♪ ♪ ELLA AL-SHAMAHI: By around 25,000 years ago, ancient humans had reached almost every part of the globe.

And then people stepped into a new world: the Americas.

♪ ♪ These are the footprints of an actual human being, who stood basically where I'm standing.

♪ ♪ (slide projector clicks) Where and when did Homo sapiens first arrive in the Americas?

They were here at one of the coldest moments that Homo sapiens had ever known.

What did they encounter when they began to explore this new continent?

And then look at these teeth-- look at these canines.

They're the stuff that nightmares are made of.

The resilience... (mammoth bellows) ...and innovation... ♪ ♪ ...that humans needed to survive their first journeys through the Americas... ...would shape the modern world in ways they could never have predicted.

More and more of us were quite literally putting down roots.

"Human: Into the Americas"-- right now, on "NOVA."

♪ ♪ ♪ ♪ AL-SHAMAHI: For much of the last 300,000 years, our species, Homo sapiens, lived in a world inhabited by other types of human.

♪ ♪ We hunted and foraged for food alongside many of our human relatives.

But one by one, we out-survived them and spread across the planet as small bands of nomads until we'd reached almost every corner of the globe.

♪ ♪ But there was a great landmass that was still unknown to us.

♪ ♪ ♪ ♪ It's possible humans took different routes to first reach the Americas.

But during the last ice age, sea levels were much lower, and so archaeologists believe the main approaches passed across a vast land bridge connecting Asia and North America: Beringia.

(wind blowing) And in this frozen north, small groups of travelers dispersed ever eastward and found themselves stepping into a new land.

♪ ♪ ♪ ♪ ♪ ♪ (gulls squawking) If you were asked to conjure up in your mind a world that was magical, that was pristine, that was primal, you'd imagine something like this.

The northwest coast of America absolutely takes your breath away.

♪ ♪ We don't know exactly when humans first arrived in North America.

Some archaeologists believe it was likely around 20,000 years ago, while others think there is evidence the first Americans were here thousands of years earlier.

But either way, it was a time when the continent was much colder than today.

They were here at one of the coldest moments Homo sapiens had ever known.

And the landscape would have looked so different.

There would have been very few trees, and as far as the eye could see, there would have been barren, icy rock.

They knew how to survive in the wide-open icy plains of Beringia, where they'd come from.

But their new environment was different in a few crucial ways.

♪ ♪ The northern half of this continent was covered in towering, impassable ice sheets reaching as far south as the Great Lakes.

From here, on the northwest coast, it blocked routes into the deep interior, mostly confining people to the ice-free land nearer the coast.

♪ ♪ All that's left from their time here are footprints, stone tools, and animal bones.

Now, we know that they sometimes would have hunted seal.

They would have eaten fish.

They would have eaten sea birds if they could catch them.

Only tiny fragments of evidence remain of the early inhabitants of this area... (slide projector clicks) ...that hint at how they survived.

(slide projector clicks) ♪ ♪ And while the ocean off this northwest coast offered them sustenance... ...the strip of land between the shore and the ice sheets promised new opportunities to find food... ...but also hid unexpected new dangers.

♪ ♪ (grunts) (inhales sharply) This is a now-extinct predator, and it would have roamed these parts in the Northwest when the first people arrived in the Americas.

And they actually call it the short-faced bear.

And there is nothing short about this bear.

When it stood on its hind legs, it would have been about 11, 12 feet tall, that's about four meters.

And so, it would have made the grizzly bear look actually somewhat manageable.

And then look at these teeth.

Look at these canines.

They're the stuff that nightmares are made of.

And when it bumped into humans, it must have been absolutely terrifying.

And just like those humans, these bears, too, would have been hungry.

♪ ♪ The early people of the Northwest did not always run from the predators that roamed this land.

Instead, it seems sometimes they went on the offensive.

♪ ♪ Evidence of this remains in caves along the Canadian coast.

Here, archaeologists sift through the muddy layers of time... DUNCAN MCLAREN: Is that what Jim had or... AL-SHAMAHI: ...to find out more about the risks these early people took to survive.

You know when people talk about archaeology?

(laughs) Yes.

At the back of a cave digging mud is... (laughs): ...is, this is the hard stuff.

One thing that has been found in a number of caves on the northwest coast is, uh, spear points in association with bear bones.

Yeah.

And these date as far back as 13,000 years.

Mm.

Is, so, is this one of these spear points?

This is a fragment of a spear point that was found in a cave not too far from here.

Yeah.

We have uncovered a bone in the wall of this unit, and it's 20 centimeters below the surface.

And, uh, so, I'm going to pull it, and we'll see if it moves.

All right.

And we don't know what species it is or what bit of bone it is?

Uh, there's not enough here to know for sure.

Yeah, yeah.

But it is a pretty big mammal, for certain.

Oh, yeah.

Oh, it's not ending.

(chuckles) Just make sure it slides out.

Ah, it's a rib, isn't it?

Looks like... Looks like a rib.

Yeah.

Yeah.

So, that could be a bear rib.

It's probably most likely what it is, 'cause it's quite robust.

How amazing.

What age do you think it is?

Well, we have some other samples from above where this bone is.

Yeah.

And they're coming back, uh, around 14,000 years old.

Okay, so it's old.

So, it's, could be the same age or older.

Yeah.

You know, one of the most wonderful things about archaeology is that sometimes you uncover something that hasn't seen the light of day in thousands of years, and in this case, well, maybe 14,000 years.

Well, we're interested in where bears were hunted in the past.

And in the winter, when there's, there's not as many resources around, and people are feeling a bit hungry, knowing where there is a bear den is quite a valuable thing, 'cause you can come up there and dispatch the bear.

You'll have a load of meat, fur, as well as bones.

AL-SHAMAHI: One theory of how they hunted bears comes from studies of the Native peoples of this region and North Asia in past centuries.

MCLAREN: Essentially, a hunter would go with a, a party to a cave, smoke the bear out of the cave, and entice that bear to attack a single hunter.

That hunter would be armed with a bracing spear.

Uh, bear would come to take the hunter up in a bear hug, which is a common thing that they do.

Yeah.

And the idea is, a bear would take that hunter and essentially, give him a good crushing.

The hunter, at the same time, would brace the spear on the ground and aim it at the bear's heart.

And so essentially... Oh.

...the bear would take the hunter and the spear into the bear hug, thereby spearing itself through the heart.

♪ ♪ AL-SHAMAHI: A successful bear hunt could have meant food through the winter.

♪ ♪ But it was a risky way to make a living.

♪ ♪ Scientists have worked with the Tlingit people of Alaska to study the fascinating fossil remains of one of their ancestors who lived around 10,000 years ago.

(slide projector clicks) And their elders gave this person a name.

(slide projector clicks) Shuká Káa.

This is the bone cast of Shuká Káa's pelvis and jaw.

And there's so much we don't know about this person.

We don't know about their family life.

We don't know if they had children.

But the amazing thing about bones is that they can tell a story if you know how to read them.

We know that this individual was a male.

We can tell that from various features, like the squareness here of the chin, like the back of the mandible, like the angle here, on the pelvis.

On a female, you would typically expect that angle to be much wider.

And it's kind of sad, because you can also tell quite a tragic story on the bones, as well.

If you notice here... ...that is a puncture wound, and it fits quite well with the canine of a bear.

Spear points found near Shuká Káa suggest he might have met his demise while hunting those bears.

The dangers those humans faced in order to survive are hard to imagine for most of us in the modern day.

But their relationship with nature had been slowly shifting.

Thanks in part to a surprising helper that they may have brought with them.

♪ ♪ (wolves barking, howling) By hunting in packs, wolves can bring down prey far larger than themselves.

A person, especially on their own, would be highly vulnerable.

SHELLY: Good girl, yeah!

It's unusual to have them all just around, hey?

Okay, come on, let's go.

AL-SHAMAHI: Wolves are, and always have been, wild animals.

Shelly, am I able to come a bit closer?

Yep.

I think the question is how close?

(chuckles) It's funny, I can feel it in my shoulders.

My shoulders are a little bit tense.

(voiceover): But, given time, wolves are able to habituate to humans.

Hello.

Hello.

(voiceover): Perhaps beginning as far back as 40,000 years ago, probably in Siberia, before humans had even reached North America, the threat they faced from wolves began to transform into something different.

Now, we're not exactly sure of the details, but it might have gone something like this.

Wolves would gather around human campsites.

Now, at first, maybe humans were terrified.

Maybe they thought that they wanted to eat them.

But actually, some of those wolves weren't interested in that at all.

They were looking for scraps.

And as they were doing that, maybe they started fending off other predators and protecting our combined territory.

And because of this, humans started tolerating some of the least aggressive, some of the most docile of these.

Maybe they even started feeding them.

In more than one place and time, our ancestors reshaped wolves into dogs.

And began to use them to guard our camps... ...hunt prey, and pull sleds.

Generation after generation, we selected the most docile animals and reared their pups... (dog barking) ...driving the evolution of a cooperative behavior that suited our needs.

This marked a turning point for the human species.

Living with dogs helped us hunt for food and survive.

It gave us this much-needed edge over hunger, but it also marked this profound and completely unprecedented shift in our relationship with nature, because never before had any living thing, whether plant or animal, been domesticated.

This was a complete first.

♪ ♪ Domestication would later become a hugely important factor in our species' fortunes.

But powerful forces far beyond the control of any human were about to open new passageways leading deeper into the North American continent.

And as people migrated beyond the mountains and glaciers... ...they would be forced to find new ways to survive.

♪ ♪ ♪ ♪ ♪ ♪ The first people to enter into the Americas were coastal people in the Northwest.

But it's likely that they eventually traveled incredibly rapidly down south, all the way to Central America, and then carried on all the way to the tip of South America.

Because remember, they were coastal people.

It's likely that they were using some kind of seafaring methods.

Very little evidence of these seafarers remains.

Rising sea levels at the end of the ice age submerged many of the coastal sites they might have occupied.

But it's thought that very early on, some of them would have branched off from this sea route and entered the continent.

Then, around 15,000 years ago, the climate began to warm.

The ice sheets and glaciers started to retreat, and as they did, the last major barrier blocking routes into the continent fell, opening new routes in and triggering a fresh wave of human innovation.

More people started traveling into the interior of the country and finding these completely new landscapes.

Whether humans first reached the interior during the height of the ice age or thousands of years later, after the thaw, is still uncertain.

But some of them left traces here in New Mexico.

(slide projector clicks) Fossilized footprints.

(slide projector clicks) Left in what was once the muddy shore of an ancient lake.

♪ ♪ They've become the subject of some of the most groundbreaking, but also most hotly debated, research in archaeology.

Thousands of footprints have been found here, among them the prints of a small adult and toddler side by side, possibly a mother and child, discovered in 2018.

For a long time, the dominant theory had been that humans were not able to penetrate the interior of the continent until the northern ice sheets had retreated.

That would mean the oldest these footprints could possibly be is around 14,000 years old.

But dating research published in 2021 suggested the footprints went back as far as 23,000 years ago.

If true, it would mean humans were able to reach the North American interior almost 10,000 years earlier than many scientists had long believed.

Well before the melting of the ice sheets.

The very early dates are controversial.

Further research will be needed to confirm how old the White Sands footprints truly are.

♪ ♪ But the people who left them are likely to have been part of one of the very earliest waves of what was to become thousands of years of human migration inland.

♪ ♪ Where there is now desert, they saw rich grasslands.

The fossilized footprints of these continental pioneers reveal what kind of a world they'd stepped into.

These are the footprints of an actual human being who stood basically where I'm standing.

And we think she was a female.

And if you look closely at those footprints, what you see is that at times, the footprints, they get broader and they slip a little in the mud.

♪ ♪ (slide projector clicks) And that's because she was carrying a child, sometimes on this hip and sometimes on this hip.

Then at other times, she stopped and put the child down, and you end up with two sets of footprints.

(slide projector clicks) And she walked for at least a kilometer north and then heads back south.

And I just can't think of anything more, more human than a mother and a child walking together, and a mother carrying her child.

And it's interesting, 'cause this whole journey has been us tracing the footsteps of our ancient ancestors.

And in a moment like this, that's actually literal.

♪ ♪ Archaeologists are finding more of these footprints hidden beneath the hard-packed sand.

It's allowing us to piece together an ever more detailed snapshot of what happened in the moments captured here.

MIKE STOWE: Let's see if we can define the footprint a little bit.

MATTHEW BENNETT: Yeah.

It's always scary when you start these things.

You've got to take them out.

STOWE: There's a subtle difference between the soil in the print.

Yeah.

BENNETT: It's looser.

It's a little damp, so it's gonna smear a bit today, but it will come out.

You see it so... So clearly.

Okay, so how have you... So, you've just traced along the... I, I just, I've literally just broken the surface with a dental pick.

Yeah.

And then, this particular example just brushes out with a little bit of encouragement.

Yeah.

You can see the contrast between the white... Yeah.

...and the fill in there.

I'm removing the... AL-SHAMAHI: Wow.

BENNETT: ...the sediment that's blown into the footprint.

So, we think she was walking quite quickly, then?

Yeah, she's walking at about 1.6, something like, meters per second.

Wow.

And, and a comfortable, normal sort of walk is about 1.3 to 1.5.

So, she, she's moving, and this surface is wet.

It's slippy.

We do know that this was a, a mission.

They were on a mission.

Yeah.

They were moving quickly.

Yeah.

At speed, for whatever reason.

And the footprint, um, tells that story.

♪ ♪ AL-SHAMAHI: We don't know why these humans were in such a hurry.

♪ ♪ But the footprints here at White Sands can tell us more about the world they were living in... ...because theirs were not the only footprints found.

Criss-crossing the human footprints are tracks from a giant sloth.

And other nearby footprints include those left by mammoths, each one around two feet in diameter.

This landscape would've been filled with mammoth and mastodon and saber-toothed cats, just huge animals.

They would have dwarfed us.

The mammoth alone would stand at about four meters high, that's about 13 feet, at the shoulders, and the mastodon were only slightly smaller.

For the humans here, this was their new world.

(slide projector clicks) The early people of the Plains... (slide projector clicks) ...probably would have given these prehistoric mammals... (slide projector clicks) ...a wide berth.

(birds calling) ♪ ♪ But they must have realized that those animals also represented opportunity.

That these giants could provide them with food.

But how on Earth could people hunt them?

One animal still exists which gives us a sense of just how difficult that would have been.

♪ ♪ This beast can sprint at up to 40 miles per hour.

The male's horns are over two feet long.

And 14,000 years ago, these bison had an even bigger prehistoric relative roaming these parts.

(whispering): Absolutely incredible, but they're also so big.

They're about one ton in size.

And the giant bison, the one that's now extinct, but would have been around back then, was up to 50, 50% bigger.

♪ ♪ To hunt those prehistoric bison, and the even larger megafauna that dwarfed them, early hunters likely used a number of different strategies.

But many of these would have relied on getting close enough to deal a powerful spear thrust.

♪ ♪ ♪ ♪ (animals roaring and bellowing) Many hunts would have ended... (animal roaring) ...in failure.

But we know sometimes they succeeded, because they left a massive clue.

(slide projector clicks) Skeletons of megafauna.

(slide projector clicks) Some clearly killed by humans.

Humans would have exploited some megafauna, some large land animals, on the coast.

But it was once they hit the interior that they saw them on a scale like something else in terms of their sheer numbers, in terms of their diversity.

♪ ♪ We don't know for sure how dependent the early North Americans were on hunting the megafauna.

♪ ♪ Or exactly how they hunted those giant animals.

♪ ♪ But they offered a huge potential source of meat for people to eat.

And it seems that hunting was shaping society here.

♪ ♪ This is absolutely stunning.

It's one of the most striking spearheads I've ever seen.

It's... It's so well-crafted, and it shines, and it looks like it was made of glass, but actually, it's made of quartz, and it's sharp.

And yet, it doesn't have any signs that it was actually ever used.

And that, along with the fact that it's so beautiful, suggests that it was ceremonial.

Now, when you've got an everyday object, and it's made to look so, so beautiful and so striking, it implies that it had become a symbol.

We're not sure of what.

Perhaps of how important hunting was, but perhaps of a cultural identity, perhaps of who they were.

♪ ♪ Feasts could bring different communities together and cement social ties.

Sharing meat would have fostered cooperation.

♪ ♪ The megafauna may have been a central part of people's culture.

♪ ♪ But their world was changing.

♪ ♪ The end of the ice age had created a warm world of plenty across much of the continent, and that shift was now beginning to have an effect they could not have foreseen.

It's thought that melting ice at the poles disrupted ocean currents.

And just as the world was entering a long-term warmer period, average temperatures in the Northern Hemisphere unexpectedly cooled by several degrees Fahrenheit.

Across North America, the vegetation had begun to alter in a number of different ways.

In some areas, trees and shrubs began to replace grassland and tundra.

(slide projector clicks) Woolly mammoths could not effectively chew or digest these woodier plants.

(insects buzzing) And as their environments transformed, the giant herbivores declined.

(insects buzzing) Over just a few hundred years, three-quarters of the large mammal species in North America became extinct, vanishing forever.

♪ ♪ Now, the main cause of the giant megafaunal extinction is climate change.

But it's likely that human hunting played a role, that it was this final nail in the coffin.

♪ ♪ The largest megafauna, that had been such a big part of these humans' lifestyle, culture, and their landscape... ...were now gone.

Bison, deer, and smaller game survived the climate upheaval, and people continued to hunt them.

But it's likely those people who relied most on the megafauna for food would have now shifted to exploiting a greater variety of resources.

One of which is something I personally would struggle with.

People needed to branch out and exploit every part of the food chain, all the way through to something you probably don't think of as food.

And that's acorns.

Now, these are incredibly bitter, because they're full of tannic acid.

And to get rid of some of that, what they would do is, they would firstly get rid of the shells.

And then they would grind the nuts up with water in the hopes of getting rid of some of that bitterness.

It's likely that the flour from these and the paste from these were some of the earliest processed plant food.

We actually have some of the grinding stones preserved in the archaeological record.

And if you look at all this, it seems so clever, it seems so inventive.

And yet, it's a lot of effort to go to.

♪ ♪ But soon, humans across the world would invent a completely different way to feed themselves.

♪ ♪ And in the Americas, it's thought this began in tropical forests to the south.

♪ ♪ ♪ ♪ Tropical forests are places of rich bounty, but where the earliest inhabitants had to make their food choices with great care.

This place, it has... It has real challenges.

There are plants, so many of them look edible, and yet some of them are definitely poisonous.

It requires a process of trial and error to find the actual food.

It was in a forest-- archaeologists think in present-day Mexico-- that a momentous change took place.

And it began with the simplest of actions.

Every so often, someone would have come across a plant that was safe to eat and would have sought out more of it.

(birds chirping) An example of this is this grass, called teosinte.

Now, the seeds are incredibly small and hard, but they can be ground up into an edible flour.

So, that same ingenuity that humans brought to acorns they were now bringing to this grass.

♪ ♪ Where people found teosinte growing, they encouraged it by weeding out other plants and collected the seeds for food.

This may have continued for centuries.

Until one individual would have become the first person in the Americas to do something completely original with a teosinte seed.

♪ ♪ There is something so magical about planting a seed, watering it, and hoping that it sprouts and becomes a tiny, little, delicate green shoot.

And there would've been somebody who planted the very, very first seed.

And they would've, they would've known that it would require effort and care and protection from herbivores if it was to ever become something big enough to feed their families with.

And anybody who's ever had an allotment or a garden or a balcony knows how much care and commitment goes into it.

♪ ♪ This was an idea whose time had come.

Because it wasn't only happening in the Americas.

Humans all over the planet were starting to plant seeds and grow them for food.

And it was an experiment that was beginning to pay off.

Because across the world, the people who did this were creating a more predictable way of feeding their families, triggering a pivotal moment for our species.

♪ ♪ In different places all over the Earth, humans were inventing farming.

Probably first around 10,000 years ago, in the Fertile Crescent of the Middle East, where they domesticated wheat.

Then rice in China.

Sugarcane in New Guinea.

Farming emerged independently in separate locations across the globe, Central and South America among the first.

Farming was a way for humans to actively manage nature in a way we'd never done before.

Here in the Americas, people created what would become one of the three most important staple crops for feeding the world.

Because as the early farmers planted and harvested teosinte, they began to shape it into a new kind of plant.

Every so often, a genetic mutation would arise in teosinte that would actually be quite beneficial for humans.

That would give rise to, say, larger seeds, or more seeds, or sweeter seeds.

And perhaps most important of all, would get rid of the hard seed covering, and humans started selecting for these better varieties.

And over thousands of years, they created something new that looked very different from teosinte, because they created maize.

It was no longer a wild plant.

It was now a domesticated crop.

♪ ♪ The invention of farming in different parts of the world was to set in motion a monumental global change that would go far beyond how we fed ourselves.

♪ ♪ Because although there was a variety of semi-nomadic lifestyles in which people now used domesticated plants in different ways, they all had one feature in common.

Even if you went away for some time to hunt or gather other foods, to benefit from the crops you'd planted, you eventually had to return to the place you'd sown them.

♪ ♪ The clue is in that word: plant.

To be put down in one place.

And just like the plants that they grew, those early farmers would've had to have adopted a very similar lifestyle, because you couldn't exactly keep moving if you had to tend to your crops.

And so, for the very first time since the birth of Homo sapiens, we were no longer a completely nomadic species.

More and more of us were quite literally putting down roots.

♪ ♪ Farming supercharged our capacity to fuel human activity, and what emerged was extraordinary.

♪ ♪ Here in Peru, there's a place where one group began a new way of living on a scale unprecedented in the Americas.

♪ ♪ The stepped pyramids of Caral were once lost under the desert sand.

Archaeologists have uncovered a vast complex of ancient structures.

The remains of what's thought to have been the first city in the Americas.

And what made it possible to build these extraordinary edifices were the fields of crops that surrounded them.

Caral became an immense hub for trading harvested maize, cotton, and fish from the coast.

It represented a new path humans could take towards permanence and stability that would become possible because of agriculture.

♪ ♪ But it's likely many of the people in this region at that time still lived as hunter-gatherers.

And as they gazed upon this new way to exist, would they have wondered if this was the choice they wanted to make?

I just can't help but think, what would it have been like for people visiting it for the first time back then?

Because they would've never seen a city before.

It must have been so alien to them, it must've looked like a place from a different world.

This was a commitment to a static way of life.

And yet, we don't consider how tumultuous the process might have been, how much social upheaval might have been involved.

Because for those who chose to lead this life, it must have come with a huge cultural shift, because humans were becoming an urban species for the very first time.

Humans around the planet stood at a crossroads.

For most of the 300,000 years our species had existed, we followed a variety of nomadic hunter-gatherer lifestyles.

But in the space of just a few millennia, a completely new way to live had become possible.

Farming in settlements offered humans an alternative to lives spent hunting and gathering as nomads.

It was the dawn of a new era that would transform the world forever.

♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪