Nova (1974–…): Season 39, Episode 14 - Mystery of Easter Island - full transcript

Easter Island has mystified the world ever since the first Europeans arrived in 1722.

Are you wondering how healthy the food you are eating is? Check it -
places on Earth,

an island shrouded in mystery.

For centuries,
people have marveled

at these giant stone statues

that dot the windswept terrain
of Easter Island.

Who carved these statues
and why?

How did they carve them and,
perhaps even more remarkable,

how could they move statues

that could be 32 feet tall
and weigh close to 82 tons?

Now, a new experiment
tests a theory

for how the statues
were moved...

Okay ready?

Pull! Release!

...and attempts to find out how it was really done.

The transportation of these statues

is perhaps the most important

of this culture to humanity.

Can just 26 people, using only ropes,

move a ten-foot-tall,
five-ton statue?

I think we can do it.

I think we have the force,
we have the manpower.

Will this experiment help solve the "Mystery of Easter Island?"

Right now, on this NOVA/
National Geographic Special.

Major funding for NOVA is
provided by the following:

Supporting NOVA and promoting
public understanding of science.

And the Corporation
for Public Broadcasting,

and by:

Additional funding from:

Inspiring tomorrow's engineers
and technologists.

Additional funding for this
program is provided by:

In the middle of the South Pacific,

over a thousand miles from land,

a tiny island emerges
from the sea.

Hundreds of years ago,

Polynesian explorers discovered
this place and settled here:

Easter Island,
also known as Rapa Nui.

What happened on this island
after they arrived

has intrigued archaeologists
for a century.

We know the islanders carved

close to 1,000 massive
stone figures

instilled with the spirits
of their ancestors.

We know they moved them--
possibly as far as 12 miles--

and placed them on sacred
platforms called ahu.

But we don't know
how they did it.

According to island lore,

the statues, called moai,
had simply walked into place.

But how could a people
who had no metal tools

carve such imposing figures?

How could prehistoric farmers
who didn't have the wheel

move enormous statues
up to 30 feet tall

and weighing close to 82 tons?

Transportation of the moai on Easter Island

is perhaps one
of the most important

archaeological problems
that we have.

It's the biggest mystery.

Sergio Rapu was born and raised on Rapa Nui

and served as governor
for six years.

Also an archaeologist,
he's long championed the idea

that the statues were moved
in an upright position.

It is to us to build a hypothesis

and go after looking for the
attributes on the statues

that allow an explanation
that they were moved vertically.

Archaeologists Terry Hunt and Carl Lipo

are heavily influenced
by Sergio Rapu's theory.

The key to proving it, they
hope, is inside this box.

Here it is.

It's a huge crate.

Oh, no.

This is going to be
sort of scary

to see it come out of there,
it's so enormous.


I don't know if I'm going
to feel better or worse

when I see it,
because the box is big,

and we're going to move it
with a small number of people.

Holy cow!

Oh, my God.

That is amazing.

The perfect replica.

You know what, this is making me feel sick to my stomach.


This precise replica of a moai

is the centerpiece of a simple
but radical experiment

being conducted in Hawaii
by Lipo and Hunt.

Over the next two days,

working with a small group of

they will attempt to move this
statue by walking it upright.

When people ask, "How did your ancestors move the statues?"

the answer was always,
"They walked."

And for the Rapa Nui,
that was the answer.

And for the foreigners asking
the question, they thought,

"Oh, that's silly,"
you know, "How crazy."

What we're trying to do is evaluate our ideas,

our ability to explain
how they were moved,

why the archaeological record
looks like it does.

What we're going to do
is tricky

and it could easily not work,

and we've never
done this before.

Rapa Nui people had centuries
to figure this out

and lots of people involved.

To conduct this experiment,

Lipo and Hunt will have just
two days and 26 volunteers.

The statue tradition
was brought by voyagers

from Polynesia to Rapa Nui.

Throughout Polynesia,

carved wooden and stone figures
are common,

but no other island can compare

with the size or number
of statues found here.

According to oral tradition,
the moai were carved

to represent the spirit
of the islanders' ancestors.

The statues are the living face
of our ancestors.

In order to look living,

you have to put the inlaid eyes
on the statues.

Some statues are topped

with a red stone hat,
or a topknot, called a pukao.

The moai were cut
from volcanic tuff,

a porous stone made
from compressed ash.

Almost all of them were carved
here at Rano Raraku,

a massive quarry
inside one of the island's

three extinct volcanoes.

Littered around the site

are statues in various stages
of completion,

some still emerging
from the rock.

The most common way
of carving the moai here

is to carve around the face
and the body,

like awakening the statues
from the rocks.

To do this,

carvers used very dense stone
tools made of basalt,

like this one, used by modern-
day carver Umi Kai in Hawaii.

What we're trying to do is

just cut a design that
we want to follow into the tuff.

Umi Kai is using a replica of the same ancient tool,

called a toki,

to carve a small version
of a moai eye socket

into volcanic tuff.

If I was to do this
with a modern tool,

it would probably take
maybe 45 minutes to an hour.

This will take maybe
a whole day to two days.

It would probably take

a team of 12 people a year
to produce a moai of this size.

Once the moai's
completely carved,

the back would be still attached
to the mother rock with a keel.

Eventually, that keel
will be perforated

and some loose rock
will be added

under the back of the moai,

so it remains floating
as they cut off

and release it
from the mother rock.

After they finish carving,
they slide it down,

brace it at the foot
of the hill,

then finish carving the back.

At this stage, the moai was ready to be moved

to a sacred platform
called an ahu,

known to be a place
of religious ritual.

There has been lots of speculation

about how the statues were
moved, from crazy theories that

they were shot out of the
volcano to aliens moved them.

But in modern research,

there's been a whole family of
ideas about using contraptions--

using palm logs for tripods
or sleds or rollers.

According to several of these theories,

the islanders used logs
to move the moai.

The most recent attempt was

when University of California

Jo Anne Van Tilburg tried
using a wooden sled

to move a moai
along wooden rails.

It's similar to a traditional
method Polynesians used

to move canoes
out of the water.

the experiment worked,

and it gained wide acceptance.

But not everyone believes
the log theory.

The problem with these theories

is that they have not drawn
on the evidence

that we see on the moai,

the statues themselves,
on the roads.

As they investigated the statues and the roads,

they began to accumulate clues

that they think
will tell a different story.

Building on another
researcher's data

and using satellite imagery,
Hunt and Lipo

have surveyed almost 20 miles
of ancient roads.

There are several roads

that begin at the statue quarry
of Raraku

and go along the south coast.

Some go north.

Some go across the center
of the island.

These roads were used
to move moai

to every corner of the island.

They think the network of roads may have been even larger,

but the degraded road beds
can be hard to find

with the naked eye.

So they're testing a drone
equipped with a camera

that will give them
more precise observations.

Three, two, one, go.


We have satellite images coverage for the entire island,

and we can see
certain kinds of features.

This gives us a way
of integrating that

at a level where we get
credible detail.

The drone may help identify new roads,

which can then be ground-truthed
with modern surveying equipment.

Hunt and Lipo believe
a crucial clue

to how the statues were moved

may lie in the slope of the
roads, which they have measured,

confirming the results
of an earlier team.

We found that the roads
generally have a maximum

of a three-degree rise
as they go uphill

and then a maximum of about six
degrees when they go downhill.

The island is fairly hilly,

and the inhabitants understood
that to move the statues,

the roads would have
to be leveled

so that they had a consistent
and fairly gentle grade.

But how did they move them?

To find out,
Hunt and Lipo studied

more than 50 statues that fell,
apparently while being moved.

We noticed that the statues that were headed uphill

away from the quarry had fallen
on their back most frequently.

We also found that when statues
were heading downhill,

they'd fallen on their face.

Statues on flat ground
were kind of 50/50

and we could see that
there was a pattern here.

We tested it statistically

and realized that we had
very clear indications

that the statues were moved
in the standing position.

There was really no other way
to explain that.

This idea has the virtue of being consistent

with oral tradition.

In fact, the Rapa Nui language
even has a word, "neke-neke,"

which translates as
"walking with no legs."

For centuries, we have known that the moai

did walk as our ancestors said.

But how exactly they did
the walking

is what we the archaeologists
are looking into.

In fact, others have tried to move them vertically,

including Thor Heyerdahl

and a Czech engineer
named Pavel Pavel.

This is the statue that Pavel
Pavel tried to move in 1986

with his experiments, moving the
statues in an upright position.

By shuffling it across the surface,

there was a lot of friction
on the base,

and as he did it, in fact,

there was damage done
to the base

that removed material
right down from the bottom here.

We thought this can't
really be quite right

because the shuffling
and the grinding

isn't consistent with what we
saw in the statue.

So on the one hand
we were like, "Yes,

they're moving standing up,"
but not exactly that way.

To figure out a less destructive way to move them,

they built on observations
first made by Sergio Rapu,

identifying differences
between statues

that made it to the platform
and those that fell on the way.

On the more than 50 fallen
statues they analyzed--

what researchers call
road moai--

the eyes hadn't been
carved yet.

They were left as
sharp angled slots.

According to Hunt and Lipo's

road moai were chunkier--

their bases were bigger, their
centers of gravity were lower,

kind of like a bowling pin.

Most of the road moai
had a D-shape base,

and the base was angled
so the statue leaned forward.

These were key features
to Lipo and Hunt.

The statues were rolled across the front edge.

And that front edge
has a characteristic shape,

especially as the statues
get larger,

that allowed that to happen.

The statues that made it to the ahu platform

show the difference.

The eyes had been carved,

their sides had been trimmed,

and their center of gravity
shifted back and up.

They'd been cut so that their
bases were no longer angled,

but flat.

They leaned forward,
but not as far as road moai.

They stood more upright and
they'd lost a little weight.

Based on all these differences,
the difficulties faced

by the Czech engineer Pavel
are understandable.

Pavel was using a statue

that had already been reshaped
for a platform.

The eyes had already been carved,

it didn't lean as far forward,
and its sides had been trimmed.

Ultimately, the evidence

for how the statues were moved

can be found on the statues

They were engineered to move.

The details of the statues
are telling us about transport.

But the only way to show that the statues could walk

is to test the theory.

To do that, they need to make
a replica moai,

the most precise replica
ever made.

They collect data embedded
in thousands of photos

of two fallen moai--

one that fell on its back
and the other on its front--

and enter it into
a 3-D modeling software.

Industrial designer Max Beach

then translates the measurements
into data,

which is used to make a mold
for the statue.

Their photos depict
an 18-foot-tall, 19-ton moai.

Because of safety concerns
and cost,

they scale the replica down.

Their statue will be ten feet
tall and weigh five tons,

about the average of nearly
1,000 moai on the island.

Hunt and Lipo nicknamed
the statue Hotu Iti

as a tribute to Easter Island's
legendary first ruler.

Max Beach is also creating
an animation

showing how Hotu Iti might move.

Carl and I started with a small scale model

to move it around on a table

to get an idea of how would this
thing walk back and forth.

We felt that there were

some challenges
with scaling this up,

so we built a five-foot model
out of wood

that would allow us to see

what some of the dynamics
involved are

as this model scaled up.

While this contraption doesn't look like a moai,

the same principles of design
and physics are still in play,

like an accurate center
of gravity

and the rounded forward edge.

It has enough of the features

that gives us a sense,
when we pull it,

that it's going to behave
something like what we expect

with the large statue.

See if you can get it up
high enough

so that it starts to fall.

You're kind of pulling it
on its side,

but you're also pulling it
so that it wants to rotate.

Bringing that center of gravity back over the...


That's the point that
coordination is key.


There you go.

That was a good step.

Yeah, beautiful.

In addition to understanding the physics

of how the statue should move,

figuring out where to tie the
ropes is going to be critical

in making the experiment

with the larger replica moai
a success.

The trick is to pull it

in the right direction with the
right force at the right time

that it rocks forward
on the forward edge

which has that rounded,
that D-shape.

But will Hunt and Lipo's 10-foot-tall replica moai

behave the same way?


Let it fall forward.

We are going to stay true to the original center of gravity.

Engineer James Diedesch is designing the mold for Hotu Iti,

paying special attention
to the center of gravity

and how the statue is balanced.

When I apply density to this model,

it calculates the exact center
of gravity

and is saved in this coordinate
system right here in the center.

This is important because if
the center of gravity was off,

it could alter the way
that these were moved,

so if the experiment
is to determine

that these could be moved
by walking them,

then the center of gravity
has to be at the same height

as it was originally.

The mold itself is comprised of four layers

and made in two halves,
split down the nose.

Hotu will come out of the machine with about

plus or minus 30,000ths
of an inch accuracy overall.

This is incredible

in comparison to any other
recreations that have been made

that have been mostly glossed
over and symmetrical.

This is nearly exact of what you
could find on Easter Island.

After nine hours of machining time,

each half of the mold is fitted
with an internal rebar structure

to support the massive weight
of the statue.

When we are ready to pour the statue,

we are going to fill this thing

with nearly six tons
of concrete.

What we'll see in this truck

is the new high-tech mix
that we've developed

for the moai statue.

It's lighter in weight,
higher in flowability.

It's more sustainable.

If you look really close, see
the little beads, the spheres?

The beads are expanded polystyrene,

a type of synthetic foam.

Putting it in the mix adds
volume without adding weight.

That makes the statue
closer in weight

to a real moai of this size
made from volcanic tuff.

We're burying him to equalize

the hydraulic pressure from
the outside so it can't move.

It took ten days

from the time the concrete was
poured into Hotu Iti's mold

to the time the five-ton,
10-foot-tall replica

was carefully extracted
from the ground.

Trying to get this right
and have him perform

like the original Polynesians

that's what our mission is.

There is a lot at stake

in figuring out
how the statues moved,

because it may cast light
on the island's troubled past.

There are vastly different ideas
about what happened here.

The story told by the islanders

speaks of different clans
and prolonged warfare.

Fractured skulls from skeletons
found on the island

seem to confirm that.

What would have
brought on this violence?

A widely accepted theory

is that different clans
around the island

competed to build more
and ever larger moai.

Needing logs to move them,

they cut down the island's lush
forest to keep up with rivals.

As the forest disappeared
and resources grew scarce,

the rivalry turned violent

and the society descended
into chaos.

Some have described this
as a case of ecocide--

a culture bent on overexploiting
its resources

spirals into cultural collapse
and disaster.

But is this a true picture
of what happened here?

Eaerstsland once looked
very different.

Pollen evidence shows that

25 various species of trees
and shrubs once grew here

and reveals a dramatic change
as the island was deforested,

something pollen expert
John Flenley

attributes to human activity.

Our pollen results

were strongly indicating to us

that people had destroyed
the forest.

In fact, it was the clearest
example in the world

that I had ever come across
of deforestation by people.

Throughout the island, excavations have revealed

the impressions of countless
palm root molds like these.

This island once had a palm
forest, and one way we know that

is because of the preservation
of these palm roots

that document that there
once was a palm forest,

a very extensive palm forest
across the island.

These lines here,
these black lines,

trace the paths that the roots
of the palm trees once made.

But some scientists believe that the trees were cut down

not in a frenzy of statue
building and moving,

but for the simple reason
that these were farmers.

These people were agriculturalists;

they needed to clear land.

So in a sense, the forests were
largely superfluous to them.

It's garden land that was
essential to them,

not palm forests
that they couldn't eat.

The whole notion that it was
the cutting down of these trees

that led to a collapse,
if you will, of Easter Island

is a bit off the mark,
in my view.

Archaeologist Pat Kirch studies human impact on island ecology.

He's done a comprehensive study
of the Mangareva Islands,

about 1,600 miles away.

After the Pitcairns, they are
the nearest islands to Rapa Nui

and striking in their

Both Mangareva and Easter Island
were nearly deforested,

and both once had large colonies
of sea birds,

whose guano fertilized the soil.

But on both islands,

people caught and ate
nearly all the birds.

When you eliminate those birds, you disrupt that nutrient flow,

and we think that on both
Easter Island and Mangareva,

the elimination of large
sea bird populations

was a key factor

in the ibility of the forest
to regenerate.

The people also slashed and burned down trees

to make way for farmland

and, combined with the loss
of sea bird fertilizer,

put their forest in jeopardy.

And there may be another factor.

During excavations here
at Anakena Beach,

the site of the first settlement
on Easter Island,

Hunt and Lipo
unearthed evidence,

identifying what they believe
dealt a significant blow

to the forest:

rats, possibly brought
as accidental hitchhikers

by the original voyagers
from Polynesia.

Hunt and Lipo believe these rats

played a decisive role in the
deforestation of the island.

We didn't really see
the full significance of that

until we started
to realize

that rats as
an invasive species

in fragile environments
like this

would play a pretty
significant role

in stopping the regeneration
of new trees.

They would eat the seeds
of the native trees,

in this case the palm trees,

and the palms
would not regenerate

and has spread through most of
the Central and Western Pacific. as they had ne

Will Pitt is a wildlife biologist

at the USDA Wildlife Research
Center in Hilo, Hawaii.

This is a female
Polynesian rat.

In the wild,
a lot of these rats

only have about a year
life expectancy,

but a female like this could
produce four litters a year.

When introduced to areas

with abundant resources
and no natural predators,

the first generation of rats
could, in theory,

have exploded to millions
in just a few years.

Even a fraction of that number

would consume
a huge amount of food.

And it turns out that the food
the rats ate was palm nuts,

inside of which are the seeds
that would spawn a new forest.

Throughout the island,

remnants of palm nuts
show gnaw marks from rat teeth,

supporting that argument.

The role that these little Polynesian rats

may have played in deforestation

is a very interesting one
and a little controversial.

It's a disruptive force

but I'm skeptical that it was
the sole or major force.

And the reason I say that is

rats were transported
to every island in the Pacific,

but not every island
got deforested.

So it had to be a combination

of some other factors
along with rats

that led to deforestation.

The forest was likely wiped out

by a perfect storm
of human impact:

slash-and-burn farming,

decimation of the sea bird

and the introduction

of an exploding rat population
on the island.

But did the demand for logs
to help move the statues

also play a role,

or will Hunt and Lipo's

deliver on an alternative

At the experiment site
in Hawaii,

the volunteers are about to get
their first lesson

in moving a moai.

So what we want to do first is
have you do a tug of war.

We want to divide you
into two groups,

roughly even
amount of strength.

The teams are learning how to work together

by working against each other.

Because cooperation is so important,

we actually want you
to be in a situation

where it's really tough to win.

On three.

One, two, three.

Pull, pull!

Balancing the teams will be vital

to balancing the moai
in the actual experiment...

Okay, you guys are a little too good.

NARRATOR: no one team can overpower the other.

Pull, pull!

I think we're balanced now.

The volunteers then graduate from tug of war

to balancing a 10-foot tall
wooden pole.




This is the maximum height
we'd tie the rope on the statue

to give you an idea.

What seems easy with a 4x4 post may not come so quickly

with a 10-foot-tall,
five-ton statue.

That's good coordination.


Through a traditional Hawaiian blessing,

everyone on site is reminded
of the cultural importance

of what they're about to do.

A Rapa Nui ritual
is also included,

and everyone shares
in the eating of a white chicken

cooked in an earthen oven.

The aroma released
upon opening the oven

is said to feed the gods.

I do worry that the base isn't sharp enough,

but the fact that
it's got the roundedness...

To maneuver the five-ton statue,

a crane operator attaches
rigging to Hotu Iti's neck.

Oh my God, look at those cables stretching.

Let's back up here.



The rigging will also act as a safety measure

to prevent the statue
from tipping over.

Well done!


So this is the real test.

We're sort of wondering,
what if he doesn't stand?

Is he resting on the ground?

Oh my God.

It's got to stand.

Yeah, we need to see that.

Worst case scenario...

It's got to stand.

It's got to stand.

That's the whole key.

It leans forward because
that's the way it was made.

Oh my God.

The statue will not stand on its own.

Hunt and Lipo struggle
to figure out why.

Well, at the moment,

you can see the way the strap
is, the way it's hanging,

the center of mass line here
goes straight down

and is in front
of the base itself.

What we need to do is
get it back

so that this strap is hanging
from over here

to get it behind
this point there.

Right now, the way it's hanging,
it's just going to fall over.

It's in a leaning position.

So what can you do?

Our plan is to turn
this truck around.

He's got rubber bumpers
on the very back.

Okay, okay.

Support it like that
so we can get the straps out.

Okay, good.

My impression is that
if he doesn't stand by himself,

we probably have
something wrong.

The ancient Rapa Nui didn't have a crane;

their statues had to stand
on their own.

The rigging straps are adjusted,

but Hotu Iti
still does not stand.

At this point, I have no idea

what we could do
to make this work.

If Hunt and Lipo can't get Hotu Iti to stand,

it will be hard to prove that
their walking theory has legs.

The only thing you could do

is either take away material
in the front

or add material on the bottom.

Finally, there's a solution.

Okay, go.

Good, okay.

We're good!

It needed that much.

It turns out that it needs
just a tiny bit of help.

In fact, it's a 2x4

that's now resting right
at the front of the base,

and that tiny bit of addition
there has balanced the moai.

He's standing on his own.

There's no pressure
on the cables.

But it may be that

in fact it was always made
to be unstable--

when they're moving,

they were carved in such a way
to always be falling--

and what you would do
is you add something

like we did with the 2x4,
maybe a stone,

things that we do find
in the archaeological record

underneath the front
to stabilize it.

Along the moai roads on Easter Island

are water-worn stones like these

that may have been used
this way.

Sergio Rapu actually

mentioned this
a number of times,

about consistently finding
these flat poro stones.

And they're not just any
old stone; they're very dense

and they tend to be really flat

and you find them on the roads
over and over again.

We're nervously learning a lot
right now

in trying to do this,
and that's science.

It's great to be wrong,

and we realize that there are
a few other things

that need a little more emphasis
in our understanding.

Before it's time to make the first attempt

at moving the replica,

the volunteers sit down
to watch the training video

to see how the statue
should move.

As we talked about, the D-shape is one of the keys.

It's being leaned over
to the side,

and then it falls forward
and rocks on that front edge.

I think we can do it.

I think we have the force,
we have the manpower,

so now the question is
getting the details.

Before they try to move Hotu Iti,

the volunteers need to make sure

they can hold the statue

I just want to see and figure out with everybody,

if we tie it at the highest
point, can we hold it back?

How many people do we want?

Ten, so five on each side.

Okay, we need five on each side,
so six more people.

Team leaders in the front,

if it seems like
you can't hold it

as he releases the pressure
from the crane,

yell out so we can stop
and he can add more pressure.

Yeah, let's move the wood.

Oh wow, okay.

Okay, so now he's going
to release the tension

and it's going
to be up to you guys

to keep it
from falling forward.

It's going to want to fall

Yell out if it's too much.

Coming down.

Can you feel it?


Is it a lot?

All off!

You guys are holding up
the statue.


Now the question is going to be

getting it to fall
on its front edge,

which I think we can do
with just two teams.

This was always our idea,

that the teams that are pulling
are actually behind the statue,

keeping it from falling forward

while rotating it
at the same time.

With the safety rigging attached to the statue,

Hunt and Lipo
finally have the chance

to test their walking theory.

Starting out with team A,

I want you to pull
a little harder

to see if we can rock it
a little bit.

Pull, pull, pull!

Okay, hold it.

I want you guys
to spread out a little more

so that you're holding it,
but more at an angle.

Does it get harder,
or is it about the same?


Easier at this angle?

I want team A to pull
to see what happens.


All right, hold.

How's that?

You guys exhausted?

The teams continue to move farther and farther apart,

simultaneously pulling
and trying to twist the statue.

But it's just not working.

We're going to want it lower,

the ropes lower
on the shoulders,

because we have
no leverage up there.

But it looks like it's not so hard to hold it back right now,

so if it's around the neck/
shoulder area,

you can hold it back
and probably tilt it.

So we're going to have
to try re-roping it.

As they reach the end of the day,

Hunt and Lipo have to face
the reality that,

so far, the experiment
has failed.

Unless they can get back
on track,

their failure will cast doubt
on the statue-moving theory

and on their other ideas
about what happened

to the island's once robust
and productive people.

No matter how this island was
deforested, without any trees,

wind and salt spray
damaged the already poor soil.

Sea birds were gone as both
a source of food and nutrients

that once increased
the land's productivity.

Some believe
the loss of large trees

meant they couldn't build canoes
to leave the island.

In one view, this is
an environmental disaster

leading to cultural collapse.

But building on previous

Hunt and Lipo came to believe

that the islanders found a new
way to adapt to the crisis.

When we were first surveying here on the island,

we were really annoyed

by the loose rocks
that we would walk over.

Then we looked a little closer
and we realized

this was actually an area that
was used for cultivation,

and then on top of that
we would see the taro

growing in the rock areas
and not in the soil areas.

It was kind of backwards from
what we might have expected.

It confirmed what previous archaeologists believed:

that what look like
random piles of rubble

are evidence
of an ingenious method

to improve the soil,
called rock mulching.

As you add the stones
to the poor soil of Rapa Nui,

you are increasing the nutrients
available to plants.

In addition to the phosphorous that leaches into the soil,

the rocks help the soil
retain moisture.

If you look at rock mulch
across the island,

there are probably billions
of stones that are moved.

I mean, it's just incredible
how much rock has been moved

and concentrated into efforts
that had to do with cultivation.

But was it enough to stave off disaster?

We have to really admire

what the Easter Islanders
were doing,

but not think that it
was making their island

into some incredibly
productive system.

It just helps to put off a worse
kind of agricultural collapse.

When Pat Kirch studied the islands of Mangareva

1,600 miles away,
he found the same kind

of deforested landscape
as on Easter Island.

But ultimately, the outcome for
the people there was different.

When you compare Easter Island and Mangareva,

both of them were
heavily deforested,

but on Mangareva, there's
a huge lagoon, barrier reef,

very rich marine resources,

so the Mangarevans turned
to those marine resources

and really depended on them
to develop their economy.

On Easter Island,
there's essentially no reef,

there's very limited coral,
very limited fish.

So with their backs to the wall,

did Easter Island
descend into conflict?

The population was growing,

the scarcity of resources
and a lot of competition,

social conflicts started
building up

and tensions between groups,

and toward the end
of Easter Island pre-history

there was a lot of war,
a lot of conflict

between one group and another.


These sharp-edged obsidian implements

found scattered
across the island

are often seen
as the smoking gun:

proof of a people at war.

What I have in my hand
is an obsidian tool,

and I think definitely

it was used for defense
or attack as a weapon.

But again, Hunt and Lipo disagree,

saying these obsidian implements
were everyday tools.

The edge here
has a lot of use wear

that's consistent with carving
wood-- hard materials--

and use with plant materials.

But these implements have actually been found

embedded in human skulls.

I think most of the evidence
that we have,

it points more
to use as a weapon.

We have found caches of them
next to a skull

that the mark exactly
the shape of this tool

engraved on the skull.

The remains of some 500 Rapa Nui people

have been studied
to get a clearer picture

of just how violent
this society was.

Enough of these bones
show signs of injury and trauma

that experts believe this was
a place of significant conflict.

In my view, it was
a society in distress.

It had a lot of problems.

They were pushing their
agricultural system very hard.

I think there's good signs

that warfare was periodic
and endemic.

This tumultuous period began before European contact,

which came in 1722
when a Dutch merchant ship

arrived on Easter morning,
hence the name of the island.

As more Westerners arrived,

stories about the island
grew more lurid,

even incorporating
tales of cannibalism.

Cannibalism seems to turn up

when Europeans start to talk
about it a lot

in the mid-19th century.

We don't see any evidence
like that on Easter Island.

We don't see chopped-up
human bones,

we don't find human remains
in the earth ovens.

There's good reason to believe

that the 19th-century idea
of cannibalism

is that you were not yet

so you're a Christian
or you're a cannibal,

and "cannibal" had
sort of a generic meaning.

So could it have been something other than violence

that eventually spelled
the downfall

of Easter Island society?

We know over and over again

when Europeans arrived
in the Americas

and in the Pacific,

they introduced disease.

They did so really unwittingly.

For example, I mean, a disease like cholera

would have a devastating impact
on this population

because it's water borne,

and once the disease
gets in the water supply,

it's going to be easily
passed on to other people,

and as they got sick,
it would pass on to them.

In the 19th century, Peruvian slave traders

abducted hundreds
of Rapa Nui people.

By 1877, ravaged by slavery
and disease,

a devastated remnant of the
people who, over the centuries,

had carved and moved
massive moai

had plummeted to only 110.

But their oral history
of the time before the Europeans

a tantalizing collection:

tales of warfare, ritual,

and statue building.

Whatever passage of oral history we have,

we protect it like
precious information,

and in our doing of archaeology,

experience tells me
how important it is

to listen carefully

to these little bits of
information from oral history.

The oral history says the statues walked,

and Hunt and Lipo are trying
to figure out whether it's true.

It's 9:00 a.m. on the last day
of the experiment.


Just eight hours left

to figure out
how to move a moai.

Let's be optimistic.

How about there?

Hunt and Lipo decide to set a goal:

marking a finish line
at 50 yards.

We've got this marked at 50 yards, 25 yards and 10 yards.

Be great if we got it
even part of that way.

What we want to do is have the knot right here.

because we want it
to pull like that.

After spending the morning tying, retying,

and tying the ropes again,

it's 11:30
before the experiment teams

make their first attempt
of the day to move Hotu Iti.

Until they master the motion
to move the statue,

the crane rigging
will act as a safety.

We're going to start with the two ropes

and the two large teams.

We've got longer ropes this time

so there's more room
for you guys to pull.

You guys ready over there?


We're going to let your side go
forward, to let it lean forward,

but you guys are going
to pull at the same time.

We're going to see if we can twist it slightly.

Ready, set, pull!



Okay, hold, hold.

With no luck on the first attempt,

the problem solving begins.

Yeah, widen that out.

That's good.




Okay, hold.

Okay, you got it twisted!

Now we want to see
if we can get the other way.

No matter what they try or how they move,

the team can't seem to twist
the statue forward even an inch.

Over the next hour,
the statue doesn't budge.

Okay, hold.

It seems to be swinging and rocking, but not moving forward.

Things are exactly what we want.

You have to trust
in the way it moves

and if it fails,
we have a crane.

Trust the ancestors here!

Okay, so you're
going to be pulling?

They continue to try,

but rocking Hotu Iti
forward and back

is the best they can do.


In fact, it's the only thing they can do for hours.

Hunt and Lipo are convinced

the ropes need to be
around the shoulders

to get the leverage needed
to twist the statue at the base.

Can we get tension
on the statue?

They adjust the ropes again, even taking the advice

of a nautical knot expert
when nothing else is working.

As long as there's tension
on here, that won't slip.

I think they really want the
purchase to come from right here

so it's on the shoulder.

Ready... go.

The clock keeps ticking.

Just three hours left
to figure this out.

Whoa, we almost lost it there.

Hunt and Lipo struggle to understand

why two ropes aren't working
to move the statue forward,

since it worked
with the wooden model.

They decide to try something
else, and everyone has an idea.

(everyone talking over
each other)

Hey, Carl, you need
to referee in this.

It was a lot easier yesterday
when we were up high.

That's where I feel like
it's going to happen, don't you?

Have a rope on the top
keeping it from falling

so there's three,
it's like a Y.

Pulling this rope right now,
it's not going to work.

We're fighting each other.

So one rope up there
just holding it back.

There'd be one rope
holding him back.

We have a third rope?

Yeah, we do.

Nothing's happening.

Basically you can move it like
this or like this,

but we can't really get it
to do what it's supposed to do.

So what we've done is
added a third rope,

which I think is going to be
really critical.

Now we think with three teams,

we're going to be able
to get the motion going,

take advantage
of the kinetic energy

that's built into the statue,

allow it to fall forward

on the front edge of the moai,

but the team in the middle not
allowing it to fall too much.

As they re-tie the ropes, Lipo and Hunt make a new observation.

Thinking back to the fallen
statues on Easter Island,

they remember moai in transport
had sideways V-shape notches

where the eyes should be,

a feature that now seems
very important.

The V-shape of the eyes and the bridge of the nose

is perfectly suited
for tying a rope around

and creating a place that you
can put ropes and have friction

and also tall enough to provide

the leverage you need
to move it.

Perhaps the finishing is done

because that area
takes a little abuse

with the ropes tied up high
for that leverage

and so you finish them,
add the eye sockets

when the statues reach their
final place on the platforms.

It's an intriguing speculation,

but it's a little late
in the day for new theories.

So we're going to alternate pulling.

You guys are going to be pulling
back and then releasing.

It's 4:00 p.m.

There's just one hour left

to figure out how
to make this statue walk.

With the ten people in back
and more people on each side,

they're ready to try
one last time.

Release the tension.

How you guys doing?



Ready, set, heave!


Oh my God.



He's walking!



Okay, that was walking.

As the statue starts to move a few feet,

it all starts coming together,

and the safety straps come off.

The crane is out, we're taking the training wheels are off.

We are going to move the statue
without any help.

How do you feel?

Exhilarated and just amazed.

Really happy, and we're going
to get right back to it.

Let's go for the finish line!

So this is how you move a moai!

Heave, ho! Heave, ho!

Once the teams get the hang of moving the statue,

it becomes easy.

Confident in their ability,
they get a little overzealous.

And Hotu Iti takes a nosedive.

But there's learning
even in failure.

When Hotu Iti fell,
he fell exactly the same way

the ancient moai
on Easter Island fell:

face first, at an angle,
right along the road.

In most cases when the statues fell,

they weren't able
to retrieve them.

We've seen a couple of examples
on the roads.

I mean, some of the smaller ones

they probably undoubtedly
propped back up,

but once they got larger
and larger,

it became a pointless effort.

Hotu Iti fares better, thanks to modern machinery.

With just minutes left
in the day,

Hunt and Lipo revise their goal
of moving the statue 50 yards.

We're going to call this point

at ten yards the goal line,

and once we get there,
that's going to be our finish

and we know we could move it
anywhere, absolutely anywhere.

Heave, ho! Heave, ho!

(volunteers chanting
"heave, ho" in rhythm)


We did it! Yay!

All right!

I feel fantastic.

This has been a great success.

About mid-afternoon
I was feeling pretty low,

and I'm pretty high right now.

It moved exactly the way
we thought it would.

We just had to figure out
how to get it started.

What struck everyone was that
once we got going,

there was almost
no effort involved.

We were on the ropes

and we could feel
that first tug was work,

and then when it started
swinging, you could feel--

I mean, we weren't even pulling
on the ropes--

that the energy of the statue
moving did all the work.

We were just kind of gently
directing it.

The method, the inputs

that we're doing in a ten-foot
version are exactly the same

that would be required
in a 30-foot version.

All that would matter

was scaling the initial
input of energy.

In later experiments,

Hunt and Lipo were able
to move the statue

more than 100 yards
in only 40 minutes.

They also successfully walked
Hotu Iti

up grades of three
to four percent.

We may never know if this is how
the statues were actually moved,

but this success presents
an intriguing new explanation.

It perhaps goes one step further

to solving the mystery of what
happened on Easter Island.

What we are doing today,

we're pinpointing
the archaeological evidence

that comes from oral history:
the moai walk.

The transportation
of the statues

is perhaps the most
important contribution

of this culture to humanity.

If this really is how the islanders moved the statues,

it raises an important question:

Do these statues that rise above
this ravaged, treeless landscape

serve as a cautionary tale
for our times,

or as a monument
to the human ability

to innovate, create
and survive?

r funding for NOVA
is provided by:

Supporting NOVA and promoting
public understanding of science.

And the Corporation
for Public Broadcasting,

and by:

Additional funding from:

Inspiring tomorrow's engineers
and technologists.

Additional funding for this
program is provided by:

The exploration continues
on NOVA's website,

where you can watch this
and other NOVA programs,

see expert interviews,

video extras and more.

Follow NOVA on Facebook
and Twitter,

This NOVA program is available
on DVD and Blu-ray.

NOVA is also available
for download on iTunes.