Original subtitles

(ancient drumming)

Deep inside a remote cave system

in northern Spain, a once-in-a-lifetime discovery

has been made.

Hundreds of ancient human remains have been uncovered.

They are remarkably well preserved,

but they are in pieces.

Investigators must reach back in time to identify the dead

and reconstruct their last days.

(stone smashing)

From the cliffs of Gibraltar

to the depths of El Sidron Cave,

scientists embark on an investigation

into one of the world's oldest cold cases

as they try to shed light on a moment

lost in time.

(mysterious music)

(pleasant music)

Time winds slowly through the quiet valleys of Pilona

in the far north of Spain.

People here take care the past is not forgotten.

Below the valleys, another world beyond memory.

Pre-history.

(water drops echoing)

In March 1994,

cavers exploring El Sidron Cave system

deviated from the main tunnel to climb up

into a small side gallery.

The cave is a favorite haunt for adventurers,

but many locals are superstitious about El Sidron.

What is about to be found may confirm their fears.

(speaking in foreign language)

Hey, I found something!

Come up.

Looks like human bones.

The remains are reported to authorities.

140 bones are exhumed, but they are all in pieces.

Police and cavers note that the bones don't look very old,

certainly no older than 60 or 70 years.

(speaking in foreign language)

After the Civil War, people hid out here

and used the cave as a refuge.

Their families brought food and left it at the entrance,

so they were able to survive for a while

until they felt safe or the fascists caught them.

And they did catch Olvido Otero González.

She was shot and bled to death right here.

It became known as The Tomb's Entrance.

Police believe they are removing the remains

of other victims of the Civil War.

(speaking in foreign language)

What was clear was that the collection

was very well preserved.

But it was also evident that the excavation method

used by the police to exhume the remains

was not appropriate.

They wouldn't be the first to touch these bones

in the wrong way.

In Madrid, investigators compared the bones

to other human remains.

They did not belong to Republicans or Nationalists.

They came from another time,

and they were another people.

Neanderthal.

(flute music)

Below the ruins of Casa Del Sidron,

the investigation continues into this prehistoric cold case.

The location where the bones were found

is now known as the ossuary gallery.

Every year, more and more relics are exhumed,

and the number of dead rises.

Scientists from across Spain have joined forces.

Human fossil expert, Antonio Rosas,

from the National Museum of Natural Sciences in Madrid

leads the investigation.

Carles Lalueza-Fox, a world-renown geneticist

from the Institute of Evolutionary Biology in Barcelona

hunts for ancient DNA.

And Archaeologist, Marco de la Rasilla is now on his way

from Oviedo University to the annual dig.

He is in charge of the excavation.

(majestic music)

His final destination, a hidden river valley

in the beautiful principality of Asturias.

(majestic music)

Most of the young researchers who join the dig

are Marco's students.

They return year after year to spend

up to a month working the site.

Marco also enlists the skills and knowledge

of a local man called Lalo.

(generator running)

The ossuary gallery is 220 meters from the main entrance.

On this, the first day of the dig,

all equipment and supplies have to be carried into the site.

The entire tunnel stretches for nearly four kilometers

through limestone and clay corridors.

It's a karst system, shaped by the incessant flow of water.

(water drops echoing)

A subterranean river called The Pando has worn away

the calciferous rock over tens of thousands of years.

Rain above can flood The Pando,

making it sometimes extremely dangerous to work here.

A puddle can grow into a raging torrent.

That's why work facilities have been built to stay.

The ossuary gallery is slightly higher

than the main gallery.

It's safe from flooding but not from looters.

In the first years of the dig, fossils were stolen.

A steel cage now keeps the precious remains safe

23 meters below the earth.

(speaking in foreign language)

Because we're used to working in caves,

this one was just another cave,

but it proved more interesting,

because it was like a container of rather unusual remains.

(ancient drumming)

Now the tiny gallery once explored by cavers

has become a chamber, hollowed out bit by bit

using only brushes and spades.

The researchers have shaped El Sidron

with precision and care.

The site is cramped and difficult to traverse,

but in this confined space, over a thousand bone fragments

and hundreds of stone tools have been found.

Every bucket full of soil taken from around the fossils

is also checked for small pieces of bone and stone.

(speaking in foreign language)

Once we had started

the excavation in El Sidron,

the big question was,

"What were the human remains doing there?"

We didn't know what it was used for.

It could have been a home, a burial ground,

or the remains could have come from somewhere else

and were in a secondary position.

We just didn't know.

Even modern humans need electricity down here

and plenty of warm clothes.

The temperature never rises above 10 degrees Celsius.

I have been in many Neanderthal sites,

and nothing compares to that.

Neanderthals usually are found in rock shelters

facing south

close to a river.

Nice place to be if you are in a glacial period.

Neanderthal occupation sites

were open to fresh air but also protected.

Neanderthal real estate ranged from humble rock shelter

by a quiet stream

to cathedral-like rock towers

along the Mediterranean.

(seagulls calling)

Neanderthals lived throughout Eurasia,

but who were these people?

Jean-Jacques Hublin is the Director of Human Evolution

at the Max Planck Institute in Leipzig.

He has led field operations in many Neanderthal strongholds

and is an expert in their evolution.

The Neanderthals were the real Europeans.

They lived in Europe for maybe 300,000 or 400,000 years,

and they have been a very successful

group of archaic humans.

They are close to us.

They are also different.

The danger, of course, and it's a danger

in which we often fall,

is to consider Neanderthals just like other humans,

other modern humans

and to put in their behavior

or in their conception of the world

our conception of the world,

but we should not forget that we're talking

about the species that separated from us

almost a million years ago.

Inside El Sidron, investigators work

to uncover a time and its people we can scarcely comprehend.

The truth behind what happened here can only be deduced

from a thorough forensics investigation.

Every specimen is logged, cleaned, and examined.

The stone tools will be transported to Oviedo

and the bones to Madrid for more rigorous studies.

(speaking in foreign language)

The abundance of the collection

was sensational.

However, the material was in pieces.

Because of that, we needed a lot of patience.

We had to wait from one excavation to the next

so that new fossils could be incorporated

into the collection.

Only then was it possible to put

the pieces of the puzzle together.

And as the pieces in their exact location

in the cave are excavated and plotted,

they discover the bones and stone tools are all being found

in the same layer of soil, made up of gravels and mud,

a meter deep, six meters square.

(tools scraping)

There are many sites in Europe where Neanderthal remains

have been found,

but in general, these remains have been accumulated

throughout a rather long period of time.

Even if in one layer we find artifacts and bones

or human remains that look like they have been left there

at the same time, in fact,

the same time may have lasted many, many years,

sometimes centuries or even millennia.

El Sidron will prove to be unique.

A random selection of relics are dated.

They are all the same age,

49,000 years old.

Did these people live at the same time?

The evidence is in the scientists' hands.

At the University of Oviedo, Marco and his team

come across proof while examining the El Sidron stone tools.

(speaking in foreign language)

What we found here is exactly

what one would find in a Neanderthal's toolbox,

tools that would have been used by an individual

for normal daily activities.

We've also found evidence of the reduction

of what we call lithic flakes.

Lithic flakes are a byproduct.

They are struck from a tough core of rock.

Some of the flakes were discarded,

others made into useful stone tools.

(speaking in foreign language)

With this tool, you can cut meat,

make other tools and even crack bones.

It's as sharp as a razor blade.

By looking closely at the edges

of lithic flakes and of what he suspects are cores,

David Santamaria sees a pattern.

He attempts to refit the pieces.

Here is irrefutable evidence of a moment

49,000 years ago when someone made stone tools.

But these tools were not made inside the El Sidron Cave.

If they were, some of the flakes would have been found

close to each other when they were excavated.

(rocks striking)

Santamaria's pieces were scattered up to a meter

away from one another.

Between the time they were made and when they were found,

they were moved by humans or nature.

The answer comes from another pattern.

The stones and bones fit within a cone shape.

It's a debris flow cone, a well-known geological phenomenon

resulting from a sudden collapse.

In El Sidron, we have a cone of sediments.

It's a pile of dirt that fell from the surface

into this cavity.

(speaking in foreign language)

When this geological phenomena occurred,

everything moved inside, so logically,

everything appeared together.

(echoing drips)

The El Sidron investigators

find a logical point where the bones

and stone tools entered, right above the ossuary gallery.

It no longer opens to the surface.

The real story of what happened

to the people of El Sidron is outside.

The karst landscape above the cave

is constantly reshaping itself.

Huge sinkholes appear when acidic rain

dissolves the limestone.

They will eventually crumble into caverns below.

But the collapse in El Sidron was not a slow process.

If it was, the remains would have been scavenged.

Wolves and other predators shared the Neanderthal's world.

(speaking in foreign language)

The fact that there were

very few carnivore teeth marks shows us

that the bones, the bodies, were only exposed to the air

for a short period.

The burial process was very fast.

We really have something that has been deposited,

not in millennia, but likely in a few hours.

El Sidron is, in fact, the only case where we have

solid evidence for having a real group of Neanderthals,

a group of people who really lived together

during their lifetime.

(fire crackling)

But did they die together?

It's difficult to know how many people were in El Sidron.

The bones are in fragments, and they don't fit together

to make even one whole person.

In Madrid, Antonio Rosas struggles to connect the pieces,

but he is certain he knows what happened to these people

49,000 years ago.

He's found cut marks in significant places on leg bones

and jaw bones.

(speaking in foreign language)

This means that parts of the bodies

were cut with the intention of ripping away the flesh.

Some of the bones have been cracked by force.

Here we can see an impact mark on this leg bone fragment.

This means that the bone has been struck and broken

with a stone in order to reach the bone marrow inside

which is very nutritious.

Evidence enough for Antonio Rosas

to come to a conclusion.

(speaking in foreign language)

In El Sidron,

there was an incident of cannibalism.

(stone crushing bone)

(bone scrapings)

And the weapons that inflicted the damage

are still as sharp as the day they were made.

(speaking in foreign language)

The fact that everything appeared together

inside the cave means there was a clear activity

related to cannibalism, and the stone tools

were used for that purpose.

But how can the investigators prove

that the perpetrators were Neanderthals

and not our ancestors?

In El Sidron, the most likely scenario

is that these Neanderthals were butchered

by other Neanderthals, because at the time they lived,

there was nothing else but Neanderthals

in this part of Europe.

(crushing strikes with stone)

(rock smashing bone)

What is the reason why humans would butcher other humans?

We can only compare our behavior with theirs.

What we find is cannibalism that resulted from starvation

and is an issue of survival,

so basically they eat dead bodies.

The most widespread kind of cannibalism is something

which is more ritual, where people have been defleshing

the remains of somebody dead in the group,

sometime eating some parts of the body,

but this has, I would say,

almost a religious dimension.

Sometimes this applies also to enemies.

(speaking in foreign language)

What is the real significance

of this occurrence of cannibalism?

Are there symbolic or cultural reasons?

At the moment, we don't have any evidence to show

that a ritual occurred here.

Was the act of cannibalism in El Sidron

a common part of Neanderthal culture?

In the far south of the Iberian Peninsula

is a rock that was a refuge where no evidence

of Neanderthal cannibalism has ever been found.

Clive Finlayson is an evolutionary ecologist.

He thinks he's found a Neanderthal Shangri-La.

As you come around in a boat and look at this cliff face,

you don't just see one cave, Gorham's Cave.

You see another cave and another cave

and others going underwater,

and they were all occupied by Neanderthals.

This was the Neanderthal city.

El Sidron is dark and cool.

The path to Gorham's Cave is bright and hot.

(dramatic orchestral music)

The Neanderthals had been living in Gibraltar

for a long time, probably much longer than 60,000 years ago.

The surprising thing here was not when they started,

but when they finished.

We found half a campfire at the top of Gorham's Cave,

which we excavated, and we took samples

for radiocarbon dating, and the surprising result

that came back was 28,000 years.

That makes them the most recent population of Neanderthals

to have survived anywhere on the planet today.

El Sidron's story is of an instance in time.

Inside Gorham's Cave, events that happened

over tens of thousands of years are being pieced together.

Clive's team have excavated

hundreds of Mousterian stone tools.

Mousterian technology is the technology

of the Neanderthals.

Underwater Archaeologist, Geraldine Finlayson,

has been working the site with Clive since 1997.

For a long time, Neanderthals were thought to have

mainly been eating meat,

but we find it certainly in this part of the world

that they eat a lot of shellfish,

and here behind me we've got different layers

like layers in a cake, and scattered among the layers,

you can still see the remains of the shells

that they have collected.

We also find fish bones and fish scales inside the cave.

It's very easy to collect fish.

You don't need a rod or a line to catch a fish.

If you just toss a stone at them, you can knock them out,

so they can be quite easy to catch.

(waves crashing)

(gentle piano music)

They ate all kinds of things, whatever was out there.

If you put it together, all that's missing

to make a good Mousterian Neanderthal paella is rice.

(waves crashing)

(gentle music)

Outside the cave, the view is not the one

the Neanderthals would have had.

For most of the time, the sea level was much lower,

because global climate was much cooler.

The coast was four to five kilometers out.

The seabed, which is well submerged now,

would have been the landscape where they went out,

hunted and gathered, and then they came back into this cave

for shelter and protection.

Geraldine and her dive buddy,

Archaeologist, Darren Fa, are about to dive

on the landscape that existed when Neanderthals lived here

and the sea level was much lower.

(diver splashes)

It's a unique and very new investigation.

Large pinnacles rise up from the seabed,

and at their base,

freshwater springs have been found.

We can see valleys.

We can see river gullies,

and we've actually found up-wellings of fresh water,

so they would have had a lagoon-type system

in front of the cave, so you can imagine,

that would have attracted water birds,

a whole bunch of other things.

It was actually quite an idyllic landscape

for them to survive in, possibly explaining

why they lasted here so long.

Collecting rock from the pinnacles

to compare with stone tools found in the cave

will connect the sites,

but the real work ahead involves undertaking

land-based archaeology at depth,

setting up grid lines,

digging and recording with meticulous method.

If this was the landscape of the Neanderthals,

perhaps their bones are still here,

but because it is now 30 meters down,

after only 20 minutes,

they have to leave the site.

Finding evidence here will be a slow process.

(instrumental music)

In Madrid, Antonio Rosas and his team have spent a a decade

trying to get to know the victims of El Sidron better.

He has led a meticulous forensics investigation

to find the age, sex, and health of the victims.

Each year more evidence is exhumed

and the death toll alters.

It started at four.

It is now much, much higher.

The reconstructions have to be done with teeth.

Scientist, Almudena Estalrrich knows every one of them.

(speaking in foreign language)

We know that the teeth belong to

a certain kind of individual for many reasons.

In the first place, the wear is the same.

In other words, all the teeth are in the same state,

eroded or not eroded,

and mainly because of the marks on the sides of the teeth

caused by friction.

They serve as a kind of fingerprint.

They're the same now as when the teeth were together.

In this way,

they discover a much higher death toll than ever expected.

(speaking in foreign language)

There are 12 individuals represented,

six adults and six children.

Among the children, there are three teenagers

close to maturity.

There is one child around five years of age,

another approximately eight years old

and a very young one of around two years of age.

The investigators know

the Neanderthals' age and sex.

They know they were cannibalized

and how they came to be inside the cave,

but there is one thing more they hope to find.

Something that may help offer the ghosts of El Sidron

a type of immortality;

their ancient DNA.

Genetics.

The new wave of Neanderthal research is about to take

the investigation into another realm.

In Barcelona, Carles Lalueza-Fox

wants to give ancient people identity.

I wanted to try to provide an image

of the Neanderthals that could be

not just genetic Neanderthals,

but persons with their own traits like in modern humans.

At the Institute of Evolutionary Biology,

Lalueza-Fox specializes in the extraction and analysis

of ancient DNA.

Because we are along, and we know for sure

that we have been along

for thousands of years on this planet,

we don't have the concept of what

a different human species would be.

For us, it's a bit difficult to imagine someone

who would be at the same time very similar to us,

but also at the same time fundamentally different to us.

That is what a Neanderthal would be.

(drips echoing)

Going into the cave, I discovered that was

a very special site, probably a unique site,

because the temperature was so stable all along the year,

and it has been stable during at least 50,000 years.

I thought we are going to find DNA

preserved in Neanderthals.

It's going to be there.

I was given a tour first to check

if there was Neanderthal DNA in it.

After several weeks, I was able to retrieve Neanderthal DNA

from that particular tooth, but also discovered

that the tooth was plagued with Homo sapiens DNA.

Our DNA is very similar to Neanderthal DNA.

Right from the very beginning of the El Sidron discovery,

cavers, police, and even the scientists

were contaminating the remnants of the Neanderthals' DNA

with their own.

It's difficult to believe,

but if you breathe over the bones or you touch

a particular bone fragment

or a Neanderthal tooth,

your DNA can go from the outside

into the inside of the specimen.

Carles knew he could not waste

this extraordinary opportunity.

I decided to implement an anti-contamination protocol

at excavation itself.

I put my lab into the excavation.

A bone being tested for ancient DNA

is not exposed to air until the dig is stopped.

The site is locked down.

The excavator suits up and then extracts the remains

with sterilized utensils.

Carles also insured that the DNA of everyone who comes close

to the bones and teeth is recorded

so he can discount their DNA signature from his results.

We are able to know exactly

who was contaminating the remains,

and we were also able to compare the Neanderthal sequences

with all the sequences of the people that had been

not just touching the remains but close to the remains

into the excavation itself.

The El Sidron protocol will change the way

that ancient DNA is collected and tested.

In his hands, Carles may hold clues to the identity

of some of the El Sidron victims.

The bone powder drilled from inside the sample

will need to go through many processes before Carles knows

if his protocol has been successful.

And if DNA is found, it will be in fragments

that will have to be magnified, replicated,

and reconstructed.

He's looking for nuclear DNA,

passed down from both parents,

the DNA responsible for an individual's traits.

(instrumental music)

The El Sidron bones will help create

a new vision of Neanderthals.

We had an image of what Neanderthals could look like

and what we could say is that Neanderthals

had lightly red hair.

They were O blood group.

They were able to had bitter taste perception,

and they probably had language abilities like us.

This is the first model of a Neanderthal

based on genetic evidence.

Carles has given physical traits to an El Sidron person,

but in this prehistoric cold case,

he has one step further to go;

to find out if members of her group were related.

To do that, he must look for another type of DNA.

Mitochondrial DNA is passed down

from mothers to their children.

Because it changes in a very predictable rate

over generations, it can trace lineage back to ancestors

who lived hundreds of thousands of years ago.

The results will soon establish

if this group of 12 are related.

(instrumental music)

The people of El Sidron were family related.

We don't know exactly which were the relationships,

but we know they were family related.

All the three other males

had exactly the same mitochondrial DNA

while the three other females

had different mitochondrial DNA,

which is shown in modern hunter-gather groups,

where the females moved from one group to another

while the males stay

in their paternal family group.

Two of the women were directly related

to children from the group.

They could have been their mothers.

This is the first real proof

of a Neanderthal social structure.

El Sidron is certainly the first family of Neanderthals

that has been ever found.

The women's DNA shows that they came from elsewhere,

from three different groups.

Finding a mate outside of the group

would have stopped inbreeding.

Marco de la Rasilla has found proof that groups did exist

in the area and that they were on the move.

(speaking in foreign language)

The silex we have discovered here

was used by these groups,

but it can also be found in other areas near and far.

Therefore, we can conclude that they've moved around

and took raw materials from one place to another

for hunting or for work,

for what they needed on their journeys to different places.

All Neanderthals may have lived

in these small family groups.

A whole family could be lost

through any number of circumstances.

What we suspect is that the interaction with other groups

was not always friendly and especially in the context

of exploiting a territory

to extract food and energy

for the group may lead to some conflicts,

and maybe this is what happened to these El Sidron people

and how they ended being butchered by somebody.

The death of a family could lead surrounding groups

into isolation.

The distance that they had to travel to exchange females

would become too great.

Eventually, inbreeding would halt the vital flow of genes

that leads to evolution.

Why did populations of Neanderthals begin to shrink?

Some say our arrival in Eurasia

was the beginning of the end.

Clive Finlayson believes climate was the killer.

Climate change affected the environments

that these people occupied across central parts of Europe

and even central parts of Asia and even northern Europe.

Ice core data from Greenland shows

that between 50 and 30,000 years ago,

the climate see-sawed between warm wet periods

and cold dry periods.

The El Sidron act of cannibalism coincides with

the very beginning of this time.

As that climate changed their landscape, their environment,

which was a wooded environment

where they would ambush-hunt animals, began to shrink.

Gradually, the population was being pushed back

into these strongholds like the one we find here.

They were becoming like pandas or tigers.

The populations were isolated from each other,

and there was very little gene flow between them.

Therefore, they were suffering from inbreeding

and all the kinds of effects that small populations have.

They were there, but their days were numbered.

Those Neanderthals were living dead.

So far there is no evidence to point to climate

as the killer in El Sidron,

but these Neanderthals would have needed to consume

a huge amount of food.

Getting enough energy to survive even an ordinary winter

would have been a challenge.

(speaking in foreign language)

It is thought that the composition

of the Neanderthal body, not only because of its size,

but also due to the muscular thickness

of the limbs and its torso,

needed a large amount of daily energy for its metabolism.

This means that an individual's daily consumption

of calories, proteins and other nutrients

must have been very high.

Thus, certain unfavorable environmental conditions

could have led to physiological stress

brought on by food shortages.

(fire crackling) (rock pounding)

A family was wiped out in El Sidron,

eaten by their own kind,

perhaps because of something as simple as hunger.

Genetic evidence shows the population of Neanderthals

reached only 10,000 across a huge geographical range.

Eventually, that population was whittled down to one person.

That last Neanderthal may have lived in a place

where food was always plentiful.

At the time of the people living in El Sidron,

in that more cold northern climate,

they're really having it hard to the point

that they're eating each other.

The Neanderthals down here carry on doing

what they've always done.

For a quarter of a million years, there's very little change

in this part of the world.

The climate's fairly mild.

It gets slightly drier, slightly wetter.

Then at 28,000 years,

the cores tell us there were a series of droughts.

There was a period which got really harsh,

not cold, but dry,

and not only did the Neanderthals disappear from here,

but nobody else lived in here.

That is quite telling, I think,

that Neanderthals survived for a quarter of a million years,

and we suddenly lose a signal

when we get the worst climatic conditions

registered by the marine cores outside this cave.

It must have been really very sad

for the last few people to stay here

and maybe realize that they didn't come into contact

with other groups like they had been used to.

(fire crackling)

They must have been the last one,

and I always feel quite emotional when I think about them.

(instrumental music)

Close by El Sidron is La Cabanina.

The investigators believe a shelter like this one

could have been directly above the ossuary gallery

49,000 years ago.

In ancient times, there was a stream nearby,

similar to the one that runs near La Cabanina today.

They suspect that a huge storm caused flash flooding

across the fragile karst areas,

resulting in the sudden collapse

that brought the remains into El Sidron.

(speaking in foreign language)

The cave must have been

practically like it is now.

And in the same way we could live here,

they could have done so in the past.

There is a roof, water,

the basic conditions that they would have needed.

There is also silex, the material they used for their tools.

They would have lived here very happily.

But there was death,

an ancient cold case that the investigators

of El Sidron have reached across time to solve.

It started

(howling wind)

with a storm.

(thunder crashing)

(rushing water)

(thunder crashing)

(heavy rains)

(rushing water)

(rushing water)

(howling wind)

1,800 bones and 400 stone relics

have been recovered,

but this is not the end of the story.

There may be more bodies in here.

Antonio Rosas and Marco de la Rasilla

will soon take this year's finds

back to their laboratories for analysis.

(speaking in foreign language)

[Antonio's Translator] Until now, there has been

no archaeological site in the world that has produced

a greater number of bones than in El Sidron.

It is an exceptional site on all counts.

Finding a hundred well-preserved Neanderthal remains

at the same site every year is highly unusual.

The extraordinary level of fossil preservation

also makes this place absolutely unique.

[Marco's Translator] There is nothing to add.

It's just unique.

Little by little,

the clues to this oldest of cold cases have been recovered

to reveal a simple truth.

An extended family group were cannibalized at El Sidron

49,000 years ago.

This is the first and likely the last Neanderthal family

ever to be found.

Their appearance in our time

offers an extraordinary opportunity.

They have been in the dark for 49,000 years,

but they have only just begun to tell their secrets.

(dramatic orchestral music)