♪
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.
♪