Original subtitles

MICHAEL MOSLEY: This man is blind.

Yet he can climb the world's most terrifying peaks.

These fishermen can see under water better than almost anyone else on Earth.

And this delightful young girl is alive and well

despite having just half a brain.

Their stories are part of YOUR story...

...the story of what makes YOU human.

Hidden deep under your skin is a wonderful inner universe...

...a place of raging torrents,

electrical storms...

...and triumph against the odds.

This is a fantastic voyage through the most extraordinary organism on Earth.

the human BODY

how our brain is made

Strange as it might seem, this bizarre-looking creature is you.

Or rather, what you look like just three weeks after your conception.

This was when your brain was born.

It was the start of an astonishing transformation...

...as you went from a small handful of brain cells...

...to the exquisite network of a hundred billion brain cells

that you carry around inside your head.

We call this transformation...

childhood.

It's a remarkable time that we'll share with three young girls,

each on the brink of momentous change.

Baby Phoebe is rapidly growing brain connections

as she discovers her senses.

Eleven-year-old Wendy is learning to speak.

Not one, but eleven different languages.

And Stephanie teenage brain is pushing her to explore a wild side.

Together, they reveal the extraordinary story of how you built your brain.

It all started before you were born.

In the womb, you grew 8,000 new brain cells every second.

By the time you were ready to be born,

you had all the brain cells you'd ever need.

But this baby is about to experience the shock of her life.

Come on, big, big push. Big push.

Push down.

Don't scream, just push. Get angry and push down into your bottom.

Come on. Push.

It's got hair!

What time is it?

It's, er, about...

This is Phoebe.

As she emerges, her eyes are dazzled by light.

She's come from a gloomy, watery world into a bright, noisy room.

It's time for her to meet Mum and Dad.

Oh, that was... that was pretty difficult.

Yeah.

And hot.

MIDWIFE: I think we gathered that.

And painful.

And...there is a reason why it's "labour"!

Phoebe's brain is being flooded with new sensations.

The chill of the room.

The smell of her dad.

Hello.

And, most puzzling of all,

the strange images that are pouring in through her eyes.

The lens that lies in the centre of the eye can't focus on anything for long.

Even so, newborns recognise their mum's face after just a few hours.

At the back of the eye is the red plane of your retina.

Here, light from outside shines down, casting images across the surface.

Underneath, these rays enter a dense forest

of 125 million light-sensitive cells.

These rod cells each detect just a tiny part of any image.

They send these fragments to your brain, which has to piece it all together.

Phoebe's rod cells give her the ability to see things that move quickly.

They also allow her to see in the dark.

(?) And incredibly ??? working when she was still in her mother's womb.

Your rods are so sensitive

they could detect the dim light that passed through your mother's belly.

So, they were training your brain to see in black and white

months before you were born.

But in daylight, the amount of light around can increase a millionfold.

And just like the moment of your birth,

this totally bleaches out your night vision.

So, a whole new set of sight cells spring into life:

your cones.

You have a richer experience of the world than most other mammals

because your cones detect not two but three different colours.

In one location, they begin to group together,

causing the retina's surface to bulge.

Year after year, they continue to rise,

creating a volcano-like structure.

It's not until you are four years old that the mound is finished.

This is your fovea.

It's the only part of your eye where your vision is crystal clear

and, thanks to your cones, capable of sensing millions of different colours.

But the complexity and the beauty of the human eye

is nothing without your brain.

You blink up to 20 times every minute.

Each blink lingers for less than half a second.

But add all those blinks of an eye up

and you're living in the dark for over an hour every day.

Your brain is so good at filling in the gaps

that you're not even aware of it.

Your eyes are an extension of your brain.

They are so adaptable that you can learn to see

in places where human eyes normally struggle.

This is the remote Thai island of Koh Surin,

home to a group of sea gypsies known as the Moken.

To survive, they've become expert underwater foragers.

Finding food underwater is difficult,

particularly without goggles.

That's because our eyes have adapted to see clearly in air.

In water, the world becomes blurry.

As you descend, light levels drop quickly.

Your eye reacts by opening the iris,

making the pupil larger and allowing more light in.

The image becomes brighter,

but underwater, a larger pupil also makes the image more blurred.

But Goon has learnt how to overrule this automatic reflex

with an astonishing adaptation

seen clearly with the help of an infrared camera.

Instead of opening his pupils, he closes them as far as they will go.

This means Goon can see twice as well underwater as you or I.

Recent studies suggest that any child can quickly learn this trick.

The Moken show how well the human brain can adapt the body to suit its needs.

This adaptability has enabled our species

to thrive on all seven of Earth's continents.

But at three months old,

Phoebe's brain is still hopeless at pretty much everything.

Hey! Hey, Phoebe!

It can tell her mouth to suck but can't feed itself,

can't maintain body temperature,

can't even control when she goes to the loo.

I now am utterly and totally responsible for another human being

who has to take priority over my life in everything.

She has to come first, otherwise she can't survive.

Phoebe is so very helpless because her brain is still getting organised.

Bit by bit, her brain is creating her mind.

This remarkable time lapse shows living brain cells

sending out tendril-like arms, which connect with each other.

Each of Phoebe's hundred billion brain cells

will, on average, make 10,000 different connections...

and we can follow this on the outside.

Oh, I've gone away!

At six months, Phoebe thinks that when she can't see someone

they vanish from the world entirely.

I'm here.

Watch Phoebe's face as Charlotte hides.

- Now you don't see me. - She immediately loses interest.

Where's Mummy gone? Where's Mummy gone? Shall I come back?

But when her mother reappears...

- I've come back! - her delight is obvious.

I'm here! Yes, I am!

Going to come back, I'm here.

- Where's Mummy gone? - Three months later,

and Phoebe's brain has now learnt

that just because something is hidden doesn't mean it's disappeared.

Here I am! Yes!

A childhood game of peekaboo has helped her build connections

that will stay with her for the rest of her life.

And the longest connection Phoebe's brain will ever make

is the one between her head and her toes.

Remarkably, the connection between your head and your toes

won't be fully mature until you are three years old.

Long before that, your brain just can't resist

the urge to take its first big step, as you try to walk.

Learning to balance and coordinate your body is so complex

that the area of your brain devoted to this one task

involves as many cells

as the whole of the rest of your brain put together.

Some people learn how to walk sooner than others.

But there is a place where people pull off this feat

sooner than anywhere else.

This is Kaumba.

She is mother to a baby girl called Kosini.

They live in Rhumsiki,

a tiny village in the remote northern highlands of Cameroon.

Here, mothers are keen to get their babies off their backs

and walking as soon as possible.

Ever since Kosini was a month old,

her mother has repeated the process of "kitete",

which means "to make jump".

Every day, she takes hold under the arms and bounces her.

Kosini responds with a kind of stepping reflex.

You had this reflex, but it disappeared after a couple of months.

But here in Rhumsiki,

this daily encouragement means that the reflex remains

and gradually develops into mature walking.

Now she's seven months old,

it's time for Kosini to try and stand up by herself.

So her mother sets about another ritual practice.

She washes her with a warm herbal liquid.

This seems to stimulate her legs, preparing them for walking.

The leftover warm leaves are laid on the ground

and Kosini is placed on them.

It's uncomfortable and she soon wants to get off

giving her the gentle encouragement she needs to use her legs.

These rituals seem to be accelerating

the connections that Kosini is making between her brain and her feet.

But before you can stand up for any length of time,

there is a strange part of your body that your brain must learn to understand.

This cavern is buried deep inside your head.

It's part of a labyrinth of twisting tunnels completely submerged in fluid.

The tunnels are the three great loops of your semicircular canals.

(?) Inside each loop, there is a saddle top flashing mountain, your crista.

(?) The mountain slips are covered in a thick forest of tiny hair cells.

For the moment, they lie still.

But this inner sea never remains calm for long.

As you move your head, it generates a shockwave

which races through the tunnel and pummels the mountain.

On its flanks, the hair cells are thrown about in the turbulent waters.

(?) The pressure builds until electricity ???

grating a powerful electrical current.

All this activity going on inside your semicircular canals

creates your sixth sense:

your sense of balance.

To walk, your brain has to sense when you are overbalancing to one side

and then instruct your body to shift your weight back to the centre.

All of this has to happen within a fraction of a second.

To begin with, it's a real struggle.

But Kosini's half-brother, Tisema, is already a master of bipedalism.

He is just ten months old.

At his age, most children are shuffling around on their bottoms.

From now on, and for the rest of Tisema's life,

walking will be automatic.

By the age of one, your brain has made over 500 trillion connections.

So many, that your brain can cope with almost anything

that life throws its way.

Angelina is a rather remarkable one-year-old

because she was born with just half a healthy brain.

She has a rare disease

which affects the blood vessels on the right side of her head.

She's a happy, active little girl, but every now and then...

Angelina? Angelina?

Angelina?

Angelina?

You all right? OK?

Angelina's having what we call a complex vocal seizure.

As you can see, she was very, very active and now she's gone very distant.

One indication is that her head lags.

She's slightly heavy in her breathing.

Angelina has a rare condition, Sturge-Weber syndrome.

This one is going on quite a bit, isn't it?

Angelina? Angelina?

Her parents, Lisa and Stephen,

have had to deal with her seizures ever since she was born.

Angelina's brain scans show the cause, abnormal blood vessels,

seen here in white, on the right side of her brain.

But they also show that the left half of her brain is perfectly healthy.

There is a treatment for her condition,

but it involves radical surgery:

cutting off the damaged half of Angelina's brain.

We're in a position we don't know what we've got to face after this operation.

I pray to God she comes back to us at all,

but what she does come back as, we accept.

The surgeon who must navigate his way through Angelina's tiny brain

is Mr. William Harkness.

We've lifted the bone flaps, so we've made our trap door in the skull.

And now we're beginning to see the brain.

It seems impossible that you can disconnect

half of someone's brain and expect them to recover,

yet that is exactly what the surgeons are hoping will happen.

Because the brain does adapt at this age of life,

we would expect most of the functions to transfer to the other...

other side of the brain.

It takes four hours of micro-surgery

to find the bridge between the two sides of Angelina's brain.

And this is what's called the corpus callosum...

which connects one side of the brain to the other.

Now, he cuts through it.

Angelina's healthy brain is finally free

from the disruption caused by the damaged right half.

Hopefully, if this child becomes seizure-free,

I think that we will have given her the best opportunity for the future

because the type of epilepsy that she had clearly is life-threatening.

She's so sleepy.

I haven't even given her a kiss yet.

- Haven't you? - No. Come here, lovely.

Come on, my darling.

Hello, sweetheart.

Who's a strong little girl, eh?

Who's Daddy's strong little girl?

You have a nice dream.

All her parents can do is wait and hope.

It was essential for Angelina to have the operation at this age

because after your first birthday

your brain loses some of its flexibility.

While there's still room for plenty of development,

there's less scope for fundamental change.

But as your young brain starts to explore the world from its new, lofty position,

there is an immediate and rather wonderful consequence.

That's because walking releases two powerful natural tools:

your hands.

I've kind of developed a skill with my hands that when I touch things,

I get information from it.

A bit more than an average human.

From a young age, street magician Dynamo

has been fine-tuning the control of his hands.

If I put a pack of cards into your hand,

you'd just feel the edges of the cardboard, right?

Whereas I can actually feel how many cards there is in the, you know, in the...

in my hand.

I've built up, you know, a sense that allows me to do it.

His hands are so nimble your brain cannot keep up with them.

Your hands' versatility springs from a mixture of strength and sensitivity.

At the tip of each finger is the densest collection of nerve receptors

found anywhere on your body...

feeding your brain with information about the temperature, pressure

and vibrations of anything you touch.

They're so sensitive they can detect lumps and bumps

less than a 100th of a millimetre across.

(?) Just reach and then pull out any card.

(?) Show it to ???

(?) I'm gonna put it about halfway down ???

Just put your hands like this, please.

(? ) Really focus on the card, all right, and watch.

- That was incredible, Dynamo, you are the man. - You are amazing, Dynamo, I'm telling all my friends.

(?) Brilliant. Group hug, thank you so much. That was amazing.

Your hands allow your brain to reach out and change the world.

As a result, our species is the only one to have built a civilisation.

Standing upright and walking

releases the potential of your wonderful hands,

and it's followed by another milestone,

an ability that is uniquely human:

the ability to talk.

When I was one, I spoke Vietnamese only, like, it was just like baby words.

When I was two,

I spoke English, Vietnamese, Spanish and Chinese,

so four languages when I was two years old.

Well, I started learning them.

(?) From an early age, Wendy ??? brain has been bursting with languages.

She hasn't stopped at just four languages.

Wendy spends an hour every week

talking to a range of different people in their native tongues.

I am Winita from India, and I teach Wendy Hindi.

My name is Rashida and I teach Wendy Arabic from Yemen.

And I teach Wendy Spanish.

She speaks Spanish a lot better than some Hispanic kids do.

At the Russian languages, she is very good.

Portuguese...

She is at the top because she can switch very...

in a few seconds, from one language to the other one.

And she can think, speak, write. It's unbelievable.

Vietnamese, English, Spanish, Chinese,

French, Japanese, Hindi, Arabic, Russian, Cantonese and Portuguese.

Add them all up and Wendy has 11 different voices packed inside her head.

But speaking is only half the story.

For meaning to fly from one person to another,

the words have to travel deep into your body.

Inside your ear, sounds set off a complex chain of events.

They enter as pressure waves,

which push and pull your eardrum, making it vibrate.

On the other side of the eardrum,

these vibrations set a series of bones jiggling.

They end with the smallest bone in your entire body, called the stirrup.

It is smaller than a grain of rice.

These bones allow you to hear.

If a sound is too loud...

..a muscle pulls the stirrup away from the most sensitive parts.

Temporarily, at least, you go a bit deaf,

but the rest of your ear is protected.

Beyond the stirrup is a fluid-filled cavern, your cochlea.

The incoming sound waves tickle clumps of tiny, hair-like sensors on the floor.

These begin to dance to the sounds of the world outside.

You have 30,000 sensors.

Each picks out a different part of the sound

and sends it straight to your brain.

The cochlea is most sensitive to the sounds of another person's voice.

SPEAKS RUSSIAN

RUSSIAN DIALOGUE

Finely-tuned ears and a wonderfully versatile voice...

have allowed humans to invent over 7,000 different languages.

SPEAKS IN FOREIGN LANGUAGE

THEY GIGGLE Hello!

Bonjour... VARIOUS FOREIGN LANGUAGES

And each of us, as we grow, pick up over a thousand new words every year.

SPEAKS IN FOREIGN LANGUAGE

By your early teens,

you have a working vocabulary of over 10,000 words,

as you head towards the brain's next challenge:

puberty.

Stephanie Bean is 14 years old

and like all teenagers she's maturing... phisically.

(?) We really don't talk about the puberty thing ???.

I know some girls think it's embarrassing.

???

Like the rest of her teenage friends, Stephanie's brain is maturing too.

The way it does this is bizarre.

During her teenage years, she will loose 40% of the connections

she spent more than a decade building.

This extraordinary image was made from hundreds of teenage brain scans.

It shows how, as the brain matures,

the areas which are packed with connections, colored red and yellow,

make way for areas that contain far fewer, colored blue.

The brain is prunning away the connections that it doesn't need.

Scientists believe that this leads to more efficient and faster thinking.

But perhaps the most puzzling change during puberty

is that your brain seems determined to travel a dark road

to risk taking and recklessness.

As well as being a cheerleader, Stephanie Bean has another hobby.

She's also the world's youngest stock car racer.

I started racing stock cars when I was ten years old,

so I've been racing them for four years.

She's competing on the Winchester Speedway,

also known as the world's fastest half mile.

At 37 degrees, these are the steepest curves in American motor sport.

It's pretty awesome 'cos whenever you go round it's like

you get all that speed in you and it builds up, and it's like, I wanna go.

Stephanie is prepared to take risks that many of her adult competitors will not.

One reason is that part of her teenage brain

is releasing neuro-chemicals that encourage risky behaviour.

There will probably be about 20 cars out there going like

around 90 to 100 miles an hour, very close, like inches away from the wall.

Whenever she takes a risk, her teen brain rewards her

with a much stronger natural high than her grown-up competitors.

Whenever a car's next to me, it just makes me want to go even more faster.

If there's a gap, then, you know, take chances.

It's her brain's accelerator pedal pushing her to take risks.

Go, Stephanie, go!

But the scan of her developing brain reveals something else.

The last part of the brain to turn blue and mature is the bit at the front,

which thinks through the consequences of taking a risk.

Stephanie's isn't fully mature,

so even when she recognises that something is dangerous,

she will probably do it anyway.

But why are teenagers wired to take risks?

One theory is it's to encourage you to try lots of new things

before you settle down into adulthood.

Ever since that time, long ago, when you were just a tiny embryo,

you've been busy nurturing your brain cells.

You've assembled so many that their numbers now rival

the hundred billion stars that populate our galaxy.

And this vast, beautiful network

has been shaped by the kaleidoscope of sights, sounds and feelings

that you've lived through.

Now, finally, after 20 years, it's done.

You are the proud possessor of an adult brain.

Until recently, scientists believed

this would pretty much be the end of the brain story.

That from then on, it was just a slow gentle decline into old age.

But we now know that your brain would retains

that wonderful child-like melody to learn throughout your life.

Adventurer Erik Weihenmayer is a striking example

of how well a middle-aged brain can respond to new challenges.

There's that step again, Erik.

Erik went blind when he was 13 years old.

Every week, you know, I would wake up with different levels of vision

because my retinas were splitting away from my eyes.

Today, Erik, with his friend, Greg Childs,

is going to attempt to scale Utah's formidable Castleton Rock.

It's Erik's first climb here.

To help him, he has brought along an impressive bit of new technology.

I don't know if you've seen this. This is a brain port device.

This is the camera on these sunglasses here.

The camera picks up images

and sends a feed to a computer on Erik's hip...

..which translates the images into a low-resolution picture of the world.

These blocky images are then sent

to one of the most sensitive parts of Erik's body.

This is the tongue display.

On the surface are hundreds of tiny electrical stimulators.

If the camera sees a distinct outline,

a corresponding line of stimulators buzz away, tickling Erik's tongue.

I can feel each dot and together they create lines and shapes

and, ultimately, images that my brain then reinterprets

as the space around me.

Three decades after he lost his sight,

the visual part of Erik's brain, his mind's eye, is back in action.

Except now, he's not seeing with his eyes.

He's seeing with his tongue.

Is that sight? Well, kind of, you know,

because I think seeing is more in your brain than in your eyes.

In rock climbing, most of the risk is taken by the lead climber.

Greg led most of the tower.

He's making sure, you know, that if I fall, I'm not going to fall too far.

OK!

Well, sometimes I like to lead the rock face too.

And that's really fun for me, because I'm now the first person

going up the rock face, and I'm taking the risk.

- Last pitch to the top. - Excellent.

OK, are you ready?

Erik is feeling so confident with the brain port device

that he decides to lead the final push.

And now I'm Greg's safety, for me, you know, that's a real honour,

being blind and still being able to be a real part of the team.

You pop over this lip and it's completely flat

and the wind just gusts in your face.

And you're up there on this flat tower, 1,000 feet above the desert floor.

- It's a privilege. - I know.

This is totally beautiful.

Erik is a great example of the brain's astonishing ability to remodel itself.

It's this that makes us so wonderfully adaptable.

And six months on from the operation to split her brain,

it's this adaptability that is giving Angelina the chance to flourish.

It's just wonderful to see now

that the development is just coming on in leaps and bounds.

Are you going to come to Mummy?

Come to Mummy. Good girl.

To hear her start to talk, start to walk, it's just absolutely amazing.

For you?! Say "hello".

Rock, paper, scissors, shoot.

Whatever your age, if you continue to stretch your brain,

you can be sure it will rise to the challenge.

Stone, paper, scissors, shoot.

This is adventure, you know, this is total adventure.

Original subtitle by: E-mail subtitling@bbc.co.uk

review for this release by: Tio Beto from Brazil

... =Peace Through Anarchy=...