Origins of Us (2011): Season 1, Episode 3 - Brains - full transcript

[Light music]

The shape of your face.

Walking on two legs.

The way you see the world.

What makes you
the person you are?

[Dramatic music]

The story of each and
every one of us can be traced

back millions of years to
the plains of ancient Africa.

The answers to the
question what makes us

human lie buried in
the ground in the fossils

and other traces
of our ancestors,



but also lie deep
within our own bodies,

in our bones, flesh and genes.

As an anatomist
I'm fascinated by

the way our bodies
have been sculpted

by our ancestor's
struggle for survival

But why did we leave behind
the other apes in the forest,

to become the only one
of our kind left today?

How did living into old
age and learning from

each other shape our
large, clever brains?

[Laughing]

The way our brains work
today, the way we think,

feel and behave, is a
direct consequence of

our ancestor's
struggle for survival.

But where other
humans species died out,



was it really our brains
that gave us the edge?

I want to find out
how our brains led us

to be the successful,
global species we are today,

and why we are the only
humans left on the planet.

[Light music]

Our bodies are amazing machines,

honed over millions
of years of evolution.

But our basic flesh and
bones aren't that different

from our closest ape
relatives, chimpanzees.

Fundamentally, we
are just another species

of ape, but we do feel
ourselves to be different,

to be special, and
that comes down to

the very striking
difference between us

and any other species on
earth, and that lies up here.

We are creatures of the mind.

We have an ability to
think, imagine and create,

that has changed the world.

We have the ability to ponder

the very nature of
our own existence.

The emergence of the
human mind is one of

the great mysteries,
and it's a question

which has been tackled by
religion, philosophy and science.

And as a scientist, I believe
the answer is physical,

the mind is a
product of the brain.

And if we want to understand
the way we think and act today,

we need to look at
where we've come from.

[Light instrumental music]

This is the rift
valley in east Africa.

It's here that the
human story began.

This beautiful landscape
is incredibly important

to our story, so many
traces of our ancestors,

going back millions of
years, have been found here.

So if we want to
understand who we are,

there's not really a better
place to start looking.

Fossilized fragments
of bones unearthed here,

show that we are
the last of a large

and ancient family of
human-like creatures.

I'm going to use the
shadow cast by these trees

to recreate the
human family tree.

It's more like a bush than
a single branch of a tree,

but what I'm
really interested in

here is the size of the skulls.

To begin with, this is
sahelanthropus tchadensis,

from Chad, dating to about
six to seven million years ago.

He's an upright Walker,
but has a tiny brain,

about the same size
as a chimpanzees.

Around four million years
ago, we see something

a bit more human appearing,
the australopithecines.

This is australopithecus
africanus, a slightly bigger brain.

The next character is the
first member of our own genus,

homo, homo habilis, the
handyman, the tool maker,

at around two and a
half million years ago.

This is homo erectus,
brain size getting bigger,

appears around about
two million years ago.

Jumping forwards in time, we
get to homo heidelbergensis,

appearing around
600,000 years ago.

The brain size is
nearly as big as ours.

And finally, there's
just one twig surviving to

the present day, and
that is us, in fact this is me,

this is a replica of my skull.

So I'm going to
represent homo sapiens.

Looks like a fairly
decent brain size in there.

[Singing in foreign language]

The skulls of our
ancestors clearly

show an increase in brain size.

This important change
defines our story.

Our evolutionary
journey starts with the

chimpanzee like sahelanthropus,
in the forests of Africa.

The first apes to
walk out of the forests,

on two legs, were
the australopithecines.

And a million years
later, homo erectus,

with a very tall, very
modern looking physique,

strode out onto the
African Savanna.

And all this time
our ancestor's bodies

and brains were getting bigger.

Today our brains
are almost four times

the volume of our
earliest ancestors,

shaping the way we
think, and behave.

So why did our ancestor's
brains get bigger?

It's such a difficult
question and we're not

going to be able to answer it,

just by looking at their skulls.

But what we can do is
look at the wider context,

the environment they lived in.

What was going on around here at

the time our ancestor's
brains were expanding?

[Light dramatic music]

The rift valley has been called

the crucible of human evolution.

It's long been thought
that it was the struggle

to survive here, in
this harsh habitat,

that drove our evolution.

But recently,
scientists have been

taking a closer look
at the rocks here,

looking back in time to
see what the environment

was really like
millions of years ago.

And here on the
side of this hill is a bit

of that environmental sequence.

And you can read it.

This area here,
that I'm standing on,

this white, chalky
layer, is sediment

from the bottom
of an ancient lake.

And inside it, there are
microscopic algae diatoms,

that tell us that this
was a very deep lake.

As we move up
to this layer here,

the lake is drying out, it's
becoming much more salty.

There are diatoms in
here that are salt loving.

Then there's another
change and we've got

this yellow brownish layer here,

and that is an ancient soil,
and it's even got the root

patterns within it of the
grass which once grew on it.

And then this gray layer here

is volcanic ash from
a distant volcano,

the ash cloud billowed
over and dumped right here.

As we walk further up, we
start to get another white layer,

so we're moving
into a lake again.

And then the lake dries out,

and we're left this
time with a salt flat,

and you can see the
surface of it just there.

And then after the salt flat,

we're back to a lake again,
with this white sediment.

And that spans just 5,000 years.

- [Wind blowing]
- [Laughing]

During our evolution, this area

was changing every
few hundred years.

This rapid rate of
change would have made

it difficult to
adapt physically.

Instead, the apes
here learnt to change

something else, their behavior.

[Dramatic music]

Only those individuals
who were clever

enough to find new
ways of getting food

and water as the
landscape changed,

would have survived
and passed on their genes.

At the time our ancestor's
brains are expanding,

they were living in this
highly fluctuating environment.

And one theory says the
two are intrinsically linked,

that those big brains
allowed our ancestors

to develop highly
flexible behavior.

So rather than that
old tale of ancient

humans adapting to
life on the Savanna,

it seems that they were
evolving to be adaptable,

to be able to
survive and flourish

in a range of
different environments.

The way our ancestors
might have behaved

isn't preserved in the
fossil record, but clues

can be found in the behavior
of our closest cousins.

Here at Edinburgh zoo,

researchers have been
studying chimpanzees,

to get insights into the
origins of human intelligence.

Hello.

What do you think of me?

I'm a bit like you.

Chimps and humans
share a common ancestor

going back some
seven million years ago.

So if we compare
ourselves with chimpanzees,

then we can assume
that any behaviors

we share may have been
there in our ancestors,

whereas any
differences have arisen on

the way to becoming
modern species.

Like us, the chimps live
in a tight-knit social group.

But the social politics
here are being thrown

into turmoil by the arrival

of a new group
from the Netherlands.

Betsy herrelko is
studying how they react.

So coming up in
the middle is claus,

who's the dominant male
from the Dutch group,

and we've got kindia and qafzeh,

the dominant males
from the Edinburgh group,

who are just starting to
kind of throw ropes around.

And it looks like there's
a little bit of a face off.

[Alice] The Dutch
chimpanzees quickly assess

who's who in the
Edinburgh group,

working out whom
they can challenge

and whom they should suck up to.

Oh, and here we've got a
little submission from lianne,

so she's just showing
her bottom to him

and she's doing a
full bare teethed grin.

[Alice] In this changing
power structure,

making and keeping
political allies is crucial.

Here we have claus, with Sophie,

claus is the dominant
male of the Dutch group

and Sophie is a, a lower
ranking female over there.

And she's lower ranking,
but she's going up to him,

she's not appeasing him,
but she's trying to touch him,

just pay attention to him
and make sure she's in

his good graces, before
she feeds right next to him.

So is it really important
for the dominant chimp

to have alliances, to
have friends in the group?

It's very much like
our political system,

you have to play the
field and see who can

be your ally and benefit
you in some ways,

and when you might
need to drop them.

[Babbling]

And if you're clever
enough to work out whom

you can bully, and whom
you need to run away from,

you can work out
other things, like how

to get that apple from
the other side of the fence.

And it's mental flexibility
like this that enabled

our ancestors to adapt to
their changing environment.

Looking at the behaviors that
we share with chimpanzees,

it's clear that we've inherited

cunning brains
from our ancestors.

We are social animals,
we have this acute sense

of political awareness,
we understand what others

are doing and where they fit in

in the social system, and
we use that to our advantage.

But we differ from chimpanzees
in a very important way.

Our ancestors developed
a mental ability so useful

that it's written
into our faces today.

They say the eyes are
the windows into the soul.

And our eyes are unique.

We are the only
animals on the planet

which show the
whites of their eyes.

We can do something
that no other animal

on earth can do, we
can tell what somebody's

thinking just by
looking at their eyes,

we can literally
read their minds.

[Kids muffled talking]

It's something most of
us start to do naturally

from the age of about four.

Children use people's eye gaze

to tell what they're thinking.

So the first thing
I'd like you to do is,

can you guess
which sweets I like?

No.

I think this.

[Kids] Chocolate
mice, chocolate mice.

[Alice] You're so clever.

How did you guess that?

Because, 'cause
you, 'cause your eyes

were looking at them.

Oh!

And you're right.

Well that seemed very simple,

but in fact our
ability to read minds

goes much further than that.

We can tell when
people are happy,

or sad, honest, or deceitful.

This mind reading
means that we don't always

take things at face value.

So here's another quick test.

I've hidden a sweet under
one of the three cups.

Yeah, I thought of that.

Can they guess where it
is, if I tell them one thing?

I'll give you a clue, he
might be under the blue cup.

But my eyes tell
a different story.

- Green.
- Green.

The kids immediately
realized I was fibbing

and by reading my mind,
go straight for the sweets.

These children
are doing something

incredibly complex,
they must be thinking.

I know you want me
to think the sweet is

under here, but I think
you actually know it's there.

So they're seeing
through my deceit.

And this degree of
mind reading ability,

this understanding
ourselves and others

and what others are
thinking, is unique to us,

and it underpins all
of our ability to share

knowledge and
ideas with each other.

[Light music]

Our unique ability
to read minds is

thought to be linked
to one of the most

important ideas to emerge in our

evolutionary history,
learning to make tools.

The ability to make
stone tools is one of the

defining features of
humans, of our genus homo.

And tools like this were
made by the earliest humans,

homo habilis, going
back about two

and a half million years ago.

[Dramatic music]

Homo habilis wasn't
much like you or me,

he only had a brain
half the size of ours.

Yet he's the first ancestor
that we know had tools,

and that's why he's called
homo, meaning human.

And these tools enabled him to

overcome the challenges
of his environment.

These tools allowed
them to extend

their own biological
capabilities,

it was as though they were
arming themselves with the,

the tusks, the sharp
teeth and the claws that

they didn't naturally possess.

And crucially, those tools
meant that they could get

to a much wider
range of food than

you'd normally expect
an ape to be eating.

And over time, those tools
because more complex.

Within a million years, a
new species had evolved,

homo erectus, slender and tall,

with a larger brain
than his predecessors.

And that brain was being shaped

by his tool making technology.

Here at olorgesailie you can see

where homo erectus
people made their tools.

Incredibly, they still lie
scattered across the ground,

where they were
dropped by ancient

hands a million years ago.

Professor Rick potts has been
studying how they were made.

He thinks it's something
you really need to be taught

because it's far
from straight forward.

The principle here is
that you strike the edge,

and it sets up force that
goes through the rock,

and out from the
other side pops a sliver.

Oh wow.

- Okay?
- Yeah, that's a decent flake.

So there's, there's
your flake here.

So why don't you have a go?

Okay, I'll try.

All right then.

- There we go.
- Ooh, that's, oh,

- that's a nice one.
- Hey, there we go,

that's a good one.

- Look at that.
- Yeah, that's,

that's pretty typical of what

you would find
at a hand ax site.

And you can see the platform,

or the edge that you struck,

and this is the piece
that came off and the scar

- where the flake came.
- Yeah.

So in fact the hand ax,
when you're finished making it,

is going to be a useful
tool in its own right,

but the flakes that come
off it are also useful?

Well that's right.

The tool can be
the sharp flake itself,

or it can be at the sharp
edge of the hand ax.

That's why they
sometimes call it the, ah,

Swiss army knife
of the stone age.

Brilliant.

Learning to make a
homo erectus hand ax

is surprisingly complex,
and it's only really possible

if you understand your
teacher's aims and intentions.

You can just
imagine homo erectus

children sitting
there watching their.

- Yeah, exactly.
- Their, their dads

and possibly their mums as well

- making these.
- That's right,

- that's right.
- Hand axes

and learning how to do it.

Here is a real hand ax
made by homo erectus

from 900,000 years ago.

Look what you've
done, very similar to this,

so I think you've
done a great job.

That's brilliant, you see that?

It's my very own
hand ax, I made that.

[Light music]

The tool making
culture of homo erectus

was a turning point
in human history.

With tools to butcher meat
and protect themselves,

our ancestors were able
to spread into new territory

and find food and shelter.

For over a million
years the hand ax was

the cutting edge of
stone tool technology.

A hand ax, together with
the flakes that come off it,

constitute an incredibly
versatile tool kit.

And all these ancient hand axes

that are found
across the rift valley,

wouldn't be there
were it not for human's

ability to copy from each other.

Stone age culture gave
us far more than just tools,

it crystallized in us an ability
to learn from one another,

and to share knowledge.

Stone hand axes
and the more complex

culture that follows them,

tell us about the
behavior of our ancestors.

But they also do more than that,

they tell us about their minds.

Because in order to be able
to make a complex stone tool,

it certainly helps to
be able to understand

what other people are thinking.

But you also have to
have a mental image,

an abstract idea
in your mind of what

that tool is going to look like.

And it's been suggested
that this mental ability,

to make stone tools, is related
to something else, language.

- [Muffled talking]
- [Silverware clanking]

And the plant life
was out of this world.

Her job paid more
and it made sense.

Once the weather improves
I'll be on the allotment.

What's it called?

Brain's gone.

But I was never
very sporty at school.

We are unique in
our ability to speak.

But the moment when
human language first

evolved is shrouded in mystery.

Language is such an
important human characteristic,

but there's no direct
evidence of when it evolved.

We can't even look at the
vocal tracts of our ancestors,

they're made of soft tissue,
cartilage, muscles, ligaments,

membranes, they don't
fossilize like bones do.

The only certainty is
that language is central

to one human species
which emerged in Africa

around 200,000 years ago,
and that is us, homo sapiens.

Well I'd always wanted
to go to Machu Picchu.

[Alice] We use language
in every aspect of our lives,

from idle gossip to sharing
our deepest thoughts.

Go to Australia,
that's even worse.

Forming this range of
sounds involves many

parts of our anatomy.

This is a scan of my
own head and neck,

showing all the
anatomy which I use to

produce speech, from
the lips at the front,

there, to the teeth,
which are there, the pallet,

hard palate and then soft
palate at the back there.

And this enormous, massive
muscle here is my tongue,

which is very
important in molding the

sounds coming out of my mouth.

There's the epiglottis,
which protects the larynx,

the voice box, and
deep within the larynx,

the vocal chords themselves.

Bulb went from my outside
light, so he changed the bulb.

And on this amazing
real-time mri scan,

you can see them all in action.

Air from my lungs
is forced between my

vocal chords, causing
them to vibrate.

The sound passes
upwards and is molded by

my tongue and my lips,
emerging as speech.

♪ Aah ♪

♪ iee ♪

♪ ooh ♪

Feel like a bit of a loony.

Our ability to vocalize
our inner thoughts

gave our species
the power to teach

and learn at a level
of complexity no

other animal on earth can match.

Human language is so much
more than just a series of sounds,

it draws on something else
which seems to be uniquely human,

and that is symbolic thought.

When we name something,
we create an abstract

representation
of it, and crucially,

we can take that idea and
share it with someone else.

With language, ideas
are not just our own,

they become common property.

Using language to share ideas,

we could build on the
knowledge and culture

of those who had gone before us.

Over time, our brains
evolved to be much larger

than those of all our ancestors.

But there is a price to
pay for having a big brain.

[Moaning]

[Heavy breathing]

Giving birth is one of the
most painful and dangerous

experiences women
have to endure.

I've come back to the
hospital where I gave

birth to my first
baby 11 months ago.

And it's very
strange being here,

it stirs up a real
mix of emotions.

I can remember back
to, certainly fear and pain,

but also of course, immense joy.

But it does seem rather
odd, given that reproduction

is essential to the
survival of any species,

that for humans childbirth
can be so difficult and painful.

Allionna is giving birth
for the second time,

and although all
is going smoothly,

even a straightforward
delivery is challenging.

And that's all down to the large

heads of our big brained babies.

[Nurse] The contraction
is good, you rest now.

- Okay?
- Okay, I'll rest.

Mm, no my baby took
quite a while to appear.

Em, she started
coming and it took about

three and a half days
for her to actually emerge.

Em, and I definitely needed
help for that to happen,

it wasn't something I
could have done on my own.

- Long pushes.
- I can't.

- Go on, yes you can.
- You can, you can,

you should get the
baby out now, okay?

Breath in and push.

[Alice] Humans
are the only species

that need help to give birth.

- Keep going.
- Keep going.

[Alice] Our babies heads
are so big that it's astounding

they can get out at all.

- One more, one more.
- One more push, please.

- Go on.
- Okay,

when you feel the pain,
push against that pain, okay?

Push hard.

So you can see the
space through which the

baby has to pass, from
the inside to the outside,

and it is quite a narrow space.

If we look at the size
of the baby's head,

you can see that it is
going to be a pretty tight fit.

Now my baby got her
head stuck in that position,

which wasn't
particularly helpful.

Let's put her back in a slightly
more cooperative position,

and her head can now
drop down inside the pelvis.

But it's stuck again, so she
needs to tuck her chin in,

rotate round like that,
and then the back of

her head can come out,
and then the shoulders

can come out and
the baby is born.

[Screaming]

That's it, go on, keep
on going, keep going.

Keep going.

Come on, that's it, that's
my girl, well done, that's it.

Yes, well done, that's it.

[Nurse] Well done.

Hey, hello!

[Muffled talking]

We're born with
the biggest brain

our mother's anatomy
can cope with.

But to ensure that a baby
like Reuben can be born,

he has to come out before
his brain is really ready,

which means he's
completely helpless.

Well this is Reuben, he's
such a perfect little baby.

But compared with
most newborn mammals,

his brain is
relatively immature,

he doesn't have much
control over his body

and even less ability to make
sense of the world around him.

It will be about
eight years before his

brain reaches its full
size and he'll be in his

mid teens before
its properly mature.

Growing our big brains takes
time, and while it's happening,

our children need looking after.

And that has shaped our lives
in ways you might not expect.

[Light dramatic music]

To understand how
a long childhood

growing those big brains
has affected our species,

I've come back to Africa.

I've come to meet the hadza
tribe in northern Tanzania.

These are modern people,
but living in a similar way

to our ancestors,
and their lifestyle gives

us an insight into
how we all evolved.

I want to talk to the
women about something

which affects all
human societies,

it's a great concern to all
of us, and that's childcare.

Getting enough food to feed
everyone takes a long time.

Looking after young
children whose brains

are still developing
is hard work.

Nibala has five children and
she's got another on the way.

Nibala, how long did you
breast feed your babies for?

Yes, I've, I've got a baby
who is 11 months old.

Who is taking care of the baby?

My husband is taking
care of my baby.

[Speaking foreign language]

Who is breastfeeding

actually nibala, who
is breastfeeding?

Oh right, oh.

Um, she, I stopped
breastfeeding now,

so I breastfed her
until seven months,

and then now she is
a, is having a bottle.

[Translator] Will it grow up?

Yes, yes [laughs], yes.

- I think she...
- [Laughs]

I think she thinks
this is very strange.

And I think, you know,
I'm now looking at myself

and thinking, this
must sound really odd,

this must sound very
unnatural and very, very strange.

It is.

It's normal for
women here to have

a baby every two to three years.

Feeding the older
children while breastfeeding

is very difficult without help.

For nibala, the only
way she can collect

enough food is with
help from her mother.

As in many human cultures,

it's the grandmothers
than play a vital role in

caring for their grandchildren.

How important is
their grandmother in

providing for your children?

It's not even eight o'clock
and it's already blazing.

It's thought that the
need to have extra

help from older women
has actually affected

how long we evolved to live for.

Magdalena is in her 70s,

and helps to look
after five grandchildren.

[Singing in foreign language]

And magdalena isn't unusual.

Even without modern medicine,

many hadza live
well into their 70s.

[Speaking foreign language]

Having grandmothers
around like this to help

look after and provide
for the children is

such a great advantage,
and one that may

have driven the evolution
of our unique life histories

where women survive for decades

after their reproductive
years, after the menopause.

The fact that women
live long past the end

of their reproductive years
originally baffled scientists.

But it's now thought
that by living into old age

and looking after
their grandchildren,

grandmothers could
help their daughters

produce lots of children
in quick succession.

By living longer, our
species is able to breed

more quickly, in far greater
numbers than any other ape.

And this population
growth has ensured

the success of our species.

Grandmothers and
grandfathers would not only pass

on important information
to the younger generation,

but by supporting their
children and grandchildren,

they would help the
human population to expand,

and eventually,
spread across the globe.

With their tools, big brains
and growing populations,

successive waves of
human species left Africa.

First homo erectus,
the hand ax maker;

a million years later
they were followed

by another human species,
homo heidelbergensis.

In Europe they evolved
into the neanderthals;

and in Africa they
became us, homo sapiens.

And it was from
Africa that our species

spread out to
colonize the world.

With our large brains, we
flourished in new environments.

But we weren't alone.

We know from
fossils and archeology

that our pioneering
ancestors weren't

heading into virgin territory.

Around the world
there were other species

of humans already living
there when we arrived.

In Europe, homo
sapiens was entering

the territory of
the neanderthals.

Neanderthals were a species
of human very similar to us.

They were a physically
formidable competitor, heavily built,

with short limbs adapted
for the colder climate.

They may have been
strong, but they have

developed a reputation
for being dim witted.

Because within a
few thousand years

of homo sapiens arriving
in Europe, the neanderthals,

like every other human
species before, went extinct.

It's always been
thought the reason

for our survival was
our superior intelligence.

This is me, this is
my skull, which is a

perfect specimen, of
course, of a modern human,

and this is a neanderthal.

And I hope you'll agree that
they look distinctly different,

especially when
we look at the faces,

the neanderthal has a massive
brow Ridge over the eyes,

and then a sloped back,
a swept back forehead,

whereas I've got a
very slight brow Ridge,

if it's there at all,
and then a very,

very steep frontal
bone, a steep forehead.

The faces are very different,

but there's an
overwhelming similarity here,

and that is in the
size of the brain cases.

Neanderthals had about
the same size brains as us.

So if we're going
on brain size alone,

there's nothing to
suggest that I should

be any cleverer
than a neanderthal.

So if neanderthals
and homo sapiens both

had similarly large brains,

why is it that today
there's just us left?

To find out, I've come
to meet archaeologist

clive finlayson,
who's been studying

a site called gorham's
cave, in Gibraltar.

Today it's only
accessible by sea.

Thanks Darren.

This cave has revealed much
about the way neanderthals

lived and behaved,
compared with the way modern

humans were living
at the same time.

Yeah, it's amazing to
stand here and imagine

what it must have
been like when the,

the sea was so much lower
and so much further out.

There were times
when the sea would have

been all the way down
as far as that ship in,

in the distance there,
and all this would have

been the landscape,
you know, of,

of pine woods and
wetlands, a little paradise,

a little Eden for
the neanderthals.

[Alice] It used to be
thought that neanderthals

had a very limited diet,
mostly eating big game.

But the cave has revealed
some surprising finds.

[Clive] I can show you
little bits of marine molluscs.

[Alice] Yep,
little bits of shell.

The sea never came up here

so they would have
been transported.

And you can see the
little flakes of bits of flint,

they were transported
here by people.

It's clear evidence
that neanderthals,

at that point, are
eating marine molluscs,

one of these things
which is meant to be,

a specialty of modern humans.

Yeah.

Beyond the food
waste left behind,

the tools they used tell us
a lot about their intelligence.

This is a typical flake,
made by a neanderthal,

multi-purpose, but still got a
sharp edge as you can see.

- It's very sharp.
- So nice, nice for cutting.

The modern humans
tend to make these sort

of blades which are
more sort of long and,

and narrower
than, that the flakes.

Some people have made
this to be an important

distinction but, em, we
realize that it's probably

just a different
style of doing it.

Mm, so they're using
a different tool kit, ah,

but they're achieving
the same ends with it?

The evidence suggests that
they're just as intelligent as

we were, but maybe
did things a different way.

[Alice] It's clearly far
too simplistic to dismiss

neanderthals as being
too stupid to survive.

Further back in the cave,
clive has uncovered more

evidence of our extinct cousins.

So welcome to the
real gorham's cave.

Be careful, because it's
rained a lot and it's slippery.

But if you come along this way.

This is a huge cavern
that goes back 35 meters.

- Now...
- Can I get,

can I get in past there?

[Clive] You can get a little
bit in, yes, by all means.

[Alice] Get an idea of

- how deep it is.
- So what, what they had

was a large chamber

and they're sleeping
in there comfortably.

This is fantastic, I
mean this feels like it

would have been a very
safe place to spend the night.

[Clive] Absolutely,
it's a perfect choice.

These guys knew
what they were doing.

[Alice] It's back
here that clive made

his most important discovery.

[Clive] So are you okay there?

[Alice] Yep, yep.

In there, we excavated
a half a camp fire.

[Alice] Yep.

Made by neanderthals.

And we got radio carbon dates
to around 28,000 years ago.

And to date, it's
the last known site,

the last place where
the neanderthals lived

on the planet, is right there.

[Light dramatic music]

This is a really
special place this cave,

the archeology here
is quite remarkable.

But it's also very
emotive, it's quite sad to sit

here and know that
this was one of the last

places that the
neanderthals lived in.

So if they had
brains as big as ours,

and were just as clever as us,

why did neanderthals die out,
while we went on to flourish?

In the centuries before
the neanderthal's demise,

there was dramatic climate
change across Europe.

The woodlands that
neanderthals were used to shrank,

giving way to open landscapes,
where modern humans thrived.

Do you see the, the eventual
demise of the neanderthals

then really being,
you know, a lot of

chance but, but really being
down to climate change?

Well I think their luck ran out.

They were exploiting a kind
of environment that needed

some trees for cover, they
were good ambush hunters,

they were getting
close to their prey.

But they weren't
built, if you like,

to be out on the open plains.

It just happens
that that landscape

expanded at the moment
when those modern

humans have come
in, and they just tracked

these resources, so they
spread with that environment.

And as the modern human
population increased,

the neanderthal
population declined,

leaving small, isolated groups.

Something as simple
as a bad winter,

or a prolonged drought could
have easily wiped them out.

The more we learn
about the neanderthals,

the more like us they
seem to have been.

They were just another
human population

which, like so many
others, has died out.

But as the neanderthals
were disappearing from Europe,

something extraordinary
was happening amongst

the modern human
populations who replaced them,

a huge cultural explosion.

Over the next 30,000 years,

we would leave our
Mark on the world.

Creating wonderful art
and places of worship,

inventing farming
and engineering

to create a new world,
building civilizations,

mapping and
exploring the planet,

we mechanized and
urbanized and extended

our reach up to the stars.

In the blink of an
evolutionary eye,

we have created a
world for ourselves

which has changed
beyond recognition.

There is this great
mystery which lies at

the heart of human evolution,

and it has to do with the
way we use our brains.

Because for tens of
thousands of years,

our modern human ancestors
lived very simple lives

and made basic tools
out of stone and wood.

And then look at where we
are today, at what we can build,

and our technology, it just
seems utterly mind blowing

that we're the same species
which made those stone tools.

It's been suggested
that all this cultural

change must be linked to a
biological change in our brains.

But the latest thinking
suggests it's a product

of something far more basic,
a simple increase in numbers.

As populations increase,
ideas are passed on to more

and more people, and
there's a greater chance

that any inventions,
any innovations,

will get picked
up and will spread.

The ideas then take
on a life of their own,

competing with each other,
improving and proliferating,

and that is cultural evolution.

What's it called?

Brain's gone.

Over millions of years,
our brains evolved to

enable us to pass on ideas,
to learn from one another.

Oh wow.

And to read each other's minds.

[Singing in foreign language]

Combine that with
an ability to expand

our numbers
because we live longer,

with grandmothers helping to
raise our big brained children,

and what you have
is a perfect storm

of biological and
cultural evolution

that has taken us from
making simple stone tools,

to creating the vast
edifices of the modern world.

We have evolved to
think and behave in ways

that have turned out to
be incredibly successful.

We have an unrivaled ability
to cooperate with each other,

to communicate, to understand
what others are thinking

and feeling, and to generate
culture and technology.

And as our population grew,

so too did the cumulative
effects of people's

contributions to society,
generation on generation.

But all of those abilities
that make us human,

that bring us to
where we are today,

really come down
to just one thing,

one bit of each of us,

our amazingly complex
and clever brains.

[Light music]