Original subtitles

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[narrator] Across the

planet, four times

every second,

a new human is conceived

and an extraordinary

journey begins.

In just nine months,

a single cell no bigger

than a speck of dust

transforms into the most

complex organism on Earth.

This is the most

extraordinary journey

we'll ever take.

And now, with the latest

biological science,

we can follow, week by week,

minute by minute,

the events that

shape and define us

long before we are born.

From each beat

of our heart,

to every finger

on our hands,

from our sex

to our personality

and even

how long we'll live.

Each moment will be

different for us all,

because the steps

and missteps along

the way

create variations that

make each of us unique

and ultimately human.

So, let's relive

the journey,

as we zero in on

the weeks, days,

even hours

of the greatest story

about humans ever told.

[narrator]

Right from the start,

it's a journey packed

full of surprises.

[woman] Who was born first?

Who's the oldest?

Me.

Then me.

Then me.

Then me.

I'm the youngest.

One eight minutes

between each of us.

[seagulls squawking]

[narrator] Holly, Jessica,

Ellie, and Georgie

are genetically identical.

From one egg and one sperm,

one set of

genetic instructions

somehow ended up building

not just one human life,

but four identical ones.

What happened is so unusual

that on our planet of

over seven billion,

there are just 70 like them.

[woman] 64 million to one,

the odds of my pregnancy.

Yeah, that's the odds

of the pregnancy.

To actually go through it

and survive it was

one in billions,

he said.

[narrator] These sisters'

story is exceptional,

but it started with

the same wondrous events

that happen to all of us.

Shortly after

sperm and egg meet,

an extraordinary event

takes place.

Twenty-three chromosomes

in our father's sperm

fuse with 23 from

our mother's egg,

which together create

the first-ever edition

of the unique set of

genetic instructions

for a human being.

Twenty-four hours later,

cells miraculously

begin to divide.

One cell becomes two.

Two becomes four.

Until around day five,

it's a bundle of a few

hundred interconnected cells

tightly bound together.

And it was at this point

that this story took

a dramatic turn.

[man] It was sort of arms

and legs and it was

all a bit...

Incomprehensible, I suppose,

wasn't it? You couldn't...

Yeah.

I couldn't fathom

out what was what.

And then...

I don't think the

sonographer could find

out, either, could he?

No, he went,

he went a bit, um...

Ashen.

Yeah, I suppose

that's the right word.

And he said, "Oh, right."

He said it's a multiple

pregnancy.

Um...

We sort of smiled,

thinking, oh, twins,

boy, girl, happy ever

after sort of thing.

And he said, "No,

this is really serious.

There's four babies

in here."

[narrator]

Exactly what happens

to produce twins,

triplets, or quads is still

a complete mystery.

But one idea is that around

five days into the journey,

the vital connections that

usually hold cells together

could be broken.

And separate clumps of cells

behave independently.

This incredibly rare chance

event split one into four,

with each clump

going on to build

an entirely separate

yet identical human.

[woman]

So, what's the best thing

about being a quad?

Having the best

sisters in the world.

Having fun.

Not being alone

all the time.

Yeah, having...

Having people there.

Around to help you.

'Cause...

If I didn't have any

sisters, I'd be really

sad and lonely.

[girl] They can help you.

Quite honored...

Most of the time.

Apart from when

they're playing up!

[laughs]

It's usually

your fault anyway!

Yeah, I guess so.

[all laughing]

[narrator]

Holly, Jessica,

Georgie, and Ellie

are a marvel of nature

who defy all the odds.

A living example of

the many twists and turns

that can happen along

the extraordinary journey

that shapes

and defines us...

Long before we are born.

[woman] But going from

no children to four.

Yeah.

A massive jump.

Hi, girls.

[woman] Hi, girls!

Come in and say hi.

Come here.

Hi!

Hi, filmers!

Hello.

Hello.

Just wanted to see you.

[beeping]

[narrator]

It's the end of

the first week

and this microscopic bundle

of cells is barely visible,

just a hundredth

of an inch across.

It now starts to

implant in the walls

of the mother's uterus

and at this vital time,

some momentous changes

are happening,

deep inside

every single cell.

Changes that are

dramatically influenced

by the world outside

and by what a mother

happens to be eating.

Which we're learning

could determine

the length of our lives.

[baby crying]

[man speaking in

native language]

[baby continues crying]

[narrator] Baby Nuha is

the newest life to arrive

in this remote

Gambian village.

But there's every

reason to believe

that what happened

to him just days

after being conceived

may mean he will

live as long as

the oldest member

of the village,

born over nine decades

before him.

Mr. Karmo Touray

and baby Nuha

were both conceived

in the wet season,

and this one thing may

have a dramatic impact

on their life expectancy.

[indistinct conversation]

[baby crying]

[narrator] We know this

because of an extraordinary

70-year-long study

that's been monitoring

babies through childhood

into old age.

Dr. Matt Silver is working

on this long-running study

that's revealed some

shocking results.

[Silver] This data

collection has led us

to the rather

extraordinary discovery

that the season in which

you're born here

in rural Gambia

predicts your

life expectancy.

By the time you reach

the age of 65,

you're up to six times

more likely to have died

if you were born

in the rainy season

than if you were born

in the dry season.

[narrator]

Some exciting new evidence

is suggesting this

stark difference in

life expectancy

could all come down to

what a mother is eating

very early on

in her pregnancy.

The weather in this part

of The Gambia fluctuates

dramatically

between the wet

and dry months

of the year.

And this variation

in diet could make

all the difference

to how long a person lives.

[Silver] These seasonal

differences are reflected in

big differences in

the kinds of diets

that mothers are going to

be eating around the time

they are conceiving their

babies and carrying them.

The sort of cocktail of

nutrients that the mother

is eating really will

vary quite starkly

between the seasons.

There will be more

green leafy vegetables

in the rainy season

and other nutrients

will also vary

according to season.

[bicycle bells ringing]

[children singing]

♪ Early in the morning ♪

♪ Praise the Lord ♪

♪ Good morning,

Mr. Michael ♪

♪ Good morning, friends ♪

[narrator]

Those conceived

in the dry months

appear perfectly

normal as babies,

but inside them there's

a ticking time-bomb

for later in life.

How long do you

think you stay in

the mother's womb?

[children] Nine months.

Nine months.

[teacher] Okay.

Okay, so the sperm will

try to penetrate in...

Transferred into this...

[narrator]

And it could be determined

by what's happening

during the first days of

development in the womb.

We used to think

that the genes

we inherit from our

parents are fixed...

But the latest

science shows us

that this isn't

entirely true.

In the first days

after conception,

some genes are switched on

while others

are switched off.

And a mother's diet of

green leafy vegetables

provides a cocktail

of nutrients

that bind to

strands of DNA,

which forever changes

how some genes work.

And this permanently affects

how the body is built.

Our latest discovery

is a gene

which has been shown

to regulate the immune

system,

which could affect

the body's ability

to deal with

a viral infection.

[narrator]

Here in The Gambia,

it seems that for babies

conceived in the dry season,

a key gene that should

have been switched off

has been left on,

which makes them less

able to fight infections

than those with access

to the right nutrition

in the womb.

[people chattering]

These effects are

very evident here,

but they happen

to every one of us.

[drums beating]

These types of effects

are revealed most starkly

in an environment

like we have here

in The Gambia,

where we have very

marked variations

between the seasons.

But we can expect

to see similar effects

in other parts of the world.

So, the kinds of

discoveries we

are making here,

I think really have

global significance

for global health.

[beeps]

[heart beating]

[narrator] It's day 15,

and the embryo is

now less than 1/50th

of an inch across.

It's time for a momentous

transformation to take

place.

Until this point,

each cell has been

identical.

But now, as if by magic,

every single one begins

a profound change,

turning from one cell type

into the 350 different

types of cells

that make up every

part of the body.

This highly complex

cellular metamorphosis

is the foundation of

every part of us.

Incredibly, this process

almost always runs

according to plan.

But occasionally,

a small change occurs,

and that can have

profound results.

[camera shutter clicking]

[Melanie Gaydos]

One of my earliest memories

is actually a stranger

staring at me

and asking my family

questions about me.

I didn't understand

why they were looking

at me in a certain way,

and growing up,

I didn't understand

why people treated

me differently.

In school, kids would be

really afraid of me.

If I was around them, uh,

children would run away.

I didn't really have

a lot of friends growing up.

[photographer]

So, Melanie, let's just try

a couple more of these.

[narrator] Melanie Gaydos is

now an international model.

I look like the First Lady.

[laughs]

You do.

[narrator]

In spite of her

tough early years,

she's broken down

many barriers

to make it in

the world of fashion.

That looks great.

It looks beautiful.

Yay!

I was born with

a genetic disorder

called ectodermal dysplasia.

It affects my skin,

hair, teeth, nails.

[narrator]

Melanie's condition

was determined by

a crucial moment

in time...

[camera shutter clicking]

Twenty-six years

and nine months ago,

when she was just

a bundle of cells.

[heart beating]

It happened when

Melanie's cells

first started the miraculous

transformation process

of changing into

the specialized cells

that form all

the parts of her body.

At magnificent speed,

cells begin to migrate

until three layers

are formed.

At the bottom, cells to

build the guts and liver.

In the middle,

those designed for kidneys,

muscles, bones, and blood.

And at the top, cells

to make skin, hair,

teeth, and brain.

But at this moment,

Melanie's destiny

took a dramatic turn.

[Gaydos]

I don't grow a lot of hair.

My nickname when

I was younger was

actually Tweety Bird,

because I had no hair

except for three long hairs

that sprouted from the top.

[talking indistinctly]

[narrator] When the cells

in Melanie's surface layer

should have become

specialized,

something went wrong,

so her skin became

extremely sensitive,

her teeth crumbled,

and her hair grew inwards.

And this has had

a powerful impact

on her life.

[Gaydos] I really didn't

think I had a future.

I really thought that

something really bad

would happen to me.

I never... I never

thought about

how I would kill myself.

I... I really think

I never let myself

think too clearly about it

because if I thought

about it clearly,

then I probably

would have done it.

Obviously, I'm still alive

and I still kept going.

I think my own

personal strength is

really what

helped me continue

in life because

I didn't have

anything else to

look forward to.

I knew that

through being an artist,

that was something

that I wanted to do

and something

I wanted to be

and it really

gave me hope

that, um, my life

could continue

and my life could change.

[narrator] Melanie has

never known the exact

cause of her condition.

[indistinct conversation]

But today she's finding out

for the first time.

[doctor] So, we got

your results back...

And we found a change

in your gene.

[Gaydos] You did?

We found a change

in the TP63 gene.

This change we

found in you

isn't just

a normal variation...

Right.

In the gene

but something that may

be causing your condition.

[Gaydos] So,

it's a new form.

[doctor] Yes.

It may be a new form of

ectodermal dysplasia?

You're very unique.

Right.

That this change

is your change.

That sounds very great.

It's amazing news.

It's quite cool to find

that I may be the first...

The really, truly,

the first ever of

my kind.

[laughs]

[narrator]

Melanie's genetic

test has revealed

a change in a gene

in her surface layer

never before

seen in medicine.

And so, most of the cells

that build teeth,

hair, and skin

didn't take on all

the vital properties

that should make these

parts of her body work.

So, that is where

my genetic makeup

really comes into play

when everything is formed.

Yes,

and that happens

very early on.

[narrator]

Melanie's entire body

still reflects a snapshot

of that key moment

of her time in the womb.

And the story of

her formation,

along with others,

is helping us

better understand

how this fundamental

process of cell

differentiation

unfolds in us all.

I do feel beautiful.

It's not something that

is easy for me.

But as time goes on,

it's something that

grows stronger

and stronger every day.

[camera's shutter clicking]

If I could turn back

the clock to when I

was in the womb,

to the gene that

created me,

I don't think I would.

It is the way

that I am, and

I love my life regardless.

[narrator] It's two weeks

into the nine months that

made you.

But for this journey

to continue,

we all have to pass

the next step.

We have to grow,

doubling in size

every 14 days

for the next six weeks.

And how this happens

is the result of

thousands of years

of evolution,

which have created

a wondrous balance

between the genes

we inherit from

our parents.

The genes from our father

are programed for growth,

to make us big and strong.

But our mother's genes

are designed to restrict

how big we become,

because she needs a baby

small enough to deliver.

This remarkable design has

evolved so when we are born,

most of us are

neither too big

or too small.

But sometimes,

the balancing act

can be tipped

and we arrive rather

larger than expected.

[woman] I think it

was probably after

about the 20-week scan

and they said that

the baby was big.

And then when we went

back for the next scan,

she was still big

and it sort of went

from there, really.

And she just got

bigger and bigger.

[narrator]

Nell is just seven,

but she's head

and shoulders

above her peers.

There's actually little

in the way of height

between her and her

9-year-old brother Seth.

[woman] She was nearly

five weeks early and she

was eight pound six.

So, yeah, she was pretty

big and in special care

with all the 2-pound babies.

Yeah, she was...

Seth used to go

running in,

didn't he, to visit her,

and you wouldn't have to

tell him which cot

because she'd be there...

In the big one.

[laughs]

"It's the big one,

isn't it, Mummy?

It's the big one."

So, he'd run to

the big one and that

would be Nell.

[narrator]

Early in the womb,

Nell's development took

a different course than

the rest of us.

[beeps]

Instead of getting one copy

of her father's most

powerful growth gene,

she inherited two.

And the extra set

of instructions

telling her body to grow

meant she just grew

and grew and grew.

[heart beating rapidly]

[woman]

Within sort of a few

hours, you could tell

she had a very big tongue

that was sort of

protruding outside

her mouth,

and her stomach

was huge.

It was just

really massive,

so, that's probably

when we first noticed,

and then people started

mentioning over the next

day or two,

you know, that

genetically there may

be something wrong.

[narrator] The extra gene

Nell inherited from her dad

means she overproduces

a hormone that tells

her body to grow.

But as well as accelerating

her normal growth,

it also accelerates

abnormal growth,

putting her at

risk of cancer

because her cells divide

faster than they should,

which can cause

tumors to grow.

Thanks to recent

medical advances,

Nell has always been

carefully monitored.

And today she's come

to have a checkup

on the part of her

body most at risk.

Hiya, I'm Dr. Davis.

Okay, can I have a look

at your tummy today, yeah?

Okay. So, we tuck that up

under there like that.

Right... Well,

there's the kidney.

And what we're looking

for is to make sure

that the kidney is

developing normally.

[woman]

They confirmed

that there was

abnormalities in her kidneys

when she was probably...

Or quite possibly going

to develop a tumor

at some stage,

so... [sniffs]

It was quite

scary, yeah.

Yeah... Yeah.

Yeah, very scary, yeah.

So, we've lived

with that, really.

Yes.

[woman] I suppose you

just wondered when she

was going to get...

We used to think,

"Oh, you know, it would

be better, actually,

if she got the tumors

when she was three

and then have

the treatment

and then

she would start school

and things like that.

It sounds mad

but... But that's

what we thought.

Because you just

assumed at some point

it was going to

happen... Yeah.

[Nell laughing]

That looks a lovely

normal kidney.

We'll just measure

the size on it now.

What does that mean

now for the future?

Well, at her age

now, her risk

is no different from

any other child of her age.

Lovely.

That's great.

[laughs]

[Davis] Yes.

[narrator]

Now that she's seven,

the risk of

developing tumors

will significantly reduce,

because at this age,

Nell's exceptional growth

starts to level off.

[laughs]

[woman] Yeah, pleased,

really pleased. Yeah.

Everything was fine,

so, you sort of get

a bit more

happy that, you know,

everything's fine,

everything's going

to be okay.

Go on, Nell!

[narrator]

Embracing life

at full speed,

Nell is now racing

against kids two years

older than her.

Keep going, Nell!

Keep going!

[cheering]

Keep going, Nell!

Keep going!

Well done. Excellent.

I started off slow,

but then I started

to get a bit faster

and I was coming second,

but then I was

trying my hardest

so I came first

against the other girl,

and she was

trying her hardest,

but I beat her.

Smile.

[man]

She's just a superstar.

You know, she beats

the boys, the girls,

and she's quicker

than you.

[cheering and applause]

[narrator]

450 hours, and by now,

some major milestones

have been overcome.

Cells have rapidly divided,

and become specialized.

And inside every one,

profound genetic changes

have taken place

that will reverberate

throughout our lives.

Now about half an inch long

and inside the embryo,

huge transformations

are underway as clusters

of cells

are intricately assembling

into the body's organs.

And exactly where they

end up comes down to

a few remarkable hair-like

structures called cilia.

Around day 19, these

cilia spring into life,

spinning clockwise

and creating

a leftward current

in the fluid around them.

No one really knows how,

but this current

miraculously

switches on genes

on the left,

which in time tells every

organ of the body where

to go,

and our pre-determined

layout falls into place.

But on very rare occasions,

our organs don't end up

where they should.

[Randy Foye] I first

started playing basketball

when I was, uh, seven,

eight years old.

I would go to

the basketball

courts every day.

We had a lot of fun,

a lot of battles

going back and forth

from early on.

[male commentator]

Foye on the drive.

Count it.

There's Randy Foye.

Makes it two in a row,

this one from downtown.

Foye again.

[narrator]

Randy has always

been a top athlete,

winning a scholarship

to Villanova University

followed by becoming

Big East Conference

player of the year.

He was seventh

in the 2006 NBA Draft

and has now completed

nine seasons

when most careers

last just four or five.

But there's something else

special about Randy,

which happened just 19 days

into his development.

[Foye]

I went to the hospital.

The nurse was doing

some type of test on me

and I think she

couldn't find a pulse

where it was supposed

to be. [chuckles]

Usually, everyone's heart

is on the left side.

My heart is on

the right side.

My liver is on

the left side.

So, everything is basically

a mirror image in my body.

[narrator] Randy has

a rare condition called

situs inversus,

which only happens to

one in every 10,000 of us.

In Randy's case,

the moment when his cilia

were supposed to spin,

sending his organs

to the right place,

they didn't spin at all.

Without his cilia

to direct things,

his left gene somehow

became a right gene

instead

and everything that should

have gone left went right.

Randy Foye from

Villanova University.

[crowd cheering]

[narrator] Randy feared

his rare condition

could affect his career,

so initially, he tried

to keep it secret.

[man] Is he a two guard?

As great as he is,

you put the ball

in his hands...

[Foye] I was worried later

on when I went for the draft

because I didn't want

my stock to fall.

I thought if I let them know

that my heart was

on the side,

if I had situs inversus,

you know,

my stock would drop

and, you know, if my stock

dropped, it would like...

All the work that I did

leading up into the draft,

um, that it would

just be, um,

it just would be

devastating to,

you know,

let this small thing

that really never

affected me,

you know, hurt me.

[men shouting]

My teammates laugh

at me when we do

the national anthem

and I put my hand,

um, over my...

Right here, over my heart,

but my heart

is over here,

and my teammates

would like,

"Man, why you put

your hand over, um,

over your chest right

there? You're supposed

to put it this way."

I'm extremely

blessed and lucky

to be a perfect

mirror image.

[narrator] Randy is

luckier than he knows.

If only a few of his organs

had switched sides,

his heart would have

been severely affected,

and this is fatal

for 30% of embryos

with this condition

and the remainder

suffer heart problems

for the rest of their lives.

You don't hear it?

You don't hear it...

Boom, boom, boom, boom.

That's your heart.

Yeah, that's your

heart beating.

You hear it?

[narrator]

Situs inversus

can be inherited,

so, Randy and his wife

were concerned for their

children.

[Foye]

When she was pregnant, like,

we let the doctors know

that I had situs inversus,

so, that was the first thing

that they would check for.

They... They knew

right away that

with the technology

now that

none of my daughters

have situs inversus.

[narrator] Randy's life

could have turned out

so differently.

But with a little luck

and a lot of determination,

he's become the most

successful mirror man

on the planet.

[Foye] I done been to China,

I've been to London.

I done been to Turkey,

Amsterdam, Germany,

Malaysia, and the list

goes on and on and on,

and I just think

that without this...

This beautiful game

of basketball,

I wouldn't be able to

experience those things

that I have experienced.

[crowd cheering]

Being able to play

basketball has saved

my life.

[crowd cheering]

[male commentator]

Nuggets win!

[narrator] 21 days,

and this mass of cells

is still only a flat disk.

But now an awe-inspiring

transformation begins.

The entire disk

starts to fold,

creating a tube

and along the edge,

a sheath of cells

that will become the control

center of the entire body,

the central nervous system.

This is the remarkable

moment the body begins

to take shape.

And right in the center,

a collection of

tiny muscle cells

is assembling

into a new organ.

It's no bigger than

a grain of sand

but remarkably,

barely four weeks old,

it begins.

[heart beating rapidly]

The heart will make

over three billion beats

throughout the course

of a lifetime.

But it's

a precarious moment

because the astonishing

design of this vital organ

is so intricate

that every step

in its development

must be completed

accurately,

or corrected with

precision once born.

[heart beating rapidly]

[heart beating over monitor]

[indistinct talking]

So, if we, um, decided

that we didn't

want to go ahead

with the operation,

what would sort of

be the outcome

with the baby then...

Would it survive?

The heart pumping

chambers will dilate

and then eventually,

um, don't work

and no blood would

go down to the rest

of the body,

to the kidney,

to the brain,

so, the baby actually

wouldn't survive.

So, the operation

is life-saving

and is necessary.

So on the right side,

you can see...

[narrator] Hannah is

now 36 weeks pregnant,

but several months ago,

shortly after the embryo's

heart made its first few

beats,

something was not right.

Within a week of being born,

it will need

a life-saving operation.

So, this is your baby's

heart now at 36 weeks.

As you can see,

the right pumping

chamber

is rather large

in comparison to

the left.

Baby's just moved...

Moving.

[Adam] Our lives almost

seemed as if they flipped

upside down.

We went there all

happy... Sort of

looking forward

to seeing

a bit more in-depth

pictures of the baby

and, um...

Then all of a sudden

we were being told

that actually,

your baby's got, um,

an issue with the heart.

[heart beating over monitor]

Well, that first one

we were just both

too distraught, really,

to understand, really,

what was going on.

And I don't really suppose

you can sum it up any better

than

just saying, yeah,

your baby's broken.

[inhales sharply]

[narrator]

At their 20-week scan,

Hannah and Adam

discovered that

during early development,

the aorta, the main

artery that takes

blood to the body,

was too narrow,

so blood couldn't

get through.

They know that in the womb,

the fetus is coping

because a bypass vessel

keeps blood moving.

But shortly after birth,

doctors will need

to operate.

We sort of...

Didn't really know what

to do with ourselves

more than anything.

It was...

Yeah, quite...

It has been a massive

roller coaster, really.

But yeah, we're confident

that the team

at the end can fix it...

Almost put a plaster on it.

Um...

And then we can

carry on with our

happy little family

that we first sort of

planned.

[woman] I know.

[sniffs]

[machine beeping]

[narrator] Unexpectedly,

their baby arrived three

weeks early...

And is rushed into

intensive care.

[monitor beeping]

And we've got four

needle holders.

One, two, three, four.

[narrator] After five days,

doctors decide to operate,

in order to fix the mistakes

that happened in the womb.

[woman]

Two, four, six, eight.

[indistinct talking]

[monitors beeping]

[narrator] Dr. Pandey

is going to hone in

on the moment

when things went wrong...

Removing the obstruction

that's causing

all the trouble.

Amelia's heart is just

a couple of centimeters big,

which makes surgery

highly risky.

But with incredible

skill and precision,

doctors are able to

successfully remove

the microscopic blockage.

[woman] How did it go?

It went well.

We're pleased.

Small but...

Yes, I mean,

it's a tiny baby,

so, as expected,

all the structures

were small,

but we managed

to repair it.

[woman]

You joined the bits up.

Yeah, we joined the bits

up, so, yes, as far as

I'm concerned,

the repair looks good

and let's see how she

grows.

[narrator] Baby Amelia will

always need to be monitored.

But thanks to today's

cutting-edge medicine,

it's possible to repair

her tiny heart.

So life at home with

her parents can begin.

[monitor beeping]

[Hannah] She sings

to herself late at

night and it

makes you feel like

the luckiest person

in the world,

given everything

that's happened.

[baby cooing]

Yeah.

Who's there?

And even at 3:00

in the morning when

she's screaming

her head off and

you look in there

and she gives you

a little smile,

it just makes it

all worthwhile.

Um,

you actually just forget

about the time and

that you actually got

to be up in two hours

for work and

you just spend

20 minutes, half an hour

having a cuddle.

It's not until we give her

a bath and you remember,

when you look at her scar,

how much she's been through

in just three months

of her life that

makes you feel like

a special parent and

makes you

value just that little

bit extra how much

she's been through,

and the fact that

she's actually

still here after

everything.

[fussing]

[beeping]

[narrator]

In only six weeks,

so much has happened.

Millions of intricately

organized groups of cells

form the basis of all

the body's major systems.

It's 130 times larger,

but still no bigger

than a bean,

and yet the foundations

of the brain and spinal

cord are in place.

And the microscopic heart

is already beating.

The embryo is growing

more and more distinct

every day.

But something vital

still has to emerge

that starts around 38 days.

Cells within two

flattened paddles

at the end of each limb

slowly die away,

revealing five

perfectly formed digits.

Or sometimes,

just sometimes,

six.

[playing mid-tempo tune]

[narrator]

Meet the Da Silva family.

When it came to

the moment around

seven weeks

when their hands

were first sculpted...

They got more

than most of us.

Instead of five

fingers on each hand,

they have six.

In fact, out of 22

members of the family...

Fourteen of them

have an extra finger

on each hand.

[boy] I think

it's good, because

my hand is bigger

than other hands, and

I have a better grip...

I can hold the ball

much better than

people with five fingers.

Well, it's only difficult

for me to get gloves,

so, I have to...

To buy two gloves,

cut one finger from

a glove, put in another

so I can have

a six-finger glove.

[speaking in Portuguese]

[laughs]

[translator] We can

wear more rings.

Men who marry us

spend a lot of money.

[laughs]

When we get pregnant

and go for a scan,

we just want to know

how many fingers.

We don't care if it's

a boy or a girl.

[speaking in Portuguese]

[translator]

We are delighted

to find it was six.

[speaking in Portuguese]

[speaking in Portuguese]

[translator]

My music teacher says

he wishes he had six fingers

so you can play easily

and you can reach more

notes.

[playing notes]

[all cheering]

[whistling]

[narrator] Although

the Da Silvas' physiology

is extraordinary,

it came about through

the same process

that builds all our hands.

By the seventh week,

a key protein known as

sonic hedgehog is activated.

This is the vital

instruction that

tells the fingers

what to become

and where to grow.

But unlike the rest of us,

the Da Silvas have

a random genetic mutation

which means they produce

more sonic hedgehog than

normal,

and so, when they

were in the womb,

they got an extra

set of instructions

to grow another finger.

[guitar playing]

[indistinct talking]

[all laughing]

[boy] Ah!

[boy] It's a thing

all of my family have.

Uh,

it's something

that makes me, me,

so I wouldn't change it.

Uh...

I wouldn't change it.

Yeah, that's who I am.

This makes me who I am.

[seagulls squawking]

[narrator]

From just a single cell,

a series of moments

of development have

been adding up.

But there's one more

piece of the jigsaw

that has to fall

into place.

The piece that allows us

to walk upright

through life.

[eagle shrieks]

[man] Breathe deep.

I think it's the only

way that I have

to control my... My fear.

[laughs]

[inhales deeply]

[narrator] Bruno Carrera

is about to take

a dramatic leap

of faith,

crossing a ravine

844 meters above

sea level.

And he's going to do

it on a single rope

just two centimeters thick.

[eagle shrieking]

[Carrera]

It's pretty much

like flying.

You can see the birds

passing next to you

or you can hear

the birds sometimes.

Yeah, I love this feeling.

[laughs]

[narrator]

Bruno's incredible

feat is only possible

because of the extraordinary

sequence of events

that came together

in his eighth week

in his mother's womb.

Around the time the hands

and feet are being sculpted,

a series of developments

are happening

that work in perfect harmony

to give us our

remarkable ability

to balance even in

the most precarious

situation.

Deep inside the head,

a maze of looping tunnels

is being carved out

and filled with fluid

to form the inner ear.

This is what gives us

the ability to tell up

and down

and know where

we are in the world.

At the same time,

a series of blood vessels

are being connected

so blood can reach

our upright brains.

And the hips

are precisely aligned

to produce our uniquely

human upright stance.

It is the most amazing

feeling that I try in

my life,

so, it's why it

gets me so bad.

[laughs]

[narrator] And with these

last few developments,

all the furious shifting

of cells stops

and all the critical

structures of the body

are in place.

Tiny and fragile

and not yet conscious,

one single cell

has now become

a human fetus.

While we all followed

the same path

through our first eight

weeks in the womb,

we all did it in

our own unique way.

And each of us

is defined by

this extraordinary time

in our development,

a time that continues

to affects us all...

[baby cries]

From our first breath

to our very last.

[narrator] Next time,

the middle 16 weeks,

when we become

a unique individual,

as everything from our face

to our sex...

Your mom and dad

think you're a boy,

then you're

actually a girl.

[narrator]

And the color of

our skin is set.

It's even the time

when personality

starts to take shape.

[theme music playing]