The Great Sperm Race

Every day, around
350,000 babies are born.

Each one, utterly unique.

A few months ago,
this baby didn't even exist.

And the story of how it came to be
against impossible odds is extraordinary.

This is the moment of conception.

When one single sperm
fused with the mother's egg.

If another sperm got there first,
this baby would be someone else.

So what made that winning sperm so special?

Why did it succeed over billions of others?

To find out, we're going to take you on the epic
journey sperm undertake through the human body.

And we're going to do it by scaling
the whole thing up to human size.

For the first time we'll be able to appreciate
just what an extraordinary journey sperm face

as they try to reach the egg.

It's one of nature's
most spectacular stories

and it's the reason you're alive.

The sperm will face death at every turn.

There is no going back.

No surrender.

And only one winner!

Meet Glenn.

Like most average men,

Glenn has no idea about
the miracle of engineering,

tucked away in his pants.

Glenn's testicles, hanging freely to be 3
degrees cooler than the rest of his body

are producing a thousand
sperm with every heart beat.

And it's this tiny world of phrenetic activity that
fascinates the world of reproductive science.

Sperm are really quite unique because
they're almost like free living cells,

they almost have a life of their own.

They have but one aim

which is to deliver a genetic
payload from the male to the female,

through a really quite
complex series of environments,

both in the male and in the
female reproductive tracts.

Sperm move all over the place

and they like certain things,
they don't like certain things

they're very smart little creatures in a way

and they're a lot of fun to watch

in the petri dish because
they're constantly in motion.

And the fact that it's occurring
at the microscopic level

means that as scientists we have a great
deal of difficulty in studying it and observing it.

A sperm is just one five hundredth
of a million millimetre long,

so to make things easier,

Dr. Allan Pacey and the team of experts

have agreed to help us scale up them
and their world thirty four thousand times.

Along the way, they'll
give us practical advice

on how to give sperm the
best chance of reaching the egg,

or what kind of sex to
have and when to have it

to maximise the chances of conception.

The first thing we asked
our experts was quite simple,

in our people sized sperm world,

what would a testicle be like?

The testicle is a, is a roundish
kind of oblong structure,

if we cut it in half, we
cut thin layers through it

and looked at it down a microscope

we would see a series of tubules that
you might liken to floors of a building.

If we were to take a sperm

and scale it up to man's size

you would have to find a building that
was about a thousand metres cubed,

a thousand metres, by a thousand
metres, by a thousand metres.

That done, we can go inside.

Waiting in our giant testicle,

an army of freshly created sperm.

Just like the real thing,
our sperm are split by gender.

Half produce boys and half produce girls.

The information needed to
determine the sex of a baby,

is stored in the sperm's head.

Here, we find our genetic package,

23 chromosomes of DNA

including the key gender chromosome,

either x for a girl or y for a boy.

Situated just below the head,

an engine of energy producing mitochondria

that propels the sperm's mighty
tail through the female body.

There's many millions of sperm,

you could think of that as a
very, very large office building,

where there's lots and lots of elevators

and tonnes of people maybe at rush
hour all moving in different directions.

x and y sperm are produced
in almost equal numbers,

boys are thought to be faster

but the girls live longer.

Once created, each sperm
ends up in a structure

on top of the testicle cord
called the epididymis.

A tightly coiled 6 metre long tube.

Which can hold over a billion sperm.

Imagine, being crammed into a dark,
winding 200 mile pipeline with no idea

when or if you'll ever get out.

It's here, with no inkling
of the horrors to come.

Our sperm must wait.

Their fate, now,

will depend on events
unfolding in the outside world.

In contrast to the billions of sperm
produced continuously in Glenn's body.

A woman, like Emily will
produce just one egg per month.

Reaching it won't be easy.

The battle that sperm have
in order to find and fertilise an egg,

is just immense, everything
is working against sperm.

um, they're not really given a helping
hand by the female reproductive tract.

You've got, hundreds of millions of cells

that are swimming wildly about.

You've got a lot of death,

you've got a lot of obstacles to overcome.

They've got to make their way through
a complex series of environments

in a, in a kind of warfare, it is warfare.

So if conception is a war,

this is the theatre of operations.

From a sperm's point of view

landing in Emily's vagina is like D-Day.

Their first objective, whilst under non stop
attack from the female immune system,

is to reach a tiny opening high
above them at the back of the vagina,

from here, they can enter the cervix.

The terrain in the cervix
is completely different,

this, is a dark treacherous
maze of unchartered tunnels.

The sperm will need to find
a way through to the uterus.

One wrong turn and
it's a slow, lonely death.

In the uterus,

Glenn's sperm will be looking for a
doorway just a few sperm head wide

in a vast, sterile area, where once again

Emily's elite defence force
will be waiting to take them out.

Then it's on to meet the egg,

timing is everything,

get there a moment too early or too late

and your doomed.

[Lady's laughter]

Emily,

Emily,

Emily.

[Muffled singing]

Glenn's sperm are just seconds
away from participating in

one of the most enjoyable experiences
the human body has to offer.

But what would it feel like, to
be propelled along a narrow pipe

covering 50 miles in less than
2 seconds whether you like it or not.

[Dramatic music]

For each individual sperm, this is a wet and
wild high speed one way ticket to oblivion.

aaarrrrgggghhhh!!

They're not swimming, they're being
forced there by muscular contractions

and by peristaltic contractions.

From the point of view from the man,

it's a very pleasurable experience.

But let's think about it from
the point of view of the sperm.

250 million genetic couriers
are about to invade Emily's body.

Within minutes, most of them will be dead.

Millions of Glenn's sperm
have just entered Emily.

They're embarking on an epic
quest to find and fertilise and egg.

aaarrrrgggghhhh!!

There can be only one winner,

but what chance does an average
sperm have of succeeding?

And is there anything Glenn
can do to help his sperm along?

To find out,

we need to look more closely
at the state of our seed.

A ritual men like Dr. Allan Pacey
have performed on themselves

since the invention of the microscope

I was in my mid twenties and I was a
researcher before I plucked up the courage to

produce a sample of my own semen
and have a look down the microscope

and I remember the first time
looking down a microscope

and I was just blown away,
I almost fell off my chair.

I remember having to stand up and walk
around the lab and go back and look down the

microscope again and is that, has that really
come from me, it was just an incredible sight.

The incredible sight of the sperm cell

was officially discovered in 1677 by a
Dutchman called Antonie van Leeuwenhoek.

The godfather of microbiology, Leeuwenhoek
built some of the earliest microscopes.

Offering him the first, if slightly unclear,

image of what he called animalcules

which he theorised contained
the nucleus of a human

and had a tail equipped with
joints, tendons and muscles

Later, other early microbiologists believed

they could see tiny fully formed
people stuffed into each sperm head.

Modern scientists of course
have a much clearer view.

But they might wish they didn't.

Because thanks to the quantity over quality

nature of sperm production, a long hard
look at an average ejaculate today gives

us the first clues as to why
men need so many sperm.

Of the many millions of
sperm that are ejaculated

we've got a huge range of different types

if we were to look at them
down the microscope

you'd see some sperm that were
really just hardly moving at all

just twitching or some
sperm that would appear dead

and may well indeed be dead.

If you looked at their shape, you
would see sperm with large heads

you would see sperm with small heads

you may see sperm two heads.

In an average fertile man that only,
18, 19, 20 per cent maximum of his sperm

will have a nice size and shape,
but the rest, the other 80 per cent

really aren't going
to get anywhere at all.

To succeed in the race,

sperm must be as fresh
and numerous as possible

any old ones won't make
it past the starting blocks

and as they decay they release substances
that can actually harm younger sperm.

What is inappropriate, is the fact that
the man may be denied by his wife from

ejaculating for 3 weeks
prior to the fertile window in

this um, bizarre thought that
they're going to be super sperm

and huge numbers of them,
that would be the wrong thing to do.

So is the right thing to do, to ejaculate
as often as possible? apparently not.

If a man is ejaculating too frequently

then the sperm production process and the
sperm stores simply won't contain enough sperm

So, just how regularly should a couple have
sex to make sure his sperm are match fit?

If a couple is having intercourse every
2 or 3 days throughout the month,

then they will hit the fertile window at some
point and their probability of conception

is probably as good as it could be.

Now, ready or not

Glenn's sperm begin their quest
for conception in the vagina.

Their objective, to find the entrance to the cervix,
high above them, at the vagina's farthest reaches

From the perspective of a sperm the
vagina is like a vast mountain range.

It's an enormous and awe-inspiring place

Five miles deep and two miles wide,

flanked with vast vaginal walls up to one mile high.

Leaving the thick semen armour
that protected them for landing

it's time for Glenn's sperm
to make a break for the cervix.

The great advance has begun.

But it's not just the
epic terrain in the vagina

or even their own physical failings that
now pose a mortal threat to sperm.

Everything in the vagina is
working against sperm survival

there's only a matter of minutes
between sperms arrival and potential death.

Sperm face attack from every angle,
the use of intimate lubricants

and even saliva here can render
sperm lifeless in minutes

Worst of all, thanks to the female immune
system, the vagina is coated with deadly acid.

The acid is there to kill and invading force,

I think that's a really important point to recognise
because as far as the female is concerned

sperm are an invading force, they're foreign cells,
they could be there to cause damage

they could be there to spread infections,
they are foreign cells to her

and as far as her immune system is
concerned they need to be destroyed.

Within 30 minutes of entering the vagina, over
99 per cent of sperm will be dead or dying.

For our sperm people, it would
be a scene of devastation.

A few million survivors press on
into the dark side of the vagina.

Desperate to somehow escape death by
reaching the cervix high above them.

But the entrance is out of reach,

now to avoid total annihilation,

Emily's body needs to come to the rescue.

To understand how, meet Zita West

Zita is a mid-wife who specialises in helping
couples conceive using natural methods.

And she knows the odds of any sperm
making it past the vagina are slim at best.

For most of the month these
sperm aren't going anywhere

you know, the female body isn't allowing them to.

Her cervix will be shut and there'll be a plug of mucous
there that's stopping any sperm getting through.

But there will be an opportunity when a lifeline is given
to enable the sperm to actually reach the egg.

And that lifeline is the egg itself.

The cervix is usually sealed to protect the
inside of the body from anything nasty.

But as ovulation approaches
oestrogen surges through the female body

causing the body's mucous to
undergo a radical transformation.

So this is what the sperm will be hoping for.

It's the same consistency as cervical secretions.

And these secretions will be coming
from the cervix into the vagina

forming channels for the sperm to be able to swim up.

Now these secretions are alkaline
and they contain salts and sugars

which will nourish the sperm and
give them energy on their journey.

This is the first sort of fitness
test if you like for the sperm

not all the sperm will be able to swim up here, it'll depend
on the healthiest, the fittest, the fastest swimmers,

some that are more abnormal
in the shapes of their heads etc.

won't be able to fit in these channels
to be able to swim up as easily.

Back in our people sized sperm world,
what would this fitness test compare to?

Well, what if your life depended on climbing a ladder?

A ladder stretching over a mile into the sky.

It's a long gravity defying climb that only
a tiny fraction of sperm will be able to manage.

For the 60,000 or so that do, it's out
of the frying pan and into the fire.

Now they must endure stage 2 of their quest, the cervix.

The objective here, to push 4cm to the other side
and reach the wide open space of the uterus.

Sounds simple, until we take a closer look at the terrain.

The cervix is quite simply, sperm hell.

It's lined with tens of thousands of tiny
branching tunnels most roads to nowhere

and some just a single sperm head wide.

With the vast majority, if not all of Glenn's sperm will
get crushed, trapped and ultimately face a slow death.

Nature does have a selection process in the cervix,
it is selecting sperm that are well made.

It would be a bit like me dressed as a sperm,
trying to climb a staircase that's a kilometre high.

I'm defying gravity, I'm going against
the flow and when I get to the top

I find that I've gone down the wrong staircase
and I should have gone down another one

Our sperm must fight their way,

crushed amongst thousands of others up through
a twisted nightmarish urban environment

Only one per cent of sperm that make it into the
cervix have any chance of making it out alive.

But could the performance of Glenn's sperm be
affected by his performance between the sheets?

This woman thinks so

As Dr Joanna Ellington knows

an average fertile healthy couple has just a
one in five chance of conceiving every month.

And for her, success depends on
the quality of the sex they're having.

The better the sex, the better your chance of conception.

One of the things a lot of men don't realise

is that the more excited they are

the further back in the testicle
they're going to draw on reserves,

so if you have, what I like to call 'gourmet sex'

where you really spend time and you
really make it fun for both partners

that is going to make the man more excited, more
stimulated and he's going to ejaculate more sperm

and they're healthier sperm.

Research shows that men enjoying 'gourmet sex'

can ejaculate up to fifty per cent more sperm.

Good news for Glenn, but what about Emily?

Could more fun in bed for her
help the chances of conception?

Nineteen century evolutionary psychologists believed

'the purpose of female organisms was to
keep a woman lying down longer after sex

keeping sperm in the body and
increasing her probability of conception.'

More recently its been suggested the female orgasm
evolved to create a stronger bond between lovers

increasing the chances of the couple
staying together after a child is born.

Nice theories,

but there's never been any actual
evidence to support the idea

that female orgasm had any functional
relevance what so ever, until now.

I happen to be a fan of female orgasm myself, and that's

from a physiological stand point
as well as the personal one.

What happens during female orgasm is the
pH in the vagina actually is elevated some,

there's some changes in the ion concentration

and there are contractions that help
pull the sperm up into the female's body.

Strangely this remarkable theory has been supported
by a Danish study into the sex lives of pigs.

Creatures with reproductive systems
almost identical to ours.

We don't know if a pigs having an orgasm or not
but we know that if we stimulate their clitoris

when they do artificial insemination
we can increase pregnancy rates.

Some people mistakenly think that female orgasm is bad
for conception and there's certainly no evidence of that

in fact the evidence would suggest
that it's a good thing to have.

Luckily for Glenn,

three thousand of his sperm are both full
fit and manage to avoid getting lost.

But as the female immune system
prepares to mobilise its elite assassins,

the great sperm race is about to get even tougher.

Inside an unsuspecting woman,

the great sperm race is underway.

Our army of sperm, unstoppable
by sheer force of numbers

have fought their way through the
mountainous terrain of the vagina

and squeezed through the tight
passage ways of the cervix.

Getting this far has cost many lives,
now just three thousand sperm remain.

The adventure continues,

thanks largely due to the fact that Emily is ovulating.

So is it a coincidence

this couple had sex at the perfect moment during her most fertile and sperm friendly monthly period?

This man doesn't think so.

For evolutionary psychologist Geoffrey Miller

nothing in the great sperm race happens by accident.

The sperm didn't get there by chance the woman's
body and brain has arranged for it to be there.

Its made choices, in its life and its mate search
and its discrimination between male partners

and its sexual behaviour that
led to the sperm being there.

Female choice runs evolution, largely

Unlike men, who can produce
millions of sperm every day,

women are born with all the eggs
they will ever have, about a million.

By menopause that number has fallen to zero,

making them the most important
commodity in the natural world.

A fertile egg from a healthy and intelligent egg
donor costs about $30,000 on the open market.

If you take the size of the egg that adds out to
about a thousand trillion dollars per pound.

So even in strictly economic terms a fertile egg,
it's rare, it's special, it's valuable

Each egg is made even more precious

because one will appear for just a few days per month.

Many female animals make the most
of ovulation by experiencing oestrous,

where their physical appearance, scent and
behaviour will change to advertise their fertility.

Geoffrey Miller believes woman do the same thing.

It used to be thought that humans uniquely lost oestrous

that human females don't go
into oestrous when they ovulate.

That somehow we have this
pair bond that trumps oestrous,

but in fact the new research is showing
human females do go through oestrous,

it serves exactly the same functions
that it does for other mammals,

all the same hormones all the same
psychology is still right there

under the surface of human culture.

So could women effectively go on heat every month?

Could their reproductive systems be unconsciously
controlling their actions and men's responses?

Miller believes so

and to prove it he and his team at the university of New
Mexico have carried out some extraordinary research

at a gentleman's club

We know that lap dancers earnings fluctuate a lot,

so it seemed like an ideal
set-up for being able to ask them,

how much have you earned night by nightshift by shift?

and to be able to track that in relation to
where they are in the menstrual cycle.

And we thought that was a pretty cool way of,
of, quantifying female attractiveness to males

The dancers provided Miller's team with information
about their earnings and menstrual cycles

over a period of 300 work shifts.

The equivalent of about 5,000 lap
dancers for their male customers.

The results were surprisingly strong,

I was amazed at how strong the effects were

that the women in oestrous were earning about twice as
much as they were earning when they were mensturating.

If your'e ovulating you're a lot more attractive to men,

you're earning higher tips, you're
getting called over for more lap dances.

Miller's research suggests a link between
female ovulation and attractiveness to men.

But if women are unconsciously
controlling men's actions once a month,

What actually happens?

They're more sexually perceptive,
higher sex drive more interest in sex,

they dress in more stylish and revealing clothing,

their voice pitch gets more attractive to men,

breasts become more symmetrical,

um, the waist to hip ratio changes,
so the waist gets relatively thinner.

There also changes in smell, so that the women's scent
will be become more attractive to men during oestrous.

So with a little help from the unconscious power of
ovulation the great sperm race continues.

Two hundred and fifty million of Glenn's
battling sperm entered the vagina.

Just three thousand have made it through
the dark twisted hell of the cervix.

Which now opens out into an
environment that is altogether different.

Our sperm expert Dr. Allan Pacey knows,

if you or I were a sperm entering
the uterus would be quite a sight.

From a sperm's point of view the
uterus represents a vast plain

across which they have to navigate and find at the other end

actually quite a tiny opening that will lead
them through to the fallopian tubes.

Scaled up to sperm people size the uterus
becomes a large area of open country side,

two miles long and around half a mile wide.

For our sperm finding the entrance to the fallopian tubes

just a few sperm head wide is like
looking for a needle in a haystack.

Once again it's ovulation to the rescue.

Ovulation occurs on one side one month,
the other side another month.

So on the times that the egg is going to
be ovulated from the ovary on the left,

the uterus seems to preferentially
move material to the left hand side.

So the sperm are probably carried to a large
degree by these muscular contractions

and moved through the uterus relatively quickly.

But on this journey nothing is ever that easy.

Glenn's sperm are about to discover they're not alone.

They're running straight into an ambush.

The primary function of the uterus is of course to receive
the developing embryo should conception occur

and to gestate the foetus throughout pregnancy.

It's not really designed for sperm,
it's designed for something else

it will almost certainly begin to contain leukocytes

and the immune response will be
mounted to try and mop up sperm

and to try and kill the sperm before
they get to the fallopian tubes

Leukocytes are the assassins of the female body,

blood cells commanded into
action by the immune system.

Massing into the uterus in their
thousands with murderous intent.

In comparison to sperm, leukocytes are quite large,

they're big cells, they often hunt in
packs they will detect a sperm

and many leukocytes will descend upon the sperm
and encapsulate it and dismantle it slowly.

For the female body of course, lukocytes
are wonderful essential things,

fighting disease and harmful foreign materials.

But let's try to imagine them from the
perspective of a trespassing sperm.

Once again Glenn's sperm face utter decimation,

as thousands are killed by Emily's immune system.

Just a few dozen lucky ones reach
the entrance to the fallopian tubes.

Only to find that there is a strict door policy.

Sperm have to display the
correct swimming characteristics

in order to get through that uterotubal junction.

And any sperm expressing a very random
form of motion is probably excluded.

There's also potentially a molecular
recognition system there

so only sperm that are expressing the right
molecules actually are allowed through.

Sperm have faced death and
destruction in the uterine cavity,

the leukocytes have been trying to,
ah, kill them along the way

and only a lucky few in comparison to the
many millions that are ejaculated initially

actually make it into the fallopian tubes
where finally they get to sperm heaven.

Welcome to one of Emily's fallopian tubes.

10cm of what can only be
described as paradise for sperm.

The environment of the fallopian tube
is just very accommodating for sperm,

it's what sperm have been aiming for and it's set-up to
try and maintain sperm health and they can have a rest.

Its got nutrients for them, its got the right pH

it has the right ion concentration and some of these
sperm will actually bind to the fallopian tube cells

their membranes will become very closely associated

so that the fallopian tube cells can pass
nutrients and sugar and protect those sperm.

Scientists believe with no immune
system trying to kill them

sperm can blissfully hang around in the
fallopian tubes for hours, even days

but ultimately it's hard to know for sure.

At the farthest reaches of the reproductive tract
the fallopian tubes are very difficult to study,

so difficult in fact some scientists
are willing to extraordinary lengths.

When I was done having children
I choose to have my tubes tied

and I told my Dr. that I wanted to do an experiment

where I had intercourse before I had the surgery

and then she was to cut out that section of my
fallopian tubes where the sperm were stored

so that I could look at them under the electron
microscope and count how many sperm were there.

So it was pretty humorous actually because I'm
coming out of anaesthesia and I was like

did you get it, did you get it?
cause no one had ever done this before.

There were about twenty sperm
in my tubes, that we counted.

Thanks to such dedication,

we now have a clearer sense of what happens
during the final stage of the voyage to the egg.

The sperms objective, to wait for the
egg to appear ahead of them

find it, swim through its outer layer and be the
first to reach its inner core and seal victory.

But how will they know when the egg
has been released from its follicle?

We're just beginning to
understand that there is receptors

that communicate between the egg and the sperm

and the sperm smell the egg,
they're able to sense where that egg is

and you can even see this some in the petri dish

when you're doing in vitro fertilisation

if you put an egg in there, boy those sperm just
right away they orient themselves towards that egg

they're going right towards it, they're
not wandering aimlessly around the dish

hoping to encounter it, it's not left up to chance,
they know what they want to go find.

It's believed sperm wait in the fallopian tubes

until they pick up an irresistible sense signal

which intensifies as the egg draws near.

One study has shown, the scent attracting the
sperm smells just like Lily of the Valley perfume.

The egg basically lays out a
red carpet and asks the sperm

this way, this is where you want to go,
this is the end of your journey.

So instead of swimming backwards into the uterus

they head straight up that fallopian tube, right to the egg

and that's how that final step of the sperm race is won.

Back in the scaled up world of our great sperm race

an egg is finally released, making its way
towards one end of the fallopian tube.

The finish line is tantalisingly close.

And from here on in timing is everything.

She has no idea, but Emily could be
just minutes away from being pregnant.

Beating incredible odds, Glenn's sperm
have fought their way through her body

and have reached one of her fallopian tubes

where hopefully an egg will be waiting.

Just single figures have made it this far,

scaled up to people size, what happens next?

Imagine an olympic freestyle swimming final,
where the winner gains immortality

and the rest are killed.

Scent signals released during ovulation
will make the sperm hyperactive

giving them the ability to actually fertilise the egg,

shedding layers of proteins,
in a process called capacitation.

Up until now they have been
swimming in quite straight lines

but now they're swimming becomes much more erratic.

And that tail beat will give them power and propulsion
in order to get through the outer coat of the egg.

All of a sudden they are a hundred per cent on target.

They want to find that egg, they want to penetrate
that egg and it's a race for the finish.

So once they capacitate,
sperm die within just a few hours,

so it's a no going back.

On the sperm people scale, the egg
drifts just a mile or so ahead.

But as our reproductive scientists can testify

the egg's 24 hour lifespan will present
the sperm with one final, fatal hurdle.

What needs to be kept in mind
for this whole great sperm race

is timing, timing, timing, timing
because the egg has a limited lifetime.

What if the egg arrives a little earlier?, we want some
sperm to be able to capacitate relatively early.

What if that egg comes, maybe a few
hours from now or another day?

Well, you don't want all the sperm to be capacitated right
at the beginning because then they're going to die.

Having arrived hours before the egg,

these sperm reach the end of the line
falling into the abyss beyond the fallopian tubes.

Behind them, just two heroic sperm remain,

all that survives of a quarter of a billion.

These two are y chromosome bearing male sperm
and an x chromosome female

left Glenn's testicles 14 hours ago.

They've endured an incredible journey
and against overwhelming odds

they've got their timing, just right.

At the farthest reaches of Emily's reproductive system

the egg is waiting.

If you or I were a sperm, the egg would soar
into the sky as high as Nelson's column.

During the great sperm race, there's
been this great attrition of sperm

from the point of ejaculation through to the fallopian tube.

Actually at the site of fertilisation
when the egg is being fertilised

there may only be one sperm,
there may be two or three,

but only very few sperm are actually
fighting for that final prize.

Eventually one sperm will hit the outer coat of the egg

and this is it, this is the moment
that they've been waiting for.

To secure victory, all this sperm has to
do now is find a way inside

The sperm is carrying this, this genetic payload

for delivery, but that genetic payload
has to be able to get into the egg.

And the way that it gets into the egg
is the sperm literally blows its top.

Above the head of the sperm, there's kind
of a bag of juices, a bag of enzymes

that are really important at this stage
of the process

by touching an egg that bag bursts and those enzymes
will facilitate the sperm and finally penetrating through,

um the outer coat of the egg,

The great sperm race has been won.

The victorious male sperm is instantly devoured

as Glenn's genetic information
merges with Emily's waiting DNA.

So you get this elegant dance of male chromosomes
and female chromosomes coming together

which will officially announce the fact that, that egg
is fertilised and that new life is being created

and development of a new individual
has started.

Just fourteen hours ago,

hundreds of millions of sperm embarked on the
most incredible adventure in the natural world,

an adventure that claimed all their lives.

So what made that winning sperm special?

Why did it succeed over billions of others?

When you think about the odds that
any single one of us are here right now

compared to the hundreds and millions of other
sperm that in that ejaculate that were left behind

there could have been, a smarter offspring

a handsome or more athletic, a better in every way

ones that just didn't make it, because they either
weren't in the right place at the right time

or you know they just didn't find their way
through the cervix or uterotubal junction

or maybe they capacitated a little too
early before the egg got there

or maybe they were a little too late to capacitate

so there's just a lot of luck involved with it as
well as to which sperm actually is able to fertilise.

Yet one unremarkable sperm,

against odds of trillions to one did not die in vein,

it has given its life to start an utterly unique new one.