Original subtitles

Every fall there are dead leaves to rake up.

It's inevitable, from cells to stars, everything dies in the end.

That's just the way things work

But here's the thing, our strange rock itself can also be lethal.

You know up in space you're looking down at Earth and you go "wow",

what a beautiful spot that is down there, that blue orb out there in the distance."

But I'll tell you, it's an angry planet

We tend to think ofEarth as our life support but it's not there to support us at all.

And as you look down on it, it's a place that's violent, that's beautiful, that's crazy,

that's intense.

Mother Nature is a serial killer.

No one is better.

8 astronauts with over a thousand days in space between them,

can tell us how being up there helped them to truly understand what goes on down here.

We think we know our home but here's the secret...

we wouldn't be here without mass suicide, fatal passions and an event so devastating

it makes the extinction of the dinosaurs look like a tea party.

Earth might be the weirdest place in the whole universe.

You know I think every astronaut understands that going to space is a high risk endeavor

and that your life is on the line.

I came to realize this more than most when I spent 5 months living on another world,

the Russian Space Station Mir where survival was a daily struggle.

Just wanna give you a little tour of Mir.

I'm Jerry Linenger of course.

Mir Mission EO-22 would turn out to be the longest 5 months of my life.

Back on Earth sometimes I can close my eyes and I can be back up there again.

Go for shuttle hatch opening, for Delta P under point two.

We opened the hatch of the old 13 year old Mir Space Station and it's kind of like going down

into grandma's cellar.

Stuffed with leftover equipment, garbage.

I was really shocked.

It took up the majority of our time just trying to keep that thing going.

When you're up there trying to use your limited resources to stay alive,

it finally sort of hit me as wow, the survival instinct you know is a powerful enate force

within each of us.

I had about a month on Mir and when I hear that master alarm going off, blaring,

warning panel just lit up like a Christmas tree, fire warning lights, low voltage lights,

everything flashing, smoke lights.

Looked down the length of the module and coming out of a solid fuel oxygen canister

is a big flame with blow torch like intensity, 2 or 3 feet in length,

sparks flying off the end of it, sparks flying everywhere.

I have never seen smoke spread like it spread on that space station so within about 30

seconds, you know, can't see the 5 fingers in front of your face, decided better get some oxygen

while I can, getting a little peripheral vision, blurring, finally locate the mask.

Breathe in and I get nothing.

People talk about that tunnel of death, the next 60 seconds or so of my life, you know,

it's frame by frame.

First thought was of my family, never seeing them again.

My baby son and I just yelled it out, I said "Goodbye John",

you know, "I'm really sorry I'm letting you down."

At that point, I was kind of OK losing my life.

In the middle of all this flame and smoke suddenly, you know, something changed inside me.

I said "Jerry, you gotta get through this."

"And then I just scream out, I'm gonna get that fire out, gonna see my boy again."

Jerry you have to survive.

I broke into action.

1 fire extinguisher, a second fire extinguisher, a third fire extinguisher.

Somehow we managed to get the fire under control.

You know it's instinct, survive.

However much we struggle to survive, it's not only old age,

accident or injury that can get you.

Earth can be deadly.

It's hard to fathom but there have been 5 mass extinctions on the planet

and 99.9 percent of all species that have ever lived are gone.

252 million years ago Earth suddenly turned toxic to life.

Way before the dinosaurs, nearly 96 percent of species worldwide rapidly became extinct.

It's known as The Great Dying.

The Great Dying is an understatement; it all kicked off when a whole host

of super volcanoes erupted.

The land dried out.

And the oceans acidified.

Nearly all plant life perished and every forest on the planet died.

Earth turned into the biggest mass murder scene in history.

Everything that lives today owes its life to the survivors of The Great Dying.

We're all descended from the ones that scraped through.

Today, we're searching an area of prehistoric flood plain for evidence

of a creature that was an evolutionary stepping stone towards mammals.

Found something.

All over this area we've discovered ancient tunnels that have been naturally

infilled and then cast into the rock.

It wasn't long before we started finding bits of fossil bone and eventually we found complete

skeletons and those skeletons all turned out to be a mammal-like reptile called

Thrinaxodon.

A good way to picture Thrinaxodon is to think about the meerkat but without fur

and possibly laying eggs like reptiles but most importantly and similarly to the meerkat,

it lived underground digging burrows with its large claws.

They were surviving by living underground to withstand the heat of the day and the cold

of the night.

One of the really very nice specimens that we've found here are 2 infant Thrinaxodon

curled up together head to head.

They were sharing their body heat which they brought down from the surface underground

which suggests that they were beginning to regulate their temperature on their way

to becoming warm-blooded and of course true mammals.

So you can see if it had not been for creatures like Thrinaxodon,

surviving this Great Dying, we humans might never have evolved.

Our ancestors weren't the biggest or the baddest, they just happened to sleep in the dirt.

Luckily that was the safest place to be.

You never know who's gonna beat the odds.

Throughout the history of life on Earth, species have risen and they've died off

over and over again.

And now that the Earth is resplendent with life, you can't get away from life

on Earth, you dig a mile down into the rock and there's still little things living,

you go to the hottest jet in the centre of the ocean where the boiling stuff is pouring out

into the world and it's a farm of life down there.

You know the diversity of living things on Earth ensures that life will go on,

no matter what the Earth throws at it, no matter which punch it takes,

no matter which species doesn't make it, there's another one that finds a pathway to survival.

So, it's a good thing that life comes in a variety pack but variety comes from

diversity and diversity comes from what scientists call "doing it."

If you're a clone, you don't have to date.

You want kids, just copy yourself, easy.

But clones have a problem; if every individual is exactly the same, one disease,

one catastrophe could wipe them all out, so you gotta mix it up a little.

This is MUSA, it's an Underwater Museum of Art.

The sculptures are becoming home to coral species.

These animals are amazing, they can make identical clones of themselves to spread over a reef

but they also protect themselves against changing conditions by having sex, in a strange way.

Once a year, around the time of a full moon,

the corals release eggs and sperm in massive numbers.

As the eggs begin to float, it feels like you're floating on the Milky Way.

The eggs join together with sperm cells from other corals.

By all mating like this at the same time,

it increases the chances of mixing up their genes

to create more diversity in the next generation of corals.

That's how most of these reef building corals have survived in the ever changing ocean

for 250 million years.

You take 2 individuals and you mix all the DNA and you create a different creature,

a different animal than the original pair.

You know every child or offspring is different than the parent and this ensures

survivability of that species.

I look at my own family, I look at my children, oh my god, they're just totally different

human beings and hopefully better than me.

Sex.

So you may have all been doing it for fun but I'm in it for the survival of the species.

It's crucial to mix the gene pool and life goes to great lengths to do that.

Mayfly nymphs remind me of aliens from a sci-fi film.

They live and grow in the mud for a year, waiting for the right conditions to emerge.

Once the mayfly nymphs are mature, they have to swim to the surface of the water.

If they don't do this fast enough, they will be eaten by a fish.

What happens next is one of the strangest life cycles on Earth.

It's like a fish turning into a bird in just 1 day.

The adults can't eat, they have no mouth parts, they have no digestive system.

For an adult mayfly it's all about the sex.

And they have just 24 hours to find a mate and then they die.

Weirdly, their mating often coincides with the 4th of July celebrations.

The males in a swarm fly up and down, then the females fly by these males and whichever male

is fast enough to catch her is the one who gets to mate.

Once the mayflies have mated, the males are done.

The females find water and lay their eggs and then they too pass on.

They only last 24 hours.

It's amazing the lengths that life will go to, to reproduce.

Once sex came along, it was no longer enough to just survive,

you had to attract a mate and that's when life on Earth learned to dress to impress.

Sexual reproduction has made the Earth beautiful.

It's one of the greatest evolutionary tools for complex life on Earth.

And without sexual reproduction, life would not have the diversity that it needs,

that it absolutely needs to survive on this very tough demanding Earth.

We might like it, we might need it but doing the deed comes with a price.

The only thing for sure in life, you're gonna die.

Even if you don't get hit by an asteroid or eaten by a bear, keeping something as complicated

as a human going, takes a lot of upkeep.

As a physician, I'm fascinated with the whole human being and how it works.

Human body's incredible, it's like 37 trillion cells.

It's more than the stars in the galaxy.

But sitting here today I'm not the me that I was up in space; my cells have cycled,

hundreds of thousands of cells a day are dropping off of me.

And so when you look at me, this is not the hand I had back in space.

Right now there's hundreds of millions of cells dying within your body.

And your body has to replace those and it's the way we are able to stay alive as a living being.

You know most of this destruction is inside our body but out on our skin

we actually can see it, it's much more visible.

It's kind of a harmless thing down here on Earth but up in space, you know,

it's a different matter.

In microgravity, everything floats.

Your dry skin is gonna float in space.

Once a week we cleaned house.

All day Saturday.

We go around with the vacuum cleaner and clean all of our dead skin which is collecting

on all of the surfaces of the filters around the ship.

If you pull your sock off, a lot of skin, dead skin, will go flying around.

It doesn't just become something in your sock, but it becomes a floating cloud of

unused dead skin and that's a really good day to have taken off your sock right next to

an air intake so that you can just sort of turn your head and then go get the vacuum cleaner

and vacuum up the sole of your own foot.

But the clock is always ticking.

Cells can only repair so many times before it has a failure.

Each time a cell replicates, small errors creep in and along with other wear and tear,

over time, this damage builds up.

And when you have enough of that failure, when it accumulates, it's the end of life.

That's why we die.

Making a new creature can be easier than mending an old one.

That's the best way to keep your genes going, knowing that,

doesn't make it any easier when the end comes.

You know, you really need death in order to have this complex world that we have.

It sort of is the arbitrator; by having death you have new life taking its place and probably

an improved form of that life.

OK, Mission Alpha.

Make your way back, you have a spot fire behind the line.

Do you hear those gunshots?

There's probably ammo in that shed.

Stay away from there.

Every firefighter has a respect for fire, a fear for fire.

As you start fighting that fire, you're right up close to it.

The sound, it's overwhelming.

You can't see very well, your eyes are burning, your lungs are burning.

It just doesn't care what it burns; vegetation, people's property.

It's extremely unforgiving.

Fires do kill but you have to realise there is a sense of health that does come from fires

after the fact.

It burns dead trees and death away on the ground and then it allows new things to grow.

It is a part of nature and what it does.

Death is a necessary part of the cycle of life.

Mother Nature kills to regrow life.

It's death that provides the window of opportunity for new forms

of life to occur.

Death-life, death-life, death-life and it helps to perpetuate things

and improve things on the planet.

Nature takes us all in the end but She doesn't do it to be cruel,

getting rid of the old makes way for the new.

On planet Earth, death is not the end, this is not a wasteful world, the dead feed the living.

We all know it's a one way trip when salmon go to spawn.

No one knows that more than the Kamchatkans.

Every year to mark the return of the fish, they hold a dance to celebrate the connection

between life, sex and death.

It's an endurance event.

Like the salmon, they bop till they drop.

The bears and the fishermen get a bounty but they're not the only ones

who feast on the dead.

You know, Earth is really just waiting for you to drop dead so that it can recycle

you and use all your parts in some other form of life.

Salmon are packed with an element that is essential for life and that's nitrogen.

Salmon die and then the trees use the nitrogen as a type of fertiliser,

the animal body decomposing being used by plants.

The trees pick up the nitrogen and they flourish.

Those elements are now part of the ecosystem and they help out other parts of the ecosystem.

Without the salmon, you don't have the forest.

Everything benefits from this banquet of nitrogen.

Living things on Earth, they are interdependent on each other and they are interwoven.

I think as an astronaut looking down at Earth, you understand that this world

is interconnected, you know, you realise this is one heck of a system down there

and you're just in awe of it.

We used to think the world was flat.

We like to think about things in straight lines; birth, life, death, period.

But that's not really how it works, you need to take that line and bend it into a circle;

birth, life, death, birth, life, death so what does that mean for us?

Dad passed away before I was launched into space but I'll tell you,

I was up on that Mir Space Station and I could just sense my dad's presence there.

And almost out of the corner of my eye, it's almost like I'm seeing him.

And I was almost afraid to look 'cause I thought if I look, he won't be there

but by not looking, just feeling his presence, he's sort of telling me, you know,

he's proud, he's glad I made it.

It was sort of a psychological support for me up there and I had his presence there probably,

you know, 4 or 5 times near my time in space when I needed it,

it was something I could draw upon.

My father's time on this Earth has come to an end but I find comfort in knowing

that he still lives on because on our strange rock, nothing is ever truly gone.

He is forever a part of one beautiful pattern of life.

You're just a speck in this long timeline of life on Earth.

We don't really think of the string of events that had to take place for us to exist today.

From the survivors of those mass extinctions, to the cycles of death that keep the planet so

alive today, a million migrating salmon, a billion mating mayflies in the sky,

mixing the genes and all those combination and permutations.

Yet all those different things had to weave together, all those chance meetings had to take place.

Grandparents coming over from the Old Country, that all had to happen.

In my father's life, he had to survive World War II, you know his best friend Jerry

did not survive, that's why I'm Jerry, you know, named after my dad's best friend.

If you look in a history book, there's nothing special about my dad,

he's not gonna be in there but he influenced my life and he was somebody who always told me

you can be anything you set your mind to and "if you work hard and you study hard, for example",

"Jerry, you'll be an astronaut someday" and when you think of all those things that had

to happen to create the human being called Jerry Linenger at that moment,

who then becomes an astronaut, floating above the planet going 17,500 miles an hour,

a life dream.

It's incredible.

You know I had to meet my wife, we overlapped at a job by one day, you know, would John, Jeff,

Henry and Grace exist without that chance meeting, without us getting together

at the right time, at the right place on a beautiful, you know summer night?

I kind of feel that I've done my job now; my family has grown at this point and I'm proud of them

and if I move onto, you know, another life, I'm kind of OK with that at this point.

And I feel I'm gonna keep going on and on through my kids.

So I hope down the line, getting emotional here, down the line, you know,

my sons and my daughter draw upon something that their dad did for them, you know,

how I influenced them.

We're all against all odds, we are all against all odds, you know,

our very existence on Earth against all odds and so, you know, take advantage of it.

Make the most of it.

Next time, do we need to escape this one strange rock and what would happen if we did