Ice Age Footprints

♪ ♪ 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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