Original subtitles

- [ Man Narrating ] Midnight. April 18, 1775. - [ Horse Whinnies ]

A lone rider carries an urgent message that Will change the World.

His name is Paul Revere...

and this moment is revolutionary...

but not in the way you've been told before.

We think of history as a time line-

a series of events stretching a few thousand years into the past.

It's time to think bigger.

Instead of a line...

imagine a Web of infinite connections interacting over billions of years...

linked together to create everything we've ever known-

our universe, our planet...

and us.

When We consider our most epic moments through the lens of science...

We unleash a revolutionary new idea:

The movement of atoms steer the movements of men...

civilizations, galaxies.

History as we know it is about to get big.

- [ No Audible Dialogue ] - Paul Revere's Warning that the British are coming...

has become an American legend.

But While traditional history tells us that his midnight ride...

is a key moment in the American Revolution...

big history reveals connections to events that shape all mankind...

from the clothes We Wear to the rise and fall of empires...

to the revolution of language...

and it's the horse that links them all.

Big history connects back 6,000 years before Paul Revere...

to the grasslands of Central Asia.

These early nomads are speaking an ancient language...

known as "Proto-Indo-European."

Their Words Will eventually spread and evolve...

branching off from one common root...

into French, Italian...

Spanish...

Greek...

Russian...

Hindi...

German...

and English...

giving us the languages spoken by nearly half the World.

Why does the spread of language begin here?

[ Whinnying ]

Because these are the first people on earth to ride horses...

and that creates a highway for their Words.

We wouldn't be having this conversation- at least not in English-

if it was not for the role of the horse in spreading language, culture and humans.

[ Narrator] Big history shows us the hidden power of the horse...

as the messenger that gave Paul Revere his words...

and the fastest Way to spread an idea...

Whether it's a Warning or a language...

or an innovation.

Big history links back 2, 000 years...

to ancient Rome.

Roman citizens traditionally Wear tunics...

but it's hard to ride a horse in clothes like this.

As the Romans move north to conquer the barbarians...

they notice their enemies Wear something different into battle-

pants.

Pants are Warmer...

and a lot more comfortable to Wear on horseback.

The Roman cavalry makes the switch...

and soon, so do Warriors...

- and men everywhere. - [ Clamoring ]

Horses are a key reason Paul Revere-

and you, and millions of people around the World-

Wear pants.

So while traditional history follows Paul Revere into the American Revolution...

big history links his story to a series of epic transformations...

all set in motion by a revolutionary animal.

[ Whinnying ]

From the moment the first rider jumps on the back of a horse...

nearly 6, 000 years ago...

both creatures are transformed.

[ Man ] The human looks after the horse.

They clean it. They groom it.

They put shoes on it. They help it breed.

And in return, the horse gives us muscle power.

He gives us a victory in war.

On the scale of big history it's hard to think of any other mammal...

that's had such an impact on human history...

as the horse.

[ Narrator] Of all of the animals on earth...

Why did the horse become man's most important ally?

There are an estimated 6. 6 million species of land animals...

but millions of those- like insects-

are too small to be useful...

and others are too difficult to domesticate.

Carnivores, for example, are too expensive to feed.

Some, like the elephant, take too long to reach full size.

Others, like the zebra, are too ornery.

To be useful for hauling and riding...

an animal needs to Weigh at least a hundred pounds...

so that eliminates almost everything else...

leaving us with little more...

than a dozen large, plant-eating land mammals...

and among them, only the horse has the right combination...

of strength, temperament...

and above all, speed.

Each leg is like a giant spring...

that can propel a 1,200-pound animal...

at speeds six times faster than the average human.

Once you domesticate an animal that has more ability than yourself...

you've changed the entire game.

[ Whinnies ]

King Philip gives his 12-year-old son a black stallion.

- [ Whinnies ] - The horse seems untamable...

but the child breaks him.

Within a decade, the boy Will ride this same horse into history.

The boy's name? Alexander.

For 6, 000 years, horses Will be the primary vehicle of conquest.

They make massive empires possible.

At the height of his power...

Alexander the Great commands an empire...

that stretches two million square miles.

Horses help Rome expand from Britain...

to North Africa...

and the Persian Empire to grow as large as three million square miles.

These empires are big...

but what secret force keeps them from getting even bigger?

[ Narrator] Big history is a new way of looking at the World.

It reveals how the horse's unique design made it man 's best friend.

Sparking revolutions in how we speak...

What We Wear...

and making massive empires possible.

But why didn't these enormous ancient empires...

grow even bigger?

The evidence suggests a surprising theory-

that ancient empires have a size limit determined by the horse.

If the outer edges of an empire are more than 14 days ' ride from the capital...

it becomes a struggle to maintain control.

Speed of communications is essential for an empire.

You have to be able to get messages to the frontier...

and get messages back within a reasonable space of time.

If you can't do that, your empire is unwieldy.

You can't respond to attacks. You can't respond to crises.

The Mongol Empire expands Well beyond this limit...

to an unprecedented size of 13 million square miles.

The Mongols control so much land...

it could take more than a year for messages or troops...

to travel to the outer edges of the empire.

But Within a century, rebellions divide the Mongol Empire...

into four smaller territories...

each between two and five million square miles.

Not coincidentally, about the size of the Roman Empire at its height.

On the other side of the World, the empires of the Americas...

are tiny in comparison.

At its largest, the Inca Empire...

is only a fraction of the size of What Rome once Was.

To the north, the Aztecs claim just 77, 000 square miles.

[ Chattering ]

Why are these New World empires dwarfed by those in the Old World?

One important reason:

The New World doesn't have any horses.

In fact, the Inca rely on runners, called "chasquis"...

to deliver messages and goods.

On a horse you can get from point "A" to point "B"...

and they're a hundred miles apart, relatively easily.

That's not a huge deal.

People running- that's a very, very big deal.

[ Whinnying ]

Why did one side of the World have horses While the other didn't?

You might think it's because horses couldn't get to the Americas...

until Europeans brought them here on boats...

but fossil evidence reveals a twist:

Horses Were born in the Americas.

[ Whinny Echoing ]

Horses are ours. They've been ours from the dawn of time.

Big history connects back 50 million years.

As the Earth cools...

damp forests become grasslands.

The ancestors of modern horses move out of the trees...

and onto the plains.

They adapt to their new environment...

and evolve long legs and muscular bodies...

that allow them to outrun predators...

giving them the speed that Will one day be so critical...

to human history.

So What happens to these American horses?

They cross paths With the first Americans...

Who come across the Bering Land Bridge during the last ice age...

and see the horse, not as transportation, but as lunch.

They likely hunted the horse to near extinction.

But some horses make a lucky break...

by crossing the same land bridge that brought people in...

eventually putting them in the right place at the right time...

for humans in Central Asia to tame them.

The horse had a really, really good plan of "get out."

If it wasn't for that, where would we be today?

But the civilizations of the Americas...

Won't have the benefit of this critical animal ally.

When horses finally return to the Americas...

With the Spanish in the 15th and 16th centuries...

generals like Hernán Cortés...

clash With the horseless cultures of the New World...

and Win decisively.

In the first conflicts between native people and the Spaniards...

the Spaniards are able to use the horses to have surprise frontal assaults...

that would never occur if the native people had had horses.

When native people see these horses, they have three reactions-

"Holy cow. What is that?"

"Whoa1 Look at all the things it can do" ..

"I want one."

And they go from reaction one to reaction three in, like, five minutes.

Within 200 years...

Spanish horses transform Native American life...

throughout the Americas.

[ Man ] Once they got the horse and adopted horse culture...

then they became mounted warriors and also mounted hunters...

who now ranged far and wide across the Great Plains.

[ Narrator] And, just like the Mongols and the Romans before them...

these native tribes, like the Comanche...

quickly expand their empires on the backs of horses.

[ McGrath ] In fact, the Spanish had a name for it.

They called it Comancheria...

an area about 600 miles from south to north...

and about 400 miles from east to west...

and absolutely dominated that area.

So the horse entirely changed...

not only the culture of the American Indians...

but the history of the West.

Where does the horse get its horsepower?

The secret lies in the cosmos.

[ Narrator] Big history changes the Way We see the World.

It reveals that the strength and speed of horses...

connects to the size of our ancient empires...

Which allows for the spread of ideas...

and carries us beyond human limits.

[ Blusters ]

But how has horsepower dominated human history?

By giving us the power to harness energy from space.

All the energy We get from eating food can be traced back to one source:

the sun.

Humans can't directly absorb the sun's energy...

but plants can...

Which means grassy plains like this are massive energy reserves.

But eating all this grass isn't an option for humans...

since it's mostly cellulose, a substance We can't digest.

To get energy from Wild grass...

We can Wait for other animals to eat it...

and then eat them.

But there's a problem.

By the time the energy gets up the food chain to us...

most of it is gone.

Plants like grass Waste 90% of the sun's energy they take in.

Animals that eat grass lose another 90 %.

By the time We get around to eating a steak...

another 90 % is lost.

I can't eat grass because of the sort of organism I am.

So look at all that energy sitting in the grass, and it's frustrating.

I can't get at it. So what do I do, if I'm really clever?

I domesticate an animal that can get at the grass.

So as humans begin riding grass-eating horses...

We move a step closer to the energy source...

and get a major power boost.

Learning to domesticate the horse was a sort of energy revolution.

A horse can deliver about eight or nine times the wattage...

of a human being.

So if, instead of carrying goods yourself...

you can have horses carry them...

then, you know, that is an energy bonanza.

For thousands of years, the horse Will be our engine.

We will eventually find new ways to harness the power of the sun...

by burning coal and oil for energy.

But even then, We still use the language of the horse to describe it.

[ Whistle Blowing ]

The train is the iron horse.

The car is first called "the horseless carriage."

And most of all when we measure a machine's might...

We still refer back to the power of our most revolutionary animal ally.

The horse gives humans access to so much more energy...

it's no surprise we use the term "horsepower" today.

But the story of the horse is just the beginning.

There's a much bigger puzzle hidden in big history.

Each episode unlocks a clue-

megastructures...

caffeine...

and ice...

hold the key.

Watch them all, and you 'Il see this grand mystery revealed.

The big history of time, of space...

the big history... of us.