Cosmos: Possible Worlds - First Season

If an extraterrestrial scouting party were to survey Earth,

what would they make of us?

Who are we?

Are we as a species capable of fundamental change?

Or is there something in our DNA that will determine our fate?

Do the dead hands of forgotten ancestors impel us

in some direction beyond our control?

Can we free our children from the demons that torment us and

haunt our species?

Can we be trusted with our own future?

Since the civilization of Ancient Persia,

and probably even before, we've wondered if there's

something about human nature that contains the seeds of our destruction.

If there are places on Earth that are sacred to our species,

surely this must be one of them.

The earliest site we know of where fire was tamed for human needs.

More than a million years ago, here,

in what is today known as Wonderwerk Cave in South Africa,

our ancestors gathered and first kindled the hearth of human culture.

Every human being alive today on Earth is a member

of the species Homo sapiens.

The so-called "wise ones."

And our forbearers here tonight are Homo erectus,

"those who stood up."

They're not yet us, but we carry them within us.

We don't know much about them.

We think they took care of each other when they became old or ill.

We know they were skilled toolmakers.

It was around fires such as this one that we began to cook our food.

To tell each other stories.

And to create a shared learned identity with our kin.

Had life and humans first evolved only hundreds or even

thousands of years ago, we might know most of what's

important about our past and how we came to be the way we are.

But instead, our species is hundreds of thousands of years old.

Homo erectus, a couple of million.

Primates, tens of millions.

Mammals, more than 200 million.

And life, about four billion years old.

All but a few of our ancestors are wholly unknown to us,

and we sift through the Earth to find the bits of ash and

animal bone that are the only surviving evidence of our humanity.

We only began living with a future in mind,

consciously leaving a detailed record of who we were and what

we believed around 5,000 years ago.

And yet, one thing remained constant from Homo erectus to

the greatness of Ancient Persia.

Our fascination with fire.

And this was true here at Persepolis,

a magnificent complex built by the Persian emperors of the

sixth century BCE,

when Persia was the only superpower on Earth.

These great kings worshipped a God named Ahura Mazda,

whose origins in time are lost to us.

His prophet was Zoroaster.

Every Zoroastrian temple was consecrated to fire.

It played the central role in Zoroastrian worship,

symbolizing both the purity of their God and the light

of the illuminated mind.

Tending an eternal flame through the centuries was one

of the few ritual obligations of the Zoroastrians.

They chose this first truly human achievement,

the domestication of fire,

as the focal point of their worship.

The God Ahura Mazda didn't ask much.

He didn't want your ritual sacrifices,

he didn't want your money.

All he asked of human beings was good thoughts,

good words and good deeds.

But for some reason, most people couldn't fulfil

these simple requests.

Often they had bad thoughts and said evil things,

and some of them committed crimes that were evil.

Why?

It was all because of Ahura Mazda's polar opposite,

Angra Mainyu.

This is where the devil was born.

From his short horns, to his hooves,

Zoroastrianism was the dominant religion from Greece

to India for 1,000 years.

No wonder they were so influential on the religions

that came after.

For the Zoroastrians, all the evil in the world,

the crimes committed by humans,

as well as the catastrophes of natural disasters and disease,

were the results of Angra Mainyu's unceasing mischief.

Their God, Ahura Mazda,

looked to human beings to help him defeat the devil.

Any person by their actions could tip the scales of the

whole future of the universe in either the direction of good or evil.

In this prescientific world,

when evil reared its ugly head,

what better way to understand it than demonic possession?

This is not a story of good and evil,

of the struggle between a God and a demon.

It's actually just a story of a predator and its prey.

In this case, the predator is microscopic and it's been

incubating in its victim.

Diseased microbes can be formidable predators.

Not only attacking and eventually killing,

but also taking over their hosts.

Changing their behavior to spread their microorganisms to other hosts.

We're in the bloodstream of that poor,

unlucky dog, who, through no fault of his own,

just because of a chance encounter with a rabid bat,

now finds himself the main character in a zombie horror story.

Those bullets are the rabies virus.

On being injected into the bloodstream of this placid,

people-loving dog, they head to the dog's brain,

right to the limbic system,

where the control buttons for rage reside.

By attacking the nerve cells,

the rabies virus is converting the poor animal

into a marauding, snarling,

vicious predator without loyalties or love for anyone.

Rabid animals can be fearless.

Now that the limbic system has been conquered,

another detachment of rabies viruses are dispatched to the

saliva manufacturing machinery in the dog's throat.

Their assignment is to put it into overdrive,

while paralyzing the nerves for swallowing.

This maximizes the chances for the infected saliva

to leave the dog and invade the next target.

But how is such a degree of tactical coordination

possible by a virus?

How can a virus know which part of another creature's

brain is the seat of anger?

We ourselves didn't figure that out until very recently.

This is the power of evolution by natural selection.

Given enough time, a random mutation,

no matter how highly specialized...

Say, a virus' ability to paralyze a victim's throat,

will take hold.

If it enhances the virus' chance of survival,

it will be passed on.

All it needs in every generation is a victim to

carry the disease.

Keeping that wicked flame alive.

The transformation from the family guardian to the

ferocious wild-eyed demon is complete.

The dog is furious, although he has no idea why.

A helpless pawn of the viruses within him,

he can't resist the impulse to attack.

If the attack is successful,

the viruses in the dog's saliva will enter the

bloodstream of the victim through the lesion or laceration.

And then, they'll set about taking over this new victim.

The rabies virus is a brilliant manipulator.

It knows its victims and how to pull their strings.

It coordinates its attack, circumventing defenses,

infiltrating, outflanking, accomplishing a coup d'état

within its prey and turning the most gentle among us into

the most violent.

We are at the mercy of unseen forces.

Viruses, microbes, hormones, our very own DNA.

Where does the programming end and free will begin...

If it ever does at all?

Do honeybees have free will?

When a honeybee dies, it releases a special chemical.

It's a death pheromone that has a characteristic odor,

signaling its fellow bees to remove it from the hive.

The death pheromone is oleic acid.

What happens if a perfectly healthy bee is dabbed with a

drop of oleic acid?

Then, no matter how hearty it might be,

it's carried, kicking and screaming,

out of the hive by oblivious pallbearers.

Do the bees understand the danger of infection from corpses

decomposing in the hive?

Are they aware of the connection between death and oleic acid?

Do they have any idea what death is?

Do we?

In the tens of millions of years of collective bee

experience, there's never been a way that a bee could give

off oleic acid other than by dying.

So, for bees, there's no ambiguity here.

Scent of oleic acid always means dead bee.

There's been no reason for evolution to develop a greater

sense of nuance about it.

Elaborate, contemplative machinery is unnecessary to

assess the situation.

Bee perceptions are adequate for bee needs.

Something similar is true for moths.

This poor guy has no idea what the problem is.

There have been moths for 190 million years,

and clear glass windows for only about 1,000.

No wonder there isn't a voice in the moth's brain that tells it:

if you keep bumping into something,

even if you can't see it, you should try to fly around it.

Until very recently on nature's time scale,

there were no penalties for moths without any such inner voice.

Moths evolved in a world without glass windows.

What then are we to conclude when we find similar,

very simple behavioral programs unsupervised by any

apparent central executive control in so-called

"higher animals"?

When a goose egg rolls out of the nest,

does the mother goose who has been incubating her eggs

for weeks understand the importance of retrieving one that has rolled away?

Can she tell if one is missing?