NOVA

It is an epic story...

spanning all of human history.

This man was shot at a distance twice with arrows.

Torture was legal,

it was administered in front of a judge.

An age-old battle between our inner angels...

We can see how the human mind is fundamentally built.

...and our demons.

We're at war with ourselves.

But one with a surprising twist.

Contrary to what we might think from the news every day,

rates of violence are actually declining over time.

The decline of violence

might be the most significant development in human history.

Has violence really declined?

A lot of people just don't believe this.

You will not replace us!

It is extraordinarily controversial.

It's an interesting hypothesis to test.

The stakes couldn't be higher.

This is about our very existence.

Now science is tackling violence.

We're saying, like, "Here are things that we could do."

From the streets of Baltimore...

We can see shootings

go down.

To war-torn regions of Iraq.

We're not just testing things in a lab environment,

but we're really testing these in the field.

We've done something right.

Let's figure out what it is and keep doing it.

Are we on the path to a more peaceful world?

It takes just one war to destroy the whole trend.

"The Violence Paradox."

Right now, on "NOVA."

Major funding for "NOVA" is provided by the following:

The shooting started.

Shots fired. More shots fired.

This was the horrific picture

just moments after the white van...

Multiple fatalities is what we're hearing

from officials at this moment.

Kim Jong Un has detonated what is widely believed

to have been a hydrogen bomb.

The world has devolved into a place

where nobody can feel safe.

Wars is everywhere.

It's every corner of the world.

At least 40 people were killed...

Every day, when you're on the news,

there's more and more violence.

There has been tear gas,

they have been pepper sprayed.

I'm afraid for my children

in the world that they'll grow up in.

They let loose a hail of bullets.

It keeps getting worse.

And this time, gunfire aimed

at elementary school children.

This is the 22nd school shooting this year...

There's gun violence, police brutality...

I can't breathe.

People coming and attacking our country.

The first of the two explosions...

That could happen to my city.

That could happen to me.

The world is through and through a violent place.

That's just a part of existence.

Is this who we are...

a species doomed to kill and be killed...

a never-ending cycle of violence?

The reality is that

we may be living in one of the most peaceful eras

in human existence.

Peaceful?

Could this possibly be true?

Violence has been in decline.

But that just doesn't count as news.

You just never see a journalist saying,

"I'm reporting live from a country that's at peace,"

or "a school that hasn't been shot up."

Psychologist Steven Pinker was reading an obscure text

when he came across a chart that piqued his interest.

It plotted a steep decline in rates of homicide in England.

Once I stumbled upon this graph,

I mentioned it in a blog post,

and then I received correspondence from scholars

in a variety of fields,

telling me that I could've made an even stronger case.

Intrigued, he looked further.

I saw dataset after dataset,

all of which showed declines in violence,

in different parts of the world,

with different kinds of violence,

and I realized there was a story that needed to be told.

A story that spans the entirety of human history,

drawing on disciplines from archaeology to neuroscience,

and has the potential to turn conventional wisdom on its head.

To me, it's absolutely huge.

If we think that life is better by going back into the past,

we're making a very serious mistake.

The greatest thing that's happened to humanity

is that we've lowered our rates of violent death by 90%.

This is the big story.

But could it be too good to be true?

The demographics of the past are not at all clear cut.

And so as a result, we're making comparisons

that we're drawing literally out of thin air.

There's so many people who would hear Steven Pinker

and think, "What world is he living in?

This-this isn't my life at all."

It depends on who you are and where you live.

North Korea's nuclear test...

Steve's overarching claim flies in the face

of common sense.

That can't be true!

The Cossacks are always coming, there's always danger.

We may or may not agree with his conclusions...

but it is important

to understand the trends of violence

so we can prevent, if possible, violence today.

It's a controversial argument,

but if physical violence really has declined,

it presents us with a huge opportunity.

To point out that things were worse in the past

is not to say, "We should relax, our problems are all solved."

Quite the contrary; it's by understanding

how our predecessors were able to drive down rates of violence

that we can be emboldened to try to drive them down even further.

Has violence declined?

And if so, can we uncover clues in our past

to make us safer today?

To find out, we have to go back, way back,

to some of the earliest records of human prehistory...

In one of the most desolate places on earth.

Nataruk is a bleak part of the landscape.

There's no vegetation,

and it's got a dark gravel covering the surface.

Marta Mirazón Lahr started excavating this site

seven years ago.

We arrived, and already you could see

on the floor all these fragments of bones.

The first thing we saw was in this area

that we could see coming out of the ground

the broken lower legs, the shin bones, of somebody.

We started clearing and excavating,

and the bones of another one appeared,

so we would clean that one.

And the bones of another one appeared.

We found the remains of 27 people.

They're not graves that have been dug or prepared.

They are in positions that suggest

that they just lied where they died.

What we have here is actually an ancient crime scene.

A crime that took place 10,000 years ago,

when this desert looked very different.

10,000 years ago, you had a very large lake

that had formed a beach.

You would have had palm trees and gazelles and hippopotamus.

It would have been a really rich landscape.

So what we had was a population

of fisher-foragers, hunter-gatherers.

And whenever there is something that one group has

and another one doesn't, the potential for conflict exists.

A conflict recounted in bones,

now buried in a remote storeroom in northern Kenya.

You read them like a book.

And the skeletons are telling us a bit about their life

but most about their death.

When we found this skull,

all we could see was the back of the head.

But when we started excavating,

we could see the whole skeleton lying face-down.

And when you turn it around,

you can see this bone has been crushed in.

He received a blow with a blunt instrument

and another one on the side of the head.

And he wasn't alone.

Many of the skeletons bore signs of violence.

There are injuries to the head that suggest

there's a cut in the face of the skull.

Injuries to the spine that suggest projectiles, arrows.

And this one was bound at the time of death.

Inside the ribs we found the bones of a baby.

Something terrible clearly happened here, but what?

One of the most striking discoveries at Nataruk

comes from what was probably the most difficult skeleton

to excavate.

However,

we discovered the tip of an arrow

still embedded in the head.

We have direct evidence that people were attacked.

But there's more.

The arrow tip was made of obsidian,

a material that is rare

and of which we find no sources locally.

And so it tells me that

the attackers actually came from somewhere else.

It wasn't just a chance encounter

between two groups fishing that ended up in a fight.