Original subtitles

NARRATOR: Scientists uncover underwater remains

of what could be a long lost Egyptian city.

- Historians could never determine exactly where in Egypt

it was supposed to have been.

- We've never seen any proof it actually existed.

So could the city have finally been discovered.

NARRATOR: After an extinction level event that killed the dinosaurs,

new discoveries reveal a thriving ecosystem.

- This is strange because you would assume

that the closer you are to the impact crater,

the longer it would take for life to rebound.

NARRATOR: Workers uncover strange markings left in the wake of

a volcanic eruption.

- The scoria was lying above a layer of volcanic ash,

which is what protected these strange imprints

over the course of thousands of years.

NARRATOR: All over the world

incredible discoveries are being revealed by devastating events.

Floods, earthquakes, droughts,

hurricanes, volcanic eruptions,

trails of destruction expose long lost mysteries.

This is Discovered by Disaster.

In 140 BCE,

a fabled, opulent and powerful ancient port in the Nile Delta,

the revered gatekeeper of Egypt's riches,

is stricken by a sudden devastating calamity

that sends its greatest monuments tumbling into the shallow waters.

- This once legendary city never fully regained its glory.

And as the years and centuries passed,

it sunk ever deeper into the water and mud until every trace vanished.

NARRATOR: In the late 1990s,

a team of archaeologists were hoping to locate the wrecks

of late 18th century French warships,

which they had reason to believe sank somewhere in the waters

of Egypt's Bay of Abu Khdeir.

Using a nuclear magnetic resonance magnetometer to scan the sea floor,

the team gets a hit,

but whatever's there is much bigger than a shipwreck.

- The water is only about 20ft deep.

And on the bottom, veiled in silt,

is a huge line of massive rectangular limestone blocks,

a wall and it's ten feet thick.

Just the part that's visible at this point is at least 65ft long.

It's clear there's something significant here, but what?

NARRATOR: A team of divers is sent to investigate

and they find huge pieces of stone scattered about like gigantic dice.

The massive fragments are painstakingly raised and studied.

The results leave the archaeologists stunned.

- They're pieces of huge stone statues.

One of them is a male figure about 18ft tall.

He's in mid stride

and is carrying some kind of tray with four loaves of bread on it.

- The forward striding pose

signifies he's about to offer something

while the tray is what's known as an offering table.

So the interpretation is that the statue is offering abundance,

the abundance symbolised by the loaves of bread.

This is likely the Egyptian God Hapi, the Father of the gods,

the source of everything.

The other gods, the world, food, all of humanity.

- It makes perfect sense that this towering statue of Hapi

would have been positioned at the Nile's mouth,

welcoming ships coming to the kingdom of Egypt

from the outside world.

NARRATOR: The jumble of other colossal stone fragments

yields even more potent symbolism.

- The rest of the pieces belong to a pair of statues,

a male and a female carved out of pink granite

and standing about 16ft tall.

The pair dressed in a distinctively Egyptian way.

The woman is wearing the same headdress as a god Isis.

So this has got to be a royal couple. But who exactly?

NARRATOR: As the underwater excavations continue,

more sections of wall are found.

And for the archaeologists, something begins to take shape.

- This was some sort of building, but of truly impressive proportions.

Larger than 35,000 square yards,

built out of huge limestone blocks.

Radiocarbon testing reveals that it was probably erected

between 450 and 380 B.C.

NARRATOR: For archaeologists well versed in Egyptian

and Greek writings, the presence of the wall

and these colossal statues sparks a realisation.

- In the fifth century BCE,

the Greek historian Herodotus wrote about an amazing city

built on islands in a marsh.

Though he said the city was in Egypt,

he simply referred to it as Heraklion,

which means the place of the temple of Herakles,

and Herakles was a Greek god.

But historians could never determine exactly where in Egypt

this city with a Greek name was supposed to have been.

- The ancient Egyptians had records of an island city as well,

somewhere at the gateway to the Mediterranean,

the mouth of the Nile.

But they called it Thonis.

But we've never seen any proof it actually existed.

So could be cities have finally been discovered.

NARRATOR: Near the ruins of the wall,

archaeologists discover a large cabinet-like structure

nearly six feet tall,

masterfully carved from a single block of pink granite.

- The roof is pyramidal in shape

and at the corners of the top and bottom edges of the front opening,

there are holes, almost like pivot holes for hinges.

That tells us this cabinet once had double doors

that, along with where it was found, suggest that it was a naos.

- A naos is a kind of shrine that would have held a statue

or other religious artifacts.

So is this huge wall part of a temple?

NARRATOR: Further examination of the inside surfaces of the naos

reveals faint remains of chiselled writing and hieroglyphics.

- The hieroglyphics contain the name of the God in whose temple

this naos would have resided.

It's the temple of Amun-Gereb.

- According to the inscription,

the God Amun-Gereb would bequeath to each new Pharaoh

everything in their earthly and heavenly kingdom,

basically making them a king entitled to own everything.

NARRATOR: In 1866,

archaeologists excavating the ancient town of Tanis,

just 100 miles east,

discovered two copies of a stone slab

bearing Egyptian hieroglyphic writing.

- It's known as the Decree of Canopus,

and it talks about the god Amun-Gereb and his temple.

And it names the town in which his temple stood, Heracleion.

- So now we know conclusively

the lost city that Herodotus wrote about did exist.

And this is it right here.

This is Heraklion,

and this massive temple of Amun-Gereb would have been

at the heart of it.

NARRATOR: As the underwater excavation progresses,

more walls are found, but not all of them seem to belong to the temple.

Some form a network of large trenches surrounding the building.

- Samples of the silt between the walls reveal

that these are canals running around the temple,

which would have been accessed from other buildings

by way of ferries and bridges.

Heraklion was like an ancient Egyptian Venice.

NARRATOR: In the area where the canals used to be,

a great number of wrecked ships and boats are discovered,

as well as many artifacts,

including coins attesting to the city's great wealth.

- Interestingly,

a disproportionate number of the coins found are identified

as being minted between the 6th and the 4th centuries BCE.

This must have been when Heraklion was at the peak

of its prosperity and power.

NARRATOR: The discoveries keep coming,

including one found within the grounds of the temple of Amun-Gereb

that astounds the archaeologists.

- It's an inscribed stone tablet known as a stele,

6.5ft tall and in excellent condition.

The hieroglyphics carved into its face are completely legible.

It turns out the stele bears a royal decree by the Pharaoh Nectanebo I.

This decree even bore a date which in our modern calendar

equates to 380 BCE.

- The decree states that this stele should be

"erected at the entrance to the Sea of the Greeks."

That would be the Mediterranean, in a town by the name of Sais.

This is amazing.

We already know that another Egyptian name for Sais is Thonis.

- The stele confirms once and for all that Thonis and Heraklion

were the same legendary port city.

So what happened that made it disappear?

NARRATOR: Buried deep under 16ft of hard packed clay

alongside the ruins of the temple of Amun-Gareb

and under heavy limestone blocks,

the archaeologists discover the wreck

of an 80 foot long wooden ship.

- The ship's hull dimensions made it fairly sleek,

so it might have been a warship or possibly a vessel

used by customs officials to police the Nile Delta

and keep money flowing into the royal coffers.

- At the time of the ancient cataclysm,

this vessel was likely moored alongside the temple.

When disaster struck and the temple collapsed,

some of its huge limestone rocks smashed down onto the ship

and immediately pressed its remains deep into the mud.

But what was this cataclysm?

NARRATOR: Magnetic mapping of the area reveals the presence

of a number of faults or rifts that cross the temple grounds.

- These rifts likely resulted from a soil liquefaction event,

which is when water saturated soil,

like you might find in a river delta,

is subjected to vibrations like an earthquake.

Vibration causes the soil to momentarily behave

like a vicious substance incapable of supporting any weight.

- The ground turns suddenly and briefly into a muddy soup.

The temple of Amun-Gereb collapsed.

Some of its enormous limestone blocks pinned that moored ship

to the bottom, along with artifacts from the temple,

preserving a snapshot of that moment in time.

- From approximately the year 140 BCE on,

it's clear from the archaeological record

that the flow of coins into the city of Thonis-Heraklion all but stopped.

So that strongly supports an estimated date of 140 BCE

for the cataclysm.

- But the city wasn't completely destroyed at that time.

There's evidence that people lived there for the next eight centuries.

However, over the years, the sea level continued to rise

and the buildings of Thonis-Heraklion sank

under their own weight, deeper and deeper into the mud.

By 800 CE following a series of earthquakes and tidal waves,

all trace of the once legendary city was gone.

NARRATOR: Few people today have heard of Thonis-Heraklion,

but chances are that will change.

As we learn more about this great, doomed city,

we'll be forced to rethink what we know of the past

and perhaps to reevaluate our thoughts

regarding the permanence of humanity's great port cities.

NARRATOR: 66 million years ago,

the mother of all disasters tore the entire earth apart.

Not a single corner of the planet was left untouched

as the energy from an asteroid impact set the world on fire.

- This asteroid measured six miles in width.

Think about that.

That's like something bigger than Mount Everest is tall,

smashing into the earth at 150,000mph.

It hit the earth in and around what is today

Mexico's Yucatan Peninsula.

And when it did hit,

the result was apocalyptic in the truest sense of the word.

- It generated an enormous tsunami,

the size of which is difficult for us to quantify.

Then an unbelievable amount of energy created by the impact

set off a chain reaction of hell

triggering earthquakes as far south as Argentina.

-To put how big of an explosion this was into perspective,

take the biggest nuclear explosion ever created by humans -

the Tsar Bomba set off by the Soviets in the 1960s.

It measured 50 megatons,

while the impact created by this asteroid

would have been equivalent to a 20 million megaton explosion.

- Basically, what this meant was the equivalent

of a one megaton hydrogen bomb going off every six kilometres

all across the planet.

It was like the gods poured gasoline over the earth

and put a match to it.

Everything. Absolutely everything was on fire.

NARRATOR: With all the debris that was launched into the atmosphere,

the fallout from the blast created an impact winter

which blotted out the sun for at least a year.

This meant that everything that relied on sunlight for life

also died.

- This is what we call an extinction level event.

Actually, it's the extinction level event of the past 66 million years.

This is the asteroid that killed off the dinosaurs.

As a result of the asteroid's impact,

75% of all of the earth species died.

- We know about the extinction of the dinosaurs,

but what about the 25% of species that survived?

How did life on earth not just continue,

but continue evolving when the planet was one massive ashtray?

NARRATOR: The 20 mile deep and 100 mile wide crater

created by the asteroid's impact is known as the Chicxulub Crater.

In 2016,

a team of scientists were taking sediment samples from the crater

in the hope of learning more about the planet

in the years following the impact event.

- So in these sediment samples taken from deep down in the crater,

roughly 2000ft below the sea floor,

there are tiny little burrows,

as well as the fossils of a very particular organism.

- These are the tiny little sea creatures

like plankton and foraminifera,

a shelled micro-organism populating the world's oceans.

The thing is, there are a lot of them,

they're diverse and seem to have been flourishing.

The sediment cores represent the time from only

30 to 200,000 years after impact.

So how on earth did life in the ocean rebound so quickly?

-This is strange because you would assume

that the closer you are to the impact crater,

the longer it would take for life to rebound.

When an asteroid hits the earth like this,

a lot of things are killed and decompose.

And when they do, they consume oxygen.

So if the oxygen isn't replenished, somehow life suffers.

NARRATOR: The 35 million year old Chesapeake Bay crater

was formed by a much smaller asteroid than the Chicxulub

at only 2 to 3 miles wide.

Nevertheless, it still would have had a serious impact

on the surrounding environment when it hit.

Following this impact event,

the area of the crater became anoxic,

meaning the ocean was without sufficient oxygen

to sustain life as diverse as that of Chicxulub.

- The Chicxulub crater is massive,

but its northeastern section is and was open to the Gulf of Mexico.

This means that there could be circulation of seawater

in the crater, which in turn would allow for life to rebound.

On the other hand, the shape of the Chesapeake Bay crater

probably made this very difficult.

Meaning that the ocean water remained stagnant.

- So despite the entire world being devastated,

the ocean environment in the impact crater

actually rebounded extremely quickly.

Which is really incredible. But what about life on land?

How long did it take for ecosystems and animal life to recover?

- To find out, we need to look at the fossil record

from the years before and after the event.

We know that the biggest mammals that existed during the time

of the dinosaurs were only as big as your average rat.

But we have almost no evidence of what animals survived or evolved

in the thousands of years following the Chicxulub impact event.

NARRATOR: A few decades ago,

a group of palaeontologists were out hunting for fossils

in a known hotspot for dinosaur bones,

Colorado's Corral Bluffs.

When one of them stumbled upon a fossil embedded in a curious rock.

- It was the palate of a mammal that was set in a concretion,

which is a rock that over time forms around organic material,

which in this case is bone.

NARRATOR: The find alerted scientists to the idea that maybe,

just maybe,

more such fossils could be found encased in concretions.

So they began scouring the Corral Bluffs,

quickly discovering several fossils encased in concretions

from around the time after the apocalypse.

- One fossilized skull has these sharp, jagged teeth

in the front of its mouth,

whereas in the back, the teeth are broader and blunter.

This indicates that it can eat both meat and plants.

If the ecosystem of the entire world has been nearly destroyed,

it would be beneficial if you could eat everything,

which it appears this animal named the Loxolophus could do.

- It also has a hole underneath its eye.

This was a passage through which nerves could travel,

so it probably had very sensitive whiskers.

And the shape of the skull also indicates that a big portion of it

was dedicated to smell.

What we're looking at here is maybe an omnivorous,

highly adaptable, raccoon-like creature

that could scavenge what little food was available.

- So quite early on, only around 100,000 years after the event,

we're seeing bigger animals than rats living in

the post-apocalyptic world.

Mammals that were more specialised, like plant eaters,

wouldn't have been able to survive the catastrophe

and would have been among the 75% that went extinct.

NARRATOR: As the scientists continue searching the coral bluffs

for more fossils,

they discover a much larger skull than that of the Loxolophus

dated to around 300,000 years after the asteroid impact.

- This mammal has huge teeth that would be used more

for grinding than for tearing.

Which means that it was a vegetarian.

What this tells us is that in the intervening 200,000 years

between the Loxolophus and this plant eater,

mammals had become specialised.

- On an evolutionary timeline, this is very fast.

But in order for this to have happened,

the environment would have to support such a diet.

There likely would have been a wide variety of plants available,

otherwise it simply wouldn't have enough food

to have been so highly specialised.

- So after 300,000 years,

the forest environment appears to have recovered fully,

and along with it, the mammal population began to explode.

NARRATOR: Two more skull fossils

dating to 300,000 years after the impact event are discovered

in the Corral Bluffs.

One has large incisors, whereas another has very flat back teeth.

- The shape of their teeth shows us that they each had different

plant based diets and judging by the size of their skulls,

the mammal with large incisors would have weighed around 80 pounds,

whereas the one with the broad teeth would have been even bigger

and could measure up to 170 pounds.

- This is incredible because their size, relative to the size

of the mammals living only a few hundred thousand years earlier

prior to the extinction event were way smaller.

We have seen this before, mammals growing significantly in size,

but we've seen it over a 30 million year time frame,

not one of less than a million years.

It's pretty rapid. So how did they get so big, so fast?

- Again, we have to look at their diet and the food available to them.

The existence of these mammals tells us

that the ecosystem had rebounded quite well

as only a healthy, diverse environment

would be able to support such large animals.

Without protein rich foods, they could never attain such a size.

NARRATOR: Still working in Colorado's Corral Bluffs,

scientists unearth another concretion,

this time inside the rock is a rounded, oblong fossil.

- This is the fossil of a bean pod,

and it's dated to about 700,000 years

following the asteroid's impact.

- Legumes are incredibly nutritious, even today.

They are an essential food source for billions of people,

and because they provide such a good amount of calories,

eating them would also be highly advantageous for mammals

living millions of years ago.

- Eating these plants led to the evolution of mammals

the size of a modern day wolf, weighing roughly 100 pounds.

These creatures were a hundred times larger

than those that survived the mass extinction

a few hundred thousand years earlier.

The speed at which all this happened is remarkable

and entirely unexpected.

It shows us how life always finds a way,

even in the hardest of circumstances.

NARRATOR: The collapse triggered by the Chicxulub impact

was one of five mass extinctions that occurred

in the last 450 million years.

And the frightening reality is that this kind of natural,

apocalyptic event could happen at any time.

And who knows if the planet will rebound next time.

NARRATOR: In 1431, after years of unprecedented drought,

Angkor Cambodia, capital of the mighty Khmer civilization

was experiencing high levels of instability.

- This enormous city with its beautifully ornate temples

and highly sophisticated urban infrastructure,

was attacked by its number one enemy,

the people of the Ayutthaya kingdom,

who arrived from their homelands to the west.

- The Ayutthaya burned Angkor.

Anarchy reigned and the population fled en masse.

Their invasion also disrupted critical supply and trade

into the city, which contributed to its total abandonment.

-The collapse of Angkor,

one of the greatest cities the world has ever seen

has long been a mystery.

The site has been studied for over 100 years,

yet there has been little concrete historical evidence

to truly explain why it collapsed.

So there must be more to the story.

NARRATOR: Almost 600 years after the fall of Angkor,

a team of researchers

from the Tree Ring lab at Columbia University are trying

to create a holistic picture of the time period.

Working in Vietnam's Bidoup Nui Ba National Park,

they began drilling holes in old trees

in order to extract a core sample.

- Trees are incredible bookkeepers.

Their growth rings contain a detailed record

of the environmental conditions they've experienced

over their lifetime.

Each ring corresponds to one year of growth.

Generally speaking, if one year the rings are spaced further apart,

it indicates that conditions were optimal for growth

and the tree grew more.

If they're spaced closer together, it means conditions weren't as good.

And so the tree grew less.

- This remote section of the park is pristine,

and the trees that were sampled are over 1000 years old.

Some of them dating back to when Angkor was at its peak.

And it's relatively close. So historically,

it would have experienced the same environmental conditions.

- A sample taken from a cypress tree revealed an environmental record

starting in 1030 CE and ending in 2008.

The extremely narrow spacing between specific tree rings showed

that a severe drought hit the area between 1362 and 1392

and then again from 1415 to 1440,

which is more or less the exact time when Angkor collapsed.

So was there more to it than just an invasion by a regional rival?

NARRATOR: Founded in 802 C.E.,

the Khmer Empire grew to cover much of present day

Cambodia, Laos, Thailand and Vietnam.

It was enormously influential in the region

and shaped much of its political and artistic character.

At its peak, the Khmer capital of Angkor boasted what, to this day,

remains one of the world's largest religious structures.

Sophisticated urban infrastructure,

as well as a population of over a million people.

- The city spanned an area about the size of Los Angeles.

And for comparison's sake, even an important European city

like London only had a population of about half a million people

in the late 1600s.

So you can only imagine how high functioning and well-built

Angkor's infrastructure had to be to support such a population.

- The infrastructure was centred around a resource

vital to human survival.

Water.

Because water is as much an asset as it was a potential threat,

water management was integral to Khmer culture

and was treated as a religious duty.

Even today, the water that feeds the agricultural plains

is considered sacred,

and Cambodians bless themselves with it for good luck.

- It was this very advanced water management system

that allowed Angkor to grow to its incredible size.

The city was crisscrossed with an endless network of canals,

dikes, irrigation and overflow channels.

An entire river was diverted into a reservoir.

- All of this water fed one of the greatest inland fisheries

in the world, the Tonle Sap Lake,

and the land surrounding this lake is incredibly fertile,

very well-suited for rice crops.

But when you're that reliant on immense quantities of water,

what happens when it all dries up?

NARRATOR: The researchers conclude that the years of drought

left the region highly vulnerable to flooding.

So when the monsoons finally did return to their regular force,

catastrophic flooding would have ensued.

- Flooding obviously causes a lot of problems

for anyone experiencing it.

But how could it have weakened the Khmer power to such an extent

that they were left on the verge of collapse

and just needed an invasion to push them over the edge?

NARRATOR: Archaeologists wondering how flooding might impact

the urban infrastructure dig into the soil

underneath the ancient temples.

- The city of Angkor was built using a very interesting

and advanced technique.

All the city's buildings and temples were built on an artificial layer

of sand and water.

On top of this, a moat was built around the temples.

This combination provided enough support for the huge temples

whilst simultaneously allowing the moats to collect runoff water

from monsoons.

- But during the drought,

the consistency of this sand and water foundation changed.

It got weaker. When the monsoons returned,

the dry earth couldn't absorb the water fast enough,

and although there were moats around the temples,

they couldn't handle the runoff.

This caused massive damage to the urban infrastructure,

while also making it hard, impossible, to cultivate crops.

- This might have contributed to a crisis for the Khmer rulers.

When you have collapsing buildings and bridges,

widespread hunger and then you add an invasion into the mix.

It's not a surprise that things didn't go so well for them.

- We know that Angkor returned to nature after its abandonment.

But what happened to all those people?

One million people can't just disappear.

NARRATOR: Just to the south of the Tonle Sap Lake,

roughly 150 miles from the ruins of Angkor,

archaeological excavations have been taking place at a site

known as Longvek,

where the remains of a city dating to the years

after the collapse of the capital have been found.

- Longvek was the site of the Khmer capital

after Angkor was abandoned.

But from what has been found so far,

there weren't many people and there wasn't much going on here

in the years it was occupied.

NARRATOR: But the farmers working the rice fields of Longvek

keep unearthing an abundance of ceramics,

which seems to contradict what the archaeologists

thought they knew.

- Considering the volume of ceramics

that have been found in these fields,

it's clear that a lot of people lived here.

You would need a substantial population to generate

this kind of volume.

So have we been wrong in our assumptions about the city?

- It seems like maybe we were.

Some of these ceramics are truly magnificent.

There's a piece of pottery with a brown glaze

incised with a coin motif and good luck symbols.

It used to be the lid of a ceramic jar,

and it's incredibly rare.

-Very few lids like this have ever been found outside of China.

In fact, only in Japanese archaeological sites

dating to the 16th and 17th centuries

has anything remotely similar been found.

- So what this indicates is Longvek's participation

in extensive trade networks that link China, Japan

and Southeast Asia in the 16th and 17th centuries.

Having these kinds of things

when you've just been chased out of your empire's capital,

that's pretty impressive.

NARRATOR: As excavations continue,

archaeologists again and again discover rare, exquisite pottery.

- There are these green, yellow and purple glazed dishes

featuring waterfowl on a lotus pond.

This kind of pottery goes by the very original name

of tri-coloured dishes.

The artwork on here is truly delicate

and would have required considerable skill to produce.

- They also date to the same period as the jar lid,

and coming from southeastern China,

would have been very, very expensive to acquire.

These ceramics were by no means meant for everyday use.

They're far too beautiful for that.

They likely would have been in the possession

of high ranking bureaucrats

or those occupying positions in the Khmer Court.

NARRATOR: Beginning to question their assumptions,

archaeologists decide to employ the use of LIDAR

to survey the area in the hope they may learn something new.

- Putting it simply, what LIDAR does

is essentially use a laser to measure the distance

between the machine emitting the laser and the ground.

This then creates a very detailed 3D digital map,

which has become an incredible tool for archaeologists.

- And what these LIDAR scans reveal is incredible.

A series of earthen embankments forming an almost three square mile,

rectangular citadel.

Not only was it well built,

but judging by the wealth of ceramics,

it was thriving economically.

But if the Khmer had seemingly lost everything

with the abandonment of Angkor, how could this have been the case?

- Tonle Sap Lake is connected to a river of the same name

and it drains into the Mekong River,

which is one of the longest on the Asian continent.

- To this day, the Mekong remains essential to the economies

and cultures of the countries it flows through.

And it would have been the same around 600 years ago.

It connects Cambodia with central China

roughly 2500 miles to the north.

So you can imagine how many people would have relied on it for commerce

and how many people it would have connected,

trading in all kinds of different commodities.

- By maintaining their capital close to an essential river

and its tributaries,

the Khmer managed to thrive despite the incredible pressures

that would have been exerted on them by invading forces.

NARRATOR: But despite the Khmer Kingdom's resilience

in the face of powerful outside forces,

its new capital at Longvek was eventually sacked

and looted by their long time enemy, the people of the Ayutthaya Kingdom.

With the collapse of Longvek,

Khmer sovereignty suffered a serious blow.

The royals were taken into captivity

and what was once a mighty kingdom was never to rise again

to its past heights.

NARRATOR: A quarter of a million years ago,

Western Turkey's 2500ft Cakallar volcano began to erupt.

It sent lava flows cascading down its slopes,

while ash rained down thousands of feet from its vent.

- The area where this volcano field sits today is known as

the Kula region.

And it's fair to say that this landscape would have been

severely impacted back then.

Thick layers of ash coated the land, creating a ghostly landscape

that would have terrified both humans and animals,

forcing them out of the area.

- In terms of a human timescale, this is a long time ago.

Back then, Homo sapiens,

our ancestors are only found in Africa,

but Neanderthals, our cousins,

have spread north into Europe and Asia.

NARRATOR: In 1968,

just a few hundred feet from the volcano,

workers building an embankment dam were digging through

the ancient layers of scoria -

dark pocketed volcanic rock

that had been deposited 250,000 years earlier,

when suddenly they observed abnormal features in the terrain.

- The scoria was lying above a layer of volcanic ash,

which is what protected these strange imprints

over the course of thousands of years.

And it's important to note that there are little bulges

around the rim of the holes

rising up above the surface about a centimetre.

This indicates that at the time they were made,

the ash was wet and coherent,

meaning that these little pockets were made at the same time

the volcano was erupting.

- The ash layer itself measures two inches,

while the little oblong pockets are about an inch in depth.

Some of these features are wider and longer than others.

While there are also small little round holes in the hardened ash.

But what are these things?

- Now they could be the result of ejecta, basically just shrapnel

that comes flying out of the volcano during the eruption.

But the shapes of the pockets are far too similar

for that to be the case.

NARRATOR: Each hole has one or several corresponding

similar sized holes placed at an angle diagonal to it.

- All of them follow this pattern, except for the very small holes,

there are four of them,

but each of them is at a diagonal to the other.

- It may not seem so at first,

but these shapes are actually very familiar.

We see them all the time at the beach.

They're footprints!

They're from adults and from human children.

But also what appear to be some kind of canid footprints

like a wolf or something like that.

And that's super weird

because humans only domesticated dogs 40,000 years ago

and this is six times older than that.

- It seems like these are footprints of people

or a family of Neanderthals maybe,

possibly running away from the eruption.

NARRATOR: Since their discovery,

the age of the footprints has remained a curiosity for scientists

because of the difficulty in getting an exact date

for when they were created.

- This is because the volcanic rock in which they were found

is relatively young basalt

and younger basalt is very hard for geologists to date.

So the assumption has been that the prints are

hundreds of thousands of years old, but it hasn't been certain.

NARRATOR: But in 2019, armed with new state of the art techniques,

scientists decided to reassess the footprints,

hoping to obtain a more accurate date for when they were created.

- It's a pretty complicated process, but two things are measured.

First of all, the decay of the elements uranium and thorium

creates another element helium.

This helium is present in little crystals

embedded in the ancient ash.

Second, the radioactive levels of the element chlorine

can show us just how long volcanic rocks have been situated

on or near the Earth's surface.

- So this brand new dating technique tells us something

entirely unexpected.

The volcanic eruption and the prints are only 4700 years old.

So now the dog footprints make a lot more sense.

But it means we were off by almost a quarter of a million years.

And a lot has happened in that time.

- Not only did Neanderthals go extinct some 40,000 years ago,

but Homo sapiens began spreading across the face of the earth.

Considering the time scale we're looking at here,

4500 years ago is quite recent.

It puts us into the Bronze Age.

- So this means that these footprints aren't Neanderthal,

but human. Modern human footprints.

Seeing as we were wrong about the age of these prints

and the species of human that made them,

it makes you wonder what else we could have been wrong about.

NARRATOR: Spurred on by these unexpected finds,

scientists scanned the footprints using the structure

from motion method.

- The structure from motion method is a technique

that involves photographing the object -

in this case, an ancient footprint - from a few different angles

to create a three dimensional image of that same object.

- The results are surprising.

The images reveal which direction the big toe is pointing,

and that, of course, tells you which way the feet are going.

And it turns out they're going in the opposite direction

of what we thought.

We'd assumed they were going away from the volcano,

but this means they were going from west to east

towards the Cakallar volcano.

- And they were walking either while the ash was falling

or immediately after.

So it could be that they were observing the eruption

as they approached the volcano.

- The footprints are also only about 2.5ft apart,

which indicates that they were walking

at a relatively relaxed pace.

If they were running, the footprints would be spaced even further apart.

So they definitely weren't panicking,

but were rather calmly walking together towards this volcano

as it was blowing up.

NARRATOR: As the scientists are working at the site,

local reports emerge of a discovery of some rock art

a little over a mile from where the footprints are located.

- The rock art has long been known by locals

who call the boulder its painted on bloody rock.

But it's only recently become known to scientists.

- The boulder is huge, far bigger than the size of a man,

and it leans out at a 45 degree angle from the ground.

So it was probably a good place for shelter from the elements,

whether it was rain or the sun.

DAN: You can see with your naked eye,

three handprints above a circle that looks like it's bleeding.

The circle has a bunch of little dots in it.

- There are also what looks like four smudges around the circle,

followed by a longer, broader one at the base of the painting.

That definitely seems to have faded over time.

Other than the handprints, what could this represent?

What was their intention?

NARRATOR: In order to enhance the faded sections of the painting

and obtain a better understanding for what it might represent,

scientists apply a technique known as saturation stretching.

- This is basically a process that uses algorithms

to make the faded areas more intense in colours,

and that allows them to digitally reconstruct

what this painting would have looked like

when it was initially created.

NARRATOR: A much more complete picture emerges from the rock.

When it was originally painted,

the faded line at the bottom of the picture was actually thick and bold,

and the remaining lines and handprints were far more defined.

- The circle now looks like it's at the top of a triangular shape.

But what's more interesting is what we thought was may be blood

running down from underneath it.

Considering the location right in the shadow of the Cakallar volcano,

I wonder if this blood could actually be lava.

And if this is a depiction of when it erupted some 4700 years ago.

- It's definitely possible.

The boulder is so close to the footprints.

And for anyone, let alone a person living in the Bronze Age,

observing such a natural phenomenon up close

would inevitably leave quite the impression.

So what we're looking at here is maybe their reaction to the event.

- This is pretty special.

Not only does it highlight the deeply human characteristic

of recording our experiences in art,

but it's also unique in an archaeological context.

- There are some other examples of rock art depicting

what appears to be a volcanic eruption.

But there aren't any this close to the volcano and to the footprints

the artist may have made on their way to creating the painting.

NARRATOR: The rock art by the Cakallar volcano makes it possible

to follow in the footsteps of the people of the Bronze Age in Turkey,

to walk where they walked,

to imagine what they saw

and realise that the desire to memorialise such a magnificent event

is what connects us across time.

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