All language subtitles for Secrets.in.the.Sand.S01E03.1080p.WEB.h264-BAWD_track3_[eng]

NARRATOR: Mysterious stones
appear to be making their way

across one of the hottest deserts
in the world.

- Visitors begin to notice
something bizarre

along the surface
of the cracked lakebed.

- These strange rocks
seem to have all travelled with ease

across the flat.

NARRATOR: An expansive ancient site

is revealed
in a remote Chinese desert.

WAKEFIELD: This site
is 500 years older

than the first lengths
of the Great Wall.

What is this place?

NARRATOR: And enormous
ice-age bones are discovered

in the high desert of New Mexico.

- This could help rewrite everything
we know about human history

and about ancient migration patterns
all across the world.

NARRATOR: Astonishing
discoveries unearthed

from the depths of the desert.

Ancient lost cities.
Forgotten treasures.

Mysterious structures.

Extraordinary curiosities,
once lost to the sands of time,

are finally revealed.

As new technology
uncovers remarkable tales

hidden beneath
the deserts of the world,

the secrets in the sand
will finally be exposed.

On the border
of California and Nevada,

in the heart of
Death Valley National Park,

lies the remains
of a long-dead lake.

- Death Valley is the hottest place
in North America,

with the record temperature
reaching an incredible 57C.

As the name implies,
not much can live or grow here.

NARRATOR: This lake is almost
entirely dry throughout the year.

It has a cracked mud surface,

except for during periods
of heavy precipitation,

and even that quickly evaporates.

The area is unbelievably flat.

It's almost seven square kilometres,
roughly the size of Gibraltar,

and has less than
a 4cm elevation difference

from its north to south end.

- Over multiple visits to this rare
site situated in the Mojave Desert,

visitors begin to notice
something bizarre

along the surface
of the cracked lakebed.

CANTOR: What they see
is entirely impossible!

Only after returning
again and again,

to verify the facts with
their own eyes, could they be sure.

The rocks are actually moving.

- Understand that
these are not rocks rolling downhill

or stones being
pushed around by waves.

These are rocks of varying sizes,

moving along the flat earth
as if by magic.

- No-one has actually seen
the rocks moving in real time.

But the trails
left behind the stones,

and the changes
to their location over time,

make it clear
that they actually do move.

What is going on here?

- The lack of vegetation
in this region

means there is really
no wildlife here

capable of pushing stones
of this size around.

Nor are their footprints
or machine-made tracks

alongside the stones indicating that
people were them pushing around,

so we know it's not a hoax.

LEONARD: The rocks really stand out

on top of the light,
dusty mud surface.

They look almost alien
to the landscape,

like they could be
an art installation project

NARRATOR: The rocks
moving across the lakebed

originate from the dolomite cliffs
located to the south.

Freeze and thaw periods in winter
cause the cliffs to crack,

sending rocks hurtling
to the ground.

- These strange rocks
can weigh as little as 85g,

or be as heavy as 315kg.

And they seem to have all
travelled with ease across the flat.

- Regardless of their size,

the rocks appear
to bulldoze the lakebed,

creating raised edges
along their path,

while leaving
smooth trails behind them.

NARRATOR: It's called
the 'Racetrack Playa'

after the deep trails etched into
the mud by the travelling rocks.

This strange
and mysterious phenomenon

has drawn the attention
of the science world.

Death Valley is a place of extremes,

featuring rarities
like Badwater Basin,

the lowest point on the continent,

and the 2,000-year-old
Ubehebe Crater.

- These rock trails can be several
centimetres to several metres wide,

and anywhere from under a metre
in length to well over 30m long.

One rock was even found to have
travelled an astonishing 450m.

- The rocks leave
a very shallow impression,

only about 2.5cm deep,

and usually take on
a zig-zag design.

And interestingly,
most of these trails

begin far from
the edge of the lake,

as if they appeared out of nowhere.

NARRATOR: While the trail
seems to run in all directions

and vary in lengths,
each distinct trail leads to a stone

with a low pile of dried mud
at the end.

- Rocks positioned together
at the start of their path

might travel in tandem for a while
before randomly diverging

and changing direction.

And even stones
that share a similar size and shape

might not travel the same distance.

- There are many variables that
affect the movement of the rock,

such as size, weight,
shape, composition.

And that movement can clearly
be tracked by the trails.

But how? How are they doing it?

- They are commonly called
'sailing stones'.

So perhaps, like their name implies,
they are being blown by the wind?

NARRATOR: Powerful and persistent
winds carrying fine grains of sand

can transform landscapes,

even carving away
a rock's surface over time.

- But can wind
really push a rock like a sailboat?

NARRATOR: The Coyote Buttes,
lying between Utah and Arizona,

are sandstone waves
that undulate along the horizon,

created over hundreds of millions
of years by wind and rain.

The hoodoos in the Alberta badlands
are striking sandstone pillars,

capped with rock tops
that have been whittled away

by high wind and weather.

- Wind and weather
absolutely affect landscapes,

altering their appearance over time,

especially when those landscapes
feature sandstone.

But examples like the hoodoos refer
to the wind moving along the rock,

not the rocks
being moved by the wind.

- So wind alone
doesn't seem responsible,

but could water make the mud
of the lakebed slippery enough

to cause the rocks' movement even
though the Racetrack Playa is flat?

NARRATOR: 10,000 years ago,

Death Valley went through a period
of extreme climate change

that left the lake completely dry.

- While it is referred to as a lake,

it's not part
of your average lake system,

where you have rivers and streams

moving water
from high to low elevation.

- This lake is actually
an endorheic basin with no outflow,

meaning the water
can only escape through evaporation.

- It's possible a heavy rain could
create a muddy 'slip and slide',

but without an external force
acting on it,

the rocks still wouldn't
be able to move.

- One theorist wondered if high
winds could provide enough force

to move the rocks
along the slippery mud.

They even went as far as bringing
a light plane to the flat

to test how much wind it would take.

NARRATOR: After wetting
a small area of the terrain

to smooth the cracks in the mud,

an airspeed of 68km/h was used

to try to blow the stones
along the playa.

- He found little to no success:

even when they observed
the rocks sliding a bit,

the wind caused so much rippling
in the surrounding mud

that it altered and obscured
the rock's telltale trail.

- Not only that, but the presence
of the dry, flaky earth

built up in front of the rocks,

and the continued presence of
the cracked earth along the trail,

indicates the movement was happening

when the lakebed
wasn't entirely muddy.

- Ultimately, it was calculated
that the force of wind necessary

to move a 3kg stone...

would be a whopping 180km/h,

a velocity well above the average
wind speeds

recorded here on the playa.

- (wind howls)

- So, if it's not wind or mud
creating a slip and slide,

what else could be causing
this astounding movement?

NARRATOR: Speed is difficult
to observe from a distance,

and The Racetrack Playa is
a heavily protected natural wonder

that limits visitation for fear
of tampering and disturbance.

Researchers wanting to place
GPS tracking systems

on the sailing stones
to accurately track their movements

were denied by the authorities,
so they were forced to get creative.

- They returned to the playa
armed with time-lapse cameras,

wind gauges and thermometers.

They even brought dummy rocks
equipped with tracking devices

in the hopes of capturing
the faintest of movements.

- These 15 dummy limestone rocks
were from the Darwin Canyon,

which is an area of similar
geological age to the playa.

LEONARD: Though Death Valley is
the hottest place in North America,

its winters can be quite cool
and wet, relatively speaking.

Over the season,
the playa can be covered

in a few centimetres of snow,
and snow can be slippery.

So perhaps the snow has something
to do with the rock movement?

NARRATOR: Experts use time-lapse
photography to capture the sun

melting the ice and snow,
creating shallow, clear ponds.

These ponds then thaw during
the day, only to freeze at night,

repeating the process
again and again

over a period of weeks,
creating small ice floes.

- An ice floe usually refers to
a large sheet of free-flowing ice,

at least 20m wide
and up to 2m thick.

Some ice floes
can get bigger than 10km.

Clearly what is discovered here
is different

and on a much smaller scale.

- Eventually, after decades
of unanswered questions,

and failed theories,
the team finally recorded evidence

of the Racetrack Playa rocks moving.

NARRATOR: Researchers working
in Death Valley, Nevada,

were amazed
when they finally captured

evidence of what appeared
to be rocks moving.

The movement occurs when the thin,
3mm-6mm ice sheets begin to melt.

As they melt,
they break apart under light wind.

The wind is then able
to push the ice sheets,

taking the attached rocks
along for the ride.

The winds are blowing
at a mere 18km/h,

a tiny fraction
of the hurricane-force gales

that were part
of the earlier hypothesis.

- These extremely thin panes of ice,
up to tens of metres across,

freeze around the rocks
and then drag or pull them along,

which explains
how the parallel trails are created.

MIFFLIN: Not only that,
but the size of the ice sheet,

and depth of the meltwater
around each rock,

impacts the direction, speed and
duration of the time the rock moves.

This helps explain
changes in direction

and length variability
of the trails.

NARRATOR: These rocks are moving,

but at a near imperceptible
snail's pace.

This rare occurrence only
happens once or twice a year

when the conditions are perfect.

- In the end,
it was never simply one thing.

It was a perfect storm of elements

that all have to be present
for the rocks to move.

Water, sun, ice and wind.

I guess you could say
they solved a rockin' mystery.

NARRATOR: 100km from
the city of Yulin,

on the southern edge
of China's Ordos Desert,

are the dusty hills
of the Loess Plateau.

- The Loess Plateau is named
for its silt-like sediments

that are deposited
over time by the wind.

It's unlike any place
else in the world.

- The arid countryside
supports little vegetation,

and looks nearly uninhabitable,
yet it is home to many people

who have been tied
to these lands for generations.

NARRATOR: Archaeologists
working in the region heard rumours

that along the west bank
of the Yellow River,

rare stones were found in
the crumbling Great Wall of China

and went to investigate.

Taking a closer look,
experts noted something strange.

- Locals have been aware
of the crumbling rock walls

around the area
for as long as they can remember.

They live among them, but they
never gave them much thought.

They were always assumed to be
a section of the ancient structure

known as the Great Wall of China.

NARRATOR: Built over 2,000 years,

the Great Wall is the longest
man-made structure on the planet.

It traverses over 21,000km

of Northern China
and Southern Mongolia

and is a wonder of the ancient world
that has stood the test of time.

It's a perfect illustration of the
innovation and engineering prowess

of the Chinese people.

- The ancient barrier
of the Great Wall

does cut its way across
this dusty plateau,

traversing more than 1,500km
through the Loess.

But this crumbling structure
is not part of the Great Wall.

So what can it be?

NARRATOR: The Great Wall
is made of brick, stone,

wood and other materials,

including a mortar
that's made with sticky rice.

However, in this region,
it also includes rammed earth

and stones composed
of dusty loess soil,

making it look very similar
to this strange wall.

- Not connected to the Great Wall,
these walls are 2.5m wide

and sit 1m above the ground

in areas where they haven't
been entirely buried by the dust.

NARRATOR: While examining
an area of the wall

that had collapsed
many years ago,

they found strange and rare stones

that don't appear to be part
of the structural build.

These are jade pieces that have
been embedded in the wall.

For many years there were rumours of
the stone being stolen by looters.

- The placement
of the jade pieces in the wall

is not construction-related,

and definitely not a practice used
when building the Great Wall.

- These jade pieces,
many of which fell into the hands

of distant collectors - can be
traced to the Liangzhu culture,

which existed between
5,300-4,300 years ago.

NARRATOR: The Liangzhu culture
was centred

over 1,600km away from the site,

and the jade is an indication
of ancient commerce

as well as evidence
of a connection to distant lands.

Experts believe
that the jade was placed

as a symbol
of spiritual significance,

perhaps for protection
or to ward off evil.

The walls are not only
made of stone

but are also reinforced
by huge cypress beams,

a practice that is believed to have
started during the Han dynasty.

- But carbon dating of the beams
indicates that the wood is, in fact,

from 2300 BCE.

That is 2,000 years
before the Han dynasty ruled.

NARRATOR: They uncovered structures
spanning over 400 hectares of land.

The outer wall makes a 4,200m
crescent shape around the site,

while the interior wall has
a 5,700m circumference.

- Whoever built these walls
took advantage

of the natural hilly terrain,

allowing it to act
as a barrier where needed.

WAKEFIELD: These walls
would have required

a combined 125,000 cubic metres
of stone.

It's an incredible undertaking
for the time,

so they must have had
really good reason to build it.

NARRATOR: This region of northern
China has a history of conflict

between the farmers
of the Chinese lowlands

and the herders of the Mongolian
steppe that still goes on today.

Eventually, the Great Wall
was built here,

protecting China
from the nomads to the north.

But whoever built this place
clearly already felt threatened

long before the Chinese
decided to build it.

ELLIS: It's not just
a fortified outer wall,

but there are rammed
earth platforms,

gatehouses and watchtowers.

They indicate this place was
designed for security and defence.

So, perhaps the walls are part
of a fortress or military outpost?

NARRATOR: Archaeologists
uncovered a main access point,

along the wall at the northeastern
edge, known as the east gate.

The entrance is surrounded
by gate towers and guard houses

that would have been
manned around the clock.

- The gate covers an area
of about 2,500 square metres

and sits at the highest point of
the wall, making it highly visible

and providing clear views
of the plateau...

and anyone making an approach.

- Interestingly, the gate
was designed as a one-way entry:

a style known as a baffle gate,

using a curtain wall
to control the flow of traffic.

NARRATOR: On either side
of the entry, there are bastions:

structures built at an angle
to allow for defensive measures

in several directions at once.

- They, too,
were formerly understood

to have been innovations
of the Han dynasty.

NARRATOR: While examining the gate,

researchers found
two rectangular pits

containing a cache of human skulls,
but no other remains.

Tests revealed that the majority
of the skulls were female.

- These pits were hidden beneath
the foundations of the east gate,

with 24 skulls per pit.

They were likely sacrifices
made at the time of construction

as a blessing for the project.

If so, they are the oldest evidence
that we have

of human sacrifices in China.

NARRATOR: The Shang dynasty
reigned from 1600 BCE to 1046 BCE

and practised human sacrifice.

Their kings, acting as both
political and spiritual leaders,

oversaw the rituals of beheading,

burning and boiling people alive.

At a site in Yinxu, archaeologists
uncovered hundreds of human

and animal remains,
and based on physical evidence,

as well as ancient texts,

they estimated that
over the course of 200 years,

over 13,000 people
were sacrificed there.

Making them over 1,200 years older

than the skulls discovered
at this site,

which has revealed
practices and innovative designs

previously unknown
to scholars of Chinese history.

WAKEFIELD: The design of the gate
and the outer wall

makes it clear that this site was
built for defence, like a fortress.

But the equally fortified
interior wall suggests

that there was something requiring
another layer of protection,

but what was it protecting?

NARRATOR: Moving along the site,

archaeologists made
a groundbreaking discovery.

Towards the centre
of the interior wall,

along the eastern edge of a hill,

they uncovered
an extraordinary structure.

- It's a pyramid: an enormous
rammed-earth and cut-stone structure

that rivals the pyramids of Egypt,

which were built
around the same time.

NARRATOR: Standing 73m tall,

it's only half the height
of the Great Pyramid of Giza,

but its base is four times the size,

spanning 240,000 square metres.

- This immense and imposing
structure would have been visible

from every point
of the surrounding plateau.

NARRATOR: The pyramid
has eleven tiers

with buttresses
supporting each level.

The top has
an area of 80,000 square metres,

surrounded by walls
measuring between 3m and 7m high,

and contains evidence
of a stone reservoir,

roof tiles and pillars.

- The highest step of the pyramid
was likely home to elites

who lived under the protection
of the site.

NARRATOR: It's believed that at
one time, a large palatial complex,

made of packed earth and wood,

was built along
the pyramid's highest tier.

The surrounding grounds
within the inner wall

revealed several residential areas,

temples, cemeteries and workshops.

This is not just a fortress
but a monumental, neolithic city.

And at over 4,300 years old,

it would have been the oldest
and largest in China at the time...

perhaps even in the world.

And yet there is little to no
written record of its existence.

- Beyond the remarkably
crafted structure,

evidence like the jade pieces,
including moulds for bronze blades,

suggests that this
was a bustling metropolis

with an extensive economic reach.

- Historians long believed
that Chinese civilisation began

many hundreds of years later
in the Central Plains.

But this site, now called Shimao,

has shifted their understanding
by 500 years.

NARRATOR: Only a small fraction
of Shimao has been fully excavated,

and it's assumed
that new discoveries

will continue being made
in the future.

But Shimao is already
giving archaeologists a new way

of looking at the development
of early Chinese civilisation.

The high desert of New Mexico
is part of a vast plateau

significantly larger than
the Australian state of Victoria,

which covers extensive parts
of four different American states.

CANTOR: This high desert is
part of a huge geologic formation

called the Colorado Plateau.

It's an incredibly
interesting place.

- The Colorado Plateau is most
famous for the Grand Canyon,

but the entire area
is just a feast for the eyes.

- The pale colours of the land
speak to the fact

that it only receives a few hundred
millimetres of precipitation a year.

NARRATOR: In 2014,
while hiking the plateau

in an area between
La Joya del Pedrigal and Rio Puerco,

about 2,000m above sea level,

a hiker spotted what looked like
a pointed bone

protruding from the dry earth.

HARIDI: Along with
the pointed bone are four others:

a jaw bone as well as three ribs.

These bones are big, so obviously
they belong to a very large animal.

CANTOR: The area used to be home
to animals such as the grizzly bear,

grey wolf, wolverine and bison,

all of which are mostly gone
due to human activity.

However these bones don't appear
to be from any of those animals.

So if not them,
then what animal could it be?

NARRATOR: After a hiker
in New Mexico

discovered the bones
of a very large animal,

archaeologists were called
to the site to investigate...

and immediately found more bones.

CANTOR: The pointed bone is
not so much a bone as it is a tusk,

and a very peculiar,
easily identifiable one at that.

That tells me this tusk likely
belonged to prehistoric megafauna

that once roamed
across the American steppe.

That leaves us two possibilities:
the mastodon...

- (roars)
CANTOR: ..and the mammoth.

LEONARD: The mastodon's tusks
were straight,

while the mammoth's tusks
curled in towards each other.

So it's likely that these bones
belong to a mammoth.

- The archaeologists find that many
of the bones have been broken,

and quickly determine
that they actually belong to not one

but two woolly mammoths.

Discovering the remains of one
mammoth would be a rare occurrence.

But two? That's really
a once-in-a-lifetime thing.

NARRATOR: The remains were found
to be of a young female,

who was most probably
the mother of the second mammoth

in the bone pile, a calf.

HARIDI: Mammoths would have called
high plateaus like this one home,

but around 10,000 years ago, they
suffered a catastrophic habitat loss

as a result of climate change.

This caused
their eventual extinction.

But how did THESE two mammoths die?

NARRATOR: Only a few metres away
from where the bone pile was found,

the archaeologists also discovered
an obsidian projectile point.

LEONARD: This is basically a weapon
made from volcanic rock.

It likely would have
been attached to a shaft

to make a spear or an arrow.

NARDI: They quickly determine
that it has the telltale shaping

of a Clovis-period projectile,
meaning it was skilfully crafted,

with grooves cut into
the surface along the edge.

And it's shaped like a leaf.

And given its design, it is,
of course, incredibly sharp.

HARIDI: The Clovis era
refers to a roughly 300-year period

between 13,500-12,700 years ago.

This is when the culture,
and its technology,

appeared and spread
across the Americas.

- In archaeological terms,
the Clovis period is defined

by the spread of
this particular kind of technology:

projectile points that were
fashioned in a very specific manner.

- This seems to be
an ancient kill site,

so could this mammoth have been
brought down by Clovis hunters?

NARRATOR: The archaeologists
carbon-dated the bones

and were astonished to discover...

that they were approximately
38,000 years old.

And, therefore, these mammoths
couldn't have been killed

by Clovis-era hunters.

- This is truly remarkable, because
the general consensus has been

that humans only arrived in
the Americas some 16,000 years ago.

So how would this be possible?

LEONARD: The accepted theory
is humans first arrived

in the Western Hemisphere
via the Bering land bridge

that connected today's
North America with East Asia.

CANTOR: We have long
tried to map out

migration patterns
into the Americas,

and often ignored
the evidence present

in indigenous oral histories.

But academic perspectives are
changing when it comes to the value,

and accuracy, of oral histories.

Even so, we always look

for other supporting evidence
to back up our theories.

HARIDI: In order to be certain
that this is a kill site,

the archaeologists
need to inspect the bones,

looking for telltale signs
of butchering,

or processing, of the two animals.

NARRATOR: CT scans
revealed that the bone breakage

was highly patterned, a technical
term meaning that specific force

had been applied to specific places,
causing shards to break off.

CANTOR: The shards are
what are called butterfly fragments.

It's a term used to describe
when blunt force is applied

to one side of a bone
but the opposite side breaks,

sending fragments flying.

- Butterfly fragments
are an essential find here,

because only humans are capable
of causing such damage.

NARRATOR: Every bone, except
for one, showed perimortem damage,

meaning damage caused
at the time of death.

In other words,
there was no indication

that the bones had time to heal.

HARIDI: Finally, the CT scans reveal
several bones have been punctured,

likely in order to drain the marrow.

And in order to do so,

you would need a good fire
to melt that marrow into grease.

- They also found signs
of a sustained burn,

meaning that someone
was likely watching over it.

- It's clear that the mammoth
was butchered by humans,

and this would have taken place
20,000 years earlier

than what was previously
thought possible.

- This is truly
a fascinating turn of events.

This could rewrite everything
we know about human history

and about ancient migration patterns
all across the world.

NARRATOR: Archaeologists
must question...

when humans
may have arrived in North America.

The oldest human remains and DNA
found in the Americas to date

were found near Wilsall, Montana.

In 1968, a construction worker

unearthed scores
of prehistoric tools,

as well as the skull of a child, at
a location known as the Anzick site.

LEONARD: It turned out
the tools were all patterned

in the familiar Clovis style.

The skull itself
was roughly 12,700 years old,

and it belonged to a child
of the ancient Clovis culture.

- This little boy would've been the
descendent of an Asian population

that migrated across
the Bering land bridge

around 16,000 years ago,

meaning most indigenous groups
in the Americas today

can trace their ancestry
back to these specific people.

LEONARD: But how could people
have been in the Americas

almost 40,000 years ago
when these mammoths were around?

Who were they?

- Despite most of those indigenous
to the Americas descending

from an Asian population group that
arrived around 16,000 years ago,

they weren't the only ones
to have populated this hemisphere.

So who else did?

NARRATOR: Researchers have
found that the Surui and Karitiana,

people indigenous
to the Brazilian Amazon,

carry traits more closely related
to Australasian population groups

than they do to Asian groups.

- This is fascinating.
This means that the same people

that migrated into Papua New Guinea,
Australia and the Andaman Islands...

would have also made it across

the Bering land bridge
and into the Americas.

And they would've done so thousands
of years before the second group.

- Exactly when this would
have happened is unknown,

but this genetic signature
is not present at all

amongst the indigenous populations
of the people

descended from the Anzick child.

HARIDI: So there must
have been at least two groups

and two separate periods
of migration into the Americas.

And the ones who killed and ate
these two mammoths

in the high desert of New Mexico

likely had distant relatives
in Australia.

NARRATOR: As time progressed,
this initial group was replaced

by a secondary one
from Northeast Asia:

the one that has, to date,

been seen as the first
to populate the Americas.

- When it comes to discoveries
like this, we would be better served

by listening to the descendants
of the people we are discussing

in order to obtain a fuller picture
of long-ago events.

- This story is also
an important reminder

that some of the theories
we profess as absolute

aren't necessarily accurate,

and that we need to approach
this topic, and, really, any topic,

with a healthy dose
of humility and curiosity.

NARRATOR: Nabta Playa is situated
100km from the nearest settlement

of Abu Simbel,
deep in the Egyptian desert.

Absent from its endless
beige horizon are any signs of life.

Little stirs across the enormous,
empty expanse of sand.

- This inhospitable landscape

receives as little
as 1mm of rain a year.

It is crisscrossed by wadis.

These are dried-up ravines
or riverbeds,

indicating that at some point,
there was water here.

But now it is bone dry.

NARRATOR:
While traversing the desert,

a Bedouin nomad came upon
a mysterious collection of stones

scattered across the area.

- The megaliths lay
at seemingly random intervals,

extending some 2.5km
across the desert.

WEGNER: Megaliths
are huge stone slabs

and wouldn't just appear
in this environmental context.

So it's obvious that
they were placed here with intent.

It would have required
serious thought, and muscle,

to bring them all here.

- The Bedouin related what
he had seen to the archaeologists

studying the region, and sure
enough, with their curiosity piqued,

they arrived at Nabta Playa with
the purpose of solving the mysteries

posed by the stones.

MIFFLIN: This is an incredibly
hostile environment.

There is not enough water here
to sustain the kind of work

needed to erect
these massive stones.

So how could anyone have done this?

NARRATOR: Despite
its current harsh conditions,

the presence of wadis
indicate that, at some point,

water did flow through this area,

probably with enough volume to
sustain plants, animals and humans.

- Throughout prehistory,
megaliths were used singly,

or in groups, to create monuments,
often to mark a site

with supernatural
or spiritual significance,

or to indicate
the location of a grave.

So the archaeologists
suspect that some of them

could be sitting on top
of one or several tombs.

- Digging into the ground
reveals no human bodies,

however, initial excavations
reveal ancient flora

that would require much more water
than is currently available here.

NARDI:
Finding organic matter like this

is extremely helpful
for archaeologists.

It allows them
to not only understand

what kind of environment
would have existed here,

but also allows them to date
the plants fairly accurately.

- Based on the plant species
found during the excavations,

the area was probably receiving

anywhere from
30mm-200mm of rain a year

between 11,000 and 6,000 years ago.

This means that it was much wetter

and able to sustain life
and human occupation.

NARRATOR: Annual monsoon rains
arrived from the south,

creating seasonal lakes,
otherwise known as playas,

that could sustain human and animal
life for a few months a year.

The humid weather would have
turned the area into grassland.

WEGNER: Underneath
some of the megaliths,

the archaeologists do find bones.

But not human bones: instead,
they find a bunch of cattle bones.

This is interesting,
because in this region,

cattle are still
a central part of existence.

NARRATOR: Cows provided wealth
and status to those who owned them,

thereby forming an essential part
of a hierarchical system

that has existed
for thousands of years.

The more cows one had, the more
status and power they attained.

- The Beja of the Eastern
Egyptian Desert, for example,

are pastoralist people that use them
not so much for meat

but as a constant source
of sustenance,

obtaining milk from their bodies

to feed them in an otherwise barren,
harsh environment.

NARRATOR: Thousands of years ago,

at the time the cattle bones
were deposited,

it's possible people had a similar
relationship to their cattle,

meaning they were valuable
commodities that served spiritual,

political and practical purposes.

- It seems the creation of this site
would have been done

by ancient pastoralists
who held cattle as sacred.

NARRATOR: As the archaeologists
continued to explore the area,

they uncovered
15 circular depressions

with the remains
of cooking fires in the centre,

indicating that each depression
was a separate dwelling.

- By dating the charcoal
from the cooking fires,

they found that these houses
weren't occupied simultaneously,

but at different periods, starting
as far back as 9,000 years ago.

So could this have been
an ancient village?

WEGNER: The houses are aligned along
what used to be a water source.

So they had access to water.

And archaeologists
also found a number of wells,

some up to 2.5m deep.

- So, beyond
the unique circular formation,

we have evidence of cattle,

as well as the remains of several
homes that had access to water.

So this was definitely
a temporary village.

But what purpose
would all these stones have served?

NARRATOR: As they continued
their investigation,

the archaeologists found
what appeared to be ten mounds

lined up against the western bank.

As they excavated them,
they uncovered something

that left no doubt
as to what this specific site was.

- There aren't human remains here
either, but cattle, goats and sheep.

Most importantly, they find
an entire young female cow skeleton,

which shows no signs of having
been butchered or used for food.

- Considering how valuable
these animals would have been,

could this be a sacrificial site?

NARRATOR: Archaeologists
had discovered animal remains...

buried at the site
of ancient rock megaliths,

in the middle
of the arid Egyptian desert.

After finding the remains of a
sacred cow, they were left to wonder

if they'd uncovered
a place of sacrificial worship.

- The cow is found
lying on its left side,

oriented with her head
towards the south,

which, incidentally, is where
the monsoon rains come from.

WEGNER: The cow's burial
is in the wadi,

which, at the time, would have
brought water into the playa.

So it was probably a good place
to ask the gods for rain,

or thank the gods for having brought
the rains in the first place.

NARRATOR: Radiocarbon dating
of the plant matter

found in the cow's grave indicated
that she'd lived

around 5270 BCE:

almost 7,000 years ago.

- Considering that the houses
were around 9,000 years old,

this place must have seen continuous
occupation for at least 2,000 years.

NARRATOR: Other than a seasonal
village, this was an important site,

not just for practical reasons...

but for spiritual purposes as well.

It seems it could have
been a holy site

for these ancient pastoralists
moving through the desert.

- It would make sense that
it carried religious significance.

It was a frequently
and reliably watered place,

with feed for the cattle, and it
would have stood in stark contrast

to some of
the inhospitable surroundings.

ELLIS: There are a number
of puzzling megaliths

marking the wider area,
but on top of a small knoll,

there is a curious circle of stones
half-buried in the sand.

It's made of upright,
narrow slabs of stone,

and it looks like
a gathering of tombstones.

The question is...
what could this place be?

MIFFLIN: At first,
they think this is a cromlech,

which is a circle of standing stones
often used to indicate a tomb.

Yet there are no human remains
found inside the circle.

WEGNER: So if it's not
the site of a tomb,

stones placed in a circle like this

could also suggest
a connection with celestial events.

A monument can be used
to track changes in the sky,

whether as a sundial,

or a calendar used
to track the movement of the stars,

or even indicate the arrival
of the summer solstice.

ELLIS: Stonehenge in England
is one such example.

We still don't know for certain,

but it is thought
that this monument of megaliths

was used either
as a celestial observatory,

like some sort of calendar,

or it could have been
used as a religious site,

where rituals
and ceremonies were conducted.

NARDI: Regardless
of its specific use,

it was definitely
tied to the heavens.

So could this stone circle
be something similar?

If so, it would predate Stonehenge
by thousands of years.

NARRATOR: Puzzled
by what this could be,

an archaeoastronomy specialist
was called in

to bring his expertise to bear
upon these magnificent finds.

- Archaeoastronomy is the study
of astronomical practices

in the ancient past,

meaning the study
of how people used the heavens

in their respective mythology,
folklore and religion.

- By knowing the age
of the organic matter,

the specialist could then calculate
when this circle of stones

would have aligned with the stars.

So they radiocarbon-dated
samples of organic matter from fires

and from plant material
found inside the circle.

NARRATOR: The research
revealed that the stone circle

would have aligned with Arcturus,

Sirius and Alpha Centauri
around 4800 BCE:

almost 7,000 years ago.

MIFFLIN: This is really fascinating.

Arcturus is one of the five
brightest stars in the night sky.

Sirius is the brightest,

and Alpha Centauri
is the fourth-brightest.

NARDI: He quickly realised
that all the megaliths

were a part of a greater structure.

All the stone constructions
across the entire area

were interrelated,
including the stone arrangement.

ELLIS: So, like Stonehenge, this,
too, is likely an ancient sundial.

It was found in a wadi,
which, at the time,

would have been partially submerged
in water for a few months a year.

NARRATOR: Two of the stone pairs
in the circle

align along an east-west axis.

They're calculated
to have been in line

with where the sun would have risen
and set during the summer solstice.

The stone circle was a means
by which these people observed,

and marked,
changes in the celestial night sky.

At the time, one could see

the reflection of the stars
in the water, and in turn,

see how the stones lined up
with those very stars.

- For these ancient,
semi-nomadic people,

the stars would not only have been
a place where the gods resided,

but also the means
by which they navigated,

and survived, in the desert.

NARRATOR: Nabta Playa
was an ancient gathering place

where people came from far and wide
to observe the stars,

pray for rain,
and welcome the summer solstice,

which would then mark
the start of the annual monsoon.

It's one of the earliest
pieces of evidence we have

of celestial observation,

and reflects an incredibly
sophisticated understanding...

of both time and space.

- Sometime between
5000 BCE and 3000 BCE,

the climate changed,
and the area dried up.

Nabta Playa was abandoned
and fell victim to time,

slowly being buried
by the shifting sands of the desert.

Since its discovery, the Egyptian
authorities have gone through

the painstaking process
of moving the stones to a safe site

and replicating their alignment

in order to preserve it
for future generations.

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