40x07 - Decoding Neanderthals

[bunniefuu]

NARRATOR:
They were the brutes
of Ice Age Europe

Although a branch
of our human family tree,

they were seen as a dead end,
deep in our prehistoric past

They were called Neanderthals

Neanderthals have the mother
of all image problems

NARRATOR:
They eked out
a marginal existence,

hunting by brute force,
with only simple stone tools

They were considered primitive,
with no language, art

or the higher-level thinking
of advanced species like us

They lacked the same
intelligence as modern humans

NARRATOR:
They began to disappear


as modern humans, our species,
came on the scene

But this primitive picture
is being replaced

by a different image
of Neanderthals

It's bringing them
much closer to us,

as genetic evidence revises
our human family tree

and reveals their mysterious
presence right within our genes

We started to look at the
problem from different angles

They answer would come back,
"It's Neanderthal"

That was quite shaking to me,
and I thought,

"This must be
a statistical fluke"

NARRATOR:
Now archaeologists
are finding new evidence

to help resolve bitter debates

This is the smoking g*n

We have the case to settle
the controversy

NARRATOR:
In toolmaking, they're seeing
signs of language

There is some sort of advanced
talking going on

NARRATOR:
A new Neanderthal mind emerges

We're not talking about idiots

NARRATOR:
And if scientists are finally
finding the real legacy

of the Neanderthals buried deep
in our history and our genes,

what does it say
about all of us?

"Decoding Neanderthals,"
right now on N O VA.

Major funding for N O VA
is provided by the following:

Supporting N O VA and promoting
public understanding of science

And the Corporation
for Public Broadcasting,

and by PBS viewers like you

NARRATOR:
in the grip of an ice age

In harsh, unforgiving terrain

live members of an ancient
human species

The Neanderthals

It is a brutal time to be alive

Only the toughest survive

They were very muscular, short,
wide, very stocky,

very powerfully built

THOMAS WYNN:
They were hunter-gatherers

They had scarce game to find

Most Neanderthals
were probably dead

by 30 years old

So it was a brief, brutal life

NARRATOR:
Hunting was extremely dangerous

STRINGER:
They were
confrontational hunters,

so they had to get close in to
their prey with stabbing spears

This required
not only a lot of bravery

but a lot of sheer
physical strength

FREDERICK L COOLIDGE:
These Neanderthals could
bench-press 300 to 500 pounds

They had big thrusting spears

that they thrust into the side

of 2,000- and 3,000-pound
animals

NARRATOR:
The Neanderthals survived
the harsh conditions in Europe

for at least 300,000 years

Then, around 40,000 years ago,

a different human species
arrives on the scene

our species, h*m* sapiens.

They migrated from Africa,

spreading across
Neanderthal territory,

outnumbering them ten to one

Suddenly you've got two species

competing
for the same resources,

hunting the same animals,

collecting
the same plant resources,

wanting to live
in the best territories

and the best caves

NARRATOR:
After another 10,000 years,
the Neanderthals disappear

ED GREEN:
The story of the Neanderthals
is a m*rder mystery

They were there
and now they're gone,

and they go away

at about the same time as we are
showing up on the scene

NARRATOR:
So why did they vanish
while we survived?

For years, many scientists
believed we wiped them out,

a simple case of our brain
outclassing their brawn

This theory emerged
when archaeologists unearthed

the very first Neanderthal
skulls over 150 years ago

To scientists at the time,

skulls like these looked
primitive compared to ours

Chris Stringer
is one of the world's

preeminent Neanderthal experts

STRINGER:
We can tell a Neanderthal skull


We've got a very broad skull,

this double-arched brow ridge,

and perhaps
their most distinctive feature,

the middle of the face
is pulled forwards,

the cheekbones are swept back

NARRATOR:
One influential discovery
featured a skeleton

crippled by acute arthritis,
incorrectly reconstructed

with a hunched posture
and a shuffling walk

This early find helped shape
popular perceptions

of Neanderthals for decades,

launching a wave of images
of the Neanderthal

as a brutish caveman

Neanderthals have the mother
of all image problems

They're brooding,
they're stupid-looking

they have no personality

STRINGER:
They were reconstructed
as being much more apelike,

stooped, grasping big toes,

very hairy, head hung forward,

shambling in their gait

NARRATOR:
Critically, scientists believed
the Neanderthals lacked

the one thing that defines us
our brainpower

They lacked the same
intelligence as modern humans

NARRATOR:
With only limited stone tools

and no art or personal
ornaments, Neanderthals seemed

less advanced than modern humans

But was that really
the whole story?

Now, new discoveries in genetics
and archaeology are challenging

this traditional view
of the Neanderthals

[stones tapping]

Metin Eren has spent six years
studying Neanderthal technology

These Levallois flakes,

named after the place in France
where they were first found,

were the Neanderthals' tool
of choice

At first glance,
they look rudimentary,

the product more of luck
than judgment

But when Eren tried to reproduce
one, he got a surprise

I find the Levallois technology
much more difficult to make

than any of the modern
h*m* sapien technologies

It took me about 18 months
to master Levallois technology,

and this was
after I'd been flint-knapping

for a number of years

The fact that there
seems to be a goal involved

They're not simply
just striking flakes

to get a sharp cutting edge

NARRATOR:
Eren began to realize this
was no hit-or-miss process

He wanted to discover
just how they did it

So he turned to morphometrics,
a technique which analyzes

the exact shapes
and angles of objects

It revealed Neanderthals
must have used

a precise set of strikes
to turn a raw flint block

into a carefully shaped object
known as the core

The final crucial step involved
striking the core

with a single precision blow

Only if aimed just right would
this create the perfect flake

and a remarkably versatile tool

EREN:
I shape this in such a way

that the core has
a gentle convexity

such that the large flake
that comes off has a sharp edge

all around its perimeter,

and that enhances the utility
of this particular piece

in a number of ways

Because it's uniformly thick,
you can resharpen it

more times than you can
other types of stone flakes

We also found
that the Levallois flake

is statistically
more symmetrical

That means when you use it,
you basically reduce torque,

so it actually has
ergonomic properties

I can actually get
a lot more force

with each cut and each slice

I'll just put
a little more pressure

and the Levallois flake goes
right through it

and we got one big piece
of gammon

That took
about a minute and a half

No problem

This is an amazing tool

They were engineering their
rocks to get particular products

that have specific properties

They were able to discover
a technique

that is incredibly
difficult to do

It is just a testament to how
intelligent they must have been

to actually invent it
in the first place

NARRATOR:
Metin Eren's work reveals
the complexity

of Neanderthal toolmaking

But there's even more
surprising evidence

of sophisticated
Neanderthal technologies

Dutch archaeologist
Wil Roebroeks is studying

new finds,
one of them dating back

a quarter of a million years

This is a flint spearhead,

at its base,
a large sticky black mass

most likely used as a glue

Evidence from many sites
had already shown

how Neanderthals attached
stone flakes to wooden shafts,

first binding them
with sinew or leather,

then securing the binding
with a gluelike substance

This turned the flake and its
shaft into a robust weapon

ROEBROEKS:
What you see there is
a nice flint flake,

at least for an archaeologist,
a nice, sharp,

razor-sharp flint flake,
which is covered at the base

in this pitch material

It is a material that they used

probably in many aspects
of everyday life

NARRATOR:
At first, it was thought
this Neanderthal glue

was nothing more
than sap from a pine tree,

easy for them to find and use

But detailed analysis revealed
something different

It was a type of manmade pitch
from birch trees

Chemical studies have shown

that that material was produced
from heating birch bark

Neanderthals were producing
these pitches

So it is not something

like the stuff that you can
retrieve from a pine

when you hit a tree, the natural
stuff that comes out

NARRATOR:
This is the world's oldest
known synthetic material

It makes Neanderthals,
and not us,

the inventors of perhaps
the first industrial process

But how could an allegedly
primitive species

have done this?

To find out more, Wil Roebroeks
decides to mount an experiment

with a colleague,
Friedrich Palmer

They will try to replicate
the Neanderthal technique

of pitch extraction,

a complex process called
"dry distillation"

Crucially, they'll use
only materials available

to Neanderthals


an upturned animal skull
to catch the pitch

a small stone on which
the pitch would condense

some rolls of birch bark,
the source of the pitch

and a layer of ash
to exclude oxygen

and prevent the bark
from burning

Roebroeks and Palmer need
to heat the bark

to 400 degrees centigrade

Any less and it won't
produce pitch

Any more and it will simply burn

After eight hours, any pitch
should have condensed

on the stone within the skull

Yeah

Oh, look at that

Yeah, that's a bit dry

NARRATOR:
Today, Roebroeks and Palmer
manage to extract

only a tiny smear of pitch

That's not much

NARRATOR:
They are on the right track,
but it isn't nearly enough

to glue a spearhead to a shaft,
as the Neanderthals did

It seems this experiment
is on too small a scale

to produce enough pitch

Neanderthals must
have figured out

how to scale up the technique

in a way we haven't yet
reproduced

However they managed it,

the Neanderthals had
evidently mastered

a complex thermal process

The Neanderthals'
extraction of pitch

and their distinctive toolmaking

suggest their technology
was more advanced

than previously thought

What's more, artifacts
like these have been found

across a wide area of Europe

And this raises a question

How did Neanderthals communicate
these complex ideas?

Could it be they shared that
one ability we usually think of

as unique to us?

Language

One could infer that
there was some communication

maybe between generations
or between peers in a group

But language, of course,
is very difficult to excavate

NARRATOR:
Now, fresh evidence is emerging

from a completely different
branch of science,

applied to Neanderthal research
for the first time

Svante Paabo is one
of a new breed of detectives

examining our deepest past

He's not an archaeologist

He does his digging in the lab

Paabo is interested in humans

and what sets us apart
from our closest relatives

As a geneticist, his work
involves comparing

our genetic material with that
of the rest of our family tree

It's really about finding out

what makes us special
in the world

what made things such
as modern humans spreading

across the entire globe,

developing all the technology,
all the culture

that's typical in modern humans

DAVID SCOTT:
There's a fundamental truth
to our nature

Man must explore

NARRATOR:
Paabo and his colleagues want
to look at specific genes,

where you'd expect humans
and our closest relatives

to differ...

Like a gene fundamental
for language named FoxP2

FoxP2 is a very interesting gene

in that it's one of a few genes
that's directly related

to this uniquely human
characteristic,

speech and language

Four violets, a fiver!

Four violets, a fiver!

[chanting]

[phone rings]

Nine hundred, nine hundred

NARRATOR:
FoxP2 is found in many species,

although the human version
is distinctive

By comparing it with a potential
Neanderthal version,

Paabo was hoping to shed light

on what makes
human language special

But before he could even begin,

Paabo needed to have
the genetic blueprint

for both Neanderthals
and humans...

Their genomes

A genome is the distinctive
genetic recipe for a species,

made up of a specific set
of chromosomes

These are responsible
for the characteristics

that make every species
different

Within the chromosomes,
genes determine

whether we have
two legs or four,

grow feathers or fur,

and every part of this unique
recipe is encoded

within just one molecule DNA

When Svante Paabo started
his work,

the human genome had
already been decoded

No one had attempted to map
the Neanderthal genome

Paabo faced a seemingly
impossible task

in attempting to map the DNA

in the nucleus
of a 30,000-year-old cell

Ed Green is a geneticist
on Paabo's team

As soon as it was obvious that
this was possible in theory,

we started to think about
how do we do this in practice,

if we can get nuclear data,
if we can get some amount

And we did some
back-of-the-envelope
calculations

and it looked like,
yes, this is feasible

PAABO:
So we spent
a lot of time looking

at many archaeological sites
and many different bones

and eventually identified
this site in Croatia

NARRATOR:
The Vindija cave
in northern Croatia

contained genetic gold dust...

The 30,000-year-old
leg bone fragments

of three female Neanderthals

The exceptionally
well-preserved bones

offered Paabo's team
the best chance

of extracting Neanderthal DNA

In sterile conditions,
the team took samples of bone,

carefully dissolving
them in solution

before spinning them at
high speed in a centrifuge

to retrieve the strands of DNA

But then the real
difficulties began

The bone samples carried
billions of unwanted passengers

PAABO:
Most bones we look at

might contain a few molecules
of Neanderthal DNA,

but the vast, vast majority
come from bacteria and fungi

that colonized the bone when it
was in the ground in the cave

for tens of thousands of years

NARRATOR:
Before the team could go
any further,

they'd have to destroy
the rogue DNA

So they invented
a cleanup technique

using enzymes that target
and eliminate

bacterial DNA from the sample

The resulting
clean sample contained

five times the concentration
of Neanderthal DNA

compared to the original,
which made the analysis easier

Still, reconstructing the genome
remained a formidable challenge

The DNA molecule's intertwining
strands are held together

by four key chemicals,
represented by letters

These bond together as pairs...
Always C to G and A to T

These letters are
like building blocks,

repeating units which spell out
the genome's unique recipe

Their order is critical

Just one letter out of place
within three billion pairs

and the genome would be
inaccurate

But the DNA was
in tiny fragments,

like a colossal jigsaw puzzle

The team would have
to place each piece

in precisely the right order

Svante and others were
very skeptical

It was in the realm
of the impossible

that a genome would ever
be sequenced

During the course
of this project

there were actually many times
when we despaired

about being able to make it

NARRATOR:
It would take them four years

But finally, the last piece
of the puzzle fell into place

Human evolution is something
that everyone cares about

and it's such an incredible
thing, technically,

to be able to do

Add to that that it's
our closest extinct ancestor

and all that it can tell us

about human evolution
and human biology

It's the most exciting thing
I've ever worked on

NARRATOR:
This is the result of all their
work... the Neanderthal genome

Here is one tiny part
of the actual sequence

of over three billion letters

corresponding to each DNA
building block,

the genetic blueprint
of a species of human

that became extinct


Now, at last, Paabo's team could
begin comparing Neanderthal

to modern human genes

One of the first areas
they looked at was FoxP2,

the gene associated
with language

Would an identical gene
be shared

between human and Neanderthal?

Would the gene be there at all?

To my surprise, I must say,
it turned out that it's shared

NARRATOR:
Neanderthals had exactly the
same version of the FoxP2 gene

as humans...
The same chemical letters

in exactly the same order

PAABO:
I'm very sure that the
Neanderthals had communication

If it was a language exactly
as we would understand language,

that's another question

STRINGER:
I think they had language

That doesn't mean it was
the same as our language,

as complex as our language

I think, again, that modern
humans probably had

another level of complexity

But I think they had language

Yes, I absolutely think
they couldn't have survived

the way they did without it

NARRATOR:
Paabo's work adds weight
to the growing argument

that Neanderthals and modern
humans shared more abilities

than previously thought

But it begged
a billion-dollar question

Did we have enough in common
that we could have interbred?

If Neanderthals
and modern humans

had interbred successfully,

traces of their DNA
would be found in ours

Most scientists, Paabo included,
thought this highly unlikely

When different species mate,

their offspring are
usually infertile

PAABO:
I was biased
against interbreeding

There is no evidence for it so I
don't think it really happened

NARRATOR:
But with the Neanderthal genome
now sequenced,

Paabo and his team could examine
this question

The first step was to map
the individual genomes

of five people
from different ethnic groups

Then they compared this modern
DNA with Neanderthal

They focused only
on small specific regions,

called "variable areas," where
the order of the DNA letters

often differs from one
individual to the next

Here, if interbreeding
had taken place,

letter sequences typical of
Neanderthal DNA would show up

in the human DNA strand

But with no interbreeding,

there would be no trace
of Neanderthal DNA

in the variable areas

Paabo expected to see
the same negative result

in the genomes
of all five modern humans,

regardless of ethnic group

Well, if Neanderthals are
equally distantly related

to everybody,

then Neanderthal should match
the French guy

and the West African guy
equally often

NARRATOR:
But that is not what they found

When we compared one African
to a European individual,

the Neanderthal matched the
European individual more often

than the African one

NARRATOR:
The result indicated

that Neanderthals were
genetically closer

to Europeans and Asians
than they were to Africans

It meant that
somewhere along the line,

European and Asian humans had
picked up Neanderthal DNA

So that was sort
of quite shaking to me

I thought this must be
a statistical fluke

It was not quite significant

This would surely go away
when we had more data

NARRATOR:
So Paabo told his team to do
the work again

and again and again

We really needed to make it
absolutely sure

that we were right

We started to look at the
problem from different angles

And every time we would ask
the question

in a little bit different way

The answer would come back,
it's Neanderthal

We were able to convince one
another and eventually the world

that we have a little bit
of Neanderthal ancestry

in modern human genomes

NARRATOR:
The amount of Neanderthal DNA in
these modern genomes is small,

between just one
and four percent,

but the implications
are staggering

After migrating out of Africa,
early humans must have mated

with Neanderthals
and produced fertile offspring,

who inherited segments
of Neanderthal DNA

What we have shown clearly

is that we could interbreed
with them,

we could have fertile children

and at least some of these
children became incorporated

in the human community

and reproduced and contributed
to present-day humans

NARRATOR:
Paabo's groundbreaking research
forces a radical shift

in perspective
regarding Neanderthals

They were genetically close
enough to have children

with our species

They probably also had language

And there are yet
more revelations

as archaeologists reexamine
previously discounted evidence

in favor of Neanderthal skills
and abilities

A hallmark of our species is
our age-old affinity for art,

ritual and adornment

STRINGER:
We see the astonishing cave art

We see statuettes over the whole
range of modern humans

from Western Europe
right across to Siberia

And I think that's part
of the fact that modern humans

are entering new territories,
they're covering wider distances

and they're having to signal
and network with each other

NARRATOR:
Communicating with others
through art and ritual

has long been considered
a uniquely human trait

JOAO ZILHAO:
There has been the notion

that Neanderthals were
less intelligent,

and one way archaeologists have
to deal with this question

is by assessing the extent
to which people used symbols

NARRATOR:
Evidence of Neanderthal
symbolism has been elusive

until recently

This is one of many fragments
of manganese dioxide,

a black mineral found in
a Neanderthal cave in France,

its tip worn down
as if used as a crayon

In Neanderthal sites
in Gibraltar,

archaeologists have discovered
cut marks on the wing bones

of crows and birds of prey,
bones with little value as food

The marks suggest Neanderthals
were cutting off the feathers

and using them to decorate
their hair or bodies

And in Spain, seashells have
revealed faint traces

of hematite, or iron ore, a red
mineral often used as pigment

Neatly pierced holes allow
the decorated shells to be worn

as ornaments

Anthropologist Joao Zilhao
believes the evidence offers

a glimpse
into the Neanderthal mind

Now, he is reexamining finds

from a Neanderthal site
in Spain,

excavated in the '80s

ZILHAO:
This is a fragment of
a naturally pointed horse bone,

and when we looked at the tip
of the bone under the microscope

we found that there was
lots of reddish dots

NARRATOR:
Although so faded
they are hard to see,

the chemical analysis proves
the spots are

the red pigment hematite

And there is more

ZILHAO:
This shell is from
the Mediterranean oyster,

and you can see adhering

to the inner side of the shell
a remnant of a pigment

which is black and reflective

NARRATOR:
Zilhao has found
a pencil-like sliver of bone

with a red mineral at its tip,

and a shell stained
with a shiny pigment,

alongside other fragments
of colored minerals

It adds up
to a significant collection,

or so Zilhao believes

You know, they look like just
shells collected off the beach,

but the amount of information
they contain is tremendous

NARRATOR:
Putting all the pieces
of the puzzle together,

Zilhao is convinced he is
looking at the remains

of a Neanderthal
body-painting kit

ZILHAO:
This suggests

that what was being prepared
in this shell

was a cosmetic preparation
used as a tool to prepare

something like glitter makeup

This is the smoking g*n

We have here the case
to settle the controversy

concerning Neanderthal symbolism

NARRATOR:
Zilhao believes Neanderthals
used body paint

as a symbolic way of
distinguishing friend from foe,

just as we do today

[chanting]

ZILHAO:
When you go
to a football stadium

and there are two teams playing,

how do you know whether you're
safe to sit next to someone

who may be supporting the team
that hates yours?

You use an artifact that
identifies you as a supporter

And it's this kind of
information about yourself

that these kinds of objects
transmit

NARRATOR:
But even if the Neanderthals
were painting themselves

and engaging in symbolic
behavior, does it mean

they thought the same way
as modern humans?

Our modern human ancestors
practiced ritual and religion

Similar evidence for
Neanderthals has been elusive

Then a team of archaeologists
made an intriguing discovery

in southern Spain

Their finds hint
at the existence

of a Neanderthal ritual

Inside this cave, a team led
by Michael Walker excavated

a deep shaft in which they found
more than 300 bones

from around ten Neanderthals

buried by rockfalls
from the unstable ceiling

Three of the Neanderthals
stood out

Walker thinks they weren't
necessarily the victims

of a rockfall

If there are rocks falling on
you from a natural rockfall,

it would be very strange to find
nobody trying to escape

and one of them with the hands
close to the head

in almost sleeping position

NARRATOR:
Although the bones
of this young female

are fused to the limestone rock
and are hard to see,

Michael Walker thinks her body
may have been carefully arranged

in a fetal position

If he's right,
this was no rockfall

Around 50,000 years ago, someone
had intentionally buried her,

piling stones
to protect her body

And this cave had
yet more to reveal

Near the girl's body,
Walker's team uncovered

the fossilized bones
of a pair of panther paws

WALKER:
This articulated paw of
a panther was found close by

And since the panther
hadn't eaten

and disturbed the bones here,
it's more likely

that the Neanderthals disturbed
the panther and cut its paw off

I just wonder whether in the way
that today hunters in America

cut off bear paws, I'm wondering
if the Neanderthals occasionally

didn't cut off a panther paw
and keep it as a trophy

NARRATOR:
Walker's idea... that the severed
panther paws were a trophy

or funeral offering...
Is an intriguing speculation

I think that there are enough
examples of Neanderthal burials,

well-articulated individuals,

to suggest

that they are intentionally
burying their dead

Perhaps when you come
to the issue of grave goods

and whether they're putting
material in those graves

and whether they're,
if you like,

sending messages
beyond the grave

through these materials,
that's more controversial

You see in humans
elaborate ritual burials,

maybe about 27,000 years ago,
the clearest evidence

in this place in Russia

These two children are buried
with, like, 10,000 beads

There's nothing like that
in Neanderthal burials

NARRATOR:
Whether Neanderthal burials

are evidence of complex rituals
and beliefs is hotly debated

But many clues now point
to the idea

that Neanderthals were more
accomplished and advanced

than previously thought

And this opens up perhaps
the biggest question of all:

Why are we still here
and Neanderthals are not?

The Neanderthal story
seems simple

Their forerunners reached Europe
around 800,000 years ago

When h*m* sapiens joined them
around 40,000 years ago,

it marks the beginning
of the end

Some 10,000 years
after modern humans arrive,

virtually all traces
of Neanderthals are gone

Some scientists believe
we drove them into extinction

by outcompeting them
for scarce resources,

maybe even by k*lling them

But the latest evidence points
to another possibility

Soon after Svante Paabo's team
revealed

that Neanderthals and modern
humans outside Africa

had interbred,

anthropologist John Hawks
reopened the case files

He wanted to know if this
interbreeding had happened

a little or a lot

Hawks needed more than just
the five modern human genomes

that Paabo had analyzed

And he got a lucky break

A team of scientists published
a huge new database

of individual human genomes
from around the world

The 1000 Genomes Project data
began to become available

And so we were able to expand
the comparison

to literally more than
a thousand individuals

from different populations

NARRATOR:
If interbreeding had been
a relatively rare event,

then all non-African humans
across the world

would have inherited the same
small dosage of Neanderthal DNA

But that's not what Hawks found

HAWKS:
Now, my lab, we were able

to look at more people in China,

more people in Tuscany,
in the UK

And as we're doing this, we're
discovering that there are

some differences
among these populations

NARRATOR:
Hawks uses the jelly beans
to illustrate

the relative percentages
of Neanderthal DNA he found

in different groups of modern
humans across the world

We see that in China
there is a little less

In Europe it's a little more

And when we compare Europeans,
in southern Europe, in Tuscany,

it's a little more than it is
in other parts of Europe

NARRATOR:
Outside Africa, Hawks' data
showed the Chinese have

the smallest dose
of Neanderthal DNA,

some individuals having
as little as two percent

But in Tuscany, northern Italy,

this rises
to around four percent

So Hawks' data shows

that Tuscans have
more Neanderthal genes

than any other people
living today

If Hawks is right, Ice Age
Southern Europe was a hotbed

of Neanderthal-human
interbreeding

HAWKS:
This was Neanderthal habitat

Modern humans were
interbreeding with them,

for a longer time and over
a larger geographic space

And subsequently,

Europeans got a little bit more
Neanderthal DNA

NARRATOR:
Today, a simple blood test
can estimate

how much of our genetic identity
is Neanderthal

HAWKS:
Do you guys want
to find out?

STUDENTS:
Yes

Are you sure you're ready?

Yes, yes, get over it,
okay, all right

At 1 3 percent,
the least is Arial

That's very characteristic,
actually,

of African Americans
in our sample

Next, 2 5 percent, is Vang

And the most you're left

How much do you think it is?

No more than three percent

Not five?

I hope not

[everyone laughing]

All right, you're the most
with three percent, yes

NARRATOR:
This field of research is in its
infancy and evolving rapidly

Other experts report different
percentages of Neanderthal DNA

But most agree
on one key finding

There wasn't just
a handful of sexual encounters

between humans and Neanderthals,
but many

That presents a dramatically
different picture

of how humans and Neanderthals
interacted in Ice Age Europe

and leads to a new outlook on
the Neanderthals' disappearance

HAWKS:
When we think about the process
of extinction

in other kinds of animals,
we think of it usually

as a really sudden event,

like an asteroid hits the earth
and they're gone

With the Neanderthals,
what you're looking at

is a much more gradual process,

a process that unfolded
over thousands of years

NARRATOR:
Hawks believes the Neanderthals'
DNA was absorbed

by the dominant population

Outnumbered ten to one
by modern humans,

Neanderthals weren't hunted
to extinction

by a supposedly superior species

They were bred out,
genetically swamped

HAWKS:
So a million, you know,

compared to three billion base
pairs in your whole genome

I would frame the end
of the Neanderthals

as a process of interaction
and absorption

Neanderthals were sort
of on the losing end of that

And their only route
toward success

was probably interbreeding
with our population

NARRATOR:
But is our dosage
of Neanderthal DNA

just a quirk of genetic history?

Or is there a serious side
to this inheritance?

What, if anything, have
Neanderthals done for us?

Ed Green and his team
are looking closer

at the sections of Neanderthal
DNA that we inherited

One obvious follow-up question
is, what is the impact

of Neanderthal genetic
contribution into people today?

NARRATOR:
Most of the genes they examine
don't have any known function

But then the team finds
something intriguing:

Neanderthal DNA

in locations fundamental
to our immune system,

involving genes that are vital

to our ability
to fight off disease

These areas are called human
leukocyte antigens, or HLAs

They make the cells that attack
viruses and bacteria

Since Neanderthals lived
in Ice Age Europe

for hundreds
of thousands of years,

their immune systems must
have been specially adapted

to fight off the diseases there

This was something that modern
humans, arriving from Africa,

didn't have

Our ancestors, when they came
into the Neanderthal range,

were, for the first time,
encountering this environment

Our immune systems
would not be adept

at recognizing and fighting
pathogens new to us

HAWKS:
Oh, it's absolutely
a survival toolkit

HLA types are important

because they help our body
resist disease

So it's very clear that one
product of this interaction

was the inheritance of immune
system versions of genes

Maybe they conferred
some selective advantage

Maybe the Neanderthals
have a version

of these immune system genes

that were beneficial
for the Neanderthal

and they were beneficial
to human people

who got these genes
by interbreeding

NARRATOR:
This is the Epstein-Barr virus,

linked to both mononucleosis
and a type of blood cancer

Green's team found that an HLA
we inherited from Neanderthals

could reduce the risk of
contracting this deadly virus

But this may be just the tip
of the iceberg

As we look more and more
at the Neanderthal genome

and characterize
what things are where,

I think we're going
to find more of these

NARRATOR:
It seems the Neanderthals who
mated with our human ancestors

may have given their offspring
a lifesaving legacy,

a legacy that is potentially
saving lives even to this day

The genetic and archaeological
evidence is still unfolding

But already it is telling us
something profound

The Neanderthal story goes to
the heart of who we are today

We're finding out we owe a debt

to a mysterious, long-vanished
branch of the human family

in ways we are only just
beginning to discover

Major funding for N O VA
is provided by:

Supporting N O VA and promoting
public understanding of science

And the Corporation
for Public Broadcasting

And by: