bob!

00:21:03All the bones of the human body are linked to each other,

00:21:05except one.

00:21:07The ocioid bone, in the shape of an U,

00:21:09is at the base of the tongue to hold it in place.

00:21:11The bones are more resistant than steel.

00:21:13A healthy bone could theoretically

00:21:15bear the weight of five trucks.

00:21:17Yet it is not the strongest part of the body.

00:21:19The strongest element

00:21:21is the dental enamel.

00:21:23It is made of a lot of different materials

00:21:25The teeth last for a long time,

00:21:27several hundred years.

00:21:29But of course, you still have to take care of them.

00:21:31They are the only part of the body

00:21:33that cannot heal itself.

00:21:35Your heart works non-stop,

00:21:37about 3 billion times in your life.

00:21:39Just like your heart,

00:21:41your tongue never takes a vacation.

00:21:43Even when you sleep,

00:21:45it helps to pass saliva into your throat.

00:21:47By the way, where do you put your tongue when you rest?

00:21:49If you keep it at the bottom of your mouth,

00:21:51you make a mistake.

00:21:53If you keep it stuck against your teeth,

00:21:55you make a mistake too.

00:21:57This can move your teeth

00:21:59and cause chewing problems.

00:22:01Try to keep it in the middle,

00:22:03about a centimeter from your teeth.

00:22:05You can't breathe and swallow at the same time.

00:22:07The reason is that the air we breathe

00:22:09and the things we swallow

00:22:11follow the same path,

00:22:13at least at the beginning.

00:22:15It's like a little guy driving

00:22:17traffic a little further.

00:22:19Your eyes breathe too.

00:22:21If you can't breathe,

00:22:23that's why your eyes are irritated

00:22:25when it's dry outside.

00:22:27Everyone dreams.

00:22:29If some people say

00:22:31they never dreamed once in their life,

00:22:33it's just that they never remember their dream.

00:22:35Some scientists think

00:22:37the dream stage is followed by an active forgetfulness stage.

00:22:39Probably because the information contained

00:22:41in our dreams is not really important.

00:22:43Our brain is economical.

00:22:45It makes room for useful things.

00:22:47Those who are lucky enough to remember their dream

00:22:49are the ones who follow their awakening.

00:22:51And after 10 minutes,

00:22:53the dream has generally completely disappeared.

00:22:55When you blush,

00:22:57the wall of your stomach turns red too.

00:22:59This happens because your blood circulates more

00:23:01when you are embarrassed,

00:23:03your body preparing for something stressful to happen.

00:23:05Your face and the wall of your stomach

00:23:07receive more of it,

00:23:09which makes them red.

00:23:11In addition, humans are the only animals

00:23:13that can blush,

00:23:15at least the only ones who can.

00:23:17We all have 50 km of hair.

00:23:19If it never shaved,

00:23:21a man would have a beard 9 meters long.

00:23:23Hair grows a little faster in hot climates

00:23:25because heat stimulates a faster circulation

00:23:27in our body.

00:23:29Everything you can know about yourself

00:23:31is written in one of your hair.

00:23:33From a single hair,

00:23:35a scientist could say what you have eaten all your life

00:23:37and in what type of environment you have lived.

00:23:39On average, a human eats 45,000 kilos

00:23:41of food throughout his life.

00:23:43This represents about 10 big hippos.

00:23:47The lips are one of the most sensitive parts

00:23:49of the human body.

00:23:51They have a lot of nerve endings,

00:23:53even more than your fingers.

00:23:55In addition, the skin of the lips is very thin,

00:23:57so you can see the blood vessels inside.

00:23:59This is why your lips are red or pink,

00:24:01unlike the rest of your body.

00:24:03The lips are also very sensitive

00:24:05to damage caused by the sun.

00:24:07So don't forget to apply a sunscreen.

00:24:09It will protect them over time.

00:24:11In addition to your fingerprints,

00:24:13your irises and your tongue,

00:24:15which are unique.

00:24:17The total surface of your lungs

00:24:19is about the same as that of a tennis court.

00:24:21The everything and the irises are real balls.

00:24:23Everything can reach a speed of 80 km per hour.

00:24:25An iris is even faster,

00:24:27almost 160 km per hour.

00:24:29Unless you use your fingers,

00:24:31it is impossible for you to iris

00:24:33with your eyes open.

00:24:35Scientists don't really know why.

00:24:37Some say it's just a reflex,

00:24:39by definition uncontrollable.

00:24:41Others think it's to protect your eyes

00:24:43from the sun.

00:24:45All humans literally shine.

00:24:47This light comes from the heat of your body.

00:24:49It is actually a thousand times less intense

00:24:51than what you are able to perceive.

00:24:53But still, it's pretty awesome.

00:24:55The biggest USB key in the world is your brain.

00:24:57Well, anyone's brain.

00:24:59The neurons it contains combine with each other

00:25:01in such a way that your storage capacity

00:25:03is about 1 million giga-octets.

00:25:05It's enough to contain 3 million hours of film,

00:25:07like a movie night

00:25:09that would last 300 years.

00:25:11Can you pass me the popcorn?

00:25:13You start to feel thirsty

00:25:15when you lose about 1% of your body weight.

00:25:17If you lose 5%,

00:25:19you can even feel like you're going to faint.

00:25:21Fingers don't have their own muscles.

00:25:23It's the muscles located in the palm

00:25:25and the forearm that make them move.

00:25:27The word muscle actually comes from

00:25:29the old Latin word that means mouse.

00:25:31The Romans saw their biceps like that.

00:25:33On average, in their life,

00:25:35a person walks about 180,000 km.

00:25:37It's four times the distance around our planet

00:25:39and half the distance between the Earth and the Moon.

00:25:41So don't forget to wear comfortable shoes.

00:25:45Oh, the phone is ringing.

00:25:47There must be something urgent at 11 p.m.

00:25:49Except that all the gadgets in the house

00:25:51are silent.

00:25:53Oh no, it's your ears that are ringing.

00:25:55You can also hear whistling,

00:25:57rumbling and even rustling.

00:25:59But all this noise doesn't come from an external source.

00:26:01It's what we call

00:26:03phantom sounds.

00:26:05They can occur in one or two ears

00:26:07from time to time.

00:26:09They are usually more noticeable at night

00:26:11when nothing distracts you.

00:26:13The noise you hear in your ears

00:26:15is called acouphenia.

00:26:17It's quite common and affects 15 to 20% of the population.

00:26:19Acouphenia starts in the inner ear

00:26:21which looks like a snail.

00:26:23It's what we call the cochlea.

00:26:25Your average ear captures sound waves.

00:26:27They are then translated into electric impulses

00:26:29in the inner ear.

00:26:31Then the sensory nerves transmit

00:26:33these impulses to your brain.

00:26:35If your inner ear doesn't function properly,

00:26:37your brain can misinterpret the sounds.

00:26:39Acouphenia occurs when

00:26:41the cochlear nerve undergoes certain modifications.

00:26:43They can be caused by loud noises

00:26:45such as chainsaws,

00:26:47pickaxes, loud music or screams.

00:26:49Acouphenia can occur

00:26:51after a cranial trauma,

00:26:53a neck injury or an ear injury

00:26:55or after starting to take certain medications.

00:26:57You can also hear ear rumbling

00:26:59if you have arterial tension problems.

00:27:01Now let's go elsewhere

00:27:03in the incredible human body.

00:27:05Some of the bacteria living in the intestines

00:27:07can produce electricity.

00:27:09It's crazy, isn't it?

00:27:11They emit electrons, generating tiny electric currents.

00:27:13It's probably the bacteria's

00:27:15life support system,

00:27:17its way of generating energy.

00:27:19Humans are the only animals with a chin.

00:27:21Even our closest genetic parents,

00:27:23gorillas and chimpanzees,

00:27:25are deprived of this tiny piece of bone

00:27:27that protrudes from the jaw.

00:27:29Their lower jaws are tilted downwards

00:27:31compared to their front teeth.

00:27:33Scientists still don't understand this mystery.

00:27:35Their opinions differ on the reason

00:27:37why people are made this way.

00:27:39Some researchers think the chin

00:27:41helps us chew our food.

00:27:43Others think it's probably

00:27:45related to speech.

00:27:47Some of us think it's just a special place

00:27:49to grow a beard.

00:27:51Closing your eyes

00:27:53keeps it clean and moist.

00:27:55But that's not all.

00:27:57Every time you close your eyes,

00:27:59you experience a different sensation.

00:28:01You feel like you're in a forest.

00:28:03Researchers at the University of Washington

00:28:05have found that closing your eyes

00:28:07increases your vigilance

00:28:09and helps you recharge your batteries.

00:28:11Have you ever seen tiny dots

00:28:13move in a sine wave?

00:28:15Especially when you look at a blue sky.

00:28:17These dots are only visible

00:28:19for about a second

00:28:21and can look like tiny green dots.

00:28:23They are actually white globules

00:28:25that move in your hair

00:28:27Curiously, most people

00:28:29don't pay attention to these dots

00:28:31unless you ask them to.

00:28:33The pineal gland of the brain

00:28:35produces melatonin.

00:28:37It's the same hormone that regulates sleep.

00:28:39The gland looks like a pine cone

00:28:41and that's how it got its name.

00:28:43The human brain is composed of 73% water

00:28:45and the same goes for the heart.

00:28:47Therefore, if your brain loses

00:28:49only 2% of its liquid,

00:28:51you start to feel tired.

00:28:53This also deteriorates your memory,

00:28:55reduces your attention

00:28:57and ruins your mood.

00:28:59By the way, your brain

00:29:01makes sure you don't drink too much or too little water.

00:29:03After swallowing a liquid,

00:29:05your mouth and throat

00:29:07start to send signals to your brain

00:29:09to tell it to stop drinking.

00:29:11Otherwise, you will keep swallowing water

00:29:13for the 10 to 60 minutes it takes

00:29:15for the liquid to reach your cells.

00:29:17It's enough to see something

00:29:19for only 13 milliseconds

00:29:21for your brain to process this image.

00:29:23In comparison,

00:29:25the average clenching lasts from 100 to 400 milliseconds.

00:29:27Even if the tongue

00:29:29is not the strongest muscle of your body,

00:29:31it never gets tired.

00:29:33It's linked to the way it's made up.

00:29:35It's made up of 8 interlaced muscles.

00:29:37But unlike the other muscles of your body,

00:29:39these are not distributed

00:29:41around a support bone.

00:29:43The structure of the tongue is similar

00:29:45to that of the trunk of an elephant

00:29:47or the tentacles of a peacock.

00:29:49Your body emits a visible light.

00:29:51The light is a bit more intense

00:29:53than the light you perceive.

00:29:55The sweat is mainly composed

00:29:57of water mixed with proteins,

00:29:59sugar, ammonia,

00:30:01and a lot of other things.

00:30:03It even contains tiny traces of metals

00:30:05like copper, zinc, nickel,

00:30:07iron, etc.

00:30:09This gives the sweat a salty taste.

00:30:11It's the sodium it contains.

00:30:13Moreover, the more salt you eat,

00:30:15the saltier the sweat.

00:30:17Your body tries to get rid

00:30:19of the excess,

00:30:21and the quickest way

00:30:23is to sweat.

00:30:25The blood of an adult

00:30:27represents 7 to 8%

00:30:29of the total weight of your body.

00:30:31About 55% of our blood

00:30:33is made up of liquid plasma.

00:30:35The rest is made up of red,

00:30:37white, and platelet-rich blood cells.

00:30:39It creates clots

00:30:41and prevents bleeding.

00:30:43You can't swallow and breathe at the same time.

00:30:45The food you eat

00:30:47is divided into esophage,

00:30:49for food and liquid,

00:30:51and trachea, for air.

00:30:53By swallowing,

00:30:55your respiratory tract closes automatically.

00:30:57This prevents you from

00:30:59accidentally inhaling food,

00:31:01but sometimes it happens anyway.

00:31:03Your brain sometimes generates

00:31:05more than 48 thoughts in one minute.

00:31:07That's almost 3,000 thoughts per hour

00:31:09and 69,000 per day.

00:31:11Nails grow faster on the dominant hand.

00:31:13If you often use your right hand,

00:31:15your nails grow faster

00:31:17in the summer and during the day.

00:31:19You can memorize up to 10,000 different faces.

00:31:21Of course, it varies from person to person,

00:31:23and the average number is 5,000.

00:31:25That doesn't mean you can identify

00:31:27each of these faces.

00:31:29It's just about recognizing the features.

00:31:31If you ever feel like lying,

00:31:33know that your nose will always betray you.

00:31:35When someone tells a lie,

00:31:37the temperature around his nose

00:31:39and in the inner corners of his eyes rises.

00:31:41This phenomenon is known

00:31:43as the Pinocchio effect.

00:31:45Women have more taste buds

00:31:47on the surface of their tongues than men.

00:31:49This is one of the reasons

00:31:51why 35% of women and only 15% of men

00:31:53are super-tasters.

00:31:55These are people who feel the flavors

00:31:57more strongly than others.

00:31:59Teeth are the only part of the body

00:32:01that cannot heal itself.

00:32:03But the enamel they are covered with

00:32:05is one of the most resistant elements of the human body.

00:32:07Your heartbeat

00:32:09often synchronizes with the music you listen to.

00:32:11If a song has a continuous

00:32:13increase in volume or tempo,

00:32:15like rock,

00:32:17it can speed up your heartbeat.

00:32:19Some classical music lowers

00:32:21the heart rate and blood pressure.

00:32:23This phenomenon affects everyone,

00:32:25from professional musicians to amateurs and melomans.

00:32:27The human body has between

00:32:292 and 5 million sudoriparous glands.

00:32:31The sweat they produce

00:32:33is of two different types,

00:32:35stress sweat and regular sweat.

00:32:37Hey, don't sweat like an old pig!

00:32:39Stress-caused sweat contains fatty acids

00:32:41and proteins.

00:32:43Regular sweat is mainly composed

00:32:45of water, salt and a little bit

00:32:47of other substances.

00:32:49It can happen when you brush your teeth

00:32:51too deeply and hard.

00:32:53This can wear out the enamel

00:32:55and make the teeth very sensitive to cold and hot foods.

00:32:57If you walked in the same direction

00:32:5912 hours a day,

00:33:01it would take you about 800 days to travel the world.

00:33:03And don't forget to wear rubber boots

00:33:05for when you cross the ocean.

00:33:07If the acid in your stomach

00:33:09came in contact with your skin,

00:33:11chances are it would make a hole.

00:33:13All because of chloride acid.

00:33:15This type of acid is incredibly powerful.

00:33:17It can easily dissolve certain metals,

00:33:19such as magnesium or zinc.

00:33:21Chloride acid is the main component

00:33:23of gastric acid that your stomach produces.

00:33:25It protects our immune system

00:33:27and eliminates viruses

00:33:29and bacteria present in the food we eat.

00:33:31This acid also helps

00:33:33the body to decompose,

00:33:35digest and absorb all kinds of nutrients,

00:33:37including proteins.

00:33:39The lips are red

00:33:41because they contain a large concentration

00:33:43of miniature blood capillaries,

00:33:45right under the skin.

00:33:47Your little finger is very powerful.

00:33:49Without it, your hand would lose

00:33:51an important part of its strength.

00:33:53Your index and middle finger

00:33:55cooperate with your thumb

00:33:57to grab and pinch.

00:33:59And your ear,

00:34:01with your ring finger,

00:34:03with your index and middle finger.

00:34:05All of this represents

00:34:07at least 60% of your dry weight.

00:34:09This quality has allowed your brain

00:34:11to reach the Guinness World Record.

00:34:13This organ contains

00:34:15about 25% of your body's cholesterol,

00:34:17which is vital for the brain's well-being.

00:34:19Your skeleton's cells

00:34:21keep regenerating.

00:34:23That's why we make a new skeleton

00:34:25every 10 years or so.

00:34:27This process slows down with age

00:34:29and regeneration takes longer.

00:34:31Your brain is becoming more and more fragile.

00:34:33A new type of brain cell,

00:34:35recently discovered,

00:34:37is crucial for visual research.

00:34:39They are called target cells.

00:34:41Without their help,

00:34:43it would be impossible to locate

00:34:45a knowledge in a crowd

00:34:47or your dog in the park.

00:34:49It's interesting to note that target cells

00:34:51make fun of the appearance

00:34:53of the thing you're looking for.

00:34:55All they want to know is

00:34:57if an object is your target or not.

00:34:59Here are a few facts

00:35:01you may find difficult to digest.

00:35:03Your stomach has an incredible capacity,

00:35:05which can contain

00:35:07up to 2 litres of liquid.

00:35:09It's the equivalent

00:35:11of a large bottle of Coca-Cola.

00:35:13It's hard to estimate

00:35:15how much solid food you can ingest

00:35:17because it's crushed by your teeth

00:35:19before reaching your stomach.

00:35:21There's probably not enough room

00:35:23for a turkey,

00:35:25but a good-sized chicken

00:35:27If you were wondering

00:35:29where your stomach was,

00:35:31you'd probably point to your belly.

00:35:33Sorry, but that's not the case.

00:35:35It's actually here,

00:35:37hidden between your ribs.

00:35:39Scientists think

00:35:41the appendix will eventually disappear.

00:35:43No one really knows

00:35:45why we need it,

00:35:47but some researchers

00:35:49say it may have existed

00:35:51to help our ancestors

00:35:53digest tree bark.

00:35:55The appendix

00:35:57isn't the only obsolete part of our body.

00:35:59Wisdom teeth

00:36:01aren't that useful either.

00:36:03Sure, they were when our ancestors

00:36:05lost some of their teeth,

00:36:07but the only thing

00:36:09they help us lose now

00:36:11is the money we spend to extract them.

00:36:13Almost all of our body

00:36:15is covered in hair,

00:36:17even if we don't notice it.

00:36:19It grows even in the navel.

00:36:21Their function seems to be

00:36:23the same.

00:36:25Your liver acts as your personal body guard,

00:36:27protecting you from toxins

00:36:29and many other things

00:36:31you shouldn't have in your body.

00:36:33It's almost indestructible

00:36:35and can regenerate at any time.

00:36:37Only 43% of your body

00:36:39really belongs to you.

00:36:41More than 50% of your body's cells

00:36:43belong to tiny creatures

00:36:45that live mainly

00:36:47in your intestine.

00:36:49However, even if your own cells

00:36:51are as numerous as these microbial cells,

00:36:53you have an average of 100,000 billion of them.

00:36:55You see, you're not that lonely after all.

00:36:57Keeping that in mind,

00:36:59your own genes

00:37:01represent less than half

00:37:03of what you really are.

00:37:05If you take all the microbes

00:37:07that live in your body

00:37:09and count their genes,

00:37:11you'll find between 2 and 20 million.

00:37:13If you sleep,

00:37:15it doesn't mean that your whole body sleeps.

00:37:17In fact, your brain sometimes

00:37:19works harder when you sleep.

00:37:21It needs to process tons of information

00:37:23and reports usually take a lot of time.

00:37:25Your nose does rest

00:37:27while you sleep.

00:37:29Surprisingly, your odour

00:37:31practically goes off at night.

00:37:33You wouldn't even be bothered

00:37:35if there was a really bad odour in your room.

00:37:37Odour is one of the most underrated senses.

00:37:39You wouldn't even be able to enjoy

00:37:41eating without it.

00:37:43About 80% of the taste of any food

00:37:45is felt thanks to your nose

00:37:47and its ability to recognize odours.

00:37:49If you pinch your nose

00:37:51while you eat,

00:37:53you'll hardly taste anything.

00:37:55If you don't have an odour,

00:37:57you'll recognize most foods by their texture.

00:37:59So an onion could seem to have

00:38:01the same taste as an apple.

00:38:03Try it and leave us a comment with your impressions.

00:38:05Scientists thought

00:38:07we could distinguish

00:38:09about 10,000 odours, but they were wrong.

00:38:11Recent research has shown

00:38:13that humans are actually able

00:38:15to distinguish more than 1 billion odours.

00:38:17We remember them as well

00:38:19as anything else,

00:38:21and odours can even evoke distant memories.

00:38:23Your nose doesn't just help you breathe

00:38:25and sense odours.

00:38:27It filters the air

00:38:29for the throats and the sensitive lungs.

00:38:31If we inhale dry air,

00:38:33the nose humidifies and cools it

00:38:35or heats it if necessary.

00:38:37In addition, the nose cleanses the air of all impurities.

00:38:39When you get older,

00:38:41your brain shrinks little by little.

00:38:43At 75 years old,

00:38:45it's much smaller than at 30,

00:38:47and it shrinks at 40.

00:38:49This happens to everyone

00:38:51and doesn't affect your mental abilities.

00:38:53Our brain can store only 7 octets

00:38:55in its short-term memory.

00:38:57Don't even try to compare your brain

00:38:59with the capacity of a mobile phone

00:39:01or even the one you had in 2005.

00:39:03That's why you have such a hard time

00:39:05learning a phone number by heart.

00:39:07Our short-term memory

00:39:09works like a blackboard.

00:39:11You can get information,

00:39:13but sooner or later,

00:39:15you'll miss the space.

00:39:17To know the capacity of your short-term memory,

00:39:19do this test.

00:39:21Ask a friend to write a 10-word list

00:39:23and read it to you.

00:39:25Most people remember 7 words

00:39:27or less in the list.

00:39:29RAM, or short-term memory,

00:39:31is an essential thing

00:39:33that we need to do

00:39:35almost all daily activities,

00:39:37including basic conversations,

00:39:39petting your dog.

00:39:41Our strongest and most emotional memories

00:39:43are often wrong.

00:39:45Our short-term memory

00:39:47gives us the confidence

00:39:49to believe that we remember everything,

00:39:51even if most of the details

00:39:53are invented in our head.

00:39:55Not only does your brain shrink as you age,

00:39:57but you shrink spectacularly too.

00:39:59Your bones become more fragile

00:40:01and your spine is compressed.

00:40:03The opposite happens

00:40:05when you rest at night

00:40:07so you wake up a little bigger

00:40:09in the morning than in the evening.

00:40:11In mammals,

00:40:13only humans can walk

00:40:15on two legs all their lives.

00:40:17You might think that kangaroos

00:40:19or gorillas move in the same way,

00:40:21but kangaroos use their tails

00:40:23as a third leg,

00:40:25and gorillas use their long arms

00:40:27to keep their balance.

00:40:29Your bones also contribute to metabolism.

00:40:31As they are mainly made of calcium,

00:40:33when there is not enough of this element

00:40:35in your blood,

00:40:37your bones begin to reject it,

00:40:39which balances your body.

00:40:41The same reaction also works

00:40:43in the opposite direction.

00:40:45When there is too much calcium in your blood,

00:40:47it is sent to the bones

00:40:49to be stored there later.

00:40:51The only bone in your body

00:40:53that has the sense of humor

00:40:55is inside your arm.

00:40:57That's why the bone that is there

00:40:59is called the humerus.

00:41:01No, that's totally wrong.

00:41:03We can hear with our ears

00:41:05thanks to these little bones,

00:41:07because they have adapted

00:41:09to transmit sound vibrations.

00:41:11Doctors call them the ossicular chain.

00:41:13One of these auditory bones,

00:41:15the calf,

00:41:17is the smallest bone in your body.

00:41:19It is not bigger than a grain.

00:41:21Our size, the shape of our body

00:41:23and the color of our skin

00:41:25depend a lot on where our ancestors lived,

00:41:27but we can adapt to new conditions

00:41:29even during our own life.

00:41:31For example, if you move from the plains to the mountains,

00:41:33you will end up developing more red blood cells

00:41:35to compensate for the lack of oxygen.

00:41:37And naturally,

00:41:39if you go from a colder climate

00:41:41to a warmer and more sunny climate,

00:41:43your skin will become darker to adapt.

00:41:45Our lifespan is programmed

00:41:47in our cells.

00:41:49They renew and divide constantly,

00:41:51but they are a kind of internal clock

00:41:53that stops at some point.

00:41:55Some cells also stop reproducing

00:41:57earlier than others.

00:41:59On average,

00:42:01cells stop dividing

00:42:03when we reach the age of 100.

00:42:05This means that if we found a way

00:42:07to deceive our cells

00:42:09to stop the mutiny,

00:42:11we could potentially live forever.

00:42:13Body fat is not just an aesthetic nuisance.

00:42:15It acts as an insulating material,

00:42:17energy reserve

00:42:19and shock absorber.

00:42:21It is your body that sends the most fat

00:42:23into the region of your size,

00:42:25because this is where your internal organs are located.

00:42:27If something happens to you,

00:42:29this layer of fat could protect

00:42:31your vital organs from irreparable damage.

00:42:33Be careful!

00:42:35Your skull is not made of one bone.

00:42:37It is actually made up of 28 different bones,

00:42:39many of which have merged

00:42:41to protect your brain.

00:42:43The mandible, or lower jaw,

00:42:45is the only bone in the skull

00:42:47that is not attached to the surrounding bone.

00:42:49It is attached by subjunctive tissues

00:42:51and muscles.

00:42:53That's what makes it so mobile.

00:42:55You can actually chew with your jaw.

00:42:57In other words, chew.

00:42:59The strongest muscles of your body

00:43:01are not at the level of your arms

00:43:03or legs.

00:43:05They are in your head.

00:43:07The masseter is the main muscle

00:43:09responsible for chewing.

00:43:11And it must be the strongest

00:43:13so that you can eat normally.

00:43:15And do you know those muscles

00:43:17that allow you to move your ears?

00:43:19These are the temporalis,

00:43:21located above your temples.

00:43:23We have two very fast muscles,

00:43:25which control the closure of the eyelids.

00:43:27They are also the fastest muscles

00:43:29of our body.

00:43:31Our eyes are fragile

00:43:33and need protection,

00:43:35so the reflex that protects them

00:43:37must be as fast as lightning.

00:43:39These muscles can close the eyelids

00:43:41in less than a tenth of a second.

00:43:43People with double-jointed thumbs

00:43:45can bend them backwards.

00:43:47It seems very unusual

00:43:49and very few people can do it.

00:43:51In fact, it's quite common.

00:43:53Even if it looks painful,

00:43:55it doesn't hurt at all

00:43:57for someone with a double-jointed thumb.

00:43:59We only recognize blue-purple,

00:44:01yellow-green and red-yellow colors.

00:44:03Everything else is a combination

00:44:05of these three colors.

00:44:07It is impossible to calculate

00:44:09how many of these combinations

00:44:11the human eye perceives,

00:44:13because each person has

00:44:15slightly different vision.

00:44:17But we go around a million combinations

00:44:19Every time we bathe,

00:44:21we use the muscles of our mouth

00:44:23and our tongue,

00:44:25and this contact can compress

00:44:27some glands that produce saliva.

00:44:29As a result, we can project

00:44:31a tiny gush of saliva

00:44:33without even realizing it,

00:44:35but it can reach 30 cm or more.

00:44:37I had a friend at university

00:44:39who could do that at will.

00:44:41It was impressive.

00:44:43It turns out that saliva

00:44:45is actually filtered blood.

00:44:47Bacteria and special cells

00:44:49absorb these properties.

00:44:51After that, the blood becomes saliva.

00:44:53Another subject.

00:44:55If your brain was a USB disk,

00:44:57it would be a real crazy thing.

00:44:59The capacity of our brain

00:45:01is somewhere between

00:45:0310 and 100 teraoctets.

00:45:05Some scientists say that the complete spectrum

00:45:07can reach 2.5 petaoctets.

00:45:09It looks like a dog snack, doesn't it?

00:45:11When the size of the English

00:45:13complete version of Wikipedia

00:45:15was calculated in 2010,

00:45:17it only represented 5.6 teraoctets.

00:45:19Do you realize?

00:45:21The heat of our body can boil

00:45:23almost 2 liters of water in 30 minutes,

00:45:25even without doing anything.

00:45:27We should try.

00:45:29Our brain can perform

00:45:31up to 10 billion operations per second

00:45:33with only 10 watts of energy.

00:45:35A computer capable of doing so

00:45:37would need about 1 gigawatt of energy.

00:45:39This amount can power

00:45:41up to 300,000 houses.

00:45:43Our memory is affected

00:45:45by the position of our body.

00:45:47For example, you are much more likely

00:45:49to remember a situation

00:45:51where you greeted someone

00:45:53if you were standing

00:45:55and that you shook hands.

00:45:57Your brain has millions of neurons.

00:45:59They are all different

00:46:01and the connection speed

00:46:03between each one is also different.

00:46:05That's why you can remember

00:46:07some information faster than others.

00:46:09However, our nervous impulses

00:46:11can reach a speed

00:46:13of 432 km per hour,

00:46:15which is slower than

00:46:17the fastest car in the world.

00:46:19It is still quite fast

00:46:21because your brain must react

00:46:23to urgent things

00:46:25such as pain or tickling.

00:46:27Moreover, the brain itself

00:46:29does not feel pain.

00:46:31It has no nervous endings

00:46:33that are specific to it.

00:46:35People with red hair

00:46:37represent 1% of the population.

00:46:39People with brown hair

00:46:41represent 1% of the population.

00:46:43Black hair is the most common

00:46:45hair color in the world.

00:46:47Hair is not only strong

00:46:49but also elastic.

00:46:51It can stretch

00:46:53about 30% of its length

00:46:55when it is wet.

00:46:57The average hair growth rate

00:46:59is 15 cm per year.

00:47:01So, if you never cut your hair

00:47:03until you are, say, 80 years old,

00:47:05your hair will have grown

00:47:07to 4 floors.

00:47:09However, this is not really possible

00:47:11because the length of our hair

00:47:13is genetically programmed.

00:47:15The human eye is like a car engine.

00:47:17Both need liquid

00:47:19to be well lubricated.

00:47:21The engine needs oil

00:47:23and the eye needs tears.

00:47:25To make sure that the eyes work well,

00:47:27tears are distributed all over the eye.

00:47:29This is why we blink more than

00:47:3110,000 times a day.

00:47:33The ocular muscle is the fastest muscle

00:47:35that can blink 5 times per second

00:47:37and even more.

00:47:39We spend about 6 seconds

00:47:41blinking every minute.

00:47:43During the day,

00:47:45we spend 30 minutes in total darkness

00:47:47simply because we close our eyes

00:47:49without counting the time we sleep.

00:47:51The only part of the human body

00:47:53that does not receive any blood nutrients

00:47:55is the cornea of the eye.

00:47:57The only thing it needs to work well

00:47:59are tears and the liquid

00:48:01in front of the eyes.

00:48:03The tears that appear

00:48:05under the blow of emotion

00:48:07are a unique human characteristic.

00:48:09No other animal is able

00:48:11to cry with sadness or joy.

00:48:13The pupils narrow and expand

00:48:15to control the light coming in.

00:48:17If there is a lot of light,

00:48:19they narrow the passage

00:48:21so as not to harm the vision.

00:48:23In the dark, the pupils expand

00:48:25to capture as much light

00:48:27as possible.

00:48:29Now let's get back to our mouths.

00:48:31Each tongue has a lot of muscles

00:48:33and some of them can only be used

00:48:35when you learn a new language.

00:48:37A human bite is almost always infected

00:48:39because of all the bacteria

00:48:41that live in our mouth.

00:48:43In this sense, we are quite close to hyenas.

00:48:45Your bones are designed

00:48:47to be widely used on a daily basis

00:48:49and some of them can absorb

00:48:51two or even three times your body weight.

00:48:53It's impressive,

00:48:55but your teeth are even stronger.

00:48:57When you bite something,

00:48:59your teeth can exert incredible pressure

00:49:01up to 90 kg.

00:49:03By the way,

00:49:05the enamel is considered to be part

00:49:07of your skeletal system.

00:49:09Our body is composed of about 60% of water

00:49:11and we even find some in the bones.

00:49:13About 25% of the bone mass

00:49:15is made up of water.

00:49:17The chloride acid present in our stomach,

00:49:19the most important defender

00:49:21of our immune system,

00:49:23helps us get rid of

00:49:25dangerous food toxins,

00:49:27and bacteria that accompany

00:49:29the food we eat.

00:49:31The stomach itself can be digested

00:49:33by this acid, but the mucous

00:49:35protects it.

00:49:37Even if you brush your teeth twice a day

00:49:39and never forget to wash your mouth,

00:49:41your mouth remains one of the dirtiest

00:49:43parts of the human body.

00:49:45Millions of bacteria live inside.

00:49:47The good news is that

00:49:49most of these bacteria are good for the body

00:49:51and protect it from bad bacteria

00:49:53and viruses.

00:49:55Humans and giraffes have a similar neck.

00:49:57One person has the same

00:49:59number of cervical vertebrae as a giraffe.

00:50:01The difference, however,

00:50:03lies in the length.

00:50:05The giraffe's vertebrae are 25 cm long.

00:50:07Our spine

00:50:09can withstand a pressure

00:50:11up to 450 kg.

00:50:13It would resist an adult zebra.

00:50:15But please,

00:50:17don't try to do it at home.

00:50:19And there are no zebras anyway.

00:50:21When you lie on your back

00:50:23and raise your knees,

00:50:25the pressure exerted on the spine

00:50:27is about 11 kg.

00:50:29It's not a zebra,

00:50:31but rather a good-sized cat.

00:50:33Our spine is also

00:50:35very flexible.

00:50:37If we could bend it,

00:50:39it could form two-thirds of a full circle.

00:50:41Are we like snakes then?

00:50:43In the morning, you are taller than in the evening.

00:50:45During your sleep, you are no longer affected

00:50:47by the force of gravity

00:50:49and your spine stretches,

00:50:51stretching up to 1.26 cm in height.

00:50:53Too bad you're getting smaller

00:50:55every day.

00:50:57Mountaineurs move your organs.

00:50:59So when you feel like

00:51:01your stomach is falling,

00:51:03it's because it's turning

00:51:05around in your body.

00:51:07Do you think your fingerprints

00:51:09are the only thing unique in your body?

00:51:11Well, that's not the case.

00:51:13Your tongue and your smell

00:51:15are also unique.

00:51:17If someone sniffs you,

00:51:19if all your blood vessels

00:51:21were stretched on a single line,

00:51:23it would hurt,

00:51:25but you would go around the Earth

00:51:27more than twice.

00:51:29An impressive feat

00:51:31that you won't see

00:51:33because you can't live

00:51:35without your blood vessels.

00:51:37You think you're resting

00:51:39while you sleep,

00:51:41but your brain never stops.

00:51:43It's more active at night

00:51:45than during the day

00:51:47because it's the most active organ

00:51:49in the human body.

00:51:51It has more than 500 functions

00:51:53and none of them are clear

00:51:55to scientists.

00:51:57Have you ever wondered

00:51:59why you feel so sleepy

00:52:01after lunch?

00:52:03Well, it's because your circadian rhythm,

00:52:05which runs at a cycle of 24 hours,

00:52:07asks you to take a nap

00:52:09after 7 hours of sleep.

00:52:11And food only strengthens

00:52:13this effect.

00:52:15So that when you feel a toothache,

00:52:17it usually goes hand in hand

00:52:19with the headache.

00:52:21You lose calories whatever you do,

00:52:23even nothing.

00:52:25A good 8-hour sleep, for example,

00:52:27allows you to lose up to 800 calories.

00:52:29And yes, you spend energy

00:52:31even while eating.

00:52:33Like all mammals,

00:52:35we have a reflex that slows

00:52:37or even stops certain bodily functions

00:52:39to prevent us from drowning.

00:52:41This also affects the heart rate.

00:52:43A human can stay without food

00:52:45for more than 20 days.

00:52:47However, if you don't sleep for 10 days,

00:52:49your body will simply stop working.

00:52:51Speaking of sleep,

00:52:53an average person forgets

00:52:5590% of their dreams.

00:52:57And that may be a good thing.

00:52:59Otherwise, imagine how crazy the world would be.

00:53:01The color of your dreams

00:53:03is influenced by the television

00:53:05you watched as a child.

00:53:07If you are part of the older generation

00:53:09who watched television in black and white,

00:53:11your dreams will most often be monochrome.

00:53:13If you are used to colored television,

00:53:15your dreams will also be multicolored.

00:53:17Out of 10,000 people on Earth,

00:53:19one person has his organs in a mirror,

00:53:21that is, inverted

00:53:23compared to their usual and normal position.

00:53:25In other words,

00:53:27the liver would be bigger on the left side

00:53:29and the right kidney

00:53:31would be a little higher than the left.

00:53:33Speaking of kidneys,

00:53:35the left is a little higher than the right.

00:53:37It's because the liver is bigger

00:53:39People with clear eyes,

00:53:41blue or green,

00:53:43tolerate pain better than those with dark eyes.

00:53:45Scientists think it could be related

00:53:47to melanin, which affects the color of the eyes.

00:53:49The length of your foot

00:53:51is similar to that of your forearm.

00:53:53If you don't believe me,

00:53:55do the test. I'll wait for you here.

00:53:57No.

00:53:59Hey, listen to this.

00:54:01As you know, your bones are designed

00:54:03to be extremely demanding on a daily basis.

00:54:05Some of them can absorb

00:54:07up to two or even three times

00:54:09the weight of your body.

00:54:11It's impressive, but your teeth are even stronger.

00:54:13When you bite something,

00:54:15they can withstand an incredible pressure,

00:54:17up to 90.5 kg.

00:54:19Besides, the enamel is considered

00:54:21to be part of your skeleton.

00:54:23Every time you pivot your hand,

00:54:25the bones of your forearm cross.

00:54:27Grab your arm and turn the apple of your hand

00:54:29up and down. You'll see it's true.

00:54:31Not only is your body composed of 60% water,

00:54:33but your bones also contain liquid,

00:54:35about 25% of the human bone mass

00:54:37is composed of water.

00:54:39The human eye has something in common

00:54:41with the engine of a car.

00:54:43Both can't function properly without liquid.

00:54:45The eye needs tears

00:54:47as much as the engine needs oil.

00:54:49Tears must be evenly distributed

00:54:51on the surface of the eye.

00:54:53That's why you blink up to 20,000 times a day.

00:54:55And your eyelid plays the role

00:54:57of an icebreaker.

00:54:59The only part of the human body that doesn't receive

00:55:01nutrients from blood is the cornea,

00:55:03the surface before it covers the eye.

00:55:05It is fed by tears outside

00:55:07and by special fluids inside.

00:55:09When you blush,

00:55:11it means that the blood flow in your body increases.

00:55:13So it's not just your cheeks,

00:55:15but also the wall of your stomach

00:55:17that turns red.

00:55:19It's because there are a lot of blood vessels.

00:55:21When there is more blood than usual in these vessels,

00:55:23the wall blushes.

00:55:25The wall of your stomach is replaced every 3 or 4 days.

00:55:27This prevents the organ

00:55:29from eating itself.

00:55:31This is the reason why

00:55:33the human body is exceptionally powerful.

00:55:35People can accidentally swallow small objects

00:55:37like plastic, glass, coins,

00:55:39and much more.

00:55:41Normally, they do not cause any damage

00:55:43and pass through the digestive tube

00:55:45to evacuate within 48 hours.

00:55:47Small amounts of plastic that you could

00:55:49mistakenly consume will not hurt you.

00:55:51But on the other hand,

00:55:53your stomach will have trouble digesting grass.

00:55:55Grooming animals have special teeth

00:55:57and stomachs to treat leaves and fresh grass.

00:55:59They are not equipped this way.

00:56:03The stomach is the most important protector

00:56:05of the immune system.

00:56:07It contains chloride acid.

00:56:09This acid eliminates dangerous food toxins,

00:56:11viruses and bacteria

00:56:13that accompany the food you eat.

00:56:15The stomach itself would be digested by this powerful acid

00:56:17if its mucous membrane did not protect it.

00:56:19You have two really fast muscles.

00:56:21They control the closure of your eyelids.

00:56:23They are the fastest of your body.

00:56:25Your eyes are fragile

00:56:27and they need to be protected.

00:56:29When a particular reflex is triggered,

00:56:31for example, when something suddenly touches your eye,

00:56:33these muscles only need a tenth of a second

00:56:35to close the eyelids

00:56:37and protect your eye.

00:56:39Women usually blink more often than men.

00:56:41And the older you get,

00:56:43the more often you do it.

00:56:45Besides, when you watch a movie with a friend,

00:56:47you probably both blink at the same time.

00:56:49Do you think you owe your firm hand

00:56:51to your muscle exercises?

00:56:53Nope. It's thanks to your little finger.

00:56:55And yet, the ear is the strongest finger in existence.

00:56:57It is responsible for 50%

00:56:59of the strength of the hand.

00:57:01But the most used finger is the thumb.

00:57:03If a person loses it,

00:57:05his hand becomes 40% less agile.

00:57:07Oh, and the thumb has its own skin

00:57:09thanks to the artery it crosses.

00:57:11Your big toes carry more than 40%

00:57:13of your weight,

00:57:15more than all the other toes combined.

00:57:17In fact, all your toes are very important.

00:57:19They provide support and balance

00:57:21when you walk.

00:57:23They help you be faster.

00:57:25Not more than 2% of people have natural brown hair.

00:57:27They are followed by blondes,

00:57:29about 3%,

00:57:31and by all kinds of shades of brown,

00:57:33about 11%.

00:57:35But the most common hair colors in the world

00:57:37are black and French brown.

00:57:39Hair is almost indestructible.

00:57:41It can be burned or affected by strong acids,

00:57:43but that's about all you can do

00:57:45to destroy them.

00:57:47Your hair usually ceases to grow

00:57:49to a certain length.

00:57:51In fact,

00:57:53the longest nails in the world

00:57:55usually don't exceed 106 cm.

00:57:57Tell this lady,

00:57:59Xi Jinping, from China,

00:58:01who broke the Guinness World Record

00:58:03with the longest hair of all time.

00:58:05In 2004, they were 5 meters long.

00:58:07Wow!

00:58:09Nails can also become super long.

00:58:11Some of the longest nails in the world

00:58:13belonged to an Indian,

00:58:15Sridhar Shillal.

00:58:17Their total length was 9 meters,

00:58:19which was enough to catch small objects

00:58:21and unstick the stickers.

00:58:23But that's not all.

00:58:25If you didn't have a rigid structure

00:58:27against which you pressed,

00:58:29you wouldn't be able to understand

00:58:31how firmly you have to hold things.

00:58:33It's not just your hair and nails

00:58:35that can grow, but also your liver.

00:58:37It is the largest internal organ in terms of mass.

00:58:39The liver can regenerate completely,

00:58:41going from only 51% of its initial mass

00:58:43to its maximum size.

00:58:45And at the same time,

00:58:47the most important organ of your body

00:58:49is the skin.

00:58:51It represents more than 15% of your total weight.

00:58:53People lose 30,000 to 40,000 skin cells

00:58:55every minute.

00:58:57This represents up to 4 kilos of cutaneous cells

00:58:59per year.

00:59:01You know this dust in your house?

00:59:03Well, now you know where some of it comes from.

00:59:05The tongue is not the only organ

00:59:07that helps you recognize your taste.

00:59:09Your nose also plays a crucial role

00:59:11in this process.

00:59:13It is often said that the nose is responsible

00:59:15for the taste of your food.

00:59:17Try to pinch your nose the next time you eat,

00:59:19bite into an onion or eat smoked fish.

00:59:21It's not that you won't taste anything,

00:59:23but it will be much worse.

00:59:25Your taste buds won't work properly

00:59:27if your mouth is too dry.

00:59:29You won't taste as much as long as

00:59:31the food is not covered with saliva.

00:59:33It contains enzymes,

00:59:35which are complex protein molecules.

00:59:37They begin to break down your food

00:59:39as soon as it enters your mouth.

00:59:41A recent study has shown that people

00:59:43who don't have a good sense of smell

00:59:45tend to remember smells better

00:59:47than sounds or images.

00:59:49That's why smells can evoke distant memories.

00:59:51When you sleep, you don't smell anything.

00:59:53Basically, your sense of smell

00:59:55goes off at night.

00:59:57Even if there is a terrible stench

00:59:59in your room, you won't notice it.

01:00:01I'm sure my dog is relieved to hear that.

01:00:03The color of your dreams seems to be affected

01:00:05by the television you watched

01:00:07when you were a child.

01:00:09If it was black and white most of the time,

01:00:11your dreams would probably be colored.

01:00:13What kind of dreams did people have

01:00:15in the Middle Ages?

01:00:17Your heart can betray you when you lie,

01:00:19starting to beat faster.

01:00:21Women's hearts are usually smaller than men's.

01:00:23That's why they have to work harder

01:00:25and beat more.

01:00:27Otherwise, they wouldn't be able

01:00:29to pump enough blood.

01:00:31Even if you brush your teeth twice a day

01:00:33and never forget to wash your mouth,

01:00:35your mouth remains one of the dirtiest parts

01:00:37of your body.

01:00:39It protects your body

01:00:41from bad bacteria and viruses.

01:00:43The second dirtiest part

01:00:45is your navel.

01:00:47You don't really use it after you're born.

01:00:49This area accumulates all kinds of germs,

01:00:51sweat and dirt.

01:00:53The navel has more than 2,300 bacterial species

01:00:55and requires special attention.

01:00:57It is said that the eyes

01:00:59don't grow with the rest of the body.

01:01:01But that's not 100% true

01:01:03because the eyes are not fully developed

01:01:05before the age of 21.

01:01:07The only signs of absolute growth here

01:01:09are your ears and your nose.

01:01:11They keep growing.

01:01:13Wow, what was that thing with the elephants?

01:01:15Ah, that must have been another video.

01:01:17If all your blood vessels were spread

01:01:19on a single line,

01:01:21you'd be in trouble.

01:01:23On the other hand,

01:01:25they would go around the Earth

01:01:27four times.

01:01:29You can't get rid of it,

01:01:31no matter how hard you try.

01:01:33You just checked and you failed, didn't you?

01:01:35And you're not the only one stuck with it.

01:01:37Have you ever wondered why you were falling asleep

01:01:39after breakfast?

01:01:41One of the reasons is the circadian rhythm

01:01:43that works in a 24-hour cycle.

01:01:45It requires you to take a nap

01:01:47seven hours after you wake up.

01:01:49And food just adds to that effect.

01:01:51It's that simple.

01:01:53Oops, sorry, it's time.

01:01:57You can't remember a memory in its context.

01:01:59When you try to remember a detail

01:02:01like the color of the T-shirt

01:02:03you gave your friend the other day,

01:02:05you also remember other details.

01:02:07For example, the place where you saw it

01:02:09and the things you talked about.

01:02:11The hippocampus is the part of your brain

01:02:13that stores memories.

01:02:15It is used to group them,

01:02:17including multiple small details.

01:02:19The taste buds last an average of 10 days.

01:02:21They are grafts of sensory cells

01:02:23in your tongue.

01:02:25The taste buds closest to the surface

01:02:27are more ephemeral.

01:02:29That's why you don't have to wait

01:02:31for your brain to be ready to burn your tongue.

01:02:33A theory states that the already seen

01:02:35is a kind of offset

01:02:37in brain treatment.

01:02:39Scientists think this can happen

01:02:41when your brain transfers information

01:02:43from one side to the other

01:02:45and there is a delay of a fraction of a second

01:02:47in this process.

01:02:49This means that your brain

01:02:51receives the same information twice

01:02:53and treats it as an event that has already occurred.

01:02:55Only 30% of people can dilate their nostrils

01:02:57and a third can fold their thumb back.

01:02:59Some people can produce a rustling sound

01:03:01in their head.

01:03:03All they have to do is stretch their ears

01:03:05or jaws.

01:03:07There is a small muscle in the ear

01:03:09that amortizes loud sounds,

01:03:11like when you chew.

01:03:13But some people can flex this muscle

01:03:15and it creates an audible rumbling.

01:03:17The tip of your fingers is sensitive,

01:03:19but hundreds of times less than your lips.

01:03:21You inhale many different types of debris,

01:03:23including 700,000 of your own cutaneous squam,

01:03:25only in one day.

01:03:27A sypneic shake is a soft jump

01:03:29that you can feel when you fall asleep.

01:03:31It is a sudden muscle movement

01:03:33that occurs during the sleep phase,

01:03:35not REM.

01:03:37It can create an illusion of falling.

01:03:39One of the theories is that

01:03:41when you fall asleep,

01:03:43your brain perceives the relaxation of your muscles

01:03:45as a sign that you have problems

01:03:47and that you are falling.

01:03:49So it sends signals to the muscles

01:03:51to protect you by contracting.

01:03:53Synesthesia is a special and rare ability

01:03:55that consists of feeling the taste of music

01:03:57or hearing the colors.

01:03:59Only one in 2,000 people

01:04:01has it.

01:04:03For some people,

01:04:05coriander may taste similar to soap

01:04:07because the plant contains a chemical compound

01:04:09used in the manufacture of it.

01:04:11But only 4 to 14% of the world population

01:04:13have special genes

01:04:15that can detect it.

01:04:1718% of people can move

01:04:19their two ears at the same time,

01:04:21while 22% can move

01:04:23one ear at a time.

01:04:25People who do it use old weak muscles

01:04:27that we inherited from the ancestor

01:04:29that we have in common with cats.

01:04:31Hematomas change color over time.

01:04:33A blue appears

01:04:35because there is a bleeding under the skin.

01:04:37Tiny blood vessels are crushed

01:04:39and some of the blood is trapped

01:04:41in this place.

01:04:43At first, a blue is red because this blood is rich

01:04:45in oxygen, but then it turns purple,

01:04:47green, yellow or even gray

01:04:49when the oxygen level decreases.

01:04:51Sweat has no smell in itself.

01:04:53The unpleasant smell is caused

01:04:55by the bacteria present on your skin.

01:04:57When the sweat comes out

01:04:59of your pores, the bacteria

01:05:01decompose it into acid.

01:05:03What most deodorants do

01:05:05is to get rid of the bacteria on your skin.

01:05:07People used to dream

01:05:09a lot more in black and white than today.

01:05:11It's because they watched TV in black and white.

01:05:13Blue cheese can influence

01:05:15your dreams and make them more alive.

01:05:17As for shell 2,

01:05:19it could be used to grow

01:05:21new human bones.

01:05:23Chicken shells contain calcium carbonate,

01:05:25an element also contained

01:05:27in our bones.

01:05:29The food in the plane will probably have

01:05:31a different taste from the same food on the ground.

01:05:33It's because you lose up to 30%

01:05:35of the sensitivity of your

01:05:37taste buds because of the dryness

01:05:39and the pressure in the cabin.

01:05:41This is particularly true for

01:05:43salty and sweet foods.

01:05:45Your nostrils do not work with the same

01:05:47frequency all the time.

01:05:49When you breathe, a single tear

01:05:51is the main part of the job

01:05:53and it comes back every two hours.

01:05:55You can't taste food without saliva.

01:05:57Your taste buds have

01:05:59chemoreceptors that recognize

01:06:01different flavors, but they need a

01:06:03liquid for these flavors to bind

01:06:05to their molecules. So you can't

01:06:07taste things that saliva doesn't dissolve.

01:06:09The brain can't really

01:06:11feel the pain. It does have

01:06:13a pain center, but it doesn't have

01:06:15a pain receptor. When your head

01:06:17hurts, you can feel it because of the nerves,

01:06:19tissues and blood vessels

01:06:21that surround your brain. A single human

01:06:23hair can support a weight of

01:06:25100 grams, or the weight of two chocolate bars.

01:06:27The nails and toes grow

01:06:29almost four times slower than the nails

01:06:31and hands, which are more exposed and used

01:06:33more frequently. There must be

01:06:35at least a few pictures where you have

01:06:37red eyes. When the flash of the camera

01:06:39turns on, your eyes are not prepared

01:06:41for such an influx of light.

01:06:43Your pupils remain dilated, which is why

01:06:45the light is reflected on the red blood vessels

01:06:47of the choroid. It is a

01:06:49layer of tissue at the back of your eye

01:06:51that nourishes your retina.

01:06:53Your right lung is larger than the

01:06:55left one because your body must make

01:06:57room for the heart. Your teeth are

01:06:59the only part of your body that can't

01:07:01heal on its own.

01:07:03The masseter is the most powerful muscle

01:07:05you have compared to its weight.

01:07:07With the rest of the muscles of the jaw,

01:07:09it can close your teeth with a force of

01:07:1190 kg on the molar and

01:07:1325 kg at the incisors.

01:07:15Onions produce a special chemical

01:07:17irritant that stimulates

01:07:19special glands in your eyes,

01:07:21which causes them to release tears.

01:07:23Your nose can memorize up to

01:07:2550,000 smells.

01:07:27Your nose can memorize up to 50,000 different smells

01:07:29and detect more than 1,000 billion smells.

01:07:31We all have a unique smell,

01:07:33except for real twins.

01:07:35This smell is partly determined by genetics,

01:07:37but it also depends on your diet,

01:07:39your hygiene and the environment.

01:07:41Eating snow is not the best way

01:07:43to stay hydrated.

01:07:45Your body needs too much energy

01:07:47to turn it into water.

01:07:49Snow can give you a little hydration,

01:07:51but it will also lower the temperature

01:07:53of your body, which is not the best scenario

01:07:55if you try to survive in difficult

01:07:57winter conditions.

01:07:59You burn between 100 and 200 calories

01:08:01per hour while standing.

01:08:03The sitting position burns 60 to 130 calories

01:08:05depending on your size, weight,

01:08:07your sex and your age.

01:08:09Brain freeze is a headache

01:08:11caused by ice.

01:08:13It's the way your brain tells you

01:08:15to slow down and maybe stop eating

01:08:17something very cold.

01:08:19The main purpose of eyelashes

01:08:21is to protect your eyes from the sand,

01:08:23moisture, dust and debris

01:08:25in the air.

01:08:27Your eyelashes detect when something

01:08:29gets too close to your eyes,

01:08:31like an insect that flies towards you

01:08:33and triggers a blinking reflex.

01:08:35You must evacuate tiny particles

01:08:37or debris stuck in your eyelids.

01:08:39These are small openings

01:08:41in your eyelids.

01:08:43This is where tears are created.

01:08:45As for your eyebrows,

01:08:47they prevent sweat from flowing

01:08:49directly into your eyes.

01:08:51Your skin in this place and the shape

01:08:53of your bones also work together

01:08:55to direct the sweat to the sides

01:08:57of your face.

01:08:59We are not the fastest, strongest

01:09:01or tallest in the animal kingdom,

01:09:03but we have long legs

01:09:05and our body can lose

01:09:07excess heat by sweating.

01:09:09A long time ago, our ancestors

01:09:11hunted animals by chasing them

01:09:13for long periods.

01:09:15This ended up exhausting

01:09:17the little creatures.

01:09:19The five basic senses are taste,

01:09:21touch, sight, sound and smell,

01:09:23but people have more sense than that.

01:09:25The proprioception is the fact

01:09:27of being aware of parts of your body

01:09:29and their position,

01:09:31if you were a pigeon,

01:09:33you wouldn't know it,

01:09:35because these creatures don't know

01:09:37that their tentacles exist

01:09:39if they don't see them.

01:09:41The thermoception is the ability

01:09:43to perceive temperature.

01:09:45The equilibrioception is the sense

01:09:47of balance.

01:09:49There is also the nociception,

01:09:51which allows you to feel pain,

01:09:53and the chronoception,

01:09:55which is the way you can feel

01:09:57the passing of time.

01:09:59There is also the magnetoreception,

01:10:01but humans don't have them.

01:10:03You can't see your taste buds.

01:10:05These little bumps on the tongue

01:10:07are lingual buds.

01:10:09There are four kinds of them,

01:10:11circumvalate, foliate,

01:10:13fosiform, filiform.

01:10:15They are all covered with taste buds,

01:10:17except the last one, filiform.

01:10:19This one is responsible

01:10:21for the sense of touch of your tongue.

01:10:23Your auricle is responsible

01:10:25for 50% of the total strength

01:10:27The liver is a very important organ

01:10:29that works a lot and is responsible

01:10:31for 500 individual functions.

01:10:33Up to 10% of its content

01:10:35is composed of fat.

01:10:37The liver can regenerate.

01:10:39You can burn calories

01:10:41when you take a hot bath,

01:10:43as much as if you were

01:10:45taking a walk for half an hour.

01:10:47People usually need

01:10:497 minutes to fall asleep.

01:10:51This time is shorter

01:10:53if you just ate a copious meal.

01:10:55Your brain will grow about 2%

01:10:57if you venture into space.

01:10:59Under normal gravity,

01:11:01we think that the liquid

01:11:03present in the brain

01:11:05naturally moves down

01:11:07when we stand up.

01:11:09And it is proven

01:11:11that the absence of gravity

01:11:13prevents this,

01:11:15which explains why the liquid

01:11:17would accumulate in your brain

01:11:19and in your skull.

01:11:21And no,

01:11:23it's not true,

01:11:25but people with cacosmia

01:11:27perceive things differently.

01:11:29For them,

01:11:31all the smells in the world

01:11:33are unpleasant.

01:11:35Yes, they think it stinks.

01:11:37And by the way,

01:11:39among all our senses,

01:11:41odour is the highest.

01:11:43We still remember 65%

01:11:45of the odours after a year,

01:11:47but only 50%

01:11:49of what we saw

01:11:51and what we don't smell

01:11:53when we sleep.

01:11:55Well, except if, of course,

01:11:57we haven't washed for a while.

01:11:59Your odour becomes veiled

01:12:01when you sleep.

01:12:03That's why it's almost impossible

01:12:05to notice a gas leak at night.

01:12:07During our sleep,

01:12:09there are only noises

01:12:11that can save us

01:12:13because our hearing

01:12:15continues to work.

01:12:17Almost half of your taste buds

01:12:19are affected by odour.

01:12:21For taste,

01:12:23we pay special attention

01:12:25to our odour

01:12:27because it helps us

01:12:29to perceive up to 95%

01:12:31of the flavours.

01:12:33Without odour,

01:12:35it would be difficult

01:12:37to distinguish an apple

01:12:39from a turnip.

01:12:41When you cough,

01:12:43you expel air

01:12:45at about 100 km per hour.

01:12:47When the doors close,

01:12:49the air is blocked

01:12:51and the noise we all know

01:12:53is heard.

01:12:55We need our ears

01:12:57not only to hear,

01:12:59but also for our balance.

01:13:01Our vestibular system

01:13:03is located in the inner ear.

01:13:05Canals contain liquid

01:13:07and tiny sensors

01:13:09that help you keep your balance.

01:13:11In fact,

01:13:13ears have bones

01:13:15as well as the ossicular chain.

01:13:17They consist of the malleus,

01:13:19the incus and the stapes,

01:13:21also known as hammer,

01:13:23anvil and calf.

01:13:25They are an integral part

01:13:27of the middle ear.

01:13:29Our ears continue to grow

01:13:31throughout our life.

01:13:33They also sweat

01:13:35and the cerebellum

01:13:37is actually the sweat they produce.

01:13:39In fact,

01:13:41our nose never stops growing

01:13:43and our muscles never get tired.

01:13:45The aorta is massive.

01:13:47Its diameter is almost equivalent

01:13:49to that of a garden watering pipe.

01:13:51All the bones of our body

01:13:53are connected to each other

01:13:55except the aorta,

01:13:57which does not join the other bones.

01:13:59This bone is used as a support for your tongue

01:14:01and it is one of the most rarely broken.

01:14:03If you have red eyes in a photo,

01:14:05it is the fault of the light that bounces.

01:14:07The flash reflects on the capillaries

01:14:09of your retina,

01:14:11the most powerful camera

01:14:13has 200 megapixels.

01:14:15A human eye has 576.

01:14:17This is why sunsets

01:14:19are so much more beautiful in real life

01:14:21than in photos.

01:14:23The roller coasters really move your organs.

01:14:25When you feel like your stomach is falling,

01:14:27it is because it is really being

01:14:29thrown inside your body.

01:14:31The lips are much more sensitive

01:14:33than the fingers,

01:14:35because they have about a million

01:14:37nerve endings.

01:14:39The grooves

01:14:41and the sills of our lips

01:14:43make their imprint unique,

01:14:45just like our fingers,

01:14:47and they do not change throughout our life.

01:14:49The imprint of our tongue

01:14:51is also unique elsewhere.

01:14:53All the inhabitants of the earth

01:14:55have a smell that is their own,

01:14:57but real twins have exactly the same.

01:14:59This must be because they have

01:15:01identical genes.

01:15:03Usually, we lose about

01:15:0550 to 150 hairs a day.

01:15:07This happens every 5 years,

01:15:09and as soon as an old hair

01:15:11says goodbye to your scalp,

01:15:13a new one begins to grow immediately.

01:15:15In your body, you carry enough bacteria

01:15:17to fill a can.

01:15:19You have about 1.5 to 2 kilos

01:15:21of bacteria in you,

01:15:23or 2% of your total weight.

01:15:25But most are waste

01:15:27of our body.

01:15:29A human being has between

01:15:3120,000 and 25,000 genes.

01:15:33Pretty impressive, isn't it?

01:15:35Fortunately, it's a matter of sophistication,

01:15:37not quantity.

01:15:39Anyway, cornflakes, 1,

01:15:41human, 0.

01:15:43We are made up of many chemical elements,

01:15:45including iron.

01:15:47The iron in our body

01:15:49would be enough to produce 3 nails,

01:15:51each 2.5 cm long.

01:15:53The carbon we have

01:15:55could be used to make 900 pencils.

01:15:57We use our feathers to make pens.

01:15:59Oh no, these are the birds.

01:16:01What a distraction!

01:16:03Our liver has the superpower

01:16:05to regenerate itself if it lacks a piece.

01:16:07It can grow back and reach

01:16:09the size necessary for your body.

01:16:11Fat helps our body to assimilate vitamins.

01:16:13Vitamins A,

01:16:15D, K and E

01:16:17can only be properly absorbed

01:16:19if they are dissolved in fat.

01:16:21Our body has enough fat

01:16:23to produce 7 soap bars.

01:16:25Don't try to make some at home!

01:16:27When we are awake,

01:16:29our brain can produce enough energy

01:16:31to light an electric bulb.

01:16:33It has a power of 10 watts.

01:16:35Eureka!

01:16:37Our navels contain

01:16:39an entire animal encyclopedia

01:16:41with a range of about 70 different bacteria.

01:16:43Some of them can also be found

01:16:45in the ground in Japan

01:16:47and even in the ice cap of the poles.

01:16:49Our bodies shine,

01:16:51but we can't see it with the naked eye

01:16:53because the light we emit

01:16:55is a thousand times less intense

01:16:57than the minimum level we can perceive.

01:16:59The oil used in cheek and lipstick

01:17:01is a red glue made of

01:17:03ground beetroot.

01:17:05Our saliva helps us

01:17:07to perceive the taste of food.

01:17:09Our taste buds only work

01:17:11when they are dissolved.

01:17:13A silk has a lifespan

01:17:15of only 150 days.

01:17:17The longest silk in the world

01:17:19measures about 10 cm.

01:17:21They are also the refuge

01:17:23of tiny aquariums.

01:17:25We blink about 4,200,000 times a year

01:17:27at least once every 8 seconds.

01:17:29It would be cool if we were given

01:17:31a cent each time.

01:17:33We would earn more than 100 euros a day.

01:17:35It may seem crazy,

01:17:37but our bones are stronger

01:17:39than many building materials.

01:17:4116 cm3 of human bones

01:17:43can support about 8,600 kg,

01:17:45which is 4 times more resistant than concrete.

01:17:47The only thing that makes

01:17:49our blood group different is sugar.

01:17:51Groups A, B and AB

01:17:53contain sugars,

01:17:55but group O does not.

01:17:57And these donors are universal.

01:17:59The lack of sugar does not make

01:18:01the blood of group O less sweet.

01:18:03In fact, it attracts even more mosquitoes

01:18:05than other blood groups.

01:18:07People have only 8 blood groups,

01:18:09while cows have 800

01:18:11and maybe even more.

01:18:13Me positive and me negative,

01:18:15for example?

01:18:17The nails of our fingers grow

01:18:19much faster than those of our toes.

01:18:21The latter grows almost 4 times slower

01:18:23than the nails of our hands.

01:18:25Even if we know them often,

01:18:27the blue that forms there

01:18:29generally does not last long.

01:18:31Nails do not only help us

01:18:33to catch small things

01:18:35and to take off stickers.

01:18:37If you did not have this rigid structure

01:18:39against which to press,

01:18:41you would not be able to judge

01:18:43the firmness with which

01:18:45you have to hold objects.

01:18:47Very few people can really digest milk.

01:18:49The thing is that there is a special enzyme,

01:18:51which contains milk.

01:18:53As we grow up, we lose this enzyme.

01:18:55This sugar is called lactose,

01:18:57and adults who cannot digest it

01:18:59are said to be lactose intolerant.

01:19:01In fact,

01:19:0368% of the world's population

01:19:05cannot digest milk.

01:19:07When you sleep,

01:19:09your whole body does not rest.

01:19:11In reality, your brain

01:19:13sometimes has to work even harder.

01:19:15It has to process tons of information

01:19:17and typing the reports

01:19:19Humans cannot do

01:19:21several things at once.

01:19:23We need time to go from one task to another,

01:19:25and if we try to attack

01:19:27several things at the same time,

01:19:29we will not be very productive.

01:19:31Try this.

01:19:33Raise your right foot and turn it

01:19:35clockwise.

01:19:37Now try to write the number 6

01:19:39with your big toe in the air.

01:19:41Then check the direction

01:19:43in which your foot is moving.

01:19:45It moves in the opposite direction

01:19:47of the needles of a watch.

01:19:49A new habit

01:19:51takes a lot of time to set up.

01:19:53It is not 100% true

01:19:55that 18 or 21 days are enough,

01:19:57as many people think.

01:19:59Acquiring a new habit

01:20:01can take up to 254 days,

01:20:03but on average,

01:20:05it takes about 66 days

01:20:07for something to become automatic.

01:20:09The cornea

01:20:11is the only part of your body

01:20:13that contains living cells

01:20:15and no blood vessels.

01:20:17It receives nutrients and oxygen

01:20:19directly from the lacrimal fluid

01:20:21outside and from the thick

01:20:23substance between the corneas

01:20:25inside, as well as

01:20:27nerve fibers connected to the cornea.

01:20:29This is why contact lenses

01:20:31have first constituted

01:20:33a potential problem.

01:20:35The older ones reduced oxygen supply

01:20:37because the cornea mainly receives

01:20:39oxygen from the outside.

01:20:41This problem was solved,

01:20:43when hydrogel silicone lenses

01:20:45arrived on the market.

01:20:47The other parts of the body

01:20:49devoid of blood vessels are the nails,

01:20:51the hair, the outer layers of the skin

01:20:53and the enamel of the teeth.

01:20:55Have you noticed that your sweat

01:20:57sometimes smells like onions after sports?

01:20:59Do not worry.

01:21:01There are two types of

01:21:03sudoriparous glands in your skin.

01:21:05The first type of gland

01:21:07is located on certain parts of your body,

01:21:09such as the wool region and the armpits.

01:21:11They produce a specific oily fluid

01:21:13which is a response

01:21:15to certain emotional experiences.

01:21:17Another type of sudoriparous gland

01:21:19is much more common.

01:21:21They are distributed throughout the body

01:21:23and are responsible for the specific sweat

01:21:25you get after sports.

01:21:27This sweat refreshes your body

01:21:29by evaporating from your skin.

01:21:31It is 99% water,

01:21:33so it is practically odorless.

01:21:35At least when it leaves the pores

01:21:37and reaches the surface of the skin.

01:21:41But there are many types of bacteria

01:21:43on the human skin

01:21:45and they feed on nutrients

01:21:47contained in this sweat as well as squam.

01:21:49One of the sub-products of this process

01:21:51is a specific chemical product

01:21:53whose odor can sometimes strongly

01:21:55resemble that of onions.

01:21:57You may have noticed

01:21:59that you produce more saliva

01:22:01when you run,

01:22:03especially if it is a short jog in the cold.

01:22:05But if you run a marathon

01:22:07and the weather is nice and warm outside,

01:22:09you will produce less saliva.

01:22:11It is your body that tries

01:22:13to compensate for the effect of dehydration

01:22:15since you breathe much more through your mouth.

01:22:17But your body

01:22:19dehydrates more over long periods.

01:22:21This is why

01:22:23it tries to conserve water

01:22:25by reducing the production of saliva.

01:22:27Each exercise,

01:22:29however intense,

01:22:31leads to the secretion of a specific type of protein.

01:22:33It makes the saliva

01:22:35more viscous and sticky,

01:22:37which explains why

01:22:39you may feel like your mouth is even drier

01:22:41after your workout.

01:22:43Humans see the world

01:22:45with a 15-second delay,

01:22:47which means that your brain

01:22:49constantly leaves you a little in the past.

01:22:51This helps you stabilize

01:22:53your vision of the world around you.

01:22:55Your eyes receive a huge amount

01:22:57of visual information.

01:22:59Yes, literally millions of colors,

01:23:01shapes and movements

01:23:03in constant evolution wherever you are.

01:23:05It is not an easy task for your brain

01:23:07to process all this.

01:23:09The visual world is constantly changing

01:23:11due to changes in point of view,

01:23:13light and other external factors.

01:23:15The input of images

01:23:17in your brain also changes

01:23:19because you have to blink your eyes

01:23:21and your head, your eyes and your whole body

01:23:23are always moving.

01:23:25Your brain therefore

01:23:27had to establish a mechanism

01:23:29that can create imaginary stability.

01:23:31It automatically smooths your visual inputs.

01:23:33It does not analyze

01:23:35every little visual cliché.

01:23:37It is like a time machine.

01:23:39You actually perceive

01:23:41a synthesis of the things

01:23:43you have seen in the last 15 seconds

01:23:45at a given moment.

01:23:47The brain groups the objects

01:23:49so that they seem more similar to each other.

01:23:51This is why it makes you believe

01:23:53that you are in a stable environment.

01:23:55If your brain kept you up to date in real time,

01:23:57the world would seem very, very chaotic to you.

01:23:59With constant changes

01:24:01in movement, light and shadow,

01:24:03you would probably

01:24:05feel like you are hallucinating all the time.

01:24:09Your bones are very strong,

01:24:11but your teeth, which we consider

01:24:13to be part of the skeletal system,

01:24:15are even stronger.

01:24:17This is due to the enamel,

01:24:19the hard outer layer of the teeth.

01:24:21Enamel protects the delicate tissues

01:24:23and nerves inside the teeth.

01:24:27Know that you burn calories

01:24:29when you think.

01:24:31When you rest and do not do

01:24:33any particular activity

01:24:35except the essentials,

01:24:37such as digesting, breathing and warming up,

01:24:39your brain uses

01:24:41up to 20 to 25%

01:24:43of the total energy of your body.

01:24:45This means

01:24:47that your body burns

01:24:49about 350 to 450 calories per day

01:24:51by doing practically nothing.

01:24:53We are not the only ones

01:24:55in the animal kingdom

01:24:57with this type of brain.

01:24:59Some small mammals,

01:25:01such as the tiny Wistiti pygmae

01:25:03and the tiny Musareni arboricolle,

01:25:05devote the same percentage

01:25:07of their total body energy

01:25:09to their brain.

01:25:11Most of the energy

01:25:13consumed by the brain

01:25:15is used to help these cells,

01:25:17neurons, communicate with each other.

01:25:19They do so through chemical signals

01:25:21that the brain transmits

01:25:23through the synapses,

01:25:25your brain never really rests.

01:25:27Even when you sleep,

01:25:29some parts are active.

01:25:31Your brain therefore needs

01:25:33its fuel to function

01:25:35and you burn essentially calories

01:25:37during your sleep.

01:25:39The more demanding mental tasks

01:25:41you do during the day,

01:25:43the more calories you burn.

01:25:45So if you do not exercise today,

01:25:47save at least a few bucks.

01:25:49Do you like to devour your ice cream?

01:25:51Sometimes it's super nice,

01:25:53but often you have to know

01:25:55this sensation of brain freeze.

01:25:57It is a rather intense

01:25:59and unpleasant sensation

01:26:01that occurs at the front

01:26:03or on the sides of your head

01:26:05just after drinking or eating

01:26:07something very cold,

01:26:09such as an iced drink,

01:26:11an ice cream or a water ice cream.

01:26:13Some people even experience

01:26:15a similar sensation

01:26:17when they are just exposed

01:26:19to the cold air.

01:26:21The cold substance stimulates

01:26:23a group of nerves located

01:26:25at the back of the palate.

01:26:27According to another theory,

01:26:29the blood vessels of the palate

01:26:31and the sinuses contract quickly

01:26:33due to the drop in temperature

01:26:35in the mouth before

01:26:37dilating again.

01:26:39Brain freeze is not something

01:26:41dangerous that you should

01:26:43seriously worry about.

01:26:45And no,

01:26:47hanging on a table,

01:26:49even sleeping a lot,

01:26:51I plead guilty.

01:26:53But others have a kind of disease

01:26:55called FNSS,

01:26:57which means

01:26:59that they are in some way

01:27:01immune to lack of sleep.

01:27:03About 1% of our population

01:27:05is affected.

01:27:07They may lack sleep,

01:27:09but they feel pretty good.

01:27:11They have no problem sleeping

01:27:13just 6 hours a night.

01:27:15This low amount of rest

01:27:17usually means 3 cones.

01:27:19This means that we can recognize

01:27:21about 1 million different shades

01:27:23in the green, red and blue spectrum

01:27:25of colors.

01:27:27But some people with a rare disease

01:27:29called tetrachromatia

01:27:31have 4 cones in their eyes.

01:27:33This allows them to see

01:27:35ultraviolet shades,

01:27:37which means they can distinguish

01:27:39100 million distinct colors.

01:27:41Did you know that your skeleton

01:27:43is all wet?

01:27:45It's mainly made up of water,

01:27:47up to 60%.

01:27:49This liquid is not only in your organs,

01:27:51your muscles and your skin.

01:27:53It's also in your skeleton.

01:27:55Your bone mass is composed of

01:27:57about a third of water.

01:27:59The human body contains

01:28:01an amazing hidden network.

01:28:03Blood vessels are really small,

01:28:05but if you could align them all,

01:28:07you would get something huge.

01:28:09Your whole body has a network

01:28:11of 96,560 km of blood vessels.

01:28:13One way to keep your network healthy

01:28:15is to eat well.

01:28:17Have you ever wondered why

01:28:19our distant parents, the primates,

01:28:21are so much stronger than us?

01:28:23In many ways, our bodies are very similar.

01:28:25Look at the muscular structure

01:28:27of chimpanzees, for example.

01:28:29But our closest primate parents

01:28:31are about 1.35 times stronger

01:28:33than us.

01:28:35The human body has developed

01:28:37more muscle fibers at slow contraction

01:28:39than the rest of the primates.

01:28:41This type of muscle fiber is less powerful,

01:28:43but it allows us to last longer

01:28:45than other primates,

01:28:47and to do things like

01:28:49hunt for food and activities

01:28:51that helped our distant ancestors survive.

01:28:53This is also the reason

01:28:55why we can run a marathon.

01:28:57A monkey could never do it,

01:28:59but we would lose anyway

01:29:01in a strength competition.

01:29:03Laughter is contagious.

01:29:05It's not just a metaphor.

01:29:07Researchers have discovered

01:29:09how to synchronize

01:29:11the brain activity of different people.

01:29:13Laughter is a phenomenon

01:29:15that science generally associates

01:29:17with social creatures.

01:29:19People have nearly 30 times more chances

01:29:21to laugh when they are in social situations,

01:29:23with their friends,

01:29:25or with people they feel good with.

01:29:27A scientific theory states

01:29:29that we want to join people who laugh,

01:29:31because humans are empathetic beings.

01:29:33Your brain releases endorphins

01:29:35when you laugh.

01:29:37These endorphins make you feel safe and comfortable.

01:29:39We don't know exactly

01:29:41why our laughter is contagious,

01:29:43but we feel really good,

01:29:45so...

01:29:49In the meantime,

01:29:51join us on the fun side of life

01:29:53and laugh with all your heart.

01:29:55Most people are convinced

01:29:57that humans only have 5 senses,

01:29:59but this is not entirely true.

01:30:01Taste, touch, smell, sight, and hearing

01:30:03are not the only senses we have.

01:30:05Scientists claim

01:30:07that people have between 9 and 20 senses in total.

01:30:09Among them,

01:30:11thermoception, which is the sense of heat,

01:30:13equilibrioception,

01:30:15which is the sense of balance.

01:30:17There is also the sense of time passing,

01:30:19although not everyone seems to master it perfectly.

01:30:21Until recently,

01:30:23it was thought that there were only

01:30:258 different blood groups,

01:30:27but in reality,

01:30:29there are more than 30 systems of known blood groups.

01:30:31For every kilo of fat you take,

01:30:33you generate 1 km of new blood vessels

01:30:35to provide oxygen

01:30:37and nutrients to your body.

01:30:39Your stomach produces a new package

01:30:41every 6 days

01:30:43to avoid digesting itself.

01:30:45Nervous cells transmit

01:30:471000 nerve impulses per second.

01:30:49They travel at a speed

01:30:51of 1 to 431 km per hour.

01:30:53Our DNA contains

01:30:55100,000 viruses.

01:30:57Scientists have discovered

01:30:59one that goes back 100 million years.

01:31:01Your body emits a visible light.

01:31:03It is at 4 p.m. that you are the brightest

01:31:05and it is at 10 a.m.

01:31:07that your glow is the least obvious.

01:31:09Unfortunately, this glow is 1000 times

01:31:11less intense than what your eyes can perceive.

01:31:13Sweat is mainly

01:31:15water mixed with proteins,

01:31:17sugars, ammonia

01:31:19and many other elements.

01:31:21It even contains tiny amounts of metals

01:31:23in the state of trace, such as copper,

01:31:25zinc, nickel, iron, etc.

01:31:27What gives a salty taste to sweat

01:31:29is the sodium it contains.

01:31:31In addition, the more salt you eat,

01:31:33the saltier your sweat is.

01:31:35Your body tries to get rid of excess

01:31:37and the fastest way is to sweat.

01:31:39If you walk at 3 km per hour,

01:31:41you have to do it for 40 hours in a row

01:31:43to lose a kilo.

01:31:45And it would take you

01:31:47518 days and 8 hours

01:31:49to go around the equator.

01:31:51The human brain is not really wax.

01:31:53It contains fat,

01:31:55skin cells, sweat and dirt.

01:31:57Your brain becomes three times bigger

01:31:59during the first year of your life

01:32:01and reaches its full maturity at the age of 25.

01:32:03It is composed of 60% fat.

01:32:05It generates about

01:32:0723 watts of electric energy,

01:32:09which is enough to run

01:32:11a small light bulb.

01:32:13Humans can't really do

01:32:15several tasks at once.

01:32:17Your brain can't do more than one action at a time.

01:32:19It goes from one to the other,

01:32:21which doesn't save time, as you might think.

01:32:23But it increases the chance

01:32:25that you make a mistake

01:32:27and makes the process longer.

01:32:29When you have an exam to pass

01:32:31or you are at work

01:32:33and you try to focus on an important task,

01:32:35try chewing gum.

01:32:37Studies have shown that it can help you

01:32:39to stay focused longer

01:32:41on tasks that require all your attention.

01:32:43Some even say it's a better help

01:32:45to the exams than caffeine.

01:32:47There is nothing special about chewing gum,

01:32:49but the act of chewing wakes your brain.

01:32:51However, the effect doesn't last long,

01:32:53as embryos develop fingerprints

01:32:55at the age of 3 months.

01:32:57Your bones are 4 times harder than concrete.

01:32:59Your body's strongest bone

01:33:01is the femur.

01:33:03It can withstand up to 30 times the weight

01:33:05of an adult.

01:33:07What's even crazier is that our bones

01:33:09are composed of a composite material,

01:33:11which means they are both hard and elastic.

01:33:13Sunburns are the result

01:33:15of exposure to radiation.

01:33:17When your body's natural defense mechanism

01:33:19is overloaded by trying to fight UV rays,

01:33:21a toxic reaction occurs

01:33:23and causes sunburns.

01:33:25Chicken's skin is an evolutionary reflex

01:33:27inherited from our ancestors.

01:33:29The release of adrenaline

01:33:31made their hair stand up

01:33:33and they looked more frightening

01:33:35to predators approaching.

01:33:37Your body produces 0.5 to 1.5 liters

01:33:39of saliva per day.

01:33:41It helps you digest food

01:33:43and fight infections.

01:33:45You also have a lot of bacteria in your mouth.

01:33:47The average amount of bacteria

01:33:49in a person is almost the same

01:33:51as the number of people living on Earth.

01:33:53Every human has

01:33:55about 150,000 hairs on their head.

01:33:57Each strand weighs

01:33:59about 13 millimeters per month.

01:34:01If we added the growth of each strand,

01:34:03we could reach

01:34:0516 kilometers in just one year.

01:34:07Your hair is also much more resistant

01:34:09than you think.

01:34:11A single strand can support 85 grams,

01:34:13which corresponds to the weight of an apple.

01:34:15If we combined the strength of all the hairs

01:34:17it could support the weight of two elephants.

01:34:19The sound of your heart beating

01:34:21is the sound of the valves opening

01:34:23and closing.

01:34:25Your heart does not respond to these cells,

01:34:27except if you have an injury.

01:34:29Your corneas are the only parts

01:34:31of your body that do not receive blood.

01:34:33They receive oxygen

01:34:35directly from the air.

01:34:37When you are sitting or standing,

01:34:39it is easier for you to remember

01:34:41positive memories that do you good.

01:34:43Some people think it's because

01:34:45the flat back stimulates blood circulation

01:34:47and your brain receives more oxygen,

01:34:49which helps it to function better.

01:34:53Man, who has the deepest voice in the world,

01:34:55can produce sounds that humans,

01:34:57including him, cannot hear at all.

01:35:01But elephants can hear these sounds.

01:35:03The veins look blue

01:35:05because the light must pass through layers

01:35:07of skin and fat to reach them.

01:35:09Your skin scatters a large part

01:35:11of the red portion of the white light

01:35:13to produce blood.

01:35:15There is only the blue light left

01:35:17to bounce back to your eyes.

01:35:19A person suffering from anosmia

01:35:21is unable to detect smells.

01:35:23Phantosmia is the opposite condition

01:35:25when a person smells a smell

01:35:27that is not really present.

01:35:29The human brain has 100 billion neurons.

01:35:31It is made up of 73% water

01:35:33and the same goes for the heart.

01:35:35That's why if your brain loses

01:35:37only 2% of the fluid,

01:35:39you start to feel tired.

01:35:41Your memory decreases your attention

01:35:43and deteriorates your mood.

01:35:45The oldest person

01:35:47to have blue eyes

01:35:49lived at the Stone Age 7,000 years ago.

01:35:51Your right kidney

01:35:53is probably smaller

01:35:55and is lower than your left kidney

01:35:57to make room for your liver.

01:35:59Your brain makes sure

01:36:01you don't drink too much or too little water.

01:36:03After swallowing fluid,

01:36:05your mouth and throat

01:36:07start to send signals to your brain

01:36:09to tell it to stop drinking.

01:36:11Otherwise, you will keep swallowing water

01:36:13for the 10 to 60 minutes

01:36:15it takes your fluid to reach your cells.

01:36:17Your eyes can see something

01:36:19for just 13 milliseconds.

01:36:21And your brain is already processing this image.

01:36:23An average eye blink

01:36:25lasts between 100 and 400 milliseconds.

01:36:27Even if the tongue

01:36:29is not the strongest muscle of your body,

01:36:31it never gets tired.

01:36:33It is because of the way it is designed.

01:36:35It is made up of 8 interlaced muscles.

01:36:37The tongue is the only muscle

01:36:39whose extremities are not connected to a bone.

01:36:41Other muscles connect

01:36:43two bones to two extremities

01:36:45because this is how we pull

01:36:47and make a movement.

01:36:49There are about 700 different species

01:36:51of bacteria in your mouth.

01:36:53More than 6 billion of them live there.

01:36:55Your skin is your largest organ.

01:36:57It can cover the surface

01:36:59of two bath towels.

01:37:01It represents about 16%

01:37:03of your body weight

01:37:05in square meters.

01:37:07If you were to type 60 words per minute

01:37:09for 8 hours a day,

01:37:11it would take you 50 years

01:37:13to type the human genome.

01:37:15You get tired faster when it is hot.

01:37:17This happens because your body

01:37:19tries to keep cool,

01:37:21which requires a lot of additional work.

01:37:23You are therefore tired

01:37:25even if you do not do anything physically demanding.

01:37:27Your body has 78 organs,

01:37:29but only 5 of them

01:37:31are essential to your survival.

01:37:33The brain, the liver, the kidneys,

01:37:35the lungs and the heart.

01:37:37The phone is ringing.

01:37:39It must be something urgent.

01:37:41But all the gadgets in the house

01:37:43are silent.

01:37:45It is your ears that are ringing.

01:37:47You can also hear whistling,

01:37:49rumbling and even rustling.

01:37:51But all these noises

01:37:53have no external source.

01:37:55This is why they are called

01:37:57ghost sounds.

01:37:59They can occur in one or two ears

01:38:01constantly or from time to time.

01:38:03They are generally more noticeable at night

01:38:05when nothing distracts you.

01:38:07Women have more taste buds

01:38:09at the surface of their tongues than men.

01:38:11This is one of the reasons why

01:38:1335% of women and only 15%

01:38:15of men are super-tasters.

01:38:17These are people who feel the flavors

01:38:19more strongly than others.

01:38:21Left-handed people prefer

01:38:23to chew on the left side

01:38:25and right-handed people,

01:38:27you guessed it, on the right side.

01:38:29If your fingerprints are damaged,

01:38:31they will grow back with the same unique pattern.

01:38:33When they breathe,

01:38:35a single lung uses

01:38:37only 5% of the oxygen you inhaled.

01:38:41About 6% of people

01:38:43can quickly vibrate

01:38:45their front and back eyeballs.

01:38:47This does not mean

01:38:49that something is wrong with their eyes.

01:38:51It's just a unique trick

01:38:53they are able to perform.

01:38:55Your bones are designed to be

01:38:57able to absorb

01:38:592 or even 3 times your weight.

01:39:01It's impressive, but your teeth

01:39:03are even stronger.

01:39:05When you bite something,

01:39:07your teeth can exert an incredible pressure

01:39:09up to 90 kg.

01:39:11Besides, the enamel is considered

01:39:13as part of your skeletal system.

01:39:15Your stomach has an incredible

01:39:17capacity, up to 2 liters of liquid,

01:39:19equivalent to a large bottle of Coca-Cola.

01:39:21It is quite difficult to estimate

01:39:23the amount of hard food

01:39:25in your stomach,

01:39:27because the food is transformed by your teeth

01:39:29before getting inside.

01:39:31There is certainly not enough room for a turkey,

01:39:33but a good-sized chicken

01:39:35will probably fit in there.

01:39:37Every time you turn your hand,

01:39:39the waters inside cross.

01:39:41Hold your forearm and check.

01:39:43Now you know where exactly

01:39:45your stomach is.

01:39:47If you think it's in your stomach,

01:39:49sorry, but you're wrong.

01:39:51It's here, hidden between your ribs.

01:39:53But what is less known

01:39:55is that your bones are also part of it.

01:39:57About 25% of the bone mass

01:39:59is composed of water.

01:40:01Scientists think the appendix

01:40:03is doomed to disappear.

01:40:05No one really knows why we need it,

01:40:07but some researchers claim

01:40:09that it helped our ancestors

01:40:11to assimilate the tree bark they ate.

01:40:13As it is no longer part of our daily diet,

01:40:15the appendix could disappear from our body

01:40:17without any consequences.

01:40:19The human eye has a certain resemblance

01:40:21to a car.

01:40:23They both need different liquids

01:40:25to function properly.

01:40:27An engine needs fuel,

01:40:29and an eye needs tears.

01:40:31To function properly,

01:40:33tears must be well distributed

01:40:35throughout the eye.

01:40:37That's why we blink

01:40:39up to 20,000 times a day.

01:40:41So we can say that the eyelid

01:40:43plays a bit the same role

01:40:45as the windshield wiper.

01:40:47Almost all of our body

01:40:49consists of blood and the cornea of the eye.

01:40:51Instead, it is fed by tears

01:40:53and the liquid in front of your eyes.

01:40:55If you never knew you had

01:40:57a personal bodyguard,

01:40:59think about it more seriously.

01:41:01Your liver is your personal safety agent

01:41:03that protects you from toxins

01:41:05and many other things you don't want to have.

01:41:07It is almost indestructible

01:41:09and can regenerate.

01:41:11When you blush,

01:41:13it indicates an increase

01:41:15in blood flow in your body.

01:41:17That's because it contains a lot of blood vessels.

01:41:19And when there is more blood than usual,

01:41:21it turns red.

01:41:23About 43% of your body really belongs to you.

01:41:25You are made up of more than 50%

01:41:27of tiny little creatures

01:41:29that live mainly in your intestine

01:41:31and other parts of your body

01:41:33without ever leaving it.

01:41:35However, even if your own cells are less numerous

01:41:37than microbial cells,

01:41:39you still have about 100 trillion.

01:41:41Don't hesitate to count them if you don't believe it.

01:41:43The wall of your stomach is renewed

01:41:45every four days

01:41:47to prevent it from eating itself.

01:41:49The digestive acids we have

01:41:51can be very harmful.

01:41:53One thing that surely rests

01:41:55while you sleep is your nose.

01:41:57You won't feel anything unpleasant in your sleep.

01:41:59The fact is that your odor

01:42:01is practically deactivated at night.

01:42:03If there is a nauseating smell in your room,

01:42:05you won't even be disturbed.

01:42:07We can accidentally digest

01:42:09small plastic objects,

01:42:11glass, coins and many others.

01:42:13Digestive system in 48 hours.

01:42:15No need to do the test,

01:42:17you can trust us on this.

01:42:19Scientists used to think

01:42:21that we could distinguish about 10,000 odors.

01:42:23But recent research has shown

01:42:25that we are actually able to distinguish

01:42:27more than a trillion.

01:42:29We also remember it better than anything else.

01:42:31And odors can even evoke distant memories.

01:42:33We can digest tiny amounts of plastic,

01:42:35but the human digestive system

01:42:37can't really stand grass.

01:42:39Animals that brood have special teeth

01:42:41and several stomachs

01:42:43to treat leaves and raw grass,

01:42:45while we don't have any of that.

01:42:47Among mammals, only humans

01:42:49can walk only on their two hind limbs

01:42:51and keep this posture all their lives.

01:42:53You could argue that kangaroos

01:42:55or gorillas move in the same way,

01:42:57but the first use their tails

01:42:59as a third leg,

01:43:01and the second use their long arms

01:43:03to keep their balance.

01:43:05The stomach is the most important defender

01:43:07of the immune system.

01:43:09The stomach kills dangerous food toxins,

01:43:11viruses and bacteria

01:43:13that enter through the food you eat.

01:43:15This acid can even digest the stomach itself,

01:43:17but the mucous protects it.

01:43:19Body fat is not totally bad.

01:43:21It serves as an insulating material,

01:43:23energy reserve and cushion.

01:43:25Your body sends the most fat

01:43:27in the region of your waist,

01:43:29because that's where your internal organs are.

01:43:31If something happens to you,

01:43:33this layer of fat could protect

01:43:35your vital organs from irreparable damage.

01:43:37We have two really fast muscles,

01:43:39which control the closure of the eyelids.

01:43:41These are even the fastest muscles

01:43:43of our body.

01:43:45The eyes are fragile and need to be protected.

01:43:47That's why when the reflex is triggered,

01:43:49these muscles close the eyes

01:43:51in about 100 milliseconds,

01:43:53or a tenth of a second.

01:43:55We only perceive blue,

01:43:57green and red.

01:43:59Everything else is a combination

01:44:01of these three nuances.

01:44:03It is impossible to calculate

01:44:05because each person has slight visual differences.

01:44:07But there are about a million

01:44:09combinations on average.

01:44:11Even if you brush your teeth twice a day

01:44:13and never forget to bathe your mouth,

01:44:15your mouth remains one of the dirtiest parts

01:44:17of the human body.

01:44:19Millions of bacteria live there.

01:44:21The good news is that most of these bacteria

01:44:23are good for the body and protect it

01:44:25from bad bacteria and viruses.

01:44:27The second dirtiest place is your navel.

01:44:29And that's probably because it's the first

01:44:31unknown place.

01:44:33It's really after our birth,

01:44:35so this neglected area accumulates

01:44:37all kinds of germs, sweat and dirt.

01:44:39The navel houses more than

01:44:412,300 bacterial species.

01:44:43And it needs special attention.

01:44:45Do you think you owe your solid hand

01:44:47to your acidic weight training sessions?

01:44:49Well, you should rather thank

01:44:51your little finger.

01:44:53Well, maybe not, but the ear is the strongest finger.

01:44:55It is responsible for 50%

01:44:57of the strength of your hand.

01:44:59However, the most used finger is the thumb.

01:45:01It alone ensures 40%

01:45:03of the action of the hand.

01:45:05This makes it probably the most important finger too.

01:45:07As for your toes,

01:45:09they support about 40% of your weight.

01:45:11If you've already heard that humans

01:45:13don't really need their toes,

01:45:15that's wrong.

01:45:17They are also the main support of walking.

01:45:19Tomatoes have more genes than humans.

01:45:21But that shouldn't worry you,

01:45:23because it's not the number of genes that count,

01:45:25but the complexity of their connection.

01:45:27Nails don't just help us open plastic packages

01:45:29and take off stickers.

01:45:31If you didn't have a rigid structure

01:45:33against which to press,

01:45:35you wouldn't be able to judge the firmness

01:45:37with which you have to hold anything.

01:45:39The color of our hair is easily explained

01:45:41by genes.

01:45:43There are no more than 2% of people in the world

01:45:45with naturally red hair.

01:45:47They are followed by blondes, about 3%,

01:45:49and by all shades of brown,

01:45:51only about 11%.

01:45:53The vast majority of humans have black hair.

01:45:55Your hair can stop growing

01:45:57at any time.

01:45:59It usually grows for 2 to 7 years,

01:46:01and it usually doesn't exceed 106 cm.

01:46:03However, a Chinese woman

01:46:05broke the record for the longest hair

01:46:07of all time.

01:46:09In 2004, her hair was 5.60 meters long.

01:46:11Even better than Réponse.

01:46:13When we laugh,

01:46:15think, look at something,

01:46:17dream, move, or do any other activity

01:46:19with our body,

01:46:21small electrical and chemical signals

01:46:23circulate between neurons along these connections.

01:46:25Our brain is always active,

01:46:27sometimes even more when we sleep than when we are awake.

01:46:29And during this process,

01:46:31neurons produce and send more information

01:46:33than all the phones in the world.

01:46:35You are sitting somewhere outside

01:46:37and an insect lands on your leg.

01:46:39Your skin has sensory neurons

01:46:41and they quickly send the message

01:46:43to your brain at an impressive speed

01:46:45of 193 km per hour.

01:46:47The brain sends the message back to your leg

01:46:49so that it shakes the insect very quickly.

01:46:51And the speed at which the information travels

01:46:53is even faster, 320 km per hour.

01:46:55Your toes grow about four times

01:46:57as fast as your fingers.

01:46:59This happens because we do more

01:47:01with our hands than with our feet

01:47:03and so we damage our fingernails more.

01:47:05There is a good chance

01:47:07that your right hand houses different types

01:47:09of microbes than your left hand.

01:47:11This happens because they cover our skin

01:47:13from head to toe and their variety

01:47:15depends on the thickness of our skin,

01:47:17humidity, temperature, texture,

01:47:19and chemistry, which can change

01:47:21when we use our right and left hands

01:47:23in different ways.

01:47:25Our nails and hair are made of keratin,

01:47:27a material that can also be found

01:47:29in some parts of the body of other animals,

01:47:31such as claws, soles, horns,

01:47:33wool, fur, feathers,

01:47:35beaks, turtle shells,

01:47:37or porcupine spikes.

01:47:39Our body is made of star dust.

01:47:41The most complex elements

01:47:43of our body can only come

01:47:45from supernovas.

01:47:47The first stars were only gaseous amalgams

01:47:49that were pulled together and at some point

01:47:51started the combustion process.

01:47:53This eventually led to a nuclear reaction

01:47:55in its center.

01:47:57The stars that were there just after the Big Bang

01:47:59were more than 50 times bigger

01:48:01than our current sun.

01:48:03Inside it, there was a constant process

01:48:05of making elements, and these big stars

01:48:07burned their fuel faster.

01:48:09Most of the elements of the human body

01:48:11were formed in these stars for billions of years.

01:48:13And so we can say that

01:48:15a part of you is immortal.

01:48:17Not bad, isn't it?

01:48:19Trap question.

01:48:21Do you think you know everything about your own body?

01:48:25Do you know, for example, that 25%

01:48:27of an adult's bones are in his feet?

01:48:29Or that the taste buds

01:48:31are not actually these little bumps on your tongue?

01:48:33Get ready to take a full look.

01:48:37Don't worry, we're not going to touch your eyes.

01:48:39Because this is not a surgery channel.

01:48:41At least, not yet.

01:48:43We're just going to show you

01:48:45a crowd of unusual biological facts

01:48:47about the human body that you probably didn't suspect.

01:48:49Your stomach produces a new

01:48:51lining every 3 to 4 days.

01:48:53In this way, your body prevents

01:48:55your stomach from self-digesting.

01:48:57Your brain contains more than

01:48:5986 billion nerve cells

01:49:01that are connected to each other

01:49:03by 100 trillion connections.

01:49:05That's a lot more than the number of stars

01:49:07in our Milky Way galaxy.

01:49:09Besides, if you wanted to count

01:49:11all these nerve cells in your brain,

01:49:13it would take you up to 3,000 years.

01:49:15So you'd better get started now.

01:49:17Your nails grow faster

01:49:19on your dominant hand.

01:49:21And you'll have to cut them more often.

01:49:23They grow as fast in the summer

01:49:25and during the day.

01:49:27When your brain sends messages

01:49:29to different parts of your body,

01:49:31the signals travel along your nerves

01:49:33at a speed that can reach you

01:49:35430 km per hour.

01:49:37It's much faster than a sports car.

01:49:39People spend more than 4 years of their lives

01:49:41eating.

01:49:43And even more when they have to wait

01:49:45for their meal at the restaurant.

01:49:47The fastest muscles in your body

01:49:49are the ones that make you blink.

01:49:51Their contraction speed allows you

01:49:53to blink less than a hundredth of a second.

01:49:55In one day, you can blink

01:49:57more than 15,000 times.

01:49:59During its lifetime,

01:50:01an average person eats

01:50:03more than 45 tons of food.

01:50:05That's more than the weight of 7 elephants.

01:50:07And how do you eat an elephant?

01:50:09Yes, a bite at a time.

01:50:11If someone decided to

01:50:13run human DNA,

01:50:15it would extend over 16 billion kilometers.

01:50:17That's 40,000 times the distance

01:50:19between the Earth and the Moon.

01:50:21If you're not insomniac,

01:50:23it's likely that you spend

01:50:25about a third of your life sleeping.

01:50:27But there are creatures that sleep even more.

01:50:29For example, for a dog,

01:50:31this time represents 44% of its life.

01:50:33And for a python, 75%.

01:50:35In one day,

01:50:37all the blood in your body

01:50:39travels more than 19,000 kilometers.

01:50:41That's as much as half

01:50:43the circumference of the Earth.

01:50:45Your skeleton completely renews itself

01:50:47in 10 years, without surgery.

01:50:49An adult uses

01:50:51about 200 muscles

01:50:53to take a single step.

01:50:55So even when walking,

01:50:57you exercise.

01:50:59Every minute, your body

01:51:01loses more than 3,000 skin cells.

01:51:03That's almost 200,000 skin cells per hour

01:51:05and more than 5 kilos per year.

01:51:07That's at least 7 pounds for your diet.

01:51:09But don't worry,

01:51:11you still have about

01:51:13300 million skin cells at any time.

01:51:15In addition,

01:51:17your skin completely renews itself

01:51:19every 28 to 30 days.

01:51:21The liver is the only human organ

01:51:23that can regenerate completely.

01:51:2525% of the liver's initial weight

01:51:27is enough for it to return to its normal size.

01:51:29Skin cells create

01:51:31a lot of dust,

01:51:33not only under your bed,

01:51:35but also in the Earth's atmosphere.

01:51:37If someone gathered all the skin cells

01:51:39floating in the air,

01:51:41this dust would weigh up to 1 billion tons,

01:51:43or 150 times

01:51:45the weight of the Great Pyramid.

01:51:47What do you think of this comparison?

01:51:49You can't see your taste buds

01:51:51with the naked eye because they're too small.

01:51:53The little bumps on the tongue

01:51:55that most people take for taste buds

01:51:57are called papillae.

01:51:59The real taste buds

01:52:01are at the top of these projections

01:52:03that look like hair.

01:52:05By the way, taste buds also have

01:52:07a very short life cycle.

01:52:09They don't live more than 10 to 14 days.

01:52:11On average,

01:52:13a person has more than 100,000 hairs on their head.

01:52:15And since these hairs grow

01:52:17about 15 cm per year,

01:52:19this means that they will grow

01:52:2112 meters in a lifetime.

01:52:23Some people can hear their eyeballs

01:52:25moving in orbit.

01:52:27Unlike the other parts of your body,

01:52:29your eyes and nose never stop growing.

01:52:31Your skin cracks

01:52:33if you stay in the water for too long.

01:52:35Not because it absorbs water,

01:52:37but because when your body is wet,

01:52:39your fingers and your cracked toes

01:52:41allow you to have better adhesion.

01:52:43Just like new and well-worn tires

01:52:45adhere better to the road.

01:52:47Your eyes are an incredible tool.

01:52:49They can distinguish

01:52:5110 million different colors.

01:52:53Your brain uses more than 20%

01:52:55of your body's energy

01:52:57when you rest.

01:52:59When you sleep,

01:53:01it still consumes almost as much energy

01:53:03as when you wake up.

01:53:05It also burns about 330 calories a day.

01:53:07An adult has about 25%

01:53:09of all his water in his feet.

01:53:11Most of them are tiny but crucial.

01:53:13If these waters are not aligned,

01:53:15the rest of the body is not either.

01:53:17You breathe about 20,000 times a day.

01:53:19Try not to stop.

01:53:21Today,

01:53:23you will beat your personal record

01:53:25in breathing,

01:53:27and you will surpass it tomorrow.

01:53:29Human bones are a real paradox.

01:53:31They are almost 5 times more resistant

01:53:33than a steel bar of the same width.

01:53:35But they can break at impact

01:53:37and are rather fragile.

01:53:39Fingers have no muscles

01:53:41that can move them.

01:53:43All the muscles that move

01:53:45the joints of the fingers

01:53:47are located in the forearm and the palm.

01:53:49Your body contains more than

01:53:5137 trillion cells.

01:53:53This means that there are

01:53:555 times more cells in your body

01:53:57than inhabitants on our planet.

01:53:59This surely depends on your lifestyle

01:54:01and the frequency of your travels,

01:54:03but a person walks on average

01:54:05up to 180,000 km in his life.

01:54:07That is, twice as much as the distance

01:54:09between the Earth and the Moon,

01:54:11and more than 4 times more

01:54:13than the circumference of the Earth.

01:54:15If a person is affected by anosmia,

01:54:17also called odour sensitivity,

01:54:19it cannot distinguish and detect odours.

01:54:21But it can still emit it,

01:54:23without realizing it.

01:54:25You start to feel thirsty

01:54:27when the loss of water represents

01:54:291% of your body weight.

01:54:31More than 5% and you risk fainting.

01:54:33A loss of water greater than 10%

01:54:35of the body weight

01:54:37and dehydration can be fatal.

01:54:39The most powerful muscle of your body

01:54:41related to its weight

01:54:43is the muscle of your jaw.

01:54:45At any time,

01:54:4750,000 cells of your body

01:54:49are replaced by new ones.

01:54:51At the end of her life,

01:54:53a person can remember

01:54:55on average 150 trillion pieces of information.

01:54:57Except maybe the place

01:54:59where she left her car keys.

01:55:01Even if the fingerprints are very damaged,

01:55:03they grow back with their original pattern.

01:55:05Your most powerful

01:55:07internal organ

01:55:09can travel at a speed of more than

01:55:11160 km per hour,

01:55:13almost as fast as a free-falling paratrooper.

01:55:15A person has on average

01:55:174 brains in each eyebrow.

01:55:19These brains are completely renewed

01:55:21every 4 months.

01:55:23The memory capacity of your brain

01:55:25is equivalent to about 4 Teraoctets

01:55:27on a hard drive,

01:55:29which represents more than 8 million photos.

01:55:31Humans are the only living creatures

01:55:33that can naturally sleep on their back.

01:55:35Even monkeys generally sleep

01:55:37in a sitting position,

01:55:39leaning on something.

01:55:41Your longest bone is the femur

01:55:43and the smallest is in the ear.

01:55:45It is smaller than a grain of rice.

01:55:47The largest organ of your body

01:55:49is your skin.

01:55:51Although it is thin,

01:55:53it weighs a surprising weight of 4 to 5 kg,

01:55:55which is the weight of a well-fed

01:55:57and healthy cat.

01:55:59Your skull may look like it is made

01:56:01of a single piece, but in reality

01:56:03it is composed of 29 different bones.

01:56:05The only part of your body

01:56:07that cannot heal itself

01:56:09is all of your teeth.

01:56:11What a shame!

01:56:13Most of their food

01:56:15is on the right side of their mouth,

01:56:17while lefties opt for,

01:56:19you guessed it,

01:56:21the left side.

01:56:23Among all the people

01:56:25who can move their ears,

01:56:27only 30% can move

01:56:29a single ear.

01:56:31What a talent!

01:56:33Each person has faucets

01:56:35in the lower back,

01:56:37but in some people

01:56:39they are more pronounced

01:56:41Your right lung

01:56:43is smaller than the left one

01:56:45because it must leave room for your liver.

01:56:47The left lung,

01:56:49on the other hand,

01:56:51is narrower because it must make room

01:56:53for the heart.

01:56:55The lungs of a man

01:56:57can usually contain

01:56:59more air than that of a woman.

01:57:01Surprisingly,

01:57:03you burn more calories

01:57:05when you sleep

01:57:07than when you watch TV.

01:57:09Your hair grows twice as fast

01:57:11when you travel by plane.

01:57:13This is due to the higher

01:57:15atmospheric pressure.

01:57:17The muscles that help your eyes

01:57:19to concentrate

01:57:21do about 100,000 movements per day.

01:57:23If you wanted to move

01:57:25as much as your legs,

01:57:27you would have to walk 80 km.

01:57:29When you listen to music,

01:57:31the beats of your heart

01:57:33synchronize with it.

01:57:35There are more cells

01:57:37than there are stars in the Milky Way.

01:57:39If you decided to count them all,

01:57:41it would take you 3,000 years.

01:57:43To make it easier for you,

01:57:45know that you have about 100 billion neurons

01:57:47inside your cranial box.

01:57:49The brain can't really feel pain.

01:57:51It does have a pain center,

01:57:53but it doesn't have

01:57:55a pain receptor itself.

01:57:57When your head hurts,

01:57:59you can feel it through the nerves,

01:58:01tissues and blood vessels

01:58:03that surround your brain.

01:58:05Your work memory

01:58:07is an essential thing

01:58:09that you need to do

01:58:11almost all your daily activities,

01:58:13including basic conversations,

01:58:15surfing the Internet

01:58:17and even petting your dog.

01:58:19Our strongest memories

01:58:21are often false.

01:58:23The central memory

01:58:25gives us the confidence

01:58:27to believe that we remember everything,

01:58:29even if most of the details

01:58:31are actually invented by our mind.

01:58:33When we communicate with our body,

01:58:35small electrical and chemical signals

01:58:37circulate between neurons

01:58:39along connections.

01:58:41Thanks to this,

01:58:43our neurons produce and send more information

01:58:45than all the phones in the world.

01:58:47Imagine that you are sitting somewhere outside

01:58:49and an insect lands on your leg.

01:58:51Your skin has sensory neurons

01:58:53and they quickly send the message

01:58:55to your brain

01:58:57at an impressive speed

01:58:59of 193 km per hour.

01:59:01Our brain can store only one octet

01:59:03in its short-term memory.

01:59:05Don't even think about comparing

01:59:07your brain to the capacity of a phone,

01:59:09not even the one you had in 2005.

01:59:11That's why it's hard for you

01:59:13to learn a simple phone number

01:59:15by heart.

01:59:17Our short-term memory

01:59:19works like a blackboard.

01:59:21You can save some information

01:59:23but sooner or later

01:59:25you will run out of information.

01:59:27Your brain is like a blackboard

01:59:29you can save some information

01:59:31but sooner or later

01:59:33you will run out of information.

01:59:35To check the capacity of your short-term memory,

01:59:37do this test.

01:59:39Ask a friend to write a list of 10 words

01:59:41and read it to you.

01:59:43Most people remember

01:59:45a maximum of 7 elements of the list.

01:59:47Synesthesia is a special and rare ability

01:59:49that allows people to taste music

01:59:51or hear colors.

01:59:53Only 1 person out of 2000

01:59:55is affected.

01:59:57People have more senses than that.

01:59:59For example,

02:00:01proprioception is the ability

02:00:03to be aware of parts of your body

02:00:05and their position,

02:00:07even if you don't see them.

02:00:09For example,

02:00:11if your arm is behind your back,

02:00:13you know it's there.

02:00:15If you were a peacock,

02:00:17you wouldn't know it

02:00:19because these creatures don't know

02:00:21that their arms exist

02:00:23if they don't see them.

02:00:25In addition to balance,

02:00:27there is also noniception,

02:00:29which means you can feel pain.

02:00:31Or chronoception,

02:00:33which is the way you can perceive

02:00:35the passing of time.

02:00:37And in the animal kingdom,

02:00:39there are still many senses

02:00:41that humans don't have.

02:00:43You can't remember an isolated memory

02:00:45when you try to think of a detail,

02:00:47like the color of the T-shirt

02:00:49your friend wore last week.

02:00:51You will also remember other details,

02:00:53such as the hippocampus.

02:00:55The hippocampus is the area of your brain

02:00:57that stores memories.

02:00:59It compresses them together,

02:01:01so to speak,

02:01:03including multiple small details.

02:01:05On average,

02:01:07gustatory papillae last 10 days.

02:01:09A theory affirms that déjà vu

02:01:11is a kind of offset

02:01:13in brain treatment.

02:01:15Scientists think it can happen

02:01:17when your brain transfers information

02:01:19from one side to the other

02:01:21Your brain receives the same information twice

02:01:23and treats it as the event

02:01:25that happened before.

02:01:27You can physically see your nose,

02:01:29but the brain chooses to ignore it.

02:01:31Otherwise, it would be an obstacle to your vision,

02:01:33and it wouldn't be very clear.

02:01:35Brain freeze is a headache

02:01:37caused by ice cream.

02:01:39It's the way your brain tells you to slow down,

02:01:41maybe even stop eating

02:01:43something so cold.

02:01:45People usually need 7 minutes

02:01:47to fall asleep.

02:01:49Imagine if you just ate a copycat meal.

02:01:51In the past, people dreamed

02:01:53much more in black and white than they do today.

02:01:55It's because they watched TV in black and white.

02:01:57About 12% of people can't dream

02:01:59in the color of our days.

02:02:01Just after you fall asleep,

02:02:03all your muscles relax at the same time.

02:02:05Your brain thinks you're about to fall

02:02:07and sends signals to all your muscles

02:02:09to wake them up.

02:02:11That's why you sometimes feel like you're falling.

02:02:13Even a hypnic shake

02:02:15is a sudden jump that you can feel

02:02:17during the non-REM sleep phase.

02:02:19If you sleep,

02:02:21it doesn't mean your whole body is sleeping.

02:02:23In fact, it happens that your brain

02:02:25has to work even harder

02:02:27when you snore.

02:02:29It has to process tons of information,

02:02:31and reports usually take a lot of time.

02:02:33When you wake up,

02:02:35you'll have forgotten 50% of your last dream.

02:02:37After 10 minutes,

02:02:39you'll have forgotten 90%.

02:02:41When you blush,

02:02:43the wall of your stomach blushes

02:02:45because your sympathetic nervous system

02:02:47causes an increase in blood flow

02:02:49throughout your body.

02:02:51The follicles of your hair

02:02:53have the same receptors as your nasal voices.

02:02:55That's why your hair can also detect perfumes.

02:02:57Centella's wood can help you

02:02:59develop this super power.

02:03:01Your nose rests while you sleep.

02:03:03Surprisingly, your smell goes away

02:03:05during the night.

02:03:07You wouldn't even be bothered

02:03:09if there was a really bad smell in your room.

02:03:11When you get older,

02:03:13your brain starts to shrink progressively.

02:03:15At 75, it's much smaller than at 30.

02:03:17And it starts shrinking

02:03:19at the age of 40.

02:03:21This happens to everyone

02:03:23and doesn't affect your mental abilities.

02:03:25You may have tried,

02:03:27but you'll never be able to snore.

02:03:29It's because your brain prepares your body

02:03:31for snoring and helps you avoid

02:03:33the typical reaction of laughter.

02:03:35We only recognize blue,

02:03:37yellow and red colors.

02:03:39Everything else is a combination

02:03:41and we can calculate the number of these combinations

02:03:43that the human eye perceives.

02:03:45Each person has slightly different vision.

02:03:47But it's about a million combinations on average.

02:03:49Be careful,

02:03:51your skull is not made of a single bone.

02:03:53It's actually made of 28 different bones

02:03:55many of which are welded together

02:03:57to protect your brain.

02:03:59The strongest muscles of your body

02:04:01are not in your arms or legs.

02:04:03They are in your head.

02:04:05The masseter is the main muscle

02:04:07responsible for chewing.

02:04:09And these famous muscles

02:04:11that allow you to move your ears

02:04:13are temporal muscles

02:04:15located above your temples.

02:04:17They also help chew your food.

02:04:19Now we have two very fast muscles

02:04:21that control the closure of the eyelids.

02:04:23These are the fastest muscles of our body.

02:04:25The eyes are fragile and need to be protected.

02:04:27So the reflex that protects them

02:04:29must be as fast as lightning.

02:04:31These muscles can close your eyelids

02:04:33in less than a tenth of a second.

02:04:35Our body is made of star dust.

02:04:37The most complex elements of our body

02:04:39could only appear

02:04:41thanks to supernovas.

02:04:43The first stars were only gaseous clouds

02:04:45that were gathered and at some point

02:04:47started a combustion process.

02:04:49This eventually led

02:04:51to a nuclear reaction in their center.

02:04:53The stars that were there

02:04:55just after the Big Bang

02:04:57were more than 50 times larger

02:04:59than our current sun.

02:05:01Inside it, there was a constant process

02:05:03of making elements

02:05:05invisible more quickly.

02:05:07Most of the elements of the human body

02:05:09have been formed in these stars

02:05:11over billions of years.

02:05:13So we can realistically say

02:05:15that a part of you is immortal.

02:05:17Stylish, isn't it?

02:05:19And...

02:05:21there!

02:05:23Look, it's me on a roller coaster.

02:05:25Totally impassive.

02:05:27As if I were on a children's ride.

02:05:29And not on the world's fastest Grand VIII.

02:05:31But let's start at the beginning.

02:05:33Roller coaster until two months ago.

02:05:35I'm late for work

02:05:37for the third time this week.

02:05:39And this time, I'm definitely

02:05:41going to get fired.

02:05:43Well, I didn't really like

02:05:45this boring office job anyway.

02:05:47You know what I like the most?

02:05:49The roller coasters.

02:05:51So when I saw a job offer

02:05:53for roller coaster testers,

02:05:55I immediately called them.

02:05:57And my new job was to test

02:05:59all the roller coasters

02:06:01for a duration of 60 days.

02:06:03And I was going to do roller coasters every day

02:06:05for the next two months.

02:06:07Day 1. I wasn't the only one

02:06:09to get the job.

02:06:11It turns out they hired different people

02:06:13to test the roller coasters.

02:06:15Men and women, old and young,

02:06:17young and old.

02:06:19We were supposed to just go around

02:06:21each ride and then report our feelings.

02:06:23The work started in New Jersey

02:06:25with Kingdaka, the highest roller coaster

02:06:27in the world.

02:06:29Which is higher than the Statue of Liberty

02:06:31or the Great Pyramid of Giza.

02:06:33Day 2. We went south

02:06:35and tested the rides in Pennsylvania,

02:06:37Ohio and Virginia.

02:06:39Some weren't very fun

02:06:41and I need something more exciting.

02:06:43I'm overflowing with energy

02:06:45and when I get back to the hotel

02:06:47after a long day at work,

02:06:49I'm not tired at all

02:06:51and I even do a little sport later in the evening.

02:06:53Anyway, as fun as roller coasters are for us,

02:06:55the brain of course sees

02:06:57the fact of being suspended

02:06:59hundreds of meters above the ground

02:07:01without being able to predict

02:07:03which side we will be projected on.

02:07:05When you are faced with a situation

02:07:07that seems dangerous,

02:07:09your brain releases adrenaline

02:07:11which gives you energy to help you face it.

02:07:13It also helps you manage stress,

02:07:15even minor.

02:07:17Not three days ago,

02:07:19I was rather overwhelmed by my own life.

02:07:21I was worried about having to look for a job

02:07:23and a new place to stay.

02:07:25When you do roller coasters,

02:07:27your heart rate and blood pressure increase.

02:07:29In addition, blood circulation improves

02:07:31in your body,

02:07:33which allows a greater flow of oxygen.

02:07:35Maybe that's why I feel so good.

02:07:37Whatever the reason,

02:07:39these rides are wonderful.

02:07:41Day 8

02:07:43Today, we spent part of the day

02:07:45at Six Flags,

02:07:47the most famous theme park in Latin America.

02:07:49My favorite ride there was

02:07:51Superman El Ultimo Escape.

02:07:53The ride reaches

02:07:55a speed of 120 km per hour

02:07:57and has two 360-degree loops.

02:07:59Now we have finished

02:08:01with North America

02:08:03and we are heading for South America

02:08:05where we will spend a week.

02:08:07I don't even feel tired,

02:08:09even if I literally live in trains and planes

02:08:11traveling from one theme park to another.

02:08:13And I still run these 15 km every day,

02:08:15which surprises me.

02:08:17We were also given a booklet

02:08:19to study the history of roller coasters.

02:08:21They were inspired by

02:08:23the 18th century sled races

02:08:25on snowy hills.

02:08:27This one was about 25 meters high

02:08:29and had a 50-degree slope.

02:08:31But the first Grand 8

02:08:33was built in France in 1804

02:08:35and it was a wheeled cart.

02:08:37Day 15

02:08:39We went to amusement parks

02:08:41in Brazil, Argentina and Chile.

02:08:43As a professional,

02:08:45I noticed that the catapult ride

02:08:47at Hopi Hari in Brazil was pretty nice.

02:08:49It has a vertical loop

02:08:51where you go first forward

02:08:53then suddenly backwards.

02:08:55We are finally heading for Europe.

02:08:57I have never been there

02:08:59and I am about to test all the best rides

02:09:01in France, Spain and many other countries.

02:09:03All this seems nice

02:09:05but in a way I am not very enthusiastic.

02:09:07Yes, they are fun

02:09:09but I'm starting to get a little tired.

02:09:11Well, maybe it's just the time lag.

02:09:13After South America,

02:09:15I noticed that the rides I like so much

02:09:17have stopped being so exciting.

02:09:19I don't feel so full of energy anymore.

02:09:21It's quite the opposite.

02:09:23When the working day is over,

02:09:25I am exhausted as never before.

02:09:27My brain had to get used to

02:09:29something unusual happening all the time

02:09:31and the rides become quite predictable.

02:09:33In addition, my neck and my back

02:09:35hurt me a little.

02:09:37All these brutal movements exert a strong pressure.

02:09:39And if most of my body

02:09:41is squeezed against a seat,

02:09:43my head is not.

02:09:45I have to work to support it

02:09:47and keep my head stable

02:09:49while the ride takes me in random directions.

02:09:51So it's not surprising

02:09:53that I'm starting to feel pain.

02:09:55In addition, my brain and my internal organs

02:09:57move a little inside me.

02:09:59In short, my body begins to feel

02:10:01that it needs a break.

02:10:03But I signed my contract

02:10:05and there are still six weeks to go.

02:10:07Day 30

02:10:09Europe was pretty nice.

02:10:11There were some really cool rides.

02:10:13I went to Gernan in Hansa Park, Germany.

02:10:15It starts completely in the dark

02:10:17and you ride while listening to epic music

02:10:19without having any idea

02:10:21what's going to happen next.

02:10:23I was even impressed.

02:10:25But I would have liked it more

02:10:27if it wasn't my 300th ride of the month.

02:10:29My back and neck still hurt me

02:10:31and I even had to buy ointment

02:10:33to feel better.

02:10:35But it didn't help.

02:10:37The next day, I go back to work.

02:10:39At the hotel, the only thing I do

02:10:41is try to fall asleep.

02:10:43Falling asleep has become very difficult

02:10:45because of the adrenaline.

02:10:47I relax and watch some movies.

02:10:49I would like to be able to stop the trip

02:10:51and go home to rest

02:10:53after being dragged here and there all day.

02:10:55But I can't.

02:10:57The next stop is Asia.

02:10:59Yippee, just a month to go.

02:11:01Day 45

02:11:03We went to the United Arab Emirates,

02:11:05Japan, China.

02:11:07Countries that have some of the best theme parks

02:11:09and that I have never been to.

02:11:11We did the fastest roller coasters in the world.

02:11:13They are called Formula Rossa

02:11:15and are located in the United Arab Emirates.

02:11:17They reach a speed of 240 kmh,

02:11:19which is much faster

02:11:21than any speed limit

02:11:23in most countries.

02:11:25Two months ago,

02:11:27I would have screamed like crazy

02:11:29if I had heard of such a thing.

02:11:31But now, I'm more worried

02:11:33about not collapsing.

02:11:35I don't even remember the last time

02:11:37I was on a roller coaster.

02:11:39I feel like my head is going to fall soon.

02:11:41Every time I'm on roller coasters,

02:11:43it becomes about five times heavier

02:11:45and my poor neck is all that supports it.

02:11:47This is due to the gravity

02:11:49that pulls me down,

02:11:51towards the center of the earth.

02:11:53When you are on roller coasters,

02:11:55the gravity is much stronger

02:11:57than when you just stand on the ground.

02:11:59And gravity is precisely

02:12:01what makes roller coasters work.

02:12:03They are designed in a distributed way.

02:12:05When you go up, you accumulate energy.

02:12:07Then, when you go down,

02:12:09the energy is released.

02:12:11Thus, the whole principle of roller coasters

02:12:13is a combination of going up and down,

02:12:15accumulating energy,

02:12:17and releasing energy.

02:12:19But as you go up,

02:12:21the force of gravity increases.

02:12:23Thus, 1g is the normal force

02:12:25that you feel when you stand on the ground.

02:12:27On average, a person can support

02:12:29a force of up to 5g.

02:12:31And that's about what you experience

02:12:33When you experience the gravitational force of 5g,

02:12:35you start to weigh 5 times more.

02:12:37So if you normally weigh 68 kilos,

02:12:39on a roller coaster,

02:12:41you will weigh 340 kilos.

02:12:43And your head will also weigh 5 times more.

02:12:45So yes,

02:12:47that's why my neck hurts.

02:12:49I'm going to get by.

02:12:51There are only two weeks left.

02:12:53Day 61

02:12:55I'm finally home.

02:12:57And I've never felt so good.

02:12:59I have my peace and the experience

02:13:01of being on all the best roller coasters in the world.

02:13:03But I'm so tired

02:13:05that I only worry about my bed

02:13:07and having peace.

02:13:09The good thing is that I no longer worry

02:13:11about this difficult period of my life before.

02:13:13And even if I feel tired,

02:13:15it was a rather healthy trip,

02:13:17as crazy as it may seem.

02:13:19However, I think I will stay away

02:13:21from roller coasters for a while.

02:13:23I had my dose for a while.

02:13:25Even twins

02:13:27don't have the same language.

02:13:29The language is made up of a set

02:13:31of powerful and mobile muscles

02:13:33that never tire.

02:13:35It contains between 5,000 and 10,000 taste buds.

02:13:37These little white and pink bumps

02:13:39located on your tongue are not taste buds,

02:13:41but each of them has

02:13:43several inside

02:13:45its superficial tissue.

02:13:47Evolution gave us taste buds

02:13:49so that we can stay alive.

02:13:51For example, bitter and bitter flavors

02:13:53can tell you that you are eating

02:13:55rotten food or toxic plants.

02:13:57The back of the tongue is more sensitive

02:13:59to bitter flavors, which explains

02:14:01why we can spit out bad food

02:14:03before swallowing it.

02:14:05Salty and sweet tastes allow us to know

02:14:07if the food is rich in nutrients.

02:14:09By the age of 60,

02:14:11most people lose half

02:14:13of their taste buds.

02:14:15Indeed, your tongue is pretty cool

02:14:17and its fingerprints can be used

02:14:19for biometric authentication,

02:14:21just like digital fingerprints.

02:14:23Each of us has a different and unique

02:14:25fingerprint.

02:14:27It's funny, isn't it?

02:14:29Why do we have digital fingerprints?

02:14:31Scientists had a lot of different

02:14:33theories on the subject,

02:14:35but today they believe that it is because

02:14:37digital fingerprints allow the skin

02:14:39to stretch more easily.

02:14:41Thus, they allow us to avoid bulbs,

02:14:43to protect the skin against injuries

02:14:45and to improve our sense of touch.

02:14:47Humans are not the only ones

02:14:49to have unique fingerprints.

02:14:51Koalas too.

02:14:53Most people are left-handed.

02:14:55Left-handed people chew food

02:14:57on the left side of their mouths,

02:14:59while right-handed people

02:15:01do it on the right side.

02:15:03We lose about 5 kg of skin cells

02:15:05each year, but don't worry,

02:15:07we replace them quickly.

02:15:09We produce every 15 seconds

02:15:11more cells than there are people

02:15:13living in the United States.

02:15:15Our body regenerates permanently

02:15:17and we replace our skin

02:15:19hundreds of times in a lifetime.

02:15:21Our teeth are similar to that of a shark.

02:15:23Their teeth also have a substance

02:15:25called dentin inside,

02:15:27and they are as solid as ours.

02:15:29Of course, theirs are more pointed

02:15:31and thicker, but still.

02:15:33Teeth are part of the human skeleton,

02:15:35even if they are not considered bones.

02:15:37You spend about 38 days of your life

02:15:39brushing your teeth, and guess what?

02:15:41It is possible that you brush them too much.

02:15:43Indeed, they can become more sensitive

02:15:45because they use natural enamel.

02:15:47Your left and right lungs are not

02:15:49the same size, because the left

02:15:51shares its space with the heart.

02:15:53Hooking is a symptom that almost

02:15:55all mammals know from time to time,

02:15:57and not just humans.

02:15:59The record was set by a man

02:16:01named Charles Osborne.

02:16:03He could not stop hooking

02:16:05for 68 years.

02:16:07It looks like no one told him

02:16:09about the thing that consists

02:16:11of eating sugar.

02:16:13There is only one part of your body

02:16:15that does not receive a regular blood supply,

02:16:17and your eyes can differentiate

02:16:1910 million different colors.

02:16:21The muscles that help our eyes

02:16:23to focus on something make

02:16:25about 100,000 movements per day.

02:16:27If you wanted the muscles of your legs

02:16:29to do the same job, you would have

02:16:31to walk a very long distance,

02:16:33at least 80 km.

02:16:35We can not all see the infrared light

02:16:37or the ultraviolet rays.

02:16:39Only 1% of us can.

02:16:41And if you can see one of these rays,

02:16:43it does not necessarily mean

02:16:45that you are related or at least

02:16:47share a very distant ancestor.

02:16:49Scientists have examined individuals

02:16:51with blue eyes from Turkey,

02:16:53India, Jordan and Scandinavia.

02:16:55They all had the same genetic sequence

02:16:57of the color of the eyes.

02:16:59They think that this characteristic

02:17:01comes from a person with blue eyes

02:17:03whose genes mutated about 10,000 years ago.

02:17:05Before that, the eyes were simply

02:17:07all different shades of brown.

02:17:09People with blue eyes are generally

02:17:11a little more sensitive to pain

02:17:13than people with blue eyes.

02:17:15This means that we do it more than

02:17:1710 million times a year.

02:17:19The fact that we look like sharks

02:17:21also concerns our eyes.

02:17:23If a part of your eye is damaged,

02:17:25you can replace it with that of a shark.

02:17:27It's convenient, isn't it?

02:17:29We can not be naked with our eyes open.

02:17:31Try it!

02:17:33It is very difficult to go beyond

02:17:35your natural reflexes.

02:17:37Eels also have their own life

02:17:39since a single eel lives about

02:17:41100 years.

02:17:43It's a reflex that comes from our ancestors.

02:17:45It occurs when we release

02:17:47adrenaline.

02:17:49It makes us straighten our hair

02:17:51on our head and helps us look

02:17:53more imposing.

02:17:55Scary, isn't it?

02:17:57The human brain has 100 billion neurons

02:17:59and a memory capacity

02:18:01equivalent to more than 4 teraoctets,

02:18:03which is huge.

02:18:05Your brain uses more than a quarter

02:18:07of the oxygen that your lungs absorb

02:18:09at more than 75%.

02:18:11It remains well hydrated.

02:18:13It is not true that humans

02:18:15use only 10% of their brain.

02:18:17We use much more than that,

02:18:19even during our sleep.

02:18:21Most of our brain is constantly active,

02:18:23but we do not require all parts

02:18:25at the same time.

02:18:27Of all species, humans are the only ones

02:18:29to be able to roar.

02:18:31This phenomenon is due to a boost in adrenaline.

02:18:33When you feel your face turn red,

02:18:35know that your stomach is also red.

02:18:37When you crack your joints,

02:18:39the sound you hear is that of tiny

02:18:41gas bubbles that are released.

02:18:43There are gas pockets trapped between your joints,

02:18:45so when you stretch them,

02:18:47they make a dry noise.

02:18:49Oh, how pleasant it is!

02:18:51We use 43 muscles

02:18:53when we frown,

02:18:55but only 17 when we smile,

02:18:57although scientists still do not agree on this point.

02:18:59Anyway, smile!

02:19:01An average person consumes

02:19:03about 33 tons of food in his life.

02:19:05It's the equivalent of 6 elephants!

02:19:07We breathe about 11,000 liters of air per day,

02:19:09but we cannot swallow

02:19:11and breathe at the same time.

02:19:13Most people need about 7 minutes

02:19:15to fall asleep,

02:19:17and we are about the only living beings

02:19:19to sleep on our backs.

02:19:21Randy Gardner decided to try

02:19:23the record of the longest sleepless period.

02:19:25In 1964, he stayed awake for 11 days,

02:19:27or 264 hours.

02:19:29I guess he had noisy neighbors.

02:19:31Of all animals, humans are

02:19:33the only ones to have a chin.

02:19:35When you are thirsty,

02:19:37it means that the water loss you suffer

02:19:39is equal to 1% of your total body weight.

02:19:41If it exceeds 5%,

02:19:43you can even faint.

02:19:45During your life,

02:19:47your body goes from 300 bones to 206.

02:19:49More than half of all your bones

02:19:51are in your feet, ankles,

02:19:53hands and wrists.

02:19:55The largest human bone is the thigh bone,

02:19:57and the smallest is called the calf bone.

02:19:59It is located inside your tympanum.

02:20:01Women have a different smell

02:20:03and remember 50,000 of them.

02:20:05Besides, women smell better than men,

02:20:07and the sense of smell is 10,000 times more developed

02:20:09than the sense of taste.

02:20:11The surface of our lungs

02:20:13is almost equal to that of a tennis court.

02:20:15So, what is this sensation

02:20:17you feel when you cross a ridge

02:20:19on a Russian mountain

02:20:21and your stomach goes up in your throat?

02:20:23Well, the seat belt keeps your body in place,

02:20:25but your stomach, your intestines

02:20:27and your small internal organs

02:20:29are deprived of a little freedom.

02:20:31It doesn't hurt you,

02:20:33but your nerves can't understand what's going on.

02:20:35They really think your stomach

02:20:37has made a jump in your throat.

02:20:39We are all taller in the morning,

02:20:41because during the day,

02:20:43the cartilage between our bones is compressed.

02:20:45This makes us lose about one nail

02:20:47at the end of each day.

02:20:49The nose and ears are parts of the body

02:20:51that never stop growing.

02:20:53It is mainly thanks to gravity.

02:20:55The veins and arteries inside your body

02:20:57represent about 8% of your body weight.

02:20:59When you listen to music,

02:21:01the beats of your heart

02:21:03are synchronized with the general atmosphere

02:21:05of the song.

02:21:07So, choose wisely.

02:21:09Your skin is the largest organ of your body.

02:21:11It accounts for about 15% of your total weight.

02:21:13Know that you can burn more calories

02:21:15by sleeping than by watching TV.

02:21:17Hmm, what if we slept

02:21:19while the TV was still on?

02:21:21You are a scientist

02:21:23who has spent the last few years

02:21:25building a machine capable

02:21:27of downloading any data

02:21:29in a human mind.

02:21:31You want to become a lawyer?

02:21:33Download all the legal knowledge

02:21:35on your brain.

02:21:37You need to learn a new language?

02:21:39Just put on a special headset

02:21:41that connects to your mind

02:21:43and downloads all the necessary information

02:21:45via the computer.

02:21:47Generally, you lose consciousness

02:21:49for a few minutes

02:21:51while the information is being downloaded.

02:21:53You want to download much more than a job?

02:21:55You want to download an electronic library

02:21:57with millions of books

02:21:59to become the most educated person in the world?

02:22:01You put on a headset,

02:22:03you start the program,

02:22:05but you forget a simple but important thing.

02:22:07The brain must process all the information

02:22:09before you actually start using it.

02:22:11During sleep, the human brain analyzes

02:22:13and processes all the information received

02:22:15during the day.

02:22:17You start the machine

02:22:19and you fall into an endless black abyss.

02:22:21You don't remember how you got here

02:22:23or how long you've been doing this.

02:22:25All you know is that you have to get to the top.

02:22:27You go through the clouds.

02:22:29The blue sky is replaced by black space.

02:22:31The top is higher than the International Space Station.

02:22:33You look at the mountain

02:22:35and you see that it's not just a rock

02:22:37but books.

02:22:39You are climbing a huge pile of books.

02:22:41Chemical formulas,

02:22:43fish, huge octopus,

02:22:45tables with mathematical formulas

02:22:47that fly in all directions.

02:22:49You fall, but you don't fall.

02:22:51You float in space and you fly to the top.

02:22:53There is a bright light.

02:22:55You get closer and closer.

02:22:57Something happens and you fall at full speed.

02:22:59Someone pulls you to the ground.

02:23:01You regain your senses,

02:23:03slightly annoyed that such a beautiful dream is over.

02:23:05You wake up,

02:23:07but you see nothing and don't remember anything.

02:23:09In the darkness, there are flashes of light

02:23:11and you realize that your eyes are closed.

02:23:13You make an incredible effort

02:23:15and you finally open them.

02:23:17Your brain slowly assimilates information

02:23:19about your environment.

02:23:21You want to get out of bed

02:23:23and understand what's going on,

02:23:25but you can't.

02:23:27Your muscles don't want to obey.

02:23:29You can't turn your neck.

02:23:31Each movement is difficult

02:23:33and your mouth is dry.

02:23:35Your eyes close because your eyelids

02:23:37are difficult to keep open.

02:23:39You want to call for help,

02:23:41but you can't shout.

02:23:43Your vocal cords are too weak

02:23:45and you can't speak.

02:23:47Your brain and your body

02:23:49don't want you to sleep.

02:23:51Your sleep is made up of two parts,

02:23:53non-rapid eye movements, NREM,

02:23:55and REM.

02:23:57NREM sleep

02:23:59is the deepest state of sleep

02:24:01and consists of several phases.

02:24:03We call it that because our eyes

02:24:05don't move during this period.

02:24:07The activity of the brain decreases

02:24:09and the mind rests.

02:24:11During NREM sleep,

02:24:13the brain begins to slowly

02:24:15get out of the deep phase

02:24:17to move on to REM.

02:24:19Your eyes move quickly

02:24:21behind your eyelids

02:24:23and you can have very lively dreams.

02:24:25The two phases accumulate

02:24:27for about an hour and a half to two hours

02:24:29and repeat several times

02:24:31in the same night.

02:24:33NREM lasts most of the time

02:24:35while REM lasts 15 to 30 minutes.

02:24:37If your body is sufficiently rested,

02:24:39you wake up just after a REM phase.

02:24:41If you need more rest,

02:24:43you go back to the deep phase

02:24:45after the REM phase.

02:24:47On average, a person goes through

02:24:49three or four phases per night.

02:24:51You had more than 350 of these phases

02:24:53last month.

02:24:55The REM phase is important

02:24:57because it receives all the information

02:24:59of the subconscious and treats them.

02:25:01This is how we make dreams.

02:25:03You might think that a dream

02:25:05makes no sense,

02:25:07but it is related to the events

02:25:09of your subconscious.

02:25:11You need more time

02:25:13to process as much information

02:25:15as a normal 8-hour sleep.

02:25:17You only remember a small part

02:25:19of your dream and your consciousness

02:25:21doesn't feel like a whole month has passed.

02:25:23All the processing of the downloaded

02:25:25knowledge has been hidden

02:25:27by your subconscious.

02:25:29But you saw a small part of it.

02:25:31You dreamed that you were climbing

02:25:33a summit that symbolized knowledge.

02:25:35It was your last REM phase in this dream.

02:25:37Your body has gone through

02:25:39a real ordeal this month.

02:25:41During the first days of sleep,

02:25:43your body doesn't change much.

02:25:45Your brain produces a special hormone

02:25:47that makes you not want to go to the bathroom.

02:25:49In addition, during sleep,

02:25:51your body cools down slightly

02:25:53and your muscles relax completely.

02:25:55Without physical effort,

02:25:57muscle fibers become weaker

02:25:59and smaller.

02:26:01You lose 1 to 5% of your muscle mass

02:26:03every day.

02:26:05Your muscles don't get energy

02:26:07and weaken so much that they atrophy.

02:26:09After a month, they become like a thin layer of jelly.

02:26:11It doesn't just apply to your arms and legs.

02:26:13Your face can't express emotions

02:26:15and you can't open your eyes.

02:26:17A few days after this sleep,

02:26:19your body begins to suffer

02:26:21from severe dehydration.

02:26:23After a week, a large percentage

02:26:25of the liquid contained in your body disappears.

02:26:27Humidity is extracted from the tissues

02:26:29of the skin, fat and muscles

02:26:31to maintain your overall health.

02:26:33This one cools down.

02:26:35After a few weeks,

02:26:37you're not much warmer than a soda can

02:26:39in a refrigerator.

02:26:41A month later, you look like a big piece of ice.

02:26:43Every day, less and less vitamins

02:26:45and nutrients are distributed in your body.

02:26:47Imagine that the blood system is a wide highway

02:26:49with thousands of cars

02:26:51where each car is a necessary element

02:26:53for the functioning of the body.

02:26:55Every day, the number of cars decreases

02:26:57as well as their speed.

02:26:59After a month, the road is almost empty.

02:27:01All your organs, except your heart

02:27:03and your lungs, almost stop working

02:27:05because the body doesn't need them.

02:27:07The kidneys don't filter the incoming liquids.

02:27:09The liver doesn't control the metabolism

02:27:11because no substance enters the body anymore.

02:27:13Because no substance enters the body anymore.

02:27:15The lack of vitamins and nutrients

02:27:17makes your bones as fragile as glass.

02:27:19The brain also lacks nutrition.

02:27:21It continues to acquire new knowledge

02:27:23but its reaction speed

02:27:25and its ability to analyze decreases.

02:27:27Almost all the remaining body resources

02:27:29are redirected to provide energy to the brain.

02:27:31But this is still not enough.

02:27:33After you wake up,

02:27:35you may not understand where you are,

02:27:37who you are, or what is happening.

02:27:39The TV is on in front of you

02:27:41but you need a few seconds to realize it.

02:27:43Your heart rate is reduced.

02:27:45Your heart doesn't work at full power.

02:27:47You breathe so slowly and so weakly

02:27:49that even a fly passing in front of your nose

02:27:51can barely feel your breath.

02:27:53Your body is now like a laptop

02:27:55whose battery is low.

02:27:57Energy is just enough to display the image

02:27:59but the computer needs to be charged.

02:28:01You would be at the same time

02:28:03the smartest and most powerless person in the world.

02:28:05Fortunately, this didn't happen to you

02:28:07because during all this time

02:28:09you were helped by your friend.

02:28:11She fed you with a tube

02:28:13and gave you a set of vitamins.

02:28:15Your body was covered with a blanket

02:28:17that creates electric impulses.

02:28:19Not too powerful to the point of hurting you

02:28:21but enough for your muscles to contract.

02:28:23You were in great shape during your sleep.

02:28:25Of course, this wasn't enough to wake up

02:28:27and feel revitalized.

02:28:29In the first few minutes, it was still hard to move

02:28:31but after an hour, you get out of bed.

02:28:33During the following weeks,

02:28:35you restore your diet.

02:28:37You do sports to tone your muscles.

02:28:39You meditate and do exercises to think

02:28:41to relieve your brain stress

02:28:43and restore your nervous system.

02:28:45New knowledge doesn't come immediately.

02:28:47It comes by wave every day.

02:28:49Today, you know all the works of classical writers

02:28:51and tomorrow, you will understand

02:28:53the last achievement in the field of neurosurgery.

02:28:55With this knowledge,

02:28:57you decide to start studying sleep.

02:28:59You loved climbing the mountain so much

02:29:01that you are about to create

02:29:03a device that can record your dreams.

02:29:05Your plan is to create a simple algorithm

02:29:07so that these dreams can be displayed

02:29:09on a computer screen

02:29:11once you wake up.

02:29:13Humans have tails.

02:29:15OK, it sounds weird, I know.

02:29:17But it's true.

02:29:19While our body is still forming in the uterus

02:29:21towards the 31st or the 35th day,

02:29:23we can really start to see it.

02:29:25At this precise moment,

02:29:27you have a tail.

02:29:29It is inside you.

02:29:31It is a part of your coccyx.

02:29:33To be more precise,

02:29:35if you had a x-ray right now

02:29:37and you asked the doctor to show you your tail,

02:29:39you would see small bone segments

02:29:41at the bottom of your spine.

02:29:43We have lost our tails

02:29:45over decades of evolution.

02:29:47Imagine that we still have our tails.

02:29:49We still have a special place

02:29:51or even a pocket for our tail.

02:29:53Sitting down would be a little uncomfortable.

02:29:55It's the least we can say.

02:29:57Our ancestors also had fur.

02:29:59We lost it about 1.2 million years ago.

02:30:01You may think

02:30:03that we still have fur,

02:30:05that is, our current hairs on the body.

02:30:07But that's nothing compared

02:30:09to what we used to have.

02:30:11We had thick fur,

02:30:13like chimpanzees and gorillas,

02:30:15because we needed it to stay warm.

02:30:17If you had a cold like Alaska,

02:30:19you could be opposed to having lost this fur.

02:30:21But you can also see things

02:30:23from another angle.

02:30:25The loss of our fur allows us

02:30:27to enjoy a little more beautiful days.

02:30:29When we all lived in groups,

02:30:31we shared certain things

02:30:33that were not all positive.

02:30:35It is possible that humans

02:30:37with less hair or fur

02:30:39fell less often ill

02:30:41because they did not have as many parasites

02:30:43on them as chickens or ticks.

02:30:45It is also possible that we will

02:30:47eventually lose our fur

02:30:49and become what we are today.

02:30:51Although I must admit that having

02:30:53an integrated heating system

02:30:55would be very useful right now,

02:30:57I would no longer need

02:30:59to keep this blanket on my legs.

02:31:01Oh no, not again!

02:31:03Let me just take a cup of water

02:31:05to start this hockey.

02:31:07Ah, it's much better.

02:31:09OK, in reality,

02:31:11it's not that easy to stop hockey.

02:31:13It is due to a strange characteristic

02:31:15of a past evolution.

02:31:17A theory advances that hockey

02:31:19is no longer useful

02:31:21and that we only do it

02:31:23because we are amphibians.

02:31:25Our ancestors had both lungs

02:31:27and branches.

02:31:29When they went underwater,

02:31:31the entrance or glottis

02:31:33of their lungs closed.

02:31:35Today we still have this mechanism

02:31:37of closing the glottis,

02:31:39but it is useless

02:31:41because without hockey,

02:31:43we should at least be able

02:31:45to benefit from it.

02:31:47Imagine, you start playing hockey

02:31:49and it's like a superpower.

02:31:51You stop breathing with your lungs

02:31:53and you start using branches.

02:31:55It would be great,

02:31:57especially for those who really like to swim.

02:31:59Most of our teeth

02:32:01adapt rather perfectly

02:32:03to our mouth,

02:32:05but there are four

02:32:07that arrive late

02:32:09However, lucky species

02:32:11such as tamarins

02:32:13do not have to worry about it.

02:32:15About 35% of people

02:32:17do not even have wisdom teeth.

02:32:19We may be on the verge

02:32:21of losing them completely,

02:32:23once and for all.

02:32:25No need to go to the dentist

02:32:27to remove them,

02:32:29and no more headaches either.

02:32:31In Ireland,

02:32:33there are a lot of people

02:32:35with wavy hair,

02:32:37which is a characteristic

02:32:39that is transmitted by our ancestors

02:32:41without any real reason for it.

02:32:43That's exactly why some people

02:32:45have wavy hair.

02:32:47So if you have wavy hair,

02:32:49there is no real reason for it.

02:32:51It just comes from your ancestors

02:32:53from a past era

02:32:55who passed it on to another member

02:32:57of your family,

02:32:59and finally to you.

02:33:01In our mother's uterus,

02:33:03at 16 weeks,

02:33:05there is a good explanation for this.

02:33:07It's because when they are in nature,

02:33:09they need to hang on

02:33:11to their parents' fur.

02:33:13Humans used to do the same,

02:33:15but since we lost all our fur,

02:33:17we no longer need to develop

02:33:19this involuntary prehension,

02:33:21called palmar prehension reflex.

02:33:23Open your mouth wide and say

02:33:25aaaaah.

02:33:27Well, I can see your amygdala now.

02:33:29But what is it for?

02:33:31If you think about it,

02:33:33the amygdala is only there

02:33:35to protect us from germs

02:33:37and other unpleasant things

02:33:39when we eat food.

02:33:41However, most often,

02:33:43it only gives us a terrible sore throat.

02:33:45That's why it's very common

02:33:47for people to want to get rid of it.

02:33:49Imagine a small pocket.

02:33:51We have one inside our body.

02:33:53Not exactly like that,

02:33:55but an organ that looks

02:33:57like a pocket, our appendix.

02:33:59Scientists thought it was completely useless,

02:34:01but recently discovered

02:34:03that it could actually be used for something.

02:34:05However, like the amygdala,

02:34:07it often causes more problems

02:34:09than benefits.

02:34:11It is not uncommon for people

02:34:13to have their appendix removed

02:34:15without any real consequences.

02:34:17It may have helped our ancestors

02:34:19in the past,

02:34:21but appendix problems can give

02:34:23a big stomach ache.

02:34:25OK, you know how some people

02:34:27can strangely move their ears,

02:34:29but I can't do it.

02:34:31But you could be able to,

02:34:33and it's up to you.

02:34:35Some of us can do it

02:34:37because, like other animals,

02:34:39we have a muscle called the auricular muscle,

02:34:41but it's useless.

02:34:43Cats, on the other hand,

02:34:45control their ears quite well

02:34:47if only we could learn from them.

02:34:49They look forward

02:34:51and detect a noise behind them

02:34:53without moving their heads,

02:34:55just their ears.

02:34:57If you can, your hand too.

02:34:59Now connect your thumb to your little finger.

02:35:01You may see a line appear

02:35:03on your wrist.

02:35:05What you see is called the palmaris longus,

02:35:07and about 90% of the world's population

02:35:09has it.

02:35:11Statistically speaking,

02:35:13you may also have it.

02:35:15At the time, our ancestors needed

02:35:17all the help they could get

02:35:19to climb trees and grab objects.

02:35:21But when we started walking,

02:35:23these muscles became completely useless.

02:35:25Monkeys, on the other hand,

02:35:27still climb trees easily.

02:35:29They have a muscle in their feet

02:35:31called the plantar muscle,

02:35:33also known as the monkey muscle.

02:35:35We have it too,

02:35:37but we don't really need it

02:35:39because we don't do monkey activity.

02:35:41Like the palmaris longus,

02:35:43about 10% of people are born without this muscle.

02:35:45There is a good chance

02:35:47that if monkeys hang on a branch,

02:35:49it's the muscle they use.

02:35:51If you want to eat at 3 a.m.,

02:35:53you probably already know,

02:35:55but what you don't know

02:35:57is that hunger has evolved

02:35:59like a trigger that pushes us

02:36:01to look for more food.

02:36:03So if you still have a few kilos

02:36:05in excess that you want to get rid of,

02:36:07you know what to do.

02:36:09You just have to blame evolution.

02:36:11Our most hungry ancestors

02:36:13would have been forced to look for food

02:36:15and would have survived

02:36:17to transmit this characteristic to us.

02:36:19Our love of sweet desserts

02:36:21has evolved just like hunger

02:36:23to help us find

02:36:25beneficial food for us.

02:36:27You walk around and you are struck

02:36:29by a fresh breeze.

02:36:31Since you only wear a T-shirt,

02:36:33you decide to go home.

02:36:35You go into the house

02:36:37by biting your teeth

02:36:39and you realize

02:36:41that you also have chicken skin.

02:36:43We take it from our ancestors

02:36:45with fur.

02:36:47When it was cold,

02:36:49it was not very useful.

02:36:51Evolution also explains

02:36:53why you can have chicken skin

02:36:55when you are afraid.

02:36:57Imagine you are a caveman

02:36:59in nature when suddenly

02:37:01a tiger jumps on you.

02:37:03He starts growling at you.

02:37:05Don't worry.

02:37:07Your hairs stand on end

02:37:09and you look like a giant.

02:37:11You know, in fact,

02:37:13we don't need five toes.

02:37:15You do the laundry

02:37:17with your feet, of course.

02:37:19This is possible thanks to our fifth toe,

02:37:21but we could easily do without it.

02:37:23Since we walk standing up

02:37:25and we don't need to jump from branch to branch,

02:37:27this toe is practically useless.

02:37:29We can walk very well

02:37:31and even run with four toes,

02:37:33maybe even less.

02:37:35So who knows, maybe in the future

02:37:37humans will only have four toes

02:37:39on each foot.

02:37:41Yes, it is possible to rotate your eyes,

02:37:43but you can't do it without a little training.

02:37:45Our eyes are equipped

02:37:47with four main muscles

02:37:49that allow them to move from top to bottom

02:37:51and from one side to the other.

02:37:53In fact, there are two other muscles

02:37:55that we also use without knowing it.

02:37:57These muscles help you roll

02:37:59or turn your eyes.

02:38:01We can focus on something that turns

02:38:03and our eyes will start to turn with it.

02:38:05This helps us to have a stable image

02:38:07and to keep a clear vision,

02:38:09like an autofocus on a camera.

02:38:11When you move your head from one side to the other

02:38:13the average human eye has three cones

02:38:15that allow us to distinguish

02:38:17the red, green and blue spectrums

02:38:19of light.

02:38:21This gives us the ability to see

02:38:23about a million different colors.

02:38:25Tetrachromates also perceive

02:38:27ultraviolet tones because they have

02:38:29four types of cones in their eyes.

02:38:31Pause the video to test yourself quickly.

02:38:33How many colors can you tell?

02:38:39There are 39 colors.

02:38:41If you can count more,

02:38:43you may be a tetrachromate.

02:38:45Some animals, such as bats

02:38:47and dolphins, can see

02:38:49by using echolocation.

02:38:51Some humans can also do

02:38:53something similar called sonar flash.

02:38:55They can use clickteams

02:38:57to create a 3D image of an area

02:38:59in their mind, which allows them

02:39:01to move easily.

02:39:03The more they click, the more flashes

02:39:05they receive on a room or area,

02:39:07which allows them to better understand the place.

02:39:09Surprisingly rare,

02:39:11less than 1 in 10,000 people

02:39:13have this ability.

02:39:15It allows people to identify

02:39:17musical notes with precision.

02:39:19One of the many advantages of this talent

02:39:21is that it allows people to listen to a song

02:39:23and know immediately

02:39:25in which key it is.

02:39:27People with dysthysiasis

02:39:29are born with a second series of eyelashes

02:39:31that grow from the inner layer of the eyelid.

02:39:33Although it may seem pretty to some,

02:39:35these additional eyelashes

02:39:37can irritate the eye and cause problems

02:39:39such as light sensitivity,

02:39:41drooping eyelids, tears

02:39:43and inflammation.

02:39:45There are a few ways to treat this infection,

02:39:47such as flexible lenses, lasers

02:39:49and cryotherapy.

02:39:51The Dutch health guru

02:39:53Wim Hof says that

02:39:55his breathing, meditation

02:39:57and training have helped him

02:39:59to acquire all kinds of superhuman abilities.

02:40:01He trained his body

02:40:03to adapt to extreme temperatures

02:40:05and even learned to increase

02:40:07his own body temperature.

02:40:09He has also been able to adapt more quickly

02:40:11to changes in altitude.

02:40:13He even claimed that his training methods

02:40:15and his strict diet

02:40:17have improved his immune system.

02:40:19We are supposed to sleep

02:40:21between 7 and 8 hours

02:40:23each night to function properly the next day.

02:40:25But there are lucky people

02:40:27who only need 6 hours or less

02:40:29per night.

02:40:31This is due to a genetic anomaly

02:40:33that does not seem to have a harmful effect

02:40:35to be reached by this one.

02:40:37We have about 10,000 taste buds,

02:40:39but some people have

02:40:41much more than that.

02:40:43They are called super-tasters.

02:40:45But due to their powerful ability to taste,

02:40:47sweet foods such as oranges,

02:40:49strawberries and candy are almost too sweet

02:40:51for them.

02:40:53While bitter foods such as broccoli, cabbage,

02:40:55spinach, pamplemousse

02:40:57and coffee are too strong.

02:40:59Most people have a total

02:41:01of 24 taste buds,

02:41:03but there is a chance that you are one of the few

02:41:05to have 25.

02:41:07About 1 person out of 200

02:41:09has an additional cervical taste

02:41:11just above the first taste bud.

02:41:13It is generally not noticed

02:41:15because it is above the clavicle

02:41:17and is rather thin.

02:41:19There is a good chance that you have a navel turned

02:41:21inward since only 10%

02:41:23of the world's population

02:41:25has a navel that protrudes outward.

02:41:27This has nothing to do

02:41:29with the way

02:41:31our umbilical cord is cut.

02:41:33Our navel stores a little fat

02:41:35under it and this is what determines

02:41:37the type of navel you will have in the end.

02:41:39So don't blame the wise woman,

02:41:41the type you have is entirely due to your genes.

02:41:43If you have already experienced

02:41:45high altitude, you must know

02:41:47how exhausting it is for your body.

02:41:49Even the simple fact of climbing a hill

02:41:51on foot can be a difficult task.

02:41:53But just give yourself a few days

02:41:55and things will become

02:41:57easier.

02:41:59Your lungs, your blood cells and your body

02:42:01will adapt faster than you think,

02:42:03allowing you to keep

02:42:05this precious oxygen longer.

02:42:07This adaptation will last as long

02:42:09as you stay at an altitude

02:42:11and back to a normal altitude,

02:42:13you will return to normal after a while.

02:42:15When we immerse ourselves in water,

02:42:17it lowers our heart rate

02:42:19and slows down our oxygen consumption.

02:42:21In recent years,

02:42:23apneas have pushed the limits

02:42:25of human heart rate by going down

02:42:27to a record depth of 214 meters.

02:42:29A person even held their breath

02:42:31for more than 22 minutes

02:42:33underwater.

02:42:35We don't know yet what the limit is,

02:42:37but we push it back non-stop.

02:42:39When a person has a photographic memory

02:42:41or a total memory,

02:42:43we call it eidetic memory.

02:42:45It is the ability to remember precisely

02:42:47sounds, images or other details.

02:42:49Some people can even

02:42:51have a date indicated

02:42:53on a calendar dating from years ago

02:42:55and tell you what day it was exactly.

02:42:57Unfortunately,

02:42:59you can't get an eidetic memory

02:43:01with training, you have to be born with it.

02:43:03An ultramarathon runner named

02:43:05Dean Karnadzes ran

02:43:07a distance of 563 km

02:43:09and did not sleep for three days.

02:43:11He is known for having run

02:43:1350 marathons in the 50

02:43:15American states in 50 consecutive days.

02:43:17He accomplished this feat

02:43:19by finishing the New York marathon

02:43:21in less than three hours.

02:43:23Some people have an incredible ability

02:43:25to find their way without using a compass

02:43:27or even the stars.

02:43:29This unique navigation ability

02:43:31is linked to the force of signals emitted

02:43:33in a certain part of the brain

02:43:35called the antorhinal cortex.

02:43:37Place the back of your wrist

02:43:39and your forearm on a table

02:43:41then join your thumb to your ear.

02:43:43Do you see a muscle

02:43:45rising in the middle of your forearm?

02:43:47If you don't see it,

02:43:49don't worry, it's a vestibular muscle.

02:43:51This means

02:43:53it's no longer useful.

02:43:55It's an old muscle

02:43:57that we used to climb

02:43:59and about 10% of the human population

02:44:01no longer has it.

02:44:03If you can move your ears,

02:44:05you can thank your auricular muscles.

02:44:07These are those that are

02:44:09outside your ear.

02:44:11And even if you can't,

02:44:13these muscles are still there.

02:44:15Compared to other mammals,

02:44:17they use their ears

02:44:19to locate sounds.

02:44:21Just observe your dog or cat.

02:44:23The third eye of a dog

02:44:25may be a little scary

02:44:27the first time you see it,

02:44:29but we also have a kind of third eye.

02:44:31However, this part of the human body

02:44:33cannot move on its own

02:44:35and only covers a very small part

02:44:37of the inner corner of your eye.

02:44:39It is likely that it was once used for something,

02:44:41but it is almost useless now.

02:44:43Sometimes you just need

02:44:45to cry a little

02:44:47and it's good for your health.

02:44:49Crying helps to release

02:44:51your stress hormones.

02:44:53It can also stimulate the production

02:44:55of endorphins,

02:44:57which is also the natural response

02:44:59of our body to aspirin.

02:45:01Your brain is renewed every two months.

02:45:03Your liver, every six weeks.

02:45:05Your epidermis, every month.

02:45:07Even the wall of your stomach

02:45:09is replaced every few days.

02:45:11If your body didn't do that,

02:45:13it wouldn't just digest food.

02:45:15It would also start digesting you.

02:45:17Human lungs

02:45:19contain about 2,400 km

02:45:21of respiratory path

02:45:23and a total area of about 70 m²

02:45:25if they were flattened.

02:45:27Your lungs are in service 24 hours a day

02:45:297 days a week

02:45:31to keep you alive and make you breathe.

02:45:33They perform 12 to 15 breaths per minute,

02:45:35or about

02:45:3717,000 per day.

02:45:39Your left lung is slightly smaller

02:45:41than your right lung

02:45:43to make room for your big heart.

02:45:45After years of wear and tear,

02:45:47your feet can weaken enough

02:45:49to seem to grow.

02:45:51This can lead to the flattening

02:45:53of our plantar vaults,

02:45:55which means larger and longer feet.

02:45:57It doesn't happen to everyone,

02:45:59but people with swollen feet

02:46:01or ankles are more prone to it.

02:46:03But don't worry.

02:46:05At 70 or 80,

02:46:07your feet will only have taken

02:46:09the heat of your feet.

02:46:11Your feet will be stronger

02:46:13than your ankles.

02:46:15The best way to get rid of feet

02:46:17is to take a cold coffee

02:46:19or a hot coffee,

02:46:21which is either orange or wood.

02:46:23For example, hot coffee

02:46:25seems less bitter and tastes better

02:46:27because heat deceives our taste buds

02:46:29and detects bitterness.

02:46:31It is the same for cold coffee.

02:46:33Cold coffee masks the bitterness

02:46:35and creates a more pleasant aftertaste.

02:46:37to be more sensitive to hot and cold food.

02:46:39Teeth don't heal by themselves,

02:46:41so you have to take care of them.

02:46:43Slow down your brushing and take 2 full minutes

02:46:45to clean your teeth well.

02:46:47Don't forget to use dental floss!

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