All language subtitles for NOVA.S49E09.Ice.Age.Footprints.1080p.WEB.h264-BAE_track3_[eng]

♪ ♪

KIRK JOHNSON:
White Sands National Park,
New Mexico...

A vast, open desert that
holds clues to a lost past.

DAVID BUSTOS:
At White Sands,

all good stories sort of
begin with a Bigfoot.

JOHNSON:
Footprints dating all the way
back to the last Ice Age.

All these circular things
are fossil footprints.

JOHNSON:
That's amazing.

♪ ♪

JOHNSON:
Mammoths over 13 feet tall.

(mammoth grunting)

Dire wolves, camels,

and enormous ground sloths

that roamed North America
thousands of years ago.

White Sands has so many
hidden treasures.

There's all these
trackways here,

it's just such
an incredible discovery.

♪ ♪

JOHNSON:
Alongside them,

something even more astounding.

That is a human footprint.

Yeah, so there's

a human footprint right there.

(laughing):
Wow.

JOHNSON:
Ancient human journeys

printed on the landscape.

When you make tracks in sand,

they just blow away.

When you make tracks in
a place like this,

where the chemistry
is just right,

the tracks can last forever.

(voiceover):
Now a team of experts
is investigating

how these remarkable tracks
could shed new light

on life in the Ice Age.

MATTHEW BENNETT:
There's a double trail.

Somebody going this way,
and somebody going that way.

JOHNSON:
Wow, that is really incredible.

(voiceover):
How long ago were they made?

KATHLEEN SPRINGER:
That's amazing.

MAN:
Yeah.

SPRINGER:
The Ice Age megafauna
went extinct

about 11,500 years ago.

So they're at least that old.

How much older than that

is really anyone's guess
at this point.

JOHNSON:
Could they provide
new information about

early peoples of the Americas?

It really does
put our feet prints

firmly into the past here
in North America.

KIM CHARLIE:
Here's our proof.

Footprints,
footprints of our ancestors.

♪ ♪

JOHNSON:
Can the secrets of these
ancient footprints

help answer the questions

when and how did humans first
arrive in North America?

♪ ♪

"Ice Age Footprints"...

Right now on "NOVA."

♪ ♪

JOHNSON:
The dazzling dunes of

White Sands National Park.

Sand as bright as fresh snow.

♪ ♪

But hidden within this landscape

are traces of an ancient story

dating all the way back
to the last Ice Age.

When we search
for evidence of life

in the ice ages
in North America,

we find things like
the bones of mammoths

or maybe even hearth stones
or spear points

from the people
that used to live here,

and very rarely we find
the remains of those humans.

But the story
is still so incomplete,

there's so much more
information we need to find.

♪ ♪

JOHNSON:
That's why the discovery
of footprints

here at White Sands is
so significant.

Could they help answer
some of the greatest mysteries

of the Ice Age?

♪ ♪

The precise location
of this site

is a secret.

These dunes cover

nearly 300 square miles...

with some rising over 50 feet.

I'm driving through
these snow-white dunes.

It's kind of
a surreal landscape.

Once we get through the dunes,

we'll be out in
the great ancient lakebed,

and it's absolutely
covered with tracks.

(voiceover):
I'm Kirk Johnson.

As a paleontologist,

I've spent most of my career

studying the remains
of ancient life.

But footprints can tell

really detailed stories
about the past.

♪ ♪

30 minutes later,

we've reached our destination:

a huge dried-up lakebed.

As the wind scours
this remote area,

new prints are being revealed,
and old ones disappear.

It seems like such an
improbable place

to even look for tracks.

(voiceover):
Joining me is David Bustos.

He's leading
the team of scientists

investigating the footprints.

BUSTOS:
You look out and
it's just bleak desert,

and who would think that there's
all these trackways here?

JOHNSON (voiceover):
As my eyes adjust to
the brightness,

round patterns start to appear.

So there's one there...
Yes.

And there and there,

and there and there, there...

BUSTOS:
Yeah.

Oh, yeah. Those are amazing.

Uh-huh.

♪ ♪

(voiceover):
The mysterious shapes
are over five feet apart,

and nearly two feet across.

These are the fossilized tracks
of an Ice Age giant...

a Columbian mammoth.

It died more
than 10,000 years ago,

but its footprints remain.

♪ ♪

(mammoth trumpeting)

The tracks are
preserved in various ways.

Sometimes the wind fills them
with different textured sand,

leaving ghostly impressions,

while others dry into hard casts
which are exposed

when the softer ground
around them erodes away.

One of the things that
really stand out at White Sands

is just thousands and thousands
of footprints preserved.

In this area,
we'll see trackways

that go for ten miles
in one direction

and two or three miles
in another direction.

You know, there might be

over 100,000 prints
throughout this large area.

Do...
it's okay to walk on them?

We can walk
near them and around them,

as long as we don't
disturb the surface below

or add more sediment in.

JOHNSON (voiceover):
We need to be careful not to

step on the fragile prints...

and the team tries to only
visit the trackway areas

when the ground is dry,

and hard enough
to support their weight.

The surface is always changing.

We are seeing more erosion.

Every year, more and more prints
are becoming visible.

JOHNSON (voiceover):
And along with the many
mammoth prints here,

we soon spot traces of another
large creature.

BUSTOS:
They're very common,

they'll sort of
look like an S shape...

Yep.
You'll see them connecting
to each other.

There's one here, right?

Yep. There's another one
coming through...

I think as well, right there.

JOHNSON (voiceover):
Twice the size of a human foot,

and with giant, curved claws,

these are the prints of
a massive ground sloth,

a beast more than double
the weight of a grizzly bear,

that walked this land
thousands of years ago.

(sloth panting)

So that's sort of how the story
of White Sands began.

People, they've seen these
incredible footprints,

and they thought
that it was Bigfoot.

(chuckling):
Bigfoot with three weird claws.

Yes.

JOHNSON (voiceover):
Then we discover something
even more special.

That is a human footprint.

Yeah, so there's... there's a
human footprint right there.

(laughing):
Wow.

Yeah, so if you look...

That is amazing.

Here's the heel.

Okay.
Right here.

JOHNSON (voiceover):
Scattered across the landscape

are human footprints

from thousands of years ago.

Each track is the
trace of an ancient person,

the shape of their bare feet
locked in the sediment.

Look at this,
this is amazing here.

This actually looks like
a human print right in there.

♪ ♪

JOHNSON (voiceover):
Could these extraordinary
human footprints

help answer two big questions:

when did people first set foot
in North America?

And did their arrival
contribute to

the disappearance of
giant Ice Age animals?

20,000 years ago,

Earth was
in the grip of an ice age.

The climate was colder,

vast ice sheets covered
much of North America...

and White Sands
was not a desert,

but a huge lake... Lake Otero.

♪ ♪

The lakeshore surrounding it
teemed with life.

Giant ground sloths
wielding big claws

shared this wetland with
mammoths

weighing up to ten tons.

Alongside them,

packs of dire wolves
hunting for a kill,

and hardy North American camels.

These Ice Age giants disappeared
from the fossil record

over 10,000 years ago.

So the human footprints here
are probably at least that old.

♪ ♪

But they could be much older.

What can they reveal
about the deep history

of humans on this continent,

and how they met the challenges
of life in the Ice Age?

♪ ♪

To find out,

David has assembled
a team of scientists

to uncover the tracks'
hidden secrets.

BENNETT:
I'm confident in it now,

that that's mammoth, and
it links to your one in the,

um, that you've got
in cross section there.

Cross section over there?
Okay.
Yeah.

JOHNSON:
One of them is Matthew Bennett,

a forensic footprint expert
from England.

♪ ♪

On the eastern side of
the ancient lake,

close to the restricted area of

the White Sands Missile Range,

Matthew is excavating
a remarkable set

of human footprints.

JOHNSON:
Hey, Matthew,

how's it going?

It's going well.

These are amazing.
They are.

Are these... so, are these

just the ones you've exposed
this afternoon, then?

Yep, there's a double trail.

Um, somebody going this way,
and somebody going that way.

How far do they go off
in that direction?

So, in that direction,

about three-quarters of a mile,

something like that,
and then they go to

the boundary fence
on the missile range

and an unknown distance
into the missile range.

♪ ♪

JOHNSON:
How common is it to have
a track this long?

BENNETT:
Okay, so I've looked at tracks

all around the world,
and this, to my knowledge,

is the longest human trackway
anywhere in the world.

JOHNSON:
Oh, that's amazing.

Could it be the same person
going away and coming back?

Absolutely.
They're the same size.

It's actually
quite a small individual.

It could be a woman,

but could be
a male adolescent equally.

The size is...

Looks like a size five
or something.
Yeah.

But the tracks are very big.

There's sort of
30% of the track,

maybe more is pure slippage.

It's very wet and
slippery conditions

as the individual
has been moving.

JOHNSON (voiceover):
Some are clearly defined
imprints,

but many are
stretched out and distorted,

an indication that
the walker was moving fast,

and slipping
on wet, muddy ground.

Some prints are bent
out of shape,

from a foot sliding sideways,

which could mean

the person was carrying
something on their journey.

BENNETT:
They were also carrying a child.

Oh, they're
carrying a child as well?

They're carrying a child.

How do you know that
they're carrying a child?

BENNETT:
Along the trackway,
there are very small,

tiny little children's prints.

They sort of face
the direction of travel.

So if you imagine you were
carrying a child on your hip

and you wanted
to readjust, you...

you put it down...
Right.

...and then you readjust,

and there's
a few small child prints,

pick the child up again
and carry on.

Just over to here...

JOHNSON (voiceover):
A little farther along
the same trackway,

Matthew discovers
a twist in the story.

The travelers were not alone.

What's this
unusual set of tracks?

So there are a series
of sloth tracks here

entering from, from...

to the left there...
So this is the first one.

And then it comes out over here.

That's really the amazing one,

you can see the claws
of the sloth so clearly.

BENNETT:
You can, yeah.

It's a beautiful,
a beautiful track.

They're not large tracks.
Yeah.

So it's a relatively
small sloth.

Bear-size,
I would have suggested.

JOHNSON (voiceover):
Was this sloth here

at the same time as the humans?

The sloth's footprints
are right on top of

the outbound human track.

Which means this animal
must have arrived

after the travelers
first passed by.

Where do they actually
step on the human track?

So...
Is it this one?

It's actually just over there.

There's an example where they,

they cut across the human track.

But the sloth did
something quite cool.

It seems to have gone from
all fours up onto its hind legs.

It's done
a little dance around...

And then it goes off that way.

So it crawls in kind of
like sloth-like,

and then as it gets here,

it kind of pivots around and up

and looks, looks...

Looks, scents the air, and off.

...and pivots

and then heads off that way.

That's correct.

A little sloth dance.

Yeah, that's exactly what it is.

JOHNSON (voiceover):
Matthew thinks the sloth

noticed the human tracks
and reacted.

Either the sloth's either
visually responding to the track

or it smells something.

My instinct is smell.

It basically reared up to scent
the air a little bit more

and then decided to,
to disappear off.

They're not here
at the same time,

but within a few minutes,
hours of each other,

they're here.

(chuckling):
That's a phenomenal thing.

Some small person
having a stroll

on a landscape full of
giant ground sloths.

(voiceover):
The tracks at White Sands show

just how close humans here
came to Ice Age animals.

Imagine what
it must have been like

to meet one of these
enormous beasts in the flesh.

(sloth groaning)

♪ ♪

You can get a sense of
these Ice Age encounters

at La Brea Tar Pits
in Los Angeles.

Here, animals that wandered
into tar deposits were trapped,

and their bones were preserved.

In the last century,
experts have unearthed

more than a million fossils
here.

EMILY LINDSEY:
Hey.

Hey Emily, how are you doing?

Good, how are you?

Nice to see you again.
Good to see you.

Welcome to the Tar Pits.
Thanks.

Oh, here's our sloth, huh?
Yeah.

This thing is amazing,
so massive.

It's majestic.

JOHNSON (voiceover):
Curator Emily Lindsey works with
fossils of the giant beasts

that lived in North America
during the last Ice Age.

So how much do you think
this guy weighed?

Probably more than a ton.

And when people
talk about sloths,

they talk about
how they move so slowly,

would this guy have
moved slowly?

You know,
it wouldn't have been like,

a runner...
Yeah.

...but it wouldn't have been
so slow as the modern sloths

that are really only adapted
for living in trees.

What would
an animal like this eat?

So they were mostly herbivores,

and it looks like they
were eating a lot of

kind of desert shrubs

that would have
been prevalent in the area.

Sloths are part of this
very strange group of animals

called Xenarthrans,
and it includes the sloths,

the armadillos,

and the anteaters.

And like armadillos,
some species

produced bony armor,
only in this case,

it's in the form of these

small sort of pebble-like bones

that were embedded
inside its skin.

Oh, that's why
I love sloths so much.

(laughing):
They're so cool,

they're such amazing animals.

Yeah, they're one of the
weirdest animals,

and it's a piece of ecology

that has just
completely gone from earth.

(indistinct chatter)

JOHNSON (voiceover):
Nearby, I've spotted another

lost species whose tracks
we see at White Sands.

This is an amazing beast,
isn't it?

Yeah, the Columbian mammoth.

JOHNSON (voiceover):
From fossil evidence,

we know that mammoths
arrived in North America

around 1.8 million years ago.

When you stand beneath the
skeletons of these huge animals,

you can't help but wonder,

why did they go extinct
less than 13,000 years ago?

Was it because of
a change in climate?

Or human influence?

Or a combination of the two?

LINDSEY:
It seems to have been
a really rapid event.

As we we're
coming out of the Ice Age,

we're going through all
these big climate upheavals,

so we need to know
how much overlap

there actually was
between when humans arrived

and when the
last animals disappeared

in order to know what role
humans might have played

in that extinction.

♪ ♪

JOHNSON (voiceover):
The footprints at White Sands

might be the oldest human prints
ever found in North America.

They could shed new light on
the lives of Indigenous peoples

and their long history
on this continent.

It's, it's just so amazing
to see these tracks...

There's another one
crossing there.

Yeah.

JOHNSON (voiceover):
Today, I'm visiting

the U.S. Army's
White Sands missile range,

just across the boundary
from the national park.

Here there are
more animal prints,

including those of a mammoth,

and this magnificent trackway
of a ground sloth,

crossed by the footprints
of an ancient camel.

Can you imagine this whole area

with all these animals here?

Would have been amazing, huh?
(sighing):
Oh.

Mammoths, sloths, cats, dogs.
Yeah.

Right?
Yes.

I always say we need
to build a time machine.

(laughter)

JOHNSON (voiceover):
Joining me are Joe Watkins,

an archaeologist and member of

the Choctaw Nation of Oklahoma,

and Kim Charlie from the
Pueblo of Acoma in New Mexico.

They want to
see the prints for themselves,

and learn more about

the people who once walked
across this landscape.

We have this tie
where us Native Americans

have been here
for a very long time.

And I believe that, you know,
I really believe that.

And that ties back into,
you know,

our migration stories where

we evolved somewhere,
but we don't

specifically know where.

These are stories that

we believe in our hearts
as tribes,

pueblos, you know, that we take,
that we hold sacred to us.

So when we come back to
these areas

and we find
evidence of footprints

of our thousands of
great ancestors,

you know, we just kind of, like,
it's amazing.

So we did exist here.

The tribes talk about
going way back.

We all talk about
having been here forever.

We've never been anywhere else.

We have the evidence,
it really does

put our feet prints

firmly into the past here
in North America.

These are our relatives.

We've been here since
time immemorial

and hopefully we'll continue on.

JOHNSON (voiceover):
When Europeans arrived

on this continent,
they began a pattern of

ignoring the rights and stories

of Indigenous peoples.

With the colonization
in the 14, 1500s,

a lot of tribal histories
have either been lost

or have been pushed back
or have been tossed aside.

This was once
our land, you know.

Mother Earth
was our mother...
Mm-hmm.

...and we're
the descendants of her.

And we're the people
that try to take care of it,

but you've got the
Western people

have come in and just
taken over areas where,

you know, they have no respect.

Please understand that

we Native Americans
were here first.

It's kind of an awful thing

where we've been put on
little reservations.

You know, where we once had
the freedom to roam.

♪ ♪

JOHNSON (voiceover):
European-Americans not only

took control of
Indigenous territories,

but some also spread

misleading narratives
about Indigenous people.

(indistinct chatter)

♪ ♪

WATKINS:
There's pretty much always
been a conflict

between archaeologists
and American Indians.

In many ways,

archaeologists have taken over.

They've sort of colonized
American Indian history,

and they felt that they,
they're the ones

who tell
the true story of the past.

So there's been
that conflict between

whose story is the true history.

Archaeologists also

came out to
archaeological sites,

started excavating,

took the materials,
took them back to museums,

and tribal people
never saw them again.

♪ ♪

JOHNSON:
Over the centuries,

some white scholars
used archaeology

as a way to dismiss
Indigenous people's accounts

and ancestral connections
to the land.

It really wasn't
until 40 years ago

that Indians had a say in
who was excavating

and what happened with the
results of those excavations.

♪ ♪

JOHNSON:
Here at White Sands,

the scientists are consulting
with local tribes

and pueblos to study and record
these important prints.

They hope to solve one of
the biggest mysteries of all:

when did humans first arrive
in North America?

Fossil records show that by
at least 100,000 years ago,

modern humans... Homo sapiens...

Began spreading
from Africa across the planet.

The Americas
were surrounded by ocean

and out of reach.

But during the last Ice Age,
massive ice sheets formed

and sea levels
dropped by over 400 feet,

exposing land
between Siberia and Alaska.

Many scientists agree

that this is how humans
got to North America.

But when exactly
did they first arrive?

Throughout the 20th century,
many archaeologists

thought the answer lay in
these stone projectile points

found all across North America.

They were made by people from
what became known as

the Clovis culture.

WATKINS:
I have a replica

Clovis point with me.

They look about like this.

Some are larger,
some are smaller.

There's a very characteristic
flake

that's taken out of the base

up to the middle of the point.

JOHNSON:
The oldest known Clovis points

are about 13,000 years old.

And for a long time,
many archaeologists

thought that humans
arrived in North America

no earlier than that.

So these Clovis points
have been found

all across North America,

from the Atlantic coast
on the east,

all the way out into the,
the west coast.

So with this, such a broad
geographical span of material,

it's why most
archaeologists thought

that Clovis was the
first archaeological culture

in North America.

JOHNSON (voiceover):
More recently,

this view has been challenged
by the excavation of

older sites,
with stone artifacts

that suggest humans lived
in North America

at least 2,000 years

before the Clovis culture.

♪ ♪

There are some
archaeological sites...

one in Florida, one in Texas...

that date about 15,000,
15,200 years ago.

So those are currently
the oldest dates we have

for the early peopling
of the New World.

♪ ♪

JOHNSON:
But now the discoveries
at White Sands

may support even earlier dates,

and could shed new light on

how people
came to North America.

About 20,000 years ago was
the peak of the last Ice Age,

the Last Glacial Maximum.

Gigantic ice sheets blocked
the route into North America.

But there's geological evidence
that as the climate warmed,

an ice-free corridor opened up.

Was this how humans reached
the rest of the continent?

So one thing about the
ice-free corridor,

it didn't really open up

until 13, 14,000 years ago.

So if it wasn't open,

it wasn't likely that anyone
could have come that way

and come in to North America.

JOHNSON:
If the tracks at White Sands
pre-date the ice-free corridor,

they will add more weight

to the idea that humans
arrived here earlier

than many archaeologists
previously thought.

♪ ♪

Searching for clues,

David Bustos is studying some
other remarkable human prints.

I don't know if you can
see right here,

this might be more of a child.

It's about, maybe, four,
four inches or so across.

And it's right next to
an adult print.

You don't normally think of,
you know,

taking your child all the way
across the country or so,

unless you're, um,
if you're hunting,

you might leave the child
back at home,

but we see the children
everywhere,

so they're part of the scene
or part of the landscape.

♪ ♪

JOHNSON:
The footprints tell stories
of Ice Age life.

But how long ago were
these people here?

♪ ♪

In order to date the prints,

the team has dug a trench.

(rocks rumbling)

It reveals layers of sediment,

deposited over many years,

along the shore of this
ancient lake.

Stamped on these buried
surfaces are human prints,

and the further down they are,
the older they are.

But just how old are they?

I can put them both on.

Okay, sure.

JOHNSON:
To help find the answer,
David has been joined

by geologists Kathleen Springer
and Jeff Pigati,

who is also an expert in
radiocarbon dating.

♪ ♪

You've cut a cross section...
What are you trying to see

with the cross section?
SPRINGER:
So the footprints themselves

are just an impression
on a surface,

there's nothing to date.

It's an inorganic thing, you
have to find something organic

that you can date above
and below the footprints,

and get good dates on them,

so that you can actually say,

"That footprint is between
these two ages."

JOHNSON (voiceover):
In this trench, Kathleen and
Jeff have made a crucial find.

♪ ♪

Sandwiched in the layers
above and below the footprints

are scatterings
of ancient seeds,

precious organic material
which the team can date.

That way they can establish
a window of time,

for when the prints were made.

There were actually
plants growing on this,

on the surface when, you know,

these critters
were walking around.

So the same layers that have
the tracks will have the seeds.

Absolutely,
above and below them.
Yeah.

Yes, so above and below them,

that way we can constrain
in time.

So your seeds are effectively
little timepieces, right?

They're like little clocks
or something buried in the...

They're little capsules, yeah.

And basically the, the...

these things are really
resistant to, to decay.

And so they look like
they were put down on the,

on the landscape just yesterday,
but, in fact,

they might be tens and,
you know,

tens of thousands of years old.

JOHNSON (voiceover):
Jeff will take the seeds back
to his lab in Denver,

and use radiocarbon dating
to find out how old they are.

♪ ♪

JOHNSON:
When I talk to you in
six months' time,

either you have what you expect,

PIGATI:
Mm-hm.
which is around
12,000 years,

or you have humans
here earlier than you expect,

or mammoths are here later
than you expect.

PIGATI:
Something's going to be pretty
cool either way, right?

So it seems like you're going
to get

a really interesting result no
matter what the result is here.

PIGATI:
It is a win-win,
no question about it.
Yeah.

That's a rare thing
in paleontology.

PIGATI:
It's kind of nice.
Yeah.

JOHNSON:
Dying to hear
what you find out.

Yeah.
Yeah, us too, us too.

JOHNSON (voiceover):
The trackways at White Sands
are constantly changing...

as the wind erodes away the
surface to reveal new prints,

it's also turning existing ones
to dust.

BUSTOS:
It's great because we can
see the prints,

but then they are
rapidly blowing away.

So we want to capture the data
before it's gone.

Some of these really soft ones
like this,

once they're exposed, in
a few months they'll be gone.

Some type of, you know,
priceless data is, is being...

is right here, is being lost.

It's the surface,
we're losing the surface,

and these are
where all the prints are.

♪ ♪

JOHNSON:
To record this precious evidence
before the wind blows it away,

the team is mapping the site
using aerial imagery.

BUSTOS:
One of the main reasons
is to fly over the area

and then get an elevation model

so we can see where
these prints are.

And then we're gonna
re-fly it again,

and so with that we'll be able
to look at

from this year to next year

we'll see how much erosion's
happening,

so we can see how fast

the prints are moving
and going away.

JOHNSON:
One question they hope
to answer using digital imaging

is whether the people here were
hunting the giant animals.

David shows me an intriguing set
of tracks that may hold clues.

Dave, what kind of
image is this?

BUSTOS:
It's a photogrammetry.

You know, so basically
overlapping photos.

I think in this image,

there might have been
400 or 500 different images

and they're all stitched
together.

You can, you know,
tip the images upside down,

see it in different directions.

So this image right here

is actually
a giant ground sloth.

It's walking along.

These are hind and fore feet,
so when they weave in and out,

what you see is a hind foot,

and then the forefoot comes
in front

with the very long claw.

And then right here, it changes.

So it stands up, actually.

JOHNSON (voiceover):
What caused this sudden change
in behavior?

David has a theory.

BUSTOS:
If you look close, you'll see
a set of human tracks,

And what's really exciting,
we took measurements.

You can see they're running
toward the sloth.

If you're in the field,

you'd actually see where they're
almost toe to toe, you know,

almost chest to chest,
it looks like.

I don't know if they're
throwing a spear

or what they're doing, but they
come right up to each other.

The sloth's spinning around
and making, like,

it looks like a sweeping motion.

Actually, there's claw marks
on the ground.

There's another set
of human prints

sort of running up along
this direction.

JOHNSON (voiceover):
David believes these trackways

are evidence that humans
were actually hunting sloths.

(sloth grunts)

But what was it like to take
on such big animals?

(sloth growls)

La Brea Museum curator
Emily Lindsey

has investigated
how humans hunted them.

So these are our collections

where we keep all of the fossils
that have been excavated

over the last hundred years.

There's millions
of fossils here.

Yeah, there are literally
millions of fossils here.

And here are some
of our sloth claws.

JOHNSON:
Oh man, look at those things,

these are serious claws.

What did they use the claws for?

Some paleontologists
think they might have used them

to dig roots out of the ground.

They've found burrows

that they think these guys
dug there,

where there's actually
scratch marks on the wall

that line up with the the hands
of giant sloths.

But, of course,

they would have been really
useful for defense, as well.

JOHNSON (voiceover):
But despite their fearsome
appearance,

archaeological evidence shows
that ground sloths

might have been on the menu

for hungry humans.

LINDSEY:
You know,
we have a couple of sites

that have been found where it
looks pretty clear

that humans were,
if not hunting,

at least butchering
giant ground sloths.

We've got stone tools

and we've
got cut marks on the bones.

Although we have many more sites

that show humans hunting

and eating things like mammoths
and horses and camels

than we do of giant sloths.

So, they may have been a food
source of last resort.

Maybe bison tastes better, or...

Yeah, given the types of plants

that we find in the sloth dung.

You know, desert plants

that tend to have a lot of
chemicals in them.

They might not have tasted
very good.

Huh, interesting.

So what kind of techniques
were humans using

to hunt and kill these animals?

LINDSEY:
They had spears, but, of course,

the most important tool
that humans had

were their big brains
and their social groups

and ability to communicate.
Hm.

♪ ♪

JOHNSON (voiceover):
Teamwork and planning,

these were the keys to bringing
down huge Ice Age beasts.

♪ ♪

But once the animal was dead,

what did people do
with all that meat?

♪ ♪

One of the challenges
you have, if you're,

if you're living
in this environment,

or hunting in this environment,
is how do you get your meat

from where you kill the animal
to where you camp?

♪ ♪

JOHNSON:
Dan Odess is an expert

in prehistoric archaeology.

He searches for evidence to show
how humans might have dealt

with the animals they killed.

And alongside the footprints,

he shows me
a very different kind of track.

DAN ODESS:
We have these,
these really interesting

linear structures.

There are four of them.

You can see here
one, two, three, four.

JOHNSON:
What could have caused these
strange marks in the sand?

ODESS:
We were kind of wondering

initially, could this be
a product of animal behavior

rather than human behavior?

But, interestingly,

one of the things we see

and you can see it very clearly
in this one,

we've got people walking along
behind it.

JOHNSON:
Dan believes this is important
archaeological evidence

of human engineering.

They're, they're drag lines.

So impressions left in the mud

as somebody probably pulled

a pole or poles.
Okay.

With presumably meat
or something else on them.

JOHNSON:
And that's a typical way
to move meat around?

I think this is the first time

it's been described for
the Ice Age.

JOHNSON (voiceover):
The team thinks these tracks

could be the earliest known
evidence of an ancient device

used to carry heavy loads,
such as large amounts of meat.

ODESS:
Instead of dragging
the carcass back to the camp,

they would strap it onto
a couple of poles,

and not one, or two poles.

At this point,
we're not sure whether

they're dragging a single pole

or whether they're using
two poles hitched together.

JOHNSON (off-camera):
Huh, so like a primitive
wheelbarrow, basically, right?

ODESS:
So far we, we don't have
any reason to think

they had a wheel.
Right.

Well, wheelbarrow with
no wheel, how about that?

Yeah, right, right.
(chuckles)

A barrow!
Right, there you go.

Let's just call it
a barrow.
A barrow.

♪ ♪

JOHNSON (voiceover):
But what could the device
have looked like?

(birds flapping wings,
squawking)

60 miles from the trackways
is Elephant Butte Lake.

Experts think White Sands

had a similar environment
during parts of the Ice Age.

Archaeologist Joe Watkins

has come here to conduct
an experiment.

Joining him are fellow
archaeologists Carol Ellick,

CAROL ELLICK:
I'll start with the lashing
on this corner,

all right?
Yup.

JOHNSON:
And Edward Jolie, of Lakota
and Muscogee descent,

and a citizen of the
Muscogee Nation of Oklahoma.

EDWARD JOLIE:
Is this going to be
sufficiently stout,

or should we cut a thicker one?

ELLICK:
I think that's
pretty tiny, Ed.

JOLIE:
It is.

JOHNSON:
The team wants
to carry out experiments

to try to reproduce the tracks
at White Sands.

♪ ♪

They're building two simple
structures

to see if one of them
might leave

similar drag marks to those
found in the desert.

Ed, if you want to

lash the end pieces together.
JOLIE:
Okay.

I'll grab the important piece.

JOHNSON:
The first design is an A-frame
structure,

based on a traditional device
used by Indigenous peoples

called a travois.

They're attaching
40-pound weights

to represent a hunk of meat.

I think that's the 40 pounds.

This feels, like, more than
40 pounds, is this...?

Honestly, that's 40 pounds.

Two 15-pound weights,
plus two 5-pound weights.

(chuckling)

That's...

We might have some
structural issues.

(laughter)
I don't remember my daughter

ever weighing this much!
(laughs)

JOHNSON:
Carol is going to pull
each design.

Walking barefoot,
like the people

who created the prints
at White Sands.

It feels pretty stable.

ELLICK:
It looks pretty stable.
It feels,

from my end,
it feels pretty good too.

ELLICK:
I was going to follow the
edge of the water,

is that what you were thinking?

WATKINS:
I think that's a good way.

Okay.
Okay.

(grunts)
Whoa, getting started.

JOHNSON:
Carol leaves behind clear
footprints

and drag marks in the mud.

♪ ♪

WATKINS:
Look at that.
JOLIE:
Yeah, that's great.

WATKINS:
The footprints are both on
one side.

I would have thought
there would have been footprints

on either side
and that the drag line,

would have been
between the two.
JOLIE: Mm-hm.

And it appears to me, as well,
that what we're seeing

is that the footprints
are the side opposite

the weight imbalance
on the travois.

WATKINS:
Either that or the fact
that there are two sticks

is having an impact
on the way it's moving.

JOLIE:
Looks great.

JOHNSON:
They record the
marks for further study.

WATKINS:
Let's get one up by
that footprint

where the mud has
pushed over to, okay?

That's a good start.

♪ ♪

JOHNSON:
Next, they try
the second design...

a single pole with the same
weight attached.

WATKINS:
Do you want me to come up
a little bit?

ELLICK:
Pull it forward a little bit.

So...
Put that end down.

JOLIE:
Come up parallel to
this one.

ELLICK:
All right, all right.

(stick dragging)

♪ ♪

JOHNSON:
This creates a single drag line
with a regular wobble pattern.

That feels quite
different pulling it

on the single pole
rather than the double travois.

WATKINS:
So it definitely is
wobbling back and forth

much more than the one with
the two-pole travois.

Standing and staring at them
both in parallel,

it's really drawn into
stark relief

Yeah.
How different they are.

It's a bit of a surprise,
actually.
(shutter clicks)

♪ ♪

JOHNSON:
But which design
makes a pattern closest

to the tracks found
at White Sands?

WATKINS:
My impressions are that
the straighter lines

at White Sands
pretty much equate with

the straighter lines
we're getting with the travois.

That's definitely not saying
that's the only way

they could
have had those straight lines.

But just based on
this initial experiment,

I would be more inclined
to go with the double pole.

JOHNSON:
This experiment suggests how
Ice Age humans

might have transported meat
or other heavy objects.

But how long ago
were they walking along

the ancient lakeside at
White Sands?

♪ ♪

It was time to visit Denver
to catch up

with Jeff Pigati
and Kathleen Springer.

PIGATI:
Yeah, right at the top of the
sequence there.

So that one has a stem attached.

Still has a stem attached?

Yeah.
That's awesome.

We'll go through there.
Yeah.

JOHNSON:
At the U.S. Geological
Survey Lab,

Jeff has been analyzing
the seeds they found

in the sediment layers
at White Sands.

♪ ♪

He's been using
radiocarbon dating

to calculate the age of
the seeds, and from that,

the age of the footprints.

PIGATI:
This is the carbon extraction

and graphitization system.

And, basically, what we do here
is take a seed.

We combust it in oxygen.

We turn the carbon
that's in the seed

into carbon dioxide.

We get rid of everything
else that's in the seed...

water and other other
contaminant gases

that we don't want...

and we end up with pure CO2.

♪ ♪

And we basically take that
carbon dioxide,

convert it to graphite,

and that's what we actually
send out to the AMS lab.

So you turn the seed into a gas
and then back into a solid.

That's exactly right,
we start with a solid,

we turn it into a gas,
clean it up,

and then end up with a
pure graphite pellet at the end.

In these little targets,
right here.

That's a tiny little
thing.
Exactly.

It's about the size of a pencil
lead, they're very small.

And they're sealed
into this thing?

That's right, exactly.

I see this little
closed chamber.
Yeah.

JOHNSON (voiceover):
The precious graphite pellets

are then sent to a mass
spectrometry lab to be analyzed.

So what happens at the
mass spectrometry lab?

Yeah, so that's where they
measure the ratios

of the various
carbon isotopes.
Uh-huh.

And those are the data
that we get back,

and we use those
to calculate the age.

♪ ♪

JOHNSON (voiceover):
It's the moment of truth.

After more than
a year and a half,

have Kathleen and Jeff
managed to find out

the age of the footprints?

So tell me, what were the
dates of those footprints?

We were able to document
that humans

were in White Sands
National Park

between 23,000 years ago,

and about 21,000 years ago,

JOHNSON:
23,000 years ago?

That's way older than there's
been good evidence

for humans in North America.

It's about 10,000 years older

than sort of the established,
sort of,

thought of when humans arrived
in the Americas.

JOHNSON:
And you got tracks at more
than one layer,

which means that
wasn't just one group of people

at one moment in time.
No.

That it was many groups
of people over a lot of time.

SPRINGER:
2,000 years.

I mean, 2,000 years itself

is a long duration.
It is.

But the fact that they were here

23,000 thousand years ago...
Yeah, crazy, huh?

JOHNSON:
Blows my mind,
I mean...

SPRINGER:
It blew our mind!
(laughs)

That's like 10,000 years
before Clovis.

SPRINGER:
Yes.

that's like the entire length
of human civilization

before Clovis.

SPRINGER:
Yeah, go figure.

This is not a subtle result.

♪ ♪

(voiceover):
If these dates are correct,

that would make the White Sands
footprints

the earliest direct evidence
of humans

ever found in North America.

PIGATI:
This is the Last Glacial
Maximum.

This is when the ice sheets
were at their maximum,

and it's been thought that those
ice sheets

blocked people from coming down
into North America.

And what we found was
that the people

were already here at that time.

JOHNSON:
So you couldn't be blocked
from getting here

if you're already here.

SPRINGER:
That's right.
If you're already here.

JOHNSON:
And if you've been here
for a couple thousand years?

SPRINGER:
Right.
Yeah.

JOHNSON:
What did you think when
you saw the results?

Holy...

(laughter)

It was pretty much like that.
I mean...

There was words that were spoken

that were emphatic words.
Wow. Just wow, yeah.

♪ ♪

JOHNSON (voiceover):
But some experts question
these results.

They're troubled by the lack

of additional
archaeological evidence

of this ancient population.

Others say the dating method
could be flawed

arguing that the sediment layers
may have been disturbed.

Or the seeds may have absorbed
older carbon

from surrounding groundwater,

which could skew
the carbon dating.

This is an extraordinary
discovery.

How confident are you

in the quality of the dates
that you've achieved?

We're very confident...
These, these ages,

we were able to reproduce them
extremely well.

They maintain what we call
stratigraphic order.

Basically, the oldest at the
bottom, youngest on the top.

And even though some
of these samples

were only separated by a
centimeter or two of sediment,

they still maintain that order,
and that's one of the,

one of the, one of the key
things that we wanted to see.

And so it's not just what
we see in the lab,

but it's also what we see
in the field taken together

is really what
makes this powerful.

JOHNSON:
This is a huge discovery,
how do you feel?

(laughs)
Exhausted!

(laughing)

♪ ♪

JOHNSON (voiceover):
If the results are correct,

then these prints could have
been left behind

by some of the earliest
known Americans.

Back at White Sands,
I was curious to find out

what Kim Charlie and Joe Watkins
make of the discovery.

So now that there are
dates of 23,000 years ago

with Native American footprints,
how does that make you feel?

WATKINS:
It's just amazing.

We talk about having
always been here,

it's just remarkable to put
that much of a movement

further back in time.

So now we've added another

6,000 to 8,000 years

to what archaeologists have
told us was

the time depth of our history.

And so this keeps putting
that history back in the news,

keeps telling people,
"Well, yeah,

you've been here 500 years,
we've been here for 20,000."

Here's our proof, you know?

Footprints,
footprints of our ancestors.

You know, that goes to show,
we were here.

We were here on this earth
a very long time ago.

♪ ♪

JOHNSON:
But if humans were here
23,000 years ago,

how did they get here?

At that time,

the corridor between
the ice sheets did not exist.

So humans might have followed
the Pacific shoreline,

possibly by boat,

a route known as the
"kelp highway."

But how exactly
they would have made it here

during the Ice Age is still
unknown.

JOHNSON:
These footprints tell us
that people were here

during the Last Glacial Maximum.

So how, how do you think
they got here?

WATKINS:
I think probably the
coastal highway is the best bet.

Many old sites are going to be
submerged under water now.

So I, I think that's where
we need to look.

♪ ♪

JOHNSON (voiceover):
Whatever the answer,

there's no doubt that these
astonishing discoveries

are another step forward

in scientists' understanding
of human history.

And perhaps they could also
shed new light on humans' role

in the extinction of
Ice Age animals.

So where does this leave us?

For many years, we thought that
the Ice Age animals went extinct

about the same time that people
got to North America.

Now this site is telling us
something very different.

Basically what we're seeing is
that humans were here

more than 10,000 years before
the extinction of the animals.

So the question of was the
extinction caused by climate,

or people, or both,

has just become a much more
complex problem to solve.

♪ ♪

One theory is that when humans
arrived on this continent,

their numbers were too small

to make a big impact
on the wildlife.

But at some point,
populations increased,

and they developed
better hunting techniques.

Was this what eventually spelled
the end for the animals?

People have always thought
it was either

climate or people that caused

the extinction of the Ice Age
megafauna.

What do you think?

You know, I...
we really don't know yet.

But what we do see, you know,
without a reasonable doubt,

is that, you know,
around 12,000 years,

the area starts to dry out,

the lake dries up
and then the dunes form.

So climate change might have
been influencing that as well.

Maybe someday we'll,
we'll find out.

We might not ever learn.

But, but you know, the
exciting thing about White Sands

is there's thousands
of prints to study.

So, you know, the secret
might be locked there

somewhere in the sand.

♪ ♪

JOHNSON:
The unique preservation

of these ancient footprints
could yield more clues

about the lives of
Ice Age Americans.

SPRINGER:
We're very excited because it's,
it's kind of

the tip of the iceberg,
you know?

White Sands is still there.

Those tracks are still there.

They're eroding out every day,
every minute.

And we get the opportunity to go
back and, and to learn more.

JOHNSON:
So the research goes on, then.

Yeah, it goes on, sure.

PIGATI:
Yeah, this is just the
beginning, that's exactly right.

It's a tremendous opportunity.

It... it's opening up
the world of archaeology

way beyond where it's been.

It's going to give a new
generation of archaeologists

something more to shoot for,

to see whether we can go back

any farther than 23,000 years,

or whether this, in and of
itself, is the threshold.

♪ ♪

♪ ♪

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♪ ♪

♪ ♪