Original subtitles

It looks like there's been a massacre.

- Whatever is causing these red waves and sands

is not something accidental.

[narrator] Deep in the Pacific, on the island of

St. Helena, the discovery of human

remains may be connected to a dark period

of human history.

- More than a hundred bodies in densely packed

unmarked graves.

- It's pretty evident that these people

were subjected to severe cruelty, but why?

[narrator] The discovery of a strange mountaintop site in

Indonesia has caught the attention of experts.

- Could this be some kind of megalithic monument?

- It could have the potential to rewrite human history

as we know it.

♪ ♪

[narrator] Isolated, scarce on resources, islands are worlds

unto themselves.

Bizarre creatures, ancient gods, and haunting ruins.

Baffling murders and deadly spirits.

What will be discovered on Earth's mysterious islands?

♪ ♪

[thunder rumbling]

[narrator] Nestled in the Strait of Hormuz, at the crux of the

Persian Gulf and Gulf of Oman, and just five miles off

Iran's southern coast, lies the island of Hormuz,

a curious, well-kept secret.

There's only one small town here with a population of

approximately 6,500 people.

But when you consider the topography,

you can begin to understand why.

There isn't a lot of arable land here for growing crops,

just barren hills, and this is largely due to the fact

that the island's makeup is very unique.

It's actually a salt dome, a geological feature

formed by the upward movement of ancient underground

salt deposits within the Earth's crust.

[narrator] Salt domes are created in basins of the

Earth's crust, where thick salt deposits from the evaporation

of ancient seas have been buried beneath

layers of other sediments over long periods of time.

Because salt has a lower density

compared to the surrounding layers of sediment,

it has this natural tendency to go up towards the surface,

which results in everything from salt flats

to salt waterfalls, or even dome-like islands like this one.

Salt domes have been discovered all over the world

and on nearly every continent.

They can occur on land or on the seafloor,

or, like in the case of Hormuz, as domes that push their

way above sea level.

But that's not even the most interesting thing

about this place.

[narrator] On the remote southeastern part of the island

is Turtle Beach, a protected area for hawksbill turtles,

where something totally shocking is observed.

It looks like there's been a massacre.

The edges of the sea and the waves

washing up on the shore are blood red.

Were the turtles attacked?

Okay, adult hawksbill turtles and green turtles

obviously have these big shells that can protect

them against attack.

They do get sometimes bitten by sharks or crocodiles

or even octopus that give them a good fight.

But let's think about this.

There are not really that many of these turtles,

enough that even if all of them were all massacred

at the same time somehow, which would be very weird,

it wouldn't be enough to change the color of the water.

[Amma Wakefield] In fact, there are no remains of any kind,

not turtle, not shark or fish.

So what could be causing this red sea?

Could it be a red tide?

[narrator] Red tides, better known as harmful algae blooms

or HABs, occur when colonies of plant-like organisms

that live in water grow out of control,

resulting in toxic or harmful environmental outcomes.

These harmful blooms can be seen in many places across the globe.

One of the best known examples of harmful algae blooms

occurs along Florida's Gulf Coast most summers,

when the water turns crimson with algae.

These blooms are on the rise due to warming ocean

surface temperatures.

Low salinity, high nutrient content in the water,

and calm seas that don't break up blooms,

not to mention the number of increased sunny days,

all add up to the increased propagation of the algae.

Algal blooms are a natural phenomenon.

They're part of a functional marine ecosystem.

But when the nutrients get too concentrated

or when temperatures get too high,

those blooms can get really intense,

and that can drain oxygen levels.

Or sometimes the organisms that make up those blooms

can secrete toxins into the water,

which can then kill everything from small fish to big sharks.

[Anthea Nardi] But there are no dead fish or any other marine

life here on the beaches in Hormuz.

And an algae bloom that would make the water red

would also be cloudy with the presence of algae.

But this water is eerily clear.

Red, but clear.

And if it were the result of algae,

there would most likely be dead or scummy algae

pushed up on the shore.

But the beaches here don't have any slimy residue.

However, they are stained red.

So if it's not an algae bloom, what is it?

Something else biological might be at play.

[narrator] In 1819, Bartolomeo Bizio, an Italian pharmacist in Venice,

examined reddish-yellow stains that would appear on polenta,

a cornmeal staple in Italy when the food was left in states

of high temperature and moisture.

What he discovered was a new bacteria

called Serratia marcescens.

Serratia bacteria produce a red pigment

called prodigiosin.

But that pigment's also produced by a lot of other

bacterial species, not just the bacteria

found in polenta.

And while it's been harnessed to color things

like milk or carbonated drinks, to date, it hasn't

really been used to turn huge swaths

of anything red, let alone an entire

area of a seashore.

But you know what has?

Industrial waste.

[narrator] In 2011, the Jian River that runs through the city

of Luoyang, Northern China, turned bloody red.

Officials there tracked the source of the color

to an illegal factory that was dumping red dye

in the river via the city's storm water pipes.

So could Hormuz Island's so-called blood

just be red dye?

There are no factories like that here.

And even if there were, they would have to

be dumping the dye into the water constantly

to maintain that blood-red color everybody's seeing at the beach.

Also, in Luoyang, China, and other locations affected

by industrial chemical contamination,

that red effect only lasts for a few days.

These are lasting a lot longer than that.

Whatever is causing these red waves in sands

is not something accidental.

These stains have been here on Hormuz

for a long, long time.

[narrator] Hormuz is connected to the geological

creation of the region.

When the Arabian and Eurasian tectonic plates

began to collide, forming what we now know

as the Persian Gulf region.

That collision created folding layers

that became mountains and sedimentary basins

that, over millions of years, contributed to the complex

mineral accumulation of the area.

The rising dome that forms Hormuz

is not just made of salt, but layers of clay,

carbonates, shale, and volcanic rock.

Some of these rock layers become vividly colored

as they move towards the surface through their

interaction with water, minerals from other rock layers,

and the air.

It's thanks to this natural phenomenon

that Hormuz earned its nickname Rainbow Island.

From the water to the beaches, the rocky shores,

the salt caves, the mountains, the whole island

looks like this brightly-hued land

of spectacular color.

[Anthea Nardi] And unsurprisingly, one of the most

vibrant, visible colors here is red.

Could the blood-red color be the result of

mineral oxidation?

[Anthony Cantor] Locals call this red soil gelak,

and it can be found along many of Hormuz's colorful shores.

[narrator] Gelak is largely composed of hematite,

a heavy oxide mineral that is 70% ferric

oxide, or iron, which does oxidize over time

to form a red or rust-like appearance.

[Amma Wakefield] The island is positively covered in hematite.

The root of that word is hema, which is Greek for blood.

The waves in the beach that initially sparked

notions of a turtle massacre have an extraordinarily high

concentration of hematite in the sand and rock

that makes up the shore.

When stirred by the sea, the water takes on

that tinge of red due to minute particles

being disturbed.

And there's no reason to think this is gonna fade anytime soon.

Erosion should keep that blood-red hematite,

or gelak, as it's called, in the water,

and the salt water and the sunlight

are just gonna continue to intensify those colors.

Gelak holds a special place in the hearts of the

people of Hormuz.

Once believed to be a gift from God,

it's prized as a spice that gives the local cuisine

a distinctive red hue.

[Amma Wakefield] When speaking about a place,

people will sometimes say there's something about

it that lives in the blood of its people.

Well, here on the wondrous island of Hormuz,

because of the red, iron-rich soil,

it's not just a cliche.

♪ ♪

[narrator] The island of St. Helena is a British overseas

territory located in the middle of the Atlantic Ocean,

about 1,200 miles west of Angola, Africa.

♪ ♪

St. Helena isn't particularly big,

only about 47 square miles, which is a little over

twice the size of Manhattan.

It was formed millions of years ago

by now-extinct volcanoes that created this

mountainous landscape.

The history of the island and its people

is a fascinating one.

This is where the British exiled Napoleon

after he was finally defeated in 1815.

He'd been exiled once before, but that was to an island

in the Mediterranean, from which he escaped

and returned to power in France less than a year later.

After finally defeating him at the Battle of Waterloo,

the British sent him way out here to live out his days.

[narrator] In 2006, in an area of St. Helena

called Rupert's Valley, a group of workers are constructing

the island's first airport when they unearth

something shocking.

They find two skeletons that appear to have

been laid to rest here.

What's strange is that there's no headstone

to identify them or indicate when they were buried.

So who are they?

♪ ♪

[narrator] A team of archaeologists is set out

to learn more about the burials, and it isn't long before

they begin finding more human remains

throughout the area.

More than 100 bodies are found in densely packed,

unmarked graves, with some containing as

many as six skeletons.

After ten weeks of painstaking work

excavating an 18,000-square-foot plot of land,

a total of 325 skeletons are discovered

in 178 graves.

♪ ♪

- At first glance, it's evident that most of the

remains are male.

The pelvises have thicker bones and a narrower shape

than female pelvises.

Also, a lot of the skeletons aren't that big,

indicating that they were children

between 8 and 12 years old.

♪ ♪

[narrator] Further osteological analysis indicates

that many of the individuals were suffering from

a specific disease at the time of death.

The bones show signs of scurvy,

a disease caused by a lack of nutrition,

specifically a deficiency in vitamin C.

Some of the symptoms include bleeding gums,

loose teeth, fatigue, and pain in the arms and legs.

It can be fatal if not treated.

[Sarah Klassen] In the past, scurvy was very common among

sailors because they didn't always have access

to fresh fruit and vegetables.

Considering how remote St. Helena is,

people might have contracted scurvy

on the voyage to the island.

If so, it's likely that many of these individuals

died as a result of the disease.

♪ ♪

[narrator] While scurvy and diseases related to malnutrition

are present, a striking number of the remains

also show signs of having been subjected

to extreme acts of violence.

[Alison Leonard] It's pretty evident that these people

were subjected to severe cruelty, but why?

[narrator] The archaeologists sent 63 sets of remains

off for DNA testing to learn more about

these people's origins.

Scientists are able to obtain results

for 20 of the 63 individuals.

Their genetic makeup indicates that they were most closely

related to the people in what is now Gabon

and northern Angola, areas known historically

as the location where individuals were

forced into slavery.

♪ ♪

[narrator] Over the course of 400 years, more than 15 million

people were taken from Africa and sold into slavery

by slave traders.

For many years, the most powerful actor

within this trade was Great Britain.

[Anthony Cantor] Throughout the duration of the

transatlantic slave trade, it's estimated that the British alone

forced 3.2 million people into the holds of slave ships.

We can also say that 10% to 20% of these enslaved people

died en route to the Americas due to horrendous treatment

and horrible conditions.

[James Ellis] By the end of the 17th century, almost half of

St. Helena's population was made up of enslaved people.

As Britain's empire and territorial holdings grew,

they faced an increasing demand for labor,

and they met that demand by enslaving African men,

women, and children, and trafficking

most of these enslaved people to the Americas.

♪ ♪

[Alison Leonard] Over the years, the slave trade

had created a large diaspora of Africans

from vastly different parts of the continent,

and they were sent to various colonies,

including St. Helena.

♪ ♪

[narrator] Back at the site in Rupert's Valley,

the archaeologists find coins that have been laid

over the eye sockets of newborn children

in three separate graves.

[James Ellis] The coins are mostly made from silver,

and because they're so old, the faces are worn,

and they look like little more than blank tokens,

but they're able to use X-ray analysis

to reveal their original designs.

[Sarah Klassen] It's remarkable.

One shows a portrait of Queen Victoria

and bears the inscription

"Victoria D.G. Britanniar Regina F.D."

with an inscribed date of 1843.

All the other coins are found to be British

and minted between 1838 and 1870,

after they outlawed slavery throughout the empire.

[narrator] Even after Britain banned the slave trade,

slavers tried to continue bringing enslaved people

from Africa to slaveholding societies in the New World.

The transatlantic slave trade didn't fully end until 1873.

In 1808, Britain set up a special fleet

called the West Africa Squadron to enforce the ban

on the slave trade, even though banning

the slave trade would have negative

consequences for interests in the empire that

depended on slavery.

[narrator] Owing to its strategic location,

St. Helena was chosen as a base for the

West Africa Squadron in 1840.

From here, the British fleet patrolled the Atlantic,

intercepting ships carrying enslaved people

to the Americas.

The enslaved people were liberated by the British

and taken back to St. Helena, where they were fed and housed

in what were essentially refugee camps,

one of which was in Rupert's Valley.

Many of those rescued were so mistreated

that they couldn't regain their health,

and approximately one-third of them died after arriving.

- The people who survived were technically free,

but weren't repatriated to their communities.

Instead, many were sent to the British West Indies

or to Cape Town, where they would live and work.

♪ ♪

It's difficult to come to terms with the cruelty of it all.

They were first taken from their communities

to be sold as enslaved people, then saved and

granted their freedom, only to eventually be taken

to a completely foreign place to work,

often as indentured laborers.

♪ ♪

[narrator] Between 1840 and 1867, roughly 27,000 people

rescued from slave ships were brought to St. Helena.

They became known as the Liberated Africans,

and today, many St. Helenians can trace their ancestry

directly to them.

♪ ♪

Apart from this group, it's thought that over 8,000

Liberated Africans lie buried in Rupert's Valley,

all victims of the transatlantic slave trade.

They were part of the largest forced migration

in human history, one whose violence, trauma,

and horror is still deeply felt today.

♪ ♪

[narrator] The 325 Liberated Africans exhumed in

Rupert's Valley have since been given a proper burial

and a memorial that will be erected

to honor their legacy.

The small island of St. Helena played an important role

in bringing to an end this centuries-old

crime against humanity.

♪ ♪

Framed by the Java Sea to the north and

the Indian Ocean to the south,

Java is Indonesia's political, cultural,

and economic heart and the world's most populous island.

♪ ♪

[Alison Leonard] Java is the 13th largest island on Earth

and one of its most densely populated places.

It contains over half of Indonesia's

almost 280 million residents, despite making up only

about 7% of its land area.

But even though Java is highly populated,

it still has areas of breathtaking,

unspoiled wilderness.

Running lengthwise through the middle of the island

is a mountain range dotted with volcanic peaks.

In fact, there are an impressive 112 volcanoes on the island,

but only 35 of them are active, so eruptions are rare.

[narrator] Near the village of Karyamukti in the province of

West Java, while exploring the area, one may come across

an unusual sight.

Cut into the forest are what looks like

a series of old stone steps going up a rather steep slope.

It's not an easy climb.

There are a total of 370 steps rising around 360 feet

at a 45-degree incline.

♪ ♪

[narrator] If you're able to brave the climb,

when you finally reach the top, the scenery is extraordinary.

It's a grassy terrace with hundreds of long, narrow

stones of varying sizes, some of which are strewn

about haphazardly, while others are

standing upright and appear to form patterns.

It's really strange.

What is this place?

The terrace is not quite a perfect square.

It's more like a trapezoid.

The front is about 130 feet wide,

but it tapers to around 118 feet at the back,

while both sides are pretty much the same length,

just over 92 feet.

[Anthony Cantor] The left-hand side is littered with stones,

but on the right-hand side, the stones are arranged

into a rectangle with two taller stones at

either side of the entrance, almost like gates.

Could this be some kind of megalithic monument?

[narrator] Standing stone monuments are most common

in northwestern Europe, particularly in Great Britain.

On Scotland's Isle of Lewis, the Calanais Standing Stones

have been watching over the rugged

Highland landscape for roughly 5,000 years,

predating England's famous Stonehenge.

The complex is made up of over 50 stones

in the shape of a cross, with a circle of stones

between 8 and 13 feet tall, forming the

heart of the monument.

In the middle of the arrangement is the tallest

stone at the site, which towers over the

others at 16 feet tall.

Incredibly, the layout of the stones in two locations

is so precise that they can be used

to measure the moon's most northerly position

on the horizon, an event that only happens

roughly every 18 1/2 years.

Maybe the Terra site on Java has some kind of

celestial connection.

- I suppose it's possible, but there are definitely

some key differences.

First of all, there's the shape.

Most known standing stone sites are circular, not rectangular.

The circular shape of sites such as Stonehenge

could be aligned with astronomical phenomena

like solstices, and may have served

ceremonial or calendar functions.

The scale is also different.

Those stones are generally much bigger

and spread out over a large area like Stonehenge or Callanish.

The stones on Java are densely packed together

and smaller than what is found elsewhere,

so it's unlikely it had an astronomical purpose.

[narrator] Continuing to explore the area,

you'll come across a short incline beyond the terrace

with another set of ancient stone steps.

At the top of the steps, there's another terrace.

This one is smaller than the first.

The front measures roughly 72 feet across

and narrows to about 60 feet at the back,

and it's around 80 feet long, a similar trapezoidal

shape to the first terrace.

On the second terrace, there isn't a geometrical layout

like the rectangle formation on the first terrace.

There are similar stones, but they're lying on the ground

seemingly in no discernible pattern.

[narrator] The perimeter is supported by what looks

like a retaining wall.

The wall appears to be made up of long, narrow stones,

the same kind that are found on the terraces,

but these are stacked horizontally,

giving support to the flat areas.

Given the different levels, along with the retaining wall

and the rectangular structure on the first terrace,

it looks like whatever this place is,

it was in some way constructed by human hands.

But why?

[narrator] The site, known as Gunung Padang,

consists of five terraces in total,

each one rising successively taller than the last,

climbing to a peak of over 650 feet above the forest floor.

Overall, the complex covers an area

of roughly 30,000 square feet.

That's about half the size of a football field,

making it the largest megalithic site in Southeast Asia.

[Anthea Nardi] Most of the stones found at the site

are pretty uniform in size and shape,

seeming like they might actually be hand-cut,

which supports the theory that Gunung Padang

was constructed by humans.

But they're actually naturally occurring volcanic rocks.

[narrator] The stones are the result of a geological process

called columnar jointing that occurs

when a thick body of cooling magma, usually basalt,

contracts and cracks into rock columns,

most commonly hexagonal in shape.

Famous examples of the phenomenon

are found at the Giant's Causeway in Northern Ireland

and the Devil's Postpile in California.

It's thought that the stones at Gunung Padang

may have been sourced from a volcanic quarry to the north

and then transported to the site where they were used

to build the stairs and any structures that

may have once existed on the surface of the terraces.

But some people believe there's a lot more to Gunung Padang

than what's on the surface.

One theory is that the hill is not naturally occurring at all,

but rather built by humans.

This has led some to believe that it's a

huge step pyramid-like underground complex, similar

to other ancient sites.

[narrator] On China's lowest plateau, archaeologists

unearthed the ruins of a 230-foot-high step pyramid

and the remains of a 4,300-year-old fortress city

known as Shimao.

The first pyramid the Egyptians ever built,

the Step Pyramid of Djoser, was built about 4,700 years ago

with six layers above ground and a series of tunnels below.

[Anthony Cantor] If there is, in fact, a pyramid underground

at Gunung Padang, it would be quite

different in appearance.

Egyptian pyramids are, for the most part, symmetrical,

whereas the Gunung Padang complex

is long and narrow and irregularly shaped.

[narrator] In 2011, a geologist named Danny Hillman Natawidjaja

performed another series of tests, namely core drilling,

a process that involves drilling under the ground

and removing soil to be analyzed.

The results ignite a firestorm of controversy

among the scientific community.

Based on carbon dating of the samples,

Gunung Padang contains several different layers

constructed during different time periods.

The oldest potentially dating back a shocking 28,000 years.

Unless there was some kind of lost civilization

that existed over 20,000 years ago,

humans at that time were simply not advanced enough

to build a huge pyramid complex.

So how could it be possible?

- Well, to be honest, it probably isn't.

The dating is flawed.

Anything organic can return a radiocarbon date,

but dateable raw material is not evidence of human culture.

- Really, the most plausible explanation

is that Gunung Padang is part of an extinct volcano.

The voids that were theorized to be rooms and tunnels

are probably magma chambers or air pockets created by

subterranean collapses.

- The terraces and retaining walls are most

likely the result of unique volcanic and seismic activity

over the millennia.

So while there's no doubt that ancient humans

did put their stamp on the site, creating the rock

formations and staircases probably around 2,500 years ago,

at this point, the pyramid theory

is more science fiction than science.

[narrator] Gunung Padang translates to

"mountain of enlightenment,"

and today, the site is a revered place

used for prayer and meditation.

For the time being, whatever lies beneath

this hallowed ground remains one of Java's

most enduring mysteries.

Just off the coast of Antarctica,

in the Ross Sea, sits Lamplugh Island,

a rugged ice-capped landmass around 10 miles long

and 2 miles wide.

The island was observed by famous explorer

Robert Falcon Scott during the British

National Arctic Expedition that took place

between 1901 and 1904.

Several years later, Ernest Shackleton charted Lamplugh

as an island and named it after a member of his expedition.

A little bit north of Lamplugh is the Drygalski Ice Tunnel,

a 43-mile-long expanse of ice that ranges from

9 to 15 miles wide and extends out from the

coast into the Ross Sea.

[narrator] In 2016, a team of American biologists

are conducting research on Cape Irizar,

a rocky outcropping on Lamplugh Island's north coast

when they come across a strange sight.

Scattered across the shoreline are several small mounds

made up of pebbles, all of similar size and shape.

What are these things?

They could just be natural rock formations.

I mean, this is Antarctica after all, right?

So the ice is constantly moving things around.

It's changing the landscape.

Maybe those mounds are just the result of glacial movement

depositing the stones here.

[narrator] Rocks that have been carried by glaciers

and then deposited elsewhere are known as glacial erratics.

As a glacier or ice sheet moves, it can erode bedrock,

and the resulting debris is then picked up by the ice

and transported in the direction of the flow.

When the ice retreats, it leaves behind

a different type of rock from the bedrock

where the erratic was deposited.

The largest known glacial erratic in the world

is found in Alberta, Canada.

It's a massive quartzite boulder about the size of a

three-story apartment building and weighing roughly

16,500 metric pounds.

Glacial erratics can range in size from large boulders

to smaller stones and pebbles, like what was found

on Lamplugh Island.

[narrator] Upon closer inspection, the team is able to

identify the mounds based on previous excursions

around the Antarctic coasts.

These aren't from glaciers.

They're nests, and specifically, they're the nests

of Adélie penguins.

These birds spend most of their time out at sea,

but when it's spring, they come to dry land

and painstakingly collect pebbles,

hundreds of them, to build these nests

where they can lay their eggs.

And they always pick a spot on a slope

so that when the snow melts, the water flows

away from the nest, keeping the eggs safe.

Now, finding Adélie penguin nests

in this part of Antarctica is not that shocking.

The Ross Sea supports almost one million breeding pairs a year,

but finding them on Lamplugh Island is definitely strange.

[Alison Leonard] Both Scott and Shackleton reported seeing

penguin populations along the mainland coast,

but there were never any sightings of them here.

And as of today, the nearest penguin colony

to Lamplugh Island is roughly 45 miles north

on Inexpressible Island, on the other side of

the Drygalski Ice Tone.

So why are there nests here?

[narrator] Their scientific curiosity peaked.

The team continues to explore the area.

They noticed guano stains on some of the rocks

around where the nests were found,

suggesting recent penguin activity.

But that can't be possible, because Adélie penguins

can't access Cape Irizar even if they wanted to.

Fast ice, which refers to large, solid ice sheets

that are attached to land, prevents their

entry onto beaches.

And there are daunting cliffs along other

parts of the shoreline as an added obstacle.

[narrator] Baffled by what they found so far and looking for

answers, the team expands their investigation of the area,

and it isn't long before they're face-to-face

with a macabre sight.

- They find Adélie penguin remains,

and not just one or two birds, dozens of them in various

states of decomposition.

Now, some are mummified, which presumably means

they've been here for a long time,

but others look very fresh, as though they died just recently.

[narrator] Mass penguin die-offs are not unheard of in Antarctica.

In 2016, a research team discovered

the mummified remains of hundreds of Adélie penguins

in thick layers of sediment on East Antarctica's

Long Peninsula, most of them just chicks.

Radiocarbon dating showed that this wasn't a sudden die-off.

They died gradually over the course of decades,

and this happened in two different periods,

dating to about 750 and 200 years ago.

[Alison Leonard] It's believed that their deaths were the

result of weather anomalies, unusually wet periods of rain

and snow soaked the chicks, and because they hadn't

yet developed the waterproof feathers

that adult penguins have, they died of hypothermia.

Could something similar have happened on Lamplugh Island?

It's certainly possible, given that in both scenarios

the majority of the remains were chicks,

but many of the bodies on Long Peninsula were found buried,

probably because flooding washed the penguins downhill with sediment.

But that's not what it looks like on Lamplugh.

The remains here are all just kind of scattered around

on the surface of the ground.

They're not buried at all.

[narrator] The team decides to put their paleontology skills

to use and sets about excavating penguin nests.

All of the sites are very dry and dusty

and made up of ornithogenic soil, or bird dirt.

Which is earth that is rich in carbon, nitrogen, and phosphorus

because of the presence of birds.

Polar ecosystems are notoriously nutrient-poor,

but bird populations help remedy this

by adding organic matter to the soil in the form of guano,

feathers, eggshells, and their remains.

The nests are quite shallow and at a depth

of around 4 to 6 inches.

They're able to collect various materials, including bones,

eggshell fragments, skin samples, feathers, and guano,

containing the remains of their prey, mostly fish bones.

[narrator] The organic material is sent to a lab for analysis.

Some of these penguins are over 5,000 years old,

and the so-called fresh remains that were thought

to have died recently are actually 800 years old.

The tests show that there were 3 different periods

of the Adelie penguin occupation on Cape Irizar,

beginning around 5,000 years ago and ending

roughly 685 years ago.

Their ultimate disappearance coincides

with the Little Ice Age, a period of global cooling

from around 1300 to 1850 CE, when average temperatures

dropped by as much as 3.6 degrees Fahrenheit.

The question is, why do they keep coming and going?

[Dan Riskin] It likely has something to do with the climate.

Periods of warmer weather would have resulted in the

fast ice on the shoreline melting in the early summer,

and that would have provided water access to the

penguins in breeding season.

They could have just swam right up and built

their nests on the coast.

But when the climate got colder, the beaches were

no longer accessible.

There was still ice in the way, so they had to abandon the Cape,

or maybe the penguins just all died off there.

It could have also had something to do with

changes in the thickness and size of the

Drygalski Ice Tongue over the years, impacting the ocean

conditions off Cape Irizar.

And significant calving events, which is when

ice chunks break off from the edge of a

glacier, could have caused large ice masses

to choke off the penguins' access to the shores.

What I don't understand, though, is that if

there's all this evidence of penguin populations

living on Lamplugh Island over thousands of years,

how come no one noticed it before?

[narrator] Consulting with historic satellite images,

the team quickly realizes that the most obvious answer

is usually the correct one.

Up until a few years ago, the Cape was

covered in snow and ice.

Because of climate change, since the 1980s,

temperatures in the Ross Sea have increased by

2.7 to 3.6 degrees Fahrenheit.

And as a result, Cape Irizar and all of Lamplugh Island

have been slowly emerging from a deep freeze.

[Dan Riskin] So the fresh guano stains and penguin carcasses

that don't look very old are very old.

They were perfectly preserved, spending hundreds of years

buried under ice and snow, only to be exposed by

the warming of the planet.

So how does this affect the future of Adelie penguins

in this part of the world?

[narrator] In an ironic twist, the receding ice on Lamplugh Island

may actually be beneficial to some of the penguin populations

of southern Antarctica.

Because Adelie penguins breed on land, and more and more

shorelines are being exposed, it gives them greater territory

on which to build their nests and hatch their young.

So in some areas, penguin populations are growing

rather than shrinking.

Right now, the fast ice around Cape Irizar melts

too late in the season to make it a feasible place

for the Adelies to breed.

But that could change in the future as

climate change worsens, and it could become home

to a robust penguin population once again.

But these are only regional short-term gains.

The longer-term outlook is actually quite bleak.

So while it's wonderful for some penguin populations,

in terms of our global future, it's actually pretty depressing.

Some reports predict that 30% of the Adelie population could

be gone by the year 2060, and as much as 60% of the

population will disappear by the end of the century.

The numbers are already declining around the

West Antarctic Peninsula, one of the fastest-warming

places on Earth.

And that makes it very hard to predict exactly what

the long-term outlook is for these adorable birds.

[narrator] As the ancient Antarctic climate changed,

so too did the nesting habits of the Adelie penguins.

And now, hundreds of years later, history appears

to be repeating itself.

The discovery of the long-lost colonies on Lamplugh Island

is a perfect illustration of the tenuous balance

between animal habitats and environmental conditions.