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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 humanbeing,

who stood basically
where I'm standing.

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...

...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.

And in this frozen north,

small groups of travelers

dispersed ever eastward

and found themselves stepping

into a new land.

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...

...that hint
at how they survived.

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.

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...

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?

Yes.

At the back of a cave
digging mud is...

...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 boneit 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.

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 thinkit 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.

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.

And their elders
gave this person a name.

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.

By hunting in packs,

wolves can bring down prey
far larger than themselves.

A person,
especially on their own,

would be highly vulnerable.

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?

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

My shoulders
are a little bit tense.

But, given time,

wolves are able
to habituate to humans.

Hello.

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...

...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.

Fossilized footprints.

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.

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.

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.

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

Yeah.

It's always scary
when you start these things.

You've got to

take them out.

There's a subtle difference

between the soil
in the print.
Yeah.

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.

...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.

The early people
of the Plains...

...probably would have given

these prehistoric mammals...

...a wide berth.

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.

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.

Many hunts would have ended...

...in failure.

But we know
sometimes they succeeded,

because they left
a massive clue.

Skeletons of megafauna.

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.

Woolly mammoths
could not effectively

chew or digest
these woodier plants.

And as their environments
transformed,

the giant herbivores declined.

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.

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.