Original subtitles

Narrator: New evidence of an American tragedy

is unearthed in the Sierra Nevada mountains.

Dr. Cantor: The bone showed cut marks, saw marks and shot marks,

clear evidence of butchery.

Anthea Nardi: The majority of the remains

are from three species.

Cattle, horse or mule, and bear,

but the shocking thing is that some are human!

What's going on here?

Narrator: A mysterious phenomenon is observed

in the Canadian Arctic.

And what's really odd is that this signal ended up

radiating all the way around the world,

for nine days!

So what caused it?

Narrator: A grisly discovery is made

high in Europe's Pyrenees mountains.

Dr. Riskin: In an excavated area of roughly 500 square feet,

they discovered human remains

of at least two dozen individuals.

Anthea Nardi: Who were these people, and how did they die?

♪ [show theme music]

Narator: These are the strangest mysteries

trapped in the coldest places.

♪♪

Lost relics.

♪♪

Forgotten treasures.

♪♪

Dark secrets.

♪♪

Locked in their icy tombs for ages.

♪♪

But now, as ice melts around the world,

♪♪

their stories will finally be exposed.

♪♪

♪♪

Narrator: The remote town of Truckee is almost 6,000 feet

above sea level in Northern California's rugged

Sierra Nevada mountain range.

Dr. Cantor: Truckee has a reputation for being one

of the coldest towns in the contiguous United States.

In 1993, the lowest temperature in the United States

was recorded in Truckee for 62 out of 365 days,

more than any other city or town in the lower 48.

The average minimum temperature for July and August of that year

was a frosty 31 degrees,

and that was in the middle of summer.

Dr. Agbedor: The chilly weather is largely due

to altitude and topography.

At night, cool air from surrounding mountains sinks

and gets trapped in the Martis Valley,

which is a high-elevation basin near the town.

This cold dense air settles and creates a cool microclimate.

James Ellis: Not only is Truckee one of the

coldest towns in the United States,

but it also happens to be one of the snowiest,

receiving an average of almost

207 inches of snow annually,

making it the fifth snowiest city in the country.

Anthea Nardi: Truckee was established in 1863

as a rough-and-tumble railway town, due in part

to the building of the Transcontinental Railroad.

But Indigenous people called the area home long before that,

beginning with the Martis people around 2000 BCE.

So there is some archaeological interest

in this part of California.

Narrator: A team of archaeologists is conducting

a dig along the shores of a large lake just north of Truckee

when they make a surprising discovery.

Dr. Agbedor: There are three ash deposits under the earth,

the largest being a charred log fragment

roughly six and a half feet long

and one and a half feet wide.

There's also evidence of a shallow,

bowl-shaped firepit filled with charcoal,

ash, and bone fragments.

Clearly, this is evidence of human occupation,

or at the very least, human presence at this site

from many years ago.

So who was here...and when?

Dr. Cantor: It could be the remnants

of an old Indigenous settlement.

It's believed that in pre-Colombian times,

California was the most populous area on the continent,

and also the most ethnically and linguistically diverse.

Nine language groups could be found

in the Sierra Nevada Mountains alone.

Narrator: Not far from Truckee,

Native Americans left a definitive record

of their presence in the area, in the form of petroglyphs.

Anthea Nardi: It's thought that the petroglyphs in this region

are between 1,500 and 4,000 years old,

and were created by tapping the surface of the rock

using a tool called a hammerstone.

Many are simple shapes, circles, zigzags, and wavy lines.

Animal and human images, like deer or bear tracks

or stick figures, appear less frequently.

James Ellis: The petroglyphs were likely created

by the Martis people, the ancestors of the Washoe,

who live in what is today Nevada.

The Martis disappeared from this area

around 500 BCE, and nobody knows definitively

where they went or why they left.

Dr. Cantor: In addition to the petroglyphs,

the Martis people left behind many other items.

Light stone artifacts, broken tools and dart points

have all been found throughout the Truckee basin.

And evidence of prehistoric fires, similar to what was found

near the lake has also been discovered.

So it is possible that we're looking at what's left

of an Indigenous settlement or meeting place.

Narrator: As the archaeologists continue the excavation,

they discover more evidence of fire.

Dr. Agbedor: There are areas where the thickest

charcoal deposits and the highest concentration

of charred wood fragments

seem to form a rectangular shape,

roughly 25 feet long and 18 feet wide,

oriented northeast-southwest,

along the face of a rock wall.

This indicates that these are likely the remains

of a decent-sized wooden structure of some kind

that burnt down.

J. Ellis: So it's unlikely this was an Indigenous settlement,

because the native population in this area was nomadic,

making annual migrations - hunting, gathering

and trading food, clothing materials, and other items.

They didn't establish permanent settlements

with wooden structures like this,

so some other group must have been living here.

Narrator: Searching for clues, the team expands

the excavation area and unearths a treasure trove of artifacts.

Anthea Nardi: There are beads, jewelry, toiletries,

and other personal effects.

The most abundant items are tobacco pipe fragments,

most of which come from the longstemmed clay variety

called "Dublin Pipes", which were very popular in the 1800s.

So we can safely say that this site was likely in use

during the 19th century.

Dr. Agbedor: One of the most interesting finds

is a Roman Catholic religious medal,

designed in a style similar to those produced in the U.S.

between 1825 and 1875.

So that narrows our time window

down a little bit to those years.

Dr. Cantor: There are also lead balls

and other firearm-related artifacts.

The ammunition is mostly in the 50 to 60 caliber range,

suggesting the presence of large caliber rifles,

likely hawking rifles,

which were lightweight hunting guns,

capable of taking down big game at long range.

Hawkins were the most popular rifles of the mid 1800s,

so it's reasonable to assume

that the site dates from that period.

Narrator: Bone fragments uncovered from the site

are sent for biochemical tests,

and the results leave researchers stunned.

Anthea Nardi: The majority of the remains

are from three species:

cattle, horse or mule, and bear,

but the shocking thing is that some are human!

Why are human bones intermingled with animal bones?

This is the kind of thing you might come across

at some ancient sacrificial site,

but to find it in the United States,

at a site that dates to the mid-19th century,

makes no sense at all. What's going on here?

Narrator: Acting on previously gathered information,

the team moves to another site roughly five miles north

at Alder Creek and begins another excavation.

It isn't long before they unearth more artifacts.

[workers chatter]

J. Ellis: Unlike the other site, there is an abundance

of ceramics, mostly typical tableware

from the 1830s and 1840s.

The collection includes plates, cups, and saucers,

some painted with small flowers.

But the most interesting finds are two coins:

a United States one cent coin

with a Liberty head from 1830,

and a copper farthing from England minted in 1839,

so we know that this site was occupied sometime after that.

Dr. Agbedor: Also present are the remains of a hearth,

a dark charcoal stain with a thin layer of ash

approximately two by two and half feet.

Inside, are over 16,000 tiny bone fragments,

weighing more than 5 pounds!

Surrounding the hearth are hundreds of artifacts,

including bottle fragments, clothing buttons,

and lead shot similar in caliber

to the bullets discovered at the Truckee site.

Dr. Cantor: If we assume that both sites are from

the same time frame, the mid-1800s,

then it's reasonable to conclude that the sites are connected,

especially given their relative proximity and the similarities

among some of the artifacts discovered there.

But that still doesn't tell us who was living here.

Anthea Nardi: It could be what's left of a Chinese labour camp.

One of the most important connections

across the 2,000 mile transcontinental railroad,

is close to Truckee,

15 tunnels through solid granite.

Over 12,000 of the 15,000 laborers

who built these tunnels, were Chinese.

Narrator: In 1995, a Forest Service historian in Montana,

led an expedition that discovered the site

of a Chinese camp,

which became known as 'China Gulch.'

James Ellis: Eight hand-stacked rock hearths were unearthed,

including one that was excavated

and yielded 560 artifacts.

There were nails, bottle glass, plate fragments

and several brass opium cans.

And also, roughly 350 animal bone fragments.

Dr. Cantor: The bones showed cut marks, saw marks and shot marks,

clear evidence of butchery.

And they also showed signs of what's called pot polish,

bones that have become smooth and rounded,

due to spending considerable amounts of time

boiling in pots of water.

The presence of pot polish can also indicate

that a bone was cooked more than once,

once with meat on it and again later without any meat left.

Dr. Agbedor: The fragments were so small, that only one

could be identified as a species:

domestic pig.

Tiny fragments like this and the presence of pot polish,

often represent grease processing,

which is a sign of starvation.

Basically, with no other options,

people resort to cooking bones over and over again,

to get every last bit of nutrition out of them.

James Ellis: The people of China Gulch must have suffered

some kind of crisis that caused starvation.

So is that what happened at the other sites in California?

Were they Chinese labour camps,

where people also starved to death?

Narrator: Samples of the animal bone fragments

recovered from the hearth at the Alder Creek site

are sent for analysis.

Anthea Nardi: Nearly all of the 673 samples

had some form of heat damage

from being burned and boiled,

and there's evidence of pot polish on almost half of them,

a clear sign of nutritional stress

for whoever was living here.

So it's possible that the sites are connected.

Dr. Agbedor: But analysis of the artifacts found at China Gulch

showed that the site was occupied during the 1870s,

and all evidence at the California sites points to

an earlier period, probably closer to the 1840s.

Narrator: As the excavations continue

at the Alder Creek site,

several items are discovered, that may just put

the pieces of the puzzle together.

Dr. Cantor: There's hardware from wagons,

including two iron staples,

one rectangular and the other circular,

as well as an axle ring,

and a brass hook with a threaded end

that may have been connected to a wagon box.

Anthea Nardi: Between 1840 and 1860,

an estimated 300,000 Americans travelled overland

to what is now California, Oregon, and Utah

in search of a better life,

drawn by the availability of cheap land.

The vast majority made the journey in wagon trains,

groups of covered wagons that carried people

and their supplies to the West

before the Transcontinental railroad came into existence.

James Ellis: So considering the presence of wagon parts

and the other artifacts discovered at the two sites,

what we could be looking at, is a caravan of emigrants

who were headed west, but never made it.

But who were they? And what happened?

Narrator: According to historical records,

this area was home to one of the most tragic events

in American history,

the infamous Donner Party.

Dr. Cantor: In April of 1846.

a party led by the brothers,

Jacob and George Donner, left Springfield, Illinois,

in search of a new life in California.

The initial group consisted of 31 people,

and within a month, the Donners had reached

Independence, Missouri, where they became part of

a main wagon train, headed west on the Oregon Trail.

Dr. Agbedor: After making good progress, the party,

which was now 87 people and 23 wagons strong,

initially followed the regular California Trail

to Fort Bridger, Wyoming.

But then they made a fatal error and tried to take a shortcut

along an untested route to California.

This so-called "shortcut"

proved to be anything but,

and cost them 18 days of delay.

James Ellis: In October, they finally made it

to the Sierra Nevada Mountains.

But heavy snowfall caused them to get stuck in the wilderness,

so they set up shelters, one of them being the log cabin

discovered near Truckee,

and tried in vain to ride out the winter.

Unfortunately, it was a near impossible task.

Anthea Nardi: Of the 87 person caravan, only 47 survived,

most of the others died of starvation or disease.

And when faced with life or death survival,

some members of the Donner Party did the unthinkable,

and resorted to cannibalism.

Which would explain the human bones

intermixed with the animal bones at the cabin site.

As abhorrent as that may sound,

it likely saved some of them from certain death.

Narrator: The story of the Donner Party is a dark chapter

in American history and the very name of the group

has since become synonymous with cannibalism, right or wrong.

Those who survived went on to a new life in the West,

while those that perished,

did so in pursuit of the American dream.

♪♪

♪♪

Narrator: On the northern shore of the frigid Great Slave Lake

in Canada's Northwest Territories,

lies the city of Yellowknife.

Dr. Cantor: With a population of just over 20,000,

Yellowknife is the largest community

and the only official city

in the Northwest Territories.

It was named after the local Yellowknife Dene First Nation

and serves as the principal commercial, administrative,

cultural and educational center of this huge region.

Dr. Leonard: Weather conditions can be difficult

in Yellowknife's subarctic climate, to put it mildly,

with temperatures plunging to lows of -55 degrees Fahrenheit.

The terrain is rough, comprised mainly of

large rock outcroppings

separated by boggy wetlands common in boreal areas.

But this rugged remoteness makes Yellowknife ideal

for certain disciplines of scientific study.

Narrator: A seismologist with Natural Resources Canada

is monitoring primary seismic Station 9 in Yellowknife,

one of four stations covering the far north

of the American continent,

when something strange happens.

[audio static]

James Ellis: An unusual seismic signal is detected.

The waves are oddly consistent with a continuous pattern

and constant frequency.

They're also very long,

recurring every minute and a half.

And what's really odd is that this signal ended up radiating

all the way around the world, for nine days!

So what caused it?

Dr. Riskin: Well, when it comes to seismic activity,

obviously the first thing that comes to mind

is that maybe it's an earthquake.

They don't always act in ways that we've come to expect.

Maybe it was what's called a 'slow earthquake.'

Dr. Cantor: Scientists have only become aware of slow earthquakes

in the last 25 years or so,

and much about them remains a mystery.

Standard earthquakes release seismic waves abruptly,

and with destructive power.

But slow earthquakes can last days,

months and even years.

They can move tectonic plates as much as a quake

that registers 7 on the Richter scale.

But most people don't feel them at all.

Narrator: On March 11, 2011,

a massive earthquake rattled Japan

for almost 6 minutes,

and generated a tsunami and nuclear accident

that ended the lives of almost 20,000 people.

But under the ocean, the tectonic plates

off the east coast of Japan

had quietly started moving before the catastrophe.

James Ellis: A month earlier, two earthquakes

began silently moving along the Japan Trench,

toward where the big quake would eventually begin,

but it's unclear if they triggered the main event,

or even how they were related to it.

The bottom line, is there's a lot we don't know

about slow earthquakes.

So could a slow earthquake be to blame

for the strange seismic activity

detected in Yellowknife?

Dr. Leonard: It's not out of the question,

but seismic waves from earthquakes, even slow ones,

tend to be sporadic and unpredictable,

without a repeating sequence like what we're seeing.

So I don't think it's from an earthquake.

Maybe it's picking up unusual volcanic activity.

It does happen.

Narrator: In November of 2018, just off the Island of Mayotte,

situated between Madagascar and Mozambique,

in the Indian Ocean,

a strange seismic event left scientists puzzled.

Dr. Cantor: There was a single ultra-low frequency seismic hum,

kind of like the ringing of a bell, that circled the world.

And this was strange, because seismic waves

usually vibrate at many frequencies.

Also unusual is that there were no signs of an earthquake.

No one in the area felt the earth shaking.

And the seismic waves related to the hum,

were virtually undetectable.

Dr. Leonard: The fact that the seismic waves were negligible

is very strange.

This is a hum that could normally be detected

the world over.

Stranger still, the Island of Mayotte shifted a few inches

south and east, after the mysterious event.

Narrator: Looking for answers, a team of French researchers

from the Institute of Geophysics in Paris

took to the water,

and what they found left them stunned.

Dr. Riskin: It turned out to be the largest

underwater volcanic eruption ever recorded.

[sound of explosion]

This volcano is massive.

It's over three miles long.

It rises up nearly half a mile from the ocean floor.

And here's the astounding part:

it formed in just six months!

So, could an underwater volcanic eruption

have caused the unusual seismic waves

that were detected at the Yellowknife monitoring station?

Dr. Cantor: It's possible, but unlikely.

The hums generated by the Indian Ocean volcano,

had a duration of only up to 20 minutes.

Whereas the seismic activity detected in Yellowknife,

lasted nine days.

It has to be something else.

Maybe something man-made and slightly menacing.

Narrator: In September of 2017,

North Korea tested a 250 kiloton nuclear bomb underground,

roughly 17 times the size of the bomb

that destroyed Hiroshima in 1945.

The explosion produced a magnitude 6.3 earthquake,

which was followed 8 and a half minutes later,

by a magnitude 4 quake.

James Ellis: The test and resulting quakes

were picked up by monitoring systems around the world,

and heavily reported on at the time.

Later on, seismic stations operated by South Korea,

China, and the U.S.

picked up 10 smaller aftershocks,

all emanating from within 3 to 6 miles of the test site.

Dr. Leonard: Interestingly, the Yellowknife seismic

monitoring system was originally installed in 1962,

in partnership with the British Ministry of Defence,

and its purpose was not to monitor

natural seismic activity, but nuclear testing.

And it detected a North Korean bomb test in October of 2006,

so there is precedence there.

So is it possible the station is picking up seismic activity

from another North Korean nuclear explosion?

Dr. Cantor: Probably not.

The test that produced the earthquake in 2017,

was the last known North Korean nuclear test.

And we all know the world is watching them pretty carefully.

Narrator: The unusual signal, now labeled "USO"

or "Unidentified Seismic Object",

a name used by seismologists

to describe an unexplainable seismic event,

has scientists baffled.

68 experts from 15 countries

come together in an attempt to solve the mystery.

Dr. Riskin: They were able to track the source of the signal,

but only to this huge area in eastern Greenland.

So, they contacted local scientists,

and those scientists informed them that sea level gauges

had recorded a tsunami in an uninhabited valley

on the East Coast, called Dixon Fjord.

Dr. Leonard: This wasn't just a run-of-the-mill tsunami, though,

this thing was massive, over 650 feet tall.

But what caused it, and how could it possibly be sending

these strange signals all over the world?

Narrator: Using satellite images and drone videos,

the researchers pinpoint the chain of events

that triggered this once-in-a-lifetime occurrence.

James Ellis: Around 3/4 of a mile above the fjord,

a mountaintop collapsed,

propelling more than 880 million cubic feet of rock and ice

into the ocean, enough to fill

10,000 Olympic-sized swimming pools!

This created a seismic signal that raced around the world,

traveling from Greenland to Antarctica,

in less than an hour!

Dr. Riskin: And then what happened is this huge tsunami

basically just got trapped in this fjord.

The water sloshed back and forth like it was water in a bathtub,

in what's called a seiche.

And the seiche wasn't as big as the original tsunami.

It was only about 20 feet tall.

But it lasted for ever.

Oscillating back and forth across this fjord

every 92 seconds.

Ultimately just going on and on and lasting more than nine days.

It's an incredible event.

It's Mother Nature at her most awe-inspiring.

Narrator: On top of this event, scientists discovered evidence

of at least four smaller previous ice

and rock landslides in satellite imagery.

Because of climate change, in the future,

we could see worse occurrences of cascading,

perhaps with dire consequences.

♪♪

♪♪

Narrator: The Pyrenees Mountains stretch across

270 miles of southwestern Europe,

creating a massive natural barrier

between France and Spain.

The mountain range is home to several glaciers,

with Huesca Province's Aneto glacier being the largest.

Dr. Riskin: Aneto is also the highest peak.

At 11,000 feet above sea level,

the frigid temperatures and unpredictable conditions

make it extra challenging for climbers.

Even in summertime, a sudden snowstorm isn't unheard of.

Anthea Nardi: This area of the Huesca Province is harsh,

isolated, and sparsely settled.

Anything above 8,000 feet is just alpine vegetation.

Below that, the foothills give way to pastures,

that are mostly populated by livestock,

and that's only in the warmer months.

Dr. Agbedor: The region has sporadically been home

to small communities of farmers and hunter-gatherers,

going back thousands of years.

The tough conditions and short summers are better suited

to migrant and seasonal farmers.

Narrator: A team of archeologists from Spain's

Aragon region is exploring the southern slope

of the Pyrenees' Mount El Trocs,

when they make a startling discovery inside a cave.

Dr. Leonard: They found a cave containing the remains

of a large number of sheep.

And by 'large number,' I mean, they found the bones

of 25,000 sheep!

But the biggest surprise was still waiting for them.

Dr. Riskin: In an excavated area of roughly 500 square feet,

they discovered human remains,

of at least two dozen individuals.

Most of the skeletal features are widely dispersed,

with bones laid out both horizontally and vertically.

Anthea Nardi: The sheep part of the story is easier to explain.

The area is surrounded by pastures in the Ebro Valley,

and there's thousands of years of animal husbandry

to draw upon. But the human skeletons?

Who were these people, and how did they die?

Narrator: Eager to learn more, the team conducts

radiocarbon dating on 13 different individuals.

Dr. Agbedor: The results were as surprising

as the discovery itself.

The bodies all dated back to the Neolithic period,

but within that, there were three different periods

represented between the years 3300 BC and 5300 BC!

Dr. Leonard: So clearly the deceased were not all members

of the same community.

They may not have even had the same genetic

or ethnocultural background.

And yet there they were, together in the same cave.

Dr. Riskin: Of the three identified groups,

the research team decided to focus on the oldest,

which they called the "Phase 1 Group".

They're from about 5300 BCE.

That's more than a thousand years before anybody else.

Dr. Leonard: There were nine individuals

in the Phase One group, what appeared to be

four young children and five adult-sized bodies.

Could this represent a family from 7,000 years ago?

Is it possible that as each family member passed away,

they were added to the family burial plot?

Narrator: Further testing of bone samples

from the Phase One group,

reveals that all nine individuals expired

at roughly the same time,

likely a single event.

A. Nardi: Adding to the mystery, the demographic structure

of the nine bodies was highly unusual.

The four small individuals were children

between the ages of 3 and 7, as predicted.

But the other four were considerably older adults;

one of them in their 70s.

Dr. Agbedor: There were no older children, no adolescents,

not even young adults,

just the very young and very old.

It didn't add up to a normal cross-section

of an age-balanced social community.

So what could that possibly signify?

Narrator: When the researchers take a closer look

at the skeletal remains,

they find the first clue to a likely cause of death.

Dr. Leonard: Most of the Phase One group appeared to have

serious injuries on their skulls,

lesions and fractures that were the result of

intentional violence inflicted on them.

Dr. Riskin: The size and the shape of those wounds

were extremely helpful to figure out what happened.

A couple of the parietal bones,

that's the bone on the side of the back of the head,

showed fractures that were caused by a sharp weapon.

And not only that, the size of the hole

and the impact markings on the skull indicate

that that weapon, was used with extreme force.

Anthea Nardi: So it's possible that they were deliberately

shot in the head by bow and arrow.

If that was the case, the El Trocs cave was no longer

just a burial site--it was a Neolithic Crime Scene.

Narrator: The use of arrowheads as lethal weapons

was widely practiced by hunter-gatherers

of the early Neolithic period.

Dr. Agbedor: Arrowhead technology remained mostly

unchanged until the end of the 4th millennium BC.

Essentially, they were arrows consisting of

flint or bone blades, attached to wooden shafts.

Dr. Leonard: As the technology improved, bows and arrows

played a more prevalent role in violent clashes,

due to enhanced aerodynamics and penetration power.

Dr. Riskin: If the nine bodies were victims of

murder by bow and arrow,

it's likely there was going to be more forensic evidence

at the cave site, to support that theory.

Narrator: The team expands their search by continuing

to excavate below the surface of the El Trocs cave floor.

Dr. Riskin: Sure enough, they unearthed a small inventory

of what are called flint geometric microliths,

which is just fancy talk for small stones of flint

that are made into specific shapes.

And these ones were shaped like arrowheads.

The artifacts are consistent with the skull injuries

on the Phase 1 Group.

Anthea Nardi: And it was definitely the arrowheads

that killed them, intentional injuries that occur at

or very close to the time of death are called "perimortem.'

Typically, they show no sign of healing after impact,

and they're usually the same colour

as the rest of the bone surface.

Dr. Agbedor: The picture emerging was that of a planned

and extremely violent bow and arrow attack.

But who killed these people, and why?

Narrator: The discovery inside the El Trocs cave

is not the only incident of organized, intentional violence

from Europe's Early Neolithic period.

Dr. Riskin: Neolithic skeletal remains,

dating around 5300 BCE were found in Talheim Germany,

in what was once a small farming village.

Anthea Nardi: Archeologists uncovered an ancient grave

measuring about 25 feet by 3 feet,

that was filled with the bodies of 34 individuals.

Fragments of arrowheads were found lodged

right into the bone, and from their position and angle

experts believe the victims were ambushed.

Dr. Agbedor: There were no defense wounds

found on the skeletons, which also points toward an ambush.

It also indicated the victims were on the run

and fleeing for their lives when they were attacked.

Dr. Leonard: As with the El Trocs site,

almost half of the victims were children,

no older then 7 years old.

Is it possible there were other similarities at play?

Narrator: Taking stock of the cave's dimensions,

the team makes a critical observation.

Dr. Leonard: They determined there wasn't enough

"projectile kinematic space" inside

for the bows and arrows to do the amount of bone damage

presented by the evidence.

So the Phase One victims weren't killed in the cave.

Dr. Riskin: Since the bones show no sign of exposure

from the elements or damage from foraging animals,

we can infer that someone brought these bodies

into the cave, very soon after they died.

Narrator: Further examination of the skeletal remains

reveals another critical and disturbing clue.

Anthea Nardi: In addition to the trauma caused by the arrowheads,

both skull and limb bones on all nine bodies exhibited

multiple traces of blunt force trauma.

And several skulls bore multiple fractures,

which meant more than one blow to the face.

Dr. Agbedor: In one case, forensic scientists

reconstructed the sequence of injuries to a 70 year old woman.

The shape and pattern of the fracture lines revealed

she was killed by the arrowhead first,

then received multiple blows to the head

while already on the ground.

Dr. Leonard: It was also possible to determine

that many wounds were delivered after the victims

were already dead.

Postmortem lesions on craniums tend to be more irregular,

and have sharp curved edges.

Dr. Riskin: Similar results were found in the small skeletons,

on the children.

Blunt force trauma wounds inflicted postmortem,

likely by stones or clubs.

All of this adds up to a deeply disturbing scene.

It's not just an ambush, it's a massacre.

Narrator: The early Neolithic Period marked the beginnings

of collective and intentional violence between rival groups,

including the farming cultures of Central Europe.

Anthea Nardi: We do know the area was seasonally populated

by migrant farmers, who traveled into the pastured area,

with their livestock during the summer months.

It's possible the attack came from existing or 'local' farmers

who didn't exactly appreciate the newcomers.

Dr. Agbedor: This scenario offers an explanation

for the Phase One victims containing

only young children and older adults.

If they were solely tasked with looking after

the summer livestock,

that would separate them from the main group.

It would also make them easy targets for the perpetrators.

Dr. Riskin: It's also possible the perpetrators

were local indigenous hunter-gatherers,

who saw the Neolithic farmers encroaching on their resources.

But from an 'archeoforensic' perspective,

there's just a limit to what we can infer.

Narrator: The clash at the El Trocs mountain cave

was the earliest and most bloody example

of documented violence,

between rival groups or ethnicities.

♪♪

♪♪

Narrator: South of New Zealand and extending into Antarctica,

the Ross Sea spans approximately 370,000 square miles,

and can reach depths as low as 3,000 feet.

The southern portion of the sea is bordered by

the Ross Ice Shelf, the largest ice shelf in the world.

Dr. Leonard: The climate in the Ross Sea can be harsh,

with long, cold winters

and short cool summers.

For most of the year, the sea is ice-covered,

but some areas experience ice-free conditions

during the summer months.

This allows for scientific expeditions

and fishing in certain areas.

James Ellis: Having a diverse ecosystem,

the Ross Sea is home to an amazing variety

of marine animals including half a dozen types of birds,

at least 10 mammal species, 95 species of fish,

and 1,000 invertebrates.

Several of these species' cannot be found anywhere else

in the world--they are unique only to this area.

Dr. Riskin: Because this place is basically untouched,

it's vital for scientific research on everything

from climate change, to marine ecosystems, to glaciers.

Scientists can study the sea's role in global ocean currents

and its potential impact on rising sea levels,

because ice shelves and glaciers that feed into the sea,

are all sensitive to warming temperatures.

Narrator: With a short summer, fishing boats

must work day and night to make their quotas.

The fishing ship, San Aspiring gets the surprise of a lifetime

when their lines bring up something

no one has ever caught before.

Dr. Cantor: It's a colossal squid!

[camera shutter clicking]

Not a giant squid, a colossal squid!

Which is the biggest squid there is.

This thing is massive!

We're talking 26 feet long

and weighing just over 1,000 pounds.

This is by far the largest ever caught,

and also the first intact adult male

to ever be successfully recovered.

Dr. Riskin: Similar to smaller squid species,

the colossal squid is basically just a giant squid.

It's got a head, it's got a mantle, it's got legs,

all the things you would expect on a cephalopod.

But they're just way bigger.

It's also got some unique features like

hooks at the ends of the tentacles,

and the largest eyes in the animal kingdom,

which allows them to see in the deep sea.

They hunt on big fish,

they eat things like Antarctic toothfish,

and they get eaten, by even bigger things, sperm whales.

Dr. Cantor: The colossal squid is extremely elusive

and mysterious, with only nine known specimens

above juvenile size reported in the last hundred years.

Estimated to grow 40 to 46 feet long,

which is the size of a school bus.

It's the largest and heaviest invertebrate in the world.

But how and why did it get so big?

Narrator: The theory of Polar gigantism

is a biological phenomenon observed

in some marine species living in Polar regions.

Certain animals, particularly invertebrates,

grow to much larger sizes than their counterparts

in warmer climates.

Dr. Riskin: For cold blooded animals,

metabolic rate is linked to temperature.

So the colder the temperature is,

the slower the metabolism.

And in Arctic water that's going to have a huge impact

on how an organism processes energy,

how fast it can grow,

and how it survives in its environment.

Narrator: One gigantic deep sea creature that is known

for its slow metabolism is a type of shark

mostly found in the cold water environments

of the Arctic Ocean and North Atlantic.

Dr. Leonard: The Greenland Shark is gray or brownish

in appearance, and can grow to as big as 21 feet in length

and weigh over 3,000 pounds.

They have extremely small eyes

and can get partially blinded by parasite copepods,

but they rely more on their sense of smell

to navigate their environment and find prey.

Dr. Riskin: Because of its slow metabolism,

the growth of Greenland sharks spreads out over a life span

that lasts centuries.

There are concrete examples of individuals

that are at least 272 years old,

but it's believed that some of them live more than 500 years.

They only grow 0.4 inches a year,

and they don't become sexually mature

until they're around 150 years old.

And we don't know much about how they reproduce.

But it's believed the Greenland sharks have a gestation period

that probably lasts several years.

James Ellis: The Colossal Squid also has

an extremely slow metabolism.

A single arctic toothfish that weighs roughly 11 pounds,

would be enough food for an 1,100 pound colossal squid,

for approximately 200 days!

Narrator: The impact of cold water

on these creatures' metabolism

may be just one piece of the puzzle,

when it comes to cold water's influence on colossal squids.

Dr. Cantor: Cold water environments, like those

found in Polar regions or the deep ocean,

have more dissolved oxygen available

to support larger animals.

James Ellis: Larger sea creatures need more oxygen

to support their bodies,

especially those with slow metabolisms.

So in warm waters, where there is less oxygen,

it's harder for big animals to grow.

So while abundant oxygen may not directly cause sea creatures

to become large, it likely helps make it possible.

Narrator: One species that thrives and becomes larger

in cold waters is creepy and crawly,

and not a lot of people's favorite insect.

Dr. Leonard: Sea spiders are typically much larger

in Antarctic waters than their counterparts

in warmer environments.

Antarctic sea spiders are about the size of a dinner plate

and can reach up to 20 inches across,

while those in warmer waters are often

just a few centimeters in size.

The extra oxygen in cold water makes it easier

for these animals to support larger bodies,

because they can absorb enough oxygen

to fuel their biological functions.

Dr. Riskin: Because Sea spiders don't have gills,

they rely on oxygen diffusing across their thin body walls.

The high concentration of dissolved oxygen in cold water

means as long as those things have skinny body parts,

they can get remarkably big.

Narrator: While there is no doubt the cold waters

have a profound effect on Polar gigantism,

there is one factor that cannot be overlooked -

evolution.

James Ellis: The evolution and survivalist nature

of these creatures is hugely important.

Larger animals may have fewer predators,

or they may be too big for typical predators to attack.

This obviously increases their chances of survival,

which also gives them more opportunity to grow.

Dr. Leonard: Larger animals like the colossal squid,

can also access a wider range of food sources,

such as larger prey and have the ability to dig deeper

into the ocean floor for hidden resources.

Dr. Cantor: The reproductive success of larger animals

is also an important factor in their survival.

They have more resources to produce more

or bigger offspring, which increases their chances

to pass on their genetic material,

while also allowing their young to be protected

from predatory sea creatures.

Dr. Leonard: These larger creatures can travel farther

and faster to find food or mates,

and they have more efficient metabolisms,

which helps them store food better.

When a large food source, like a carcass, sinks into deep waters,

bigger predators can eat more of it

and store the energy for a longer time,

helping them survive in resource-scarce environments,

like the lower levels of the sea.

Narrator: Polar gigantism seems to be largely driven

by the combined effects of cold water and survivalist evolution,

and while we do not know enough about these

mysterious gigantic creatures,

these are the stepping stones of understanding

what makes them unique.

♪♪