Original subtitles

♪

Narrator: Ever since humanity went into space,

We've looked down on the marvels of our civilization.

We've achieved incredible things,

But we didn't do this alone.

Thanks to space technology, we are gaining new insight

Into how the dynamic life of our planet

Has influenced the rise of our species.

♪

We're finding evidence that our exceptional brains

May be an evolutionary response to an unpredictable climate.

Man: When you really look at what our brains do,

They're our organ of adaptability.

Narrator: We're revealing how a lifestyle revolution

Triggered the growth of civilization.

Man: These are probably the earliest ancient roadways

In the world.

Narrator: And we're uncovering the full power and peril

Of unleashing the energy stored within our planet

Hundreds of millions of years ago.

Man: That's an energy revolution,

And there are climatic and ecosystem consequences to that

That are going to be present for thousands of years to come.

Narrator: Humanity's very success is pushing us

And our environment to the edge.

Man: We have become a force to match anything that you see

In a billion years of earth history.

Narrator: But our technology gives us a chance

To shape what happens next.

Man: We can actually conceive of a desirable future

And build a global plan to get to that future.

That's the challenge for humanity in the 21st century.

♪

Narrator: This is the story of us,

Of the life of earth in the age of humans.

♪

♪

From its birth 4.5 billion years ago,

Planet earth has endured constant change--

Devastating impacts from asteroids and comets,

And tectonic shifts generated

By the churning heat beneath its crust,

Transforming the planet's environment.

All life that clings to its surface

Evolves to survive

Or succumbs to extinction.

Our story begins 300,000 years ago.

Earth's climate is colder than today,

With ice sheets extending from both poles.

In the warmer equatorial zone on the african continent,

A new creature arises,

A species of ape with great potential.

They are us...

Homo sapiens.

But 300,000 years ago,

We were not the only two-legged ape

Wandering the african plains.

2015, southern africa.

In a region rich in ancient human fossils,

A fantastic new discovery awaits deep underground.

It's the first time

Paleoanthropologist dr. Lee berger

Has explored the rising star cave system.

Lee berger: I had this map I'd created

Of almost 800 cave sites

That were all entryways into the underworld

That I hadn't been in yet, and that was the mission.

Narrator: Berger has heard rumors of human remains

Glimpsed down one of these passageways.

It's challenging terrain for the scientific team.

Berger: To travel just 100 meters

Takes 20, 30, 40 minutes,

Depending on how fit you are and how good you are

At squeezing through very tight spaces.

It's a torturous journey.

♪

Narrator: The effort is worth it.

They make an incredible find.

Berger: I was speechless.

I mean, there I saw something

I thought I would never see in my entire career.

There was a clearly primitive hominid

Just lying there on the surface in the dirt.

♪

Narrator: The body is just the beginning.

Berger and his team uncover bones

From 15 separate skeletons,

Dating from the time humans first spread across africa.

Berger: We've had everything from individuals just born,

All the way to the extreme elderly,

And everybody in between.

Narrator: But the bones are not human.

They belong to a totally new species--

Homo naledi.

Berger: Imagine if you're standing out here

300,000 years ago.

A group of homo naledis from 500 meters...

They'd look very little different from humans

Because they're walking on two legs.

As they approach,

You're going to start seeing things that are different.

You're going to notice that the proportions aren't right,

That the heads are small, that the shoulders are narrow.

When they got about 50 meters from you,

You'd realize that's not a human coming at you.

There'd be no mistaking.

Narrator: Naledi now joined the ranks

Of at least three other human-like species

That existed in parallel to homo sapiens

300,000 years ago,

Exhibited here in the national museum of natural history.

Rick potts: We used to see human evolutionary history

As that March of progress from ape-like to human beings.

Instead, what we've learned is that there were contemporaries.

Our evolutionary tree is branching and diverse,

Like the evolutionary trees

Of almost all other organisms on earth.

Narrator: But if all these human-like competitors

Once shared our planet,

Why are we the only ones left?

Potts: None of them now exist on earth.

We are the last bipeds standing.

Narrator: Humanity's survival advantage may have its roots

In dramatic changes in the earth's unstable climate.

♪

Satellite images of the western sahara

Reveal remains of a major river system 250 miles long...

Evidence that this was once a lush valley.

It's now believed that every 20,000 years

Throughout humanity's evolution,

Periodic ice ages swing the african environment

From wet to dry and back again.

Potts: The past six million years

Have been the most dramatic period

Of climate oscillation and change in landscapes

Ever since the extinction of the dinosaurs

65 million years ago.

Narrator: Any species that can't cope

With rapid environmental change will not endure.

Potts: The boundary between survival and extinction

Was really adaptability,

The ability to adjust to changes in the landscape.

Narrator: Scientists think the need

To solve environmental challenges

Spurred homo sapiens to evolve a uniquely adaptive brain.

We developed imagination and language skills

Our rivals lacked.

Potts: When you really look at what our brains do,

They're our organ of adaptability.

With language, we have the ability

Of not just having our brains being inside our skulls,

We have the possibility of our brains being shared with others

In ways that go far beyond

What any other organism was capable of doing

Up to that time, including earlier humans,

And that capacity to socially network our brains

Meant that innovations could start to not only be invented

But also to accumulate.

That was our real card

That we could put down on the survival table.

♪

Narrator: Over 200,000 years of intense competition

In a fluctuating climate,

We become the only homo species still surviving in africa.

Homo naledi and our other african rivals

Are overwhelmed.

And it's time for our mental advantage to go global.

An extreme ice age causes sea levels

To drop nearly 250 feet.

Sections of the red sea narrow to just a few miles wide.

♪

It's a new route out of africa

That some of our ancestors now use

To spread across the world.

The decline and disappearance

Of all remaining rival homo species

Can be traced to this great migration.

And our rivals are not the only casualties.

We now begin to have an impact on the planet

Unlike any other animal before or since.

The latest ice age approaches its peak.

Over the last 30,000 years,

Our ancestors have spread across the globe.

But their path to the americas was hindered.

Deep oceans proved a formidable obstruction,

But now this barrier disappears.

Expanding ice caps cause sea levels

To dip to record lows.

In 2014, a satellite survey between siberia and alaska

Measures the shallow contours of the seabed.

Here is conclusive proof that 25,000 years ago,

A 600-mile land corridor opens up.

♪

Across it, animals and humans start to migrate.

But evidence from this late migration tells a bigger story--

That humans have by now amassed

The power to unbalance an entire ecosystem.

♪

In michigan, a team of paleontologists investigates

The remains of an ice age lake.

♪

Team leader dr. Dan fisher unearths incredible evidence

Of the deadly impact of this human migration.

Dan fisher: What's that?

There's something there.

Okay, this shape right here

Is the central column-like section of a vertebra,

The part that supports weight.

Oh! There's another one below this.

Narrator: These are the remains of an icon of the ice age...

The woolly mammoth.

Fisher: Humans living here at this time

Would absolutely have encountered them

On a more or less daily basis.

Narrator: Before humans arrived,

Mammoths and other large animals roamed throughout the americas.

But they had never faced a predator this cunning.

Fisher's evidence shows

Just how sophisticated these hunters were.

Fisher: I think this comes from the base of the skull

That was cleaved off.

This would suggest, not in a single piece,

Maybe in multiple pieces,

We have this very targeted damage on the skull.

They broke in just where it was necessary

To most easily remove the entire brain.

Narrator: The early humans aren't just eating

The nutritious brain.

They know how to prepare and preserve it.

Fisher: The fact that it's found in the pond

Is consistent with the notion

That they store brains in skulls in lakes for a month or two

To sort of season them

And, and get them sort of to just the right consistency,

But then they'll eat them directly.

Narrator: Mammoths once dominated this landscape.

But fossil evidence shows that by 10,000 years ago,

Their numbers are in steep decline.

And the clues point to one culprit.

Fisher: You might think that a small human population

Would never make a dent in the populations like this,

But these are slow-reproducing animals.

When they suffer losses to hunting year after year,

It has the potential to have a serious impact

On the population as a whole.

The evidence strongly supports human activity

As the principal cause of the mammoths' extinction.

Narrator: The end of the mammoths is proof

That as early as 10,000 years ago,

Our adaptive brain gives us enormous influence

Over our environment.

But globally, our scattered populations

Still total fewer than five million.

In this ice age world, our numbers are limited

By the scarcity of the wild resources we depend on.

But the planet itself will soon create opportunity

For a new way of life.

Humans will harness the power of cultivation,

Transforming not just our population,

But our societies, even the whole ecosystem.

Our planet today is lit up by civilization.

But 10,000 years ago,

Not a single town or city exists.

All humans are nomads.

They live in small groups of hunter-gatherers,

Always on the move,

Hunting wild animals and foraging wild plants.

This lifestyle has changed little for over 100,000 years.

♪

But just 5,000 years later, grand structures appear

Alongside teeming cities,

Hallmarks of civilization.

It's a dramatic turning point.

♪

And a set of top secret photographs

May just have revealed where it all began.

In the 1960s, at the height of the cold war,

America launches a spy satellite program...

Code name: Corona.

For decades, the 800,000 satellite photographs

Of the corona program remain top secret,

But in 1995, an archaeologist from the smithsonian institution

Persuades the government to declassify the images.

This treasure trove of data

May just have identified the world's first city.

Anthropologist dr. Jesse casana has spent years

Studying corona spy photographs of the middle east.

The images are invaluable

Because 50 years ago when the photos were taken,

The countryside was far less industrialized.

Ancient details remain visible, if you know what to look for.

Jesse casana: We were able to document

Something like 10,000 previously unknown archaeological sites

That, through the history of 150 years

Of archaeologists working in the middle east,

No one had ever documented.

Narrator: In 2007,

The spy images herald a breakthrough,

Revealing details that are causing experts

To reclassify one settlement as the world's first city.

4,000 years older than the pyramids of egypt,

It's called tell brak.

Casana: It looks like a gigantic hill today,

And surrounding the big hill is a fan of other settlement

That encompasses a very large area.

It's the remains of an ancient city

That was probably first founded more than 6,000 years ago,

And that makes it perhaps the oldest city in the world.

Narrator: Settlements like tell brak only start to appear

After a dramatic event transforms the environment.

It's the end of the last ice age.

Earth's climate radically shifts.

♪

The planet is at its warmest point in 100,000 years.

Where tell brak lies is an area of the middle east

Known as the fertile crescent.

It's now that it becomes fertile.

♪

Rainfall and temperatures increase,

Leading to a great expansion of grassland.

♪

Climate change is about to fuel a food revolution.

For millennia, humans foraged wild grass seeds,

But now abundant wheat and barley

Prove easy to grow and to control.

Some people begin to settle,

To nurture and protect their crops.

They gradually give up the hunter-gatherer lifestyle

To become farmers.

From this point forward,

Human reliance on cultivated plants and domesticated animals

Will begin to change the landscape.

Potts: With agriculture, people began to have an impact,

Taking a few plants, then breeding them,

Growing them, and rejecting all of the other plants around them,

Simplifying those ecosystems.

Narrator: Tell brak is special because the earliest evidence

Of this shift to agriculture

Is visible in the corona images--

The world's first roads.

Casana: What we can see

Are these, these dark linear features

That extend out from the site like the spokes on a wheel.

They're really long.

They extend four or five kilometers, and what they are

Are the remains of probably the earliest known roadways

In the world.

What we are able to reconstruct

Is that, in the immediate hinterland surrounding the city,

There would have been extensive fields

Of intensively cultivated wheat and barley.

The sheep and goat that lived with the people

Here in tell brak,

They would need to pass by those fields,

And they didn't want to trample the wheat,

So they would be kind of constrained,

And so that's how we get these roadways forming.

They served as passage

For large herds of sheep and goat and other animals

To come in and out of the city.

Narrator: The settled populations expand,

Overwhelming the remaining hunter-gatherers,

Transforming the landscape

With fields, villages, towns,

And eventually cities.

As these cities become the hubs of great civilizations,

This is the moment humanity becomes visible from space.

Over the next few thousand years,

Agricultural revolutions occur across the globe.

Each civilization is built

Around locally cultivated plants.

In china and southeast asia, rice and millet.

In the americas, corn or potatoes.

And wherever agriculture takes hold,

There is a population explosion.

By the first century a.D.,

The world population is over 170 million.

By 1500, it's 500 million.

The footprint of expanding human populations

Spreads over the entire surface of the earth.

But now, as long as we rely solely

On plants and animals for energy,

Our growth is constrained.

Further progress is unlikely

If not for a hidden source of power lying under our feet.

Above our heads today,

Scores of satellites orbit the earth.

Their mission--treasure seeking.

Using an array of sensors, they probe the planet's surface,

Seeking an energy bonanza

Buried hundreds of millions of years ago.

♪

Over the earth's 4.5-billion-year history,

It has experienced many violent transformations.

But through them all,

The sun has shone, bathing the surface with light,

A source of incredible energy.

♪

When life takes off in earnest,

It does so because it has perfected photosynthesis...

Using light energy to trap carbon from the air

In leaves, stems, and trunks.

For over 100 million years, immense forests swamp the globe,

And the seas fill with life.

As plants and animals die, their remains become fossilized.

They lock up the solar energy that created them

In coal, oil, and gas,

Which millions of years later

Will utterly transform human societies.

♪

♪

Since the start of civilization,

To keep the fires burning,

Populations rely on wood for fuel.

♪

And by around 300 years ago,

Populated areas like europe and china

Burn up most of their forests.

If they use up all their wood,

Their civilizations may soon collapse.

But in the 18th century,

Humans tap the true potential of fossil fuels...

Developing machines to harness

This buried source of rich energy.

Over just a few hundred years,

They fuel humanity's great leap forward--

The industrial revolution.

Scott wing: We're tapping into this fossilized source of carbon

That's been deposited over hundreds of millions of years,

And we're then burning that energy up,

And that's really an energy revolution that's so recent

That I, I think sometimes

We don't realize how important it is.

♪

Narrator: Access to fossilized energy

Puts human civilization into overdrive.

Wing: The energy revolution lets all of us

Consume a huge amount of power.

The amount of energy that each one of us use in our daily lives

Is equivalent to having,

You know, more than 100 people working for you full-time.

Narrator: Gasoline-fueled vehicles link cities.

Coal- and oil-powered ships link continents.

Technological innovation allows instant communication

Across the planet.

Civilization is now truly global.

But this energy revolution

Also unleashes humanity's potential

For incredible destructive power.

[explosion]

The explosion of the first atomic bomb

Marks a turning point for humankind.

[explosion]

Over the following decades,

More than 2,000 atomic warheads are tested.

♪

They generate an unprecedented release of radioactive dust

That spreads across the globe.

Wing: If you were a geologist ten million years from now,

Some of it would still be visible

In the sediments deposited in the mid-20th century.

Narrator: This is the moment

Geologists consider the official start of the age of humans,

The point when a species of ape achieved the power

To determine the destiny of all life on earth.

So far, the fear of mutual destruction

Has kept us from nuclear holocaust.

But in the age of humans,

There are other ways we can threaten our own survival.

♪

It took humanity 300,000 years

To reach a population of one billion.

But in just two centuries,

Our fossil-fueled civilization has rocketed to seven billion.

We are now spread, in increasing density,

Over the entire habitable surface of the globe.

Kirk johnson: During my life span,

The population of the planet has more than doubled.

The impact of that, of course,

Is that people need food, land, iphones,

Cars, buses, cities.

So as humans grow, they're appropriating the natural world

At a staggering rate.

Narrator: It's estimated that to feed everyone,

Farmers will need to produce

As much food in the next 40 years

As they have in the previous 8,000.

But as we turn most of the globe to agriculture,

We are destroying animal diversity.

Today, livestock farming

Covers a quarter of all available land.

In just 50 years, wild mammal numbers

Have dropped by almost 60 percent.

Johnson: One of the things we've been seeing is over time

Is that there are less animals than there used to be.

There are less fish than there used to be.

There's less wild land than there used to be.

Narrator: Extinction rates are 1,000 times higher

Than ever measured before.

Wing: How long are we going to continue

To decrease the habitat for other species?

Because if it continues, I think there's not much doubt

That we will end up in a mass extinction.

Narrator: We may not notice

The extinction of most wild animals,

But our addiction to fossilized energy

Is becoming impossible to ignore.

♪

Burning fossil fuels pumps huge quantities

Of ancient carbon into the atmosphere...

Far too much for today's plants, soils, or oceans

To reabsorb.

♪

[horns honking]

Wing: We're using the fossil fuel reservoir

A million times faster than it was generated,

And there are climatic and ecosystem consequences to that

That are going to be present for thousands of years to come.

Narrator: Measurements from space probes

Confirm that our atmosphere is altering at an alarming rate.

Gavin schmidt: We've increased the amount of carbon dioxide

By more than 40 percent.

We've more than doubled the amount of methane,

Another trace gas in the atmosphere.

Each one of those things is changing the climate,

Is changing the weather.

Narrator: Earth's history tells us

Rapid change in climate can be disastrous.

Wing: We have past examples

Where the amount of co2 has gone up

And the earth's climate has warmed,

So it's a fact.

Narrator: 56 million years ago,

The climate warmed nearly 14 degrees fahrenheit

Over a few thousand years.

Fossils show that to survive the conditions,

Most species of mammal shrank in size by over a third.

But under our watch,

The climate is changing at a much faster pace.

In the last two centuries,

Ocean acidity increased by 25 percent.

In the last 100 years, sea levels rose 8 inches,

And in just 50 years,

Nearly half of our arctic ice has disappeared.

We are creating a new planetary environment.

Schmidt: We're pushing a system

In a direction that it's never been before.

Just in the space of 150 years,

We have become a geological force

To, to match almost anything that you see

In, in a billion years of earth history.

Narrator: We face a calamity of our own making,

But our species came this far

Through brain power and the tools we created,

So can our tools come to our rescue?

The problems caused by humanity's great expansion

Have been brewing for centuries.

But scientists believe

It's the actions of this current generation

That will decide the future of the planet.

Potts: Humans are a turning point

In the history of life on earth.

We've become a global phenomenon

And responsible for the intensity

Of what is going on to our planet,

To the ecosystems on which

Not only other organisms, but human life depends.

This is, in many ways,

Our own survival challenge for the future.

Narrator: And now we have technology to help us,

Satellites to monitor our planet and help find solutions.

Our orbiting probes have already helped avert a global disaster.

In the 1980s, above antarctica,

Nasa satellites provide crucial confirmation

Of a gaping hole in the ozone layer.

This thin layer of gas high in the atmosphere

Is a vital protective shield against the harshest solar rays.

Schmidt: We tan, we enjoy being in the sun,

But if we were in the sun without an ozone layer,

We would burn almost instantly,

And it would be very, very difficult for life to exist.

Narrator: The culprit is a side-product

Of globalized industry,

Ozone-destroying man-made gases

Used in aerosols and refrigeration.

Spurred by the satellite evidence,

Politicians around the world unite in action.

Margaret thatcher: No one can opt out.

Narrator: The chemicals are banned.

Decades later,

Ozone levels are on the road to recovery.

Schmidt: We avoided the cliff. Nobody predicted this.

What would have happened?

It would have reconfigured life on earth.

Narrator: Space technology helped prevent disaster.

Given the chance,

The atmosphere has the power to heal itself.

Other satellite studies show that some animal species

Also appear to show resilience in the age of humans.

In downtown chicago,

Dr. Stan gehrt uses gps technology

To study a population of coyotes.

Stan gehrt: It's extremely difficult for us

To even pick up their signals on the ground,

But the satellites can pick them up.

Narrator: Radio-collaring over 400 coyotes,

Gehrt documents how this species is thriving in the human world.

♪

Gehrt: One of the most amazing things is just how many coyotes

Can live in a major metropolitan area

And live so close to people.

We estimate that there's 3,000 to 4,000 coyotes here.

We have coyotes that are literally

Within just a few yards from people on a regular basis

With people not knowing that they're there.

Narrator: They survive by adapting

To the urban environment.

Gehrt: Coyotes have to learn traffic patterns.

They have to learn how to cross roads

And avoid getting hit by cars,

And that is the biggest risk to their life down here,

And yet they're able to do that.

The patterns that we're seeing in chicago

With coyotes moving into the city

Is being seen in virtually every single metropolitan area

Across north america.

[train horn blows]

Narrator: If we can make space for nature,

It can survive alongside us.

Satellites can also provide

A path to preserving animal diversity.

Radio-tagging technology

Allows the mapping of wildlife migration routes

Thousands of miles long,

Maps we can use to create protected corridors

To save species from human interference.

It's just one example

Of how space data helps protect our planet.

Johnson: Truly we live in a remarkable time,

When we as humans have technology,

We have the ability to plan ahead,

We know our geologic past.

We can put all that together

And actually conceive of a desirable future

And build a global plan to get to that future.

That's the challenge for humanity in the 21st century.

♪

Narrator: From our perspective,

Our human story is epic in scope.

♪

Our civilization is measured in thousands of years...

Our species in hundreds of thousands.

♪

But the earth measures time

In millions and billions of years.

Our planet has lived only half of its life span.

For the last 4.5 billion years,

It has experienced monumental change.

Species that dominate then disappear,

Giving rise to new life.

Humanity's entire existence is a brief moment of brilliance

On this immense timeline.

And the stable environment we have relied on

Will not last.

Over earth's next few billion years,

More ice ages, epic volcanic eruptions,

Meteor impacts, and extinctions

Will be inevitable.

♪

But the planet's history

Tells us some forms of life will survive.

Where we fit into this future is up to us.

♪