- 2 hours ago
Here're the coolest body facts that'll help you realize how unique and special our bodies are. You'll find out why you produce more saliva when you go for a run. And how you can burn calories while thinking. Have you ever wondered why our distant relatives, the primates, are so much stronger than us? We're gonna explore these and more questions about human bodies...
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00:01So, let me tell you a tale about tails.
00:04There are some cases of humans being born with a tail.
00:07There are about 25 confirmed cases known to scientists.
00:11Those born with tails, though, won't have any real benefit
00:14other than what the tailbone does for balance anyway.
00:17The tails have no function other than physically being there,
00:20as they have no bones.
00:22The tails only consist of nerves, vessels, and muscles.
00:26Now, do you find that you're a picky eater?
00:28Do you think that coriander tastes like soap?
00:31Or you can't stand pineapple on pizza?
00:33Really?
00:35Well, this may be due to what kind of taster you are.
00:38Up to 30% of people are considered super tasters
00:41and will experience different levels of enjoyment or disappointment from their foods.
00:46Food that is bitter to the super taster will likely be sweet to average tasters,
00:51who make up 40% of people.
00:54There are also 30% of people who are non-tasters
00:57and won't find anything too exciting.
00:59I guess you just have to develop a taste for that.
01:03The vast majority of people have brown eyes.
01:06About 79% of the world population share this eye color.
01:10Once, all humans only had the brown pigmentation.
01:14Until around 6,000 to 10,000 years ago,
01:16and I wasn't around then,
01:18when humans migrated to Northern Europe.
01:21A mutation occurred, helping the eyes to adapt to the change of line.
01:25Blue eyes became the most common of the mutated coloration,
01:29and all of them today can be traced back to one ancestor from Europe.
01:33His name was Chadwick Abernathy.
01:35His friends called him Chad,
01:36and he was a boulder mover at Stonehenge.
01:39Well, not real.
01:40Today, blue eyes make up around 10% of the human population.
01:45Amber and hazel eyes each take up 5% respectively.
01:49Gray eyes are up to 3%.
01:51And the rarest of eye colors are green ones,
01:54consisting of only 2%.
01:56Rarer still is heterochromia iridum,
01:59where both eyes are of different colors.
02:01It's inherited and also affected by other genetic factors.
02:05Only 1% of the human population have this incredibly rare attribute.
02:11Do you have a small hole in the front of your ear above the ear canal?
02:14This is a preauricular pit.
02:17During the first six weeks of a child's development,
02:20long before being born,
02:21the auricle, which is the external part of your ear, will develop.
02:25The preauricle pit forms when the auricle doesn't fully fuse.
02:30This occurs in less than 1% of humans.
02:33Although there's speculation that having this little hole
02:36is the remnant of gills that we once had from our seafaring ancestors,
02:40there is nothing solid to confirm this theory.
02:43If you can lick your elbow easily,
02:45or touch your thumb to your forearm,
02:47congratulations!
02:48You're among the minority of people.
02:50But some people bring flexibility to the next level.
02:54This condition is called hypermobility.
02:56It allows rare individuals to twist their bodies into weird positions,
03:01just like a snake,
03:02putting their head between their feet,
03:04doing a back bridge,
03:05and all sorts of splits.
03:07But in some cases,
03:09hypermobility can increase sensitivity,
03:11because such people have a larger medulla.
03:14This brain area is responsible for processing emotions.
03:1890% of people are right-handed,
03:20and only 10% are left-handed.
03:22Yes, that adds up.
03:23But there's also a very small percentage of those
03:26who can use both hands equally well,
03:29including writing, drawing, and doing any tasks.
03:33Naturally, ambidextrous people account for only 1% of the entire population,
03:37which is about 70 million people.
03:39If you want to check whether you're one of them,
03:42try to write the same phrase with both hands,
03:44or draw a circle first with your right,
03:46and then with your left hand.
03:48If there's no difference, congrats!
03:51By the way,
03:52these exercises are very good for balancing the hemispheres of the brain,
03:56regardless of which hand is your dominant one.
03:59And if you have three hands,
04:01well, that's a different video.
04:03Your fingernails grow faster on your dominant hand.
04:06In other words,
04:07if you write with your right hand,
04:08it's alright.
04:10And you'll have to trim those nails more often.
04:12Your fingernails also grow faster in the summer and during the day.
04:17Your skeleton will renew itself completely within 10 years.
04:21And yes, without surgery.
04:23An adult uses around 200 muscles just to make one step.
04:27So don't tell me I don't work out enough.
04:31Every minute, your body sheds more than 3,000 skin cells.
04:35It's almost 200,000 skin cells per hour
04:38and more than 9 pounds per year.
04:41Hey, it's the Shedding Skin Cells Weight Loss Plan.
04:44Ooh, sign up.
04:45But hey, don't worry.
04:47You still have about 300 million skin cells at any given moment.
04:51Plus, your skin completely renews itself every 28 to 30 days.
04:55The liver is the only human organ that can regenerate completely.
05:00As little as 25% of the original liver weight
05:03can get back to its full size.
05:06Some people can hear their eyeballs moving inside the eye sockets.
05:10Wow, that must be no fun.
05:13Unlike other parts of your body, your ears and nose never stop growing.
05:17Wow, that must be no fun.
05:20Your skin wrinkles if you stay in the water for too long.
05:23But not because it absorbs water.
05:26When your body's wet, wrinkled fingers and toes provide you with a better grip.
05:31You know, like when the treads on your car tires grip the road better when they're new.
05:36Your eyes are an amazing instrument.
05:39They can distinguish between 10 million different colors.
05:43Your brain uses more than 20% of your body's energy even when you're resting.
05:48When you're asleep, it still consumes almost as much power as when you're awake.
05:53It also burns around 330 calories per day at that.
05:57An adult person has about 25% of all their bones in the feet.
06:02Most of them are tiny but crucial.
06:04If these bones are out of alignment, so is the rest of the body.
06:09You breathe around 20,000 times a day, I've counted.
06:13Try not to stop.
06:14I actually set a personal best record today for consecutive days breathing.
06:18And I plan to top that tomorrow.
06:21Human bones are a real paradox.
06:24They're almost 5 times stronger than a steel bar with the same width,
06:28but can fracture on impact and are rather brittle.
06:31If a person has asnosmia, also called smell blindness,
06:36they can't distinguish and detect smells.
06:38But they can still be smelly.
06:41Sorry.
06:42You start feeling thirsty when water loss is 1% of your body weight.
06:47More than 5% and you may faint.
06:50But water loss that's bigger than 10% of the body weight
06:53and dehydration can end a person.
06:56If you know what I mean.
06:59The strongest muscle in your body, based on its weight, is your jaw muscle.
07:03Yes, mine is way overdeveloped.
07:06At any moment, 50,000 cells in your body are getting replaced by new ones.
07:11Boy, that sounds like a company I used to work for.
07:15By the end of their life, the average person can recall up to 150 trillion pieces of information.
07:22Except for where they left their car keys.
07:24Even if fingerprints are badly damaged, they still go back with their original pattern.
07:30Don't believe me?
07:31Hey, give it a whirl.
07:32Your brain's memory capacity is equivalent to about 4 terabytes on a hard drive,
07:38which is more than 8 million photos.
07:41People are the only living creatures that can naturally sleep on their backs.
07:46Even apes usually sleep in a sitting position, leaning on something.
07:50Don't wake them up.
07:52Your longest bone is your thigh bone, not your funny bone.
07:56And the tiniest one is in the ear.
07:58It's shorter than a grain of rice.
08:01Do you feel ticklish when you tickle yourself?
08:04Normally, you wouldn't, unless someone else tickles you.
08:07It happens because the cerebellum area of the brain, which monitors movements,
08:12predicts the sensations caused by your own movements.
08:15Then it sends a signal to other parts of the nervous system to cancel these sensations.
08:20But some rare individuals can actually feel ticklish on their own.
08:25If you're not among them, touching a new texture that the brain doesn't yet recognize,
08:30or using a scalp massager, can help to excite your nerves and bring relaxation.
08:36Hey, you can give it a tickle test!
08:38If you want to check out the work of your vestibular system, try this simple trick.
08:44Stand on one foot and close your eyes.
08:47Most people lose balance at least during the first attempt.
08:50Your vestibular system includes many organs and systems throughout the body.
08:55Together, they allow your body to stay in balance in different positions.
08:59This system includes the inner ear and vision,
09:02which is why keeping balance is much easier in silence while your eyes are open.
09:08Can you wiggle your ears intentionally?
09:11Are you popular at parties for doing that?
09:13Congratulations!
09:14Around 22% of people on the Earth are capable of wiggling one ear.
09:20As for moving both ears at once, only 18% can do that.
09:24Ear wiggling used to be a common thing for our distant ancestors.
09:28Scientists believe they could perform a variety of movements with their ears.
09:32The group of muscles responsible for wiggling are called the auriculars.
09:37Mostly don't need it today.
09:39But some people claim that everyone can learn to move their ears.
09:43It only takes time and practice.
09:45Unfortunately, we still cannot acquire this classy habit of twitching an ear toward a sound source,
09:51as dogs and cats do.
09:53Nor can we actually lend an ear to someone.
09:56They're challenging to remove and reattach.
10:01Now, if you were asked where your stomach was,
10:04you'd probably point to your tummy.
10:06Sorry, but that's wrong.
10:08It's actually up here, hidden behind your ribs.
10:11Your stomach has a pretty incredible capacity,
10:14being able to hold up to a half a gallon of liquids.
10:17That's a whole large bottle of Coke.
10:19It's pretty hard to estimate how much hard food you can eat,
10:22because it's processed with your teeth before it ever gets to your stomach.
10:26There's definitely not enough room for a turkey,
10:29but a good-sized chicken would probably fit it in.
10:32Speaking of organs,
10:34scientists believe that the appendix will disappear eventually.
10:37Nobody really knows why we need it,
10:39but some researchers claim it might have existed to help our ancestors digest tree bark.
10:45Because it's no longer a part of our daily diet,
10:48the appendix isn't necessary and can disappear from our bodies without any consequences.
10:53Now, the appendix isn't the only obsolete part of our body.
10:57Wisdom teeth aren't that useful either.
10:59Yeah, they used to come in handy when our ancestors lost some of their teeth.
11:03But the only thing they help us lose now is the money we spend extracting them.
11:08In fact, you can easily survive without your appendix, stomach, one kidney, or one lung.
11:14Nice to know we have spare parts.
11:17If you never knew you had a personal bodyguard, look deeper.
11:20Your liver is your security guard,
11:23protecting you from toxins and many other things you don't want to have.
11:26It's also pretty indestructible and can even regenerate.
11:30Your liver is a very important organ that works a lot
11:33and is responsible for 500 individual functions.
11:37Up to 10% of it is made of fat.
11:40The liver can grow back.
11:42Yep, even if you only have half of your liver left,
11:45it can still regenerate to its original size.
11:49Now, on average, the heart is as big as your fist.
11:52It beats 115,000 times and pumps around 2,000 gallons of blood each day.
11:59The right lung is bigger than the left one
12:01because your body needs to make some room for the heart.
12:04You inhale a lot of different types of debris,
12:07including 7,000 of your very own skin flakes.
12:11And that's only in a day.
12:12The stomach is the most important defender of the immune system.
12:17Hydrochloric acid in our stomach kills dangerous food toxins,
12:21viruses, and bacteria that get in there with the food you eat.
12:24This acid can digest even the stomach itself,
12:27but the mucous membrane protects it.
12:30You can burn calories when you take a hot bath,
12:33as many as you would if you took a half-hour walk.
12:36You burn somewhere between 100 and 200 calories per hour while standing.
12:41Sitting burns 60 to 130,
12:44depending on your height, weight, gender, and age.
12:47Now, your own body makes mosquito bites swell and itch.
12:50A mosquito breaks your skin.
12:52Your immune system perceives the insect's saliva as a foreign substance,
12:56so it starts a special reaction to flush the intruder out of your body.
13:01A compound produced by the immune system, called histamine,
13:04makes the blood flow faster around the bitten area,
13:07and it causes swelling.
13:09The histamine also sends a signal to the nearest nerves,
13:12which makes the bite itch.
13:14Meanwhile, the food on the plane is likely to taste different than on the ground.
13:19That's because you lose up to 30% of your tastebud sensitivity
13:23due to the dryness and pressure in the cabin.
13:25It's especially true about salty and sweet foods.
13:29Now, you wouldn't be able to taste food without saliva.
13:32Your taste buds have chemoreceptors that recognize different flavors,
13:35but they need some liquid for those flavors to bind into their molecules.
13:40Also, you can't taste things saliva doesn't dissolve.
13:43You can always squeeze in some dessert,
13:45no matter how much salad, soup, or meat you've eaten before.
13:49Your body gets bored of savory tastes,
13:51but when you see and smell something sweet,
13:54like ice cream, cakes, or chocolate,
13:56your brain gets excited.
13:58It overrides all fullness signals for pleasure.
14:01Plus, your stomach is a flexible organ,
14:03and sugar helps it relax and physically make room for dessert.
14:07Hey, I rely on that information.
14:10The tongue is one of the strongest muscles in your body.
14:13This organ contains more than 10,000 taste buds,
14:16and each bud is filled with microscopic hairs.
14:20Their job is to sense your food,
14:22distinguish tastes,
14:23and send information to your brain
14:25to initiate the appropriate digestion process.
14:27During your life,
14:28all those tiny bumps and ridges on your tongue
14:31create a special individual pattern.
14:33That's why experts say that tongue prints
14:35are as unique as fingerprints.
14:37Your tongue doesn't have separate bitter, sweet,
14:40sour, or salty sections for tasting.
14:42Each of the 8,000 taste buds you have on the tongue,
14:46the roof of the mouth,
14:47and even in the throat,
14:48can detect all the tastes.
14:50For some people,
14:51cilantro may taste similar to soap
14:53because the plant contains a chemical used in soap making.
14:57But only 4 to 14% of the world's population
15:00have special genes that can detect it.
15:02The masseter is the strongest muscle you have
15:05based on its weight.
15:07Together with the rest of the jaw muscles,
15:09it can close your teeth
15:10with a force of 200 pounds on the molars
15:13and 55 pounds on the incisors.
15:16Your spine has a great memory.
15:18It remembers your posture,
15:19making it so difficult to change it for the better.
15:22You owe goosebumps to your ancestors
15:25from many, many, many years ago.
15:27Their hair used to stand up
15:29to make them look bigger and scarier to foes.
15:32Cats hiss and arch their backs for the same reason.
15:35Only about 43% of you is actually you.
15:39Over 50% of the cells in your body
15:42belong to tiny little creatures
15:43that mainly live in your gut.
15:46Still, even though your own cells
15:48are fewer than the microbial ones,
15:49there are, on average,
15:51about 100 trillion of them in you.
15:54See?
15:54You're not alone.
15:55With this in mind,
15:56your own genes are less than half
15:58of what you really consist of.
16:00If you take all the microbes
16:02dwelling within your body
16:03and count their genes,
16:05you'll find between 2 to 20 million.
16:08Now, our height,
16:09the shape of our body,
16:10and skin color
16:11depend a lot on where our ancestors used to live.
16:14But we can adapt to new conditions
16:16even within our own lifespan.
16:19For example,
16:20if you move from the plains to the mountains,
16:22you'll eventually develop more red blood cells
16:24to compensate for the lack of oxygen.
16:26And naturally,
16:28if you move from a colder climate
16:29to a hotter and sunnier one,
16:31your skin will get darker to adapt.
16:33Our lifespan is programmed within our cells.
16:36They constantly review and divide,
16:38but they have a sort of internal timer
16:41that stops at some point.
16:42Some cells also stop reproducing
16:44sooner than others.
16:46On average,
16:47cells cease dividing
16:48when we reach the age of 100,
16:50if we're that lucky.
16:51That means that
16:52if we could find a way
16:53to trick our cells
16:54into turning off the timer,
16:56we could potentially live forever
16:58and move in with our grandchildren.
17:01A human mouth is pretty unique.
17:04You won't find two identical sets of teeth
17:06even among identical twins.
17:08That's because the shape
17:10depends on how each person
17:11is using their jaw.
17:13Even the tiniest habits
17:14you used to have many years ago,
17:16such as lip biting,
17:18affect the formation of your teeth
17:19and the uniqueness
17:21of your dental impression.
17:23You've probably noticed
17:24that lipstick prints
17:25on a napkin or a mirror
17:26are always slightly different
17:28depending on who left them.
17:30All right,
17:31who left the lip prints?
17:32Studies of both females and males
17:34revealed that lip print patterns
17:36for each individual are unique.
17:38They didn't reveal
17:39any special traits
17:40based on the gender factor.
17:42The mandible,
17:43or the lower jaw,
17:44is the only skull bone
17:45that isn't fixed
17:46to the bone around it.
17:48It's attached
17:48with connective tissues
17:49and muscles.
17:50This is what makes it so mobile.
17:52You can move it
17:53in any direction you like.
17:54There are clusters
17:55of sensory cells
17:57in your tongue.
17:58The buds that are closer
17:59to the surface
17:59are more short-lived.
18:01That's the reason
18:02you don't have to wait
18:03for too long
18:03to be able to taste again
18:04after burning your tongue.
18:06Your fingertips are sensitive,
18:08but hundreds of times
18:10less so than your lips.
18:12Ah, the lips again.
18:17The cornea is the only part
18:19of your body
18:20with living cells
18:21that doesn't have blood vessels.
18:23It gets nutrients and oxygen
18:25directly from the tear fluid
18:27on the outside
18:27and the thick watery substance
18:30you have between the cornea
18:31on the inside
18:32and also from the nerve fibers
18:35connected to the cornea.
18:36That's why contact lenses
18:38used to be a potential issue.
18:40The older ones
18:41were reducing oxygen supply
18:43since the cornea
18:44mostly gets oxygen
18:45from the outside.
18:47This problem was solved
18:48or at least reduced
18:50when silicone hydrogel lenses
18:52came to the market.
18:53Some other parts of your body
18:55with no blood vessels
18:56are your nails,
18:57hair,
18:59outer skin layers,
19:00and tooth enamel.
19:02Did you notice your sweat
19:03sometimes smells of onions
19:05after your workout?
19:06You have nothing to worry about.
19:08There are two types
19:09of sweat glands in your skin.
19:12The first kind of glands
19:13are located on certain areas
19:15of your body
19:15like the groin region
19:17and the armpits.
19:18They produce a specific oily fluid
19:21which is a response
19:22to certain emotional experiences.
19:25Another type of sweat gland
19:26is way more common.
19:28They're distributed
19:28all over your body
19:30and are responsible
19:31for the specific sweat
19:32you get after the workout.
19:34The sweat cools your body down
19:36as it evaporates
19:37from your skin.
19:38It's 99% water
19:40so it's practically odorless.
19:42Well, at least
19:44when it first leaves the pores
19:45and comes to the surface
19:46of your skin.
19:47But there are many types
19:49of bacteria
19:50on the human skin
19:51and they feed on the nutrients
19:53in that sweat
19:53together with skin flakes.
19:55One of the byproducts
19:57of this is specific chemicals
19:58and their smell
19:59can sometimes strongly
20:00remind you of onion.
20:03You may have noticed
20:04you produce more saliva
20:06when you go for a run
20:07especially if it's a short jog
20:09in cold weather.
20:11But if you're running a marathon
20:13and it's a nice warm day outside
20:15you'll produce less saliva.
20:18It's your body
20:19trying to offset
20:19the drying effect
20:21since you breathe
20:22through your mouth
20:22way more.
20:25But your body
20:26becomes more dehydrated
20:27over longer periods
20:28which is why
20:30it's trying to conserve water
20:31by reducing saliva production.
20:33Every training you do
20:35no matter how intensive it is
20:36also makes you secrete
20:38more of a specific
20:39type of protein.
20:41It makes the saliva
20:42more viscous
20:43and sticky
20:44which is why
20:45you may feel like
20:46your mouth is dry
20:46way more
20:47after your workout.
20:50Humans see the world
20:5115 seconds out of date
20:53which means
20:54your brain
20:54constantly keeps you
20:55a little bit
20:56in the past.
20:57This way
20:58it helps you
20:59stabilize your vision
21:00of the world around you.
21:02Your eyes receive
21:03a huge amount
21:04of visual information.
21:05Yep
21:06literally millions
21:07of colors
21:07shapes
21:08and ever-changing motion
21:10wherever you turn.
21:11It's not an easy task
21:13for your brain
21:14to process all that.
21:15The visual world
21:16alters all the time
21:17because of changes
21:18in viewpoint
21:19light
21:20and the rest
21:21of the outer factors.
21:22Your visual input
21:24changes
21:24because you need
21:25to blink.
21:26Plus
21:27your head
21:28eyes
21:28and your entire body
21:30are always
21:31in some sort of motion.
21:32Your brain
21:33has to establish
21:34a mechanism
21:35that can create
21:36illusory stability.
21:38It automatically
21:38smooths your visual input.
21:40It doesn't analyze
21:41every little visual snapshot.
21:44It's like a time machine.
21:46You actually perceive
21:48an average of things
21:49you saw in the past 15 seconds
21:51at any given moment.
21:53The brain pulls together objects
21:55so they appear
21:56more similar to each other.
21:57That's why it tricks you
21:58into believing
21:59you're in stable surroundings.
22:01If your brain
22:02kept you updated
22:02in real time
22:03the world would feel
22:05like a very
22:05very chaotic place
22:07with constant changes
22:08in movement
22:09light
22:09and shadow
22:10which would probably
22:11feel like you were
22:12hallucinating all the time.
22:15Your bones
22:16are really strong
22:17but your teeth
22:18which we also consider
22:20as part of the skeletal system
22:21are even stronger.
22:23That's because of the enamel
22:25the hard outer layer
22:27of your tooth.
22:28The enamel
22:29keeps the tissue
22:30and the delicate nerves
22:31inside your teeth safe.
22:33You're basically
22:34burning calories
22:35while you're thinking.
22:37When you rest
22:37and don't engage
22:38in any particular activity
22:40except for the basics
22:41which includes
22:42digesting
22:42breathing
22:43and keeping yourself warm
22:45it's the stage
22:47where your brain
22:48uses up to
22:4820 to 25%
22:50of the total energy
22:51of your body.
22:52That means
22:53your body
22:53will burn
22:54around 350
22:55to 450 calories
22:57per day
22:57while pretty much
22:58doing nothing.
23:00We're not the only ones
23:02in the animal kingdom
23:02with such a mechanism.
23:04Some small mammals
23:05like the minuscule
23:06pygmy marmoset
23:08and the tiny tree shrew
23:10devote the same percentage
23:11of their total body energy
23:12to their brain.
23:14Most of the energy
23:15the brain burns
23:16is to help its cells
23:18the neurons
23:18to communicate
23:19with each other.
23:20They do it
23:21via chemical signals
23:22the brain transmits
23:23across synapses
23:25those special cell structures.
23:27So the brain
23:28directs a lot of energy
23:30towards synapses
23:31in order to make them work.
23:32Your brain
23:33never really rests.
23:35Even when you're sleeping
23:36certain parts are active
23:38so your brain
23:39needs its fuel
23:40to work
23:41and you're basically
23:42burning calories
23:43in your sleep.
23:45The more demanding
23:46mental tasks
23:47you take throughout the day
23:48the more calories
23:49you burn.
23:50So
23:51if you skip today's workout
23:53solve some sudoku.
23:55Do you like to rush
23:56with your ice cream?
23:57Sometimes it pays off
23:59but if you do it often
24:00you must know
24:01the feeling of
24:02brain freeze
24:03pretty well.
24:05It's a pretty intense
24:06and uncomfortable feeling
24:08that comes from
24:08the front or sides
24:09of your head
24:10right after you drink
24:11or eat something cold
24:13such as a slushy drink
24:14ice cream
24:15or an ice pop.
24:17Some people
24:18even go through
24:19a similar sensation
24:20whenever they're exposed
24:21to cold air.
24:22Scientists are still
24:24not sure
24:24exactly why this happens
24:25but one of the theories
24:27is
24:27the cold substance
24:28stimulates a cluster
24:30of nerves
24:30located at the back
24:31of the palate.
24:33Another theory
24:34says the blood vessels
24:35in the roof of the mouth
24:36and sinuses
24:37quickly constrict
24:38because the temperature
24:39in your mouth drops
24:40before they dilate again.
24:43Brain freeze
24:44is not something dangerous
24:45that you should be
24:46seriously worried about
24:47and no
24:48hanging over the table
24:50groaning
24:50or clasping your head
24:51in your hands
24:52won't help much.
24:54Some people
24:55like to sleep a lot.
24:57Hey
24:57guilty as charged.
24:59But
25:00some have a certain condition
25:01called familiar
25:02natural short sleepers
25:04which means
25:05they're kind of immune
25:06to sleep deprivation.
25:07about 1%
25:09of our population
25:10has it.
25:11They can fall short
25:12on sleep
25:12and feel pretty good
25:13about it.
25:14They're fine
25:15with sleeping
25:16for 6 hours per night.
25:18This amount
25:18would wreck
25:19the majority of people
25:20after a couple of nights.
25:22The human eye
25:23normally has 3 cones.
25:25That means
25:26we can recognize
25:27approximately
25:27a million different shades
25:29in the green,
25:30red,
25:30and blue spectrums
25:31of colors.
25:32But
25:33there are some people
25:34with a rare condition
25:35so-called tetrachromats
25:37that have 4 cones
25:38in their eyes.
25:39This allows them
25:40to see ultraviolet shades
25:42which means
25:43they can distinguish
25:44100 million
25:45distinct colors.
25:48Did you know
25:48your skeleton
25:49is all wet?
25:50I mean
25:51your entire body
25:52mostly consists of water
25:53up to 60%.
25:54That fluid
25:55is not only
25:56in your organs,
25:57muscles,
25:57and skin.
25:58It's in your skeleton too.
26:00Your bone mass
26:02is almost
26:02one-third water.
26:04There's this amazing
26:06hidden network
26:07a human body
26:07holds inside.
26:09Blood vessels
26:09are really small,
26:10but if you could
26:11line them all up,
26:12you'd get something huge.
26:14Your entire body
26:15boasts a network
26:16of 60,000 miles
26:18of blood vessels.
26:19One of the ways
26:20to keep your network
26:21healthy
26:21is by eating right.
26:23Have you ever wondered
26:25why our distant relatives,
26:26the primates,
26:27are so much stronger
26:28than us?
26:29In many ways,
26:31our bodies
26:31are very similar.
26:32Look at the chimp's
26:34muscle structure,
26:34for example.
26:35But our closest
26:37primate relatives
26:37are approximately
26:381.35 times
26:40stronger than us.
26:42The human body
26:43developed more
26:44slow-twitch muscle fibers
26:45compared to the rest
26:46of the primates.
26:47This type of muscle fiber
26:49is a less powerful one,
26:50but it lets us
26:52endure more
26:52than other primates
26:53and do things
26:55like foraging
26:56and hunting,
26:56activities that helped
26:58our distant ancestors
26:59to survive.
27:00That's also the reason
27:01why we can run
27:02a marathon.
27:03A monkey could
27:04never do it.
27:05But we'd still lose
27:07in a strength competition.
27:09Laughter is contagious.
27:11It's not just a metaphor.
27:13Researchers have found
27:14that strong emotions
27:16can make the brain activity
27:17of different people
27:18sink.
27:19Laughter is something
27:20science usually links
27:21with social creatures.
27:23People are almost
27:2430 times more likely
27:26to laugh
27:26when in some social situations,
27:28hanging out with their friends
27:30or people they feel
27:31relaxed with.
27:32One of the theories says
27:33that you're probably
27:34going to join
27:35when you see your friend laughing
27:36because humans
27:37are empathetic beings.
27:39Your brain will release
27:40endorphins when you're laughing.
27:42These are special chemicals
27:43that make you feel safe
27:45and at ease.
27:46So we're not sure
27:47why exactly our laughter
27:48is contagious,
27:49but it feels really good,
27:51so...
27:52laughter
27:52...
27:53...
27:54...
27:54...