51x04 - Hunt for the Oldest DNA

[bunniefuu]

♪

NARRATOR:
For centuries,
the best clues to ancient life

have come from fossils.

But now, a new window
on the past is opening.

ESKE WILLERSLEV:
How can we travel back in time?

Is there a time machine?

Yes. It's DNA.

It's ancient DNA.

MAANASA RAGHAVAN:
These are fragile molecules

that fall apart
outside the body.

NARRATOR:
How long can DNA survive?

With ancient DNA,
we're trying to go back in time.

But time is the enemy.

♪

NARRATOR:
A dramatic breakthrough
is transporting us

millions of years back
into the past,

to before the last Ice Age--

revealing surprising
creatures that thrived

when our planet was
far warmer than it is today.

[birds cawing]

Could ancient genes
from this lost world

help us adapt
to a changing planet?

[drill whirring]

♪

WILLERSLEV:
We are stealing genetic secrets
of the past...

...so we can rescue the future.

♪

NARRATOR:
Go behind the scenes on
the "Hunt for the Oldest DNA."

♪

Right now, on "NOVA."

♪

DvX3M
opensubtitles

NARRATOR:
Buried beneath Greenland's
ice sheet

are the remains
of a living world that ended

when the Ice Age began--
over two million years ago.

One scientist is on a quest

to reveal that lost world

with ancient DNA.

WILLERSLEV:
When I look at this place,

I see one huge cold
storage room for ancient DNA.

♪

I spent my life trying
to find older and older DNA.

And this is
the limit of the possible.

And maybe it's impossible.

What we are trying to recover

is DNA millions of years older
than any DNA ever recovered.

So we are trying to reach back

before the last Ice Age.

♪

NARRATOR:
Once, fossils were our only hope

of shedding light on
life in the distant past.

But ever since scientists
first recovered DNA

from an extinct
animal 40 years ago,

fossil hunters have been sharing
the stage with gene hunters.

We've peered into a fascinating
world of extinct species,

Ice Age beasts,
even our Neanderthal cousins.

SHAPIRO:
When I look back in time,

the sharpest tool I have

is DNA-- the genes
of long dead plants and animals.

This is a far more detailed
record

of the past than the fossils
alone can ever give us.

NARRATOR:
But the older DNA gets,

the fainter the signal.

The moment a living thing dies,
its DNA starts falling apart.

Of course, we are
never going to stop wondering,

"Exactly how far back
can we go?"

What is the limit
of DNA preservation?

WILLERSLEV:
You know what people mean

when they say,
mission impossible, right?

They actually mean
it might be possible.

No one has ever
succeeded in getting DNA

older than one million years.

But our tools
are getting better.

NARRATOR:
And as the technology
gets more powerful,

these scientists are
chasing a new discovery.

To everyone's surprise,

the secret to smashing the limit

could be lying
right beneath our feet.

Now, we're on the verge
of recovering

genetic traces of a lost world
from before the Ice Age.

This ancient DNA,
forged in a hotter climate,

might even help us
survive our own warming world.

♪

WILLERSLEV:
When I was in school,

if you had said to my teacher,

"Someday,
Eske will be a scientist,"

they would have laughed.

I mean,
I would have laughed too.

I was a rebel, a troublemaker.

I wasn't good
at the typical things

that people connect
to being a scientist.

I was a school failure.

That's the truth.

♪

But I think
I have one capability

which has proven super valuable:

I have a very good imagination.

♪

I used to think
I was born too late

when I realized
there's no frontiers left,

everything is mapped.

But there is a frontier.

Our frontier is the deep past.

That is where
we can still be explorers.

NARRATOR:
In Iceland,
Eske Willerslev's team

is pulling mud from
the bottom of frozen lakes,

mud laced with DNA
from a long-gone world.

[machinery whirring]

♪

WILLERSLEV:
DNA is a, a blueprint, right?

It's the code who
makes you who you are.

Different individuals
have different DNA codes.

Different species
have different DNA codes.

So, it means if you can pull out
a piece of the DNA code,

you can actually map it to all
known DNA codes,

all known blueprints.

And then you can identify, well,

what organism are
we talking about here?

NARRATOR:
On this expedition,
Eske's team is hunting for DNA

from before the Vikings settled
Iceland,

about 1,200 years ago.

♪

WILLERSLEV:
in ancient DNA research,

especially in
the Arctic where it's cold.

Still, at a certain point, DNA
becomes too difficult to read.

So, there is a limit.

♪

And I would say,

I've always been obsessed
with this limit,

to push this limit.

How far can we go?

I still haven't got
an answer to that question.

But I'm sure
it's further than what we think.

NARRATOR:
So, what is the limit?

Back in the '90s,

some scientists
got a little carried away.

SHAPIRO:
"Jurassic Park"

was not a documentary.

♪

The early days of ancient
DNA were a bit of a disaster.

Unless you were in PR,
in which case, it was fantastic.

There was a whole bunch
of what we now know

is complete nonsense that was
published with just abandon,

just excitement and enthusiasm
rather than actual science.

I mean, everybody
wants there to be dinosaur DNA.

And so, somebody who says, "Hey,

"I got this really
well-preserved dinosaur.

And guess what?
There's DNA in it!"

Of course the media are gonna
be super excited about this!

♪

NARRATOR:
And Hollywood couldn't resist.

[fans cheering]

[cameras clicking]

SHAPIRO:
So let's reconstruct
"Jurassic Park."

Scientists go somewhere hot,

because amber forms in
hot places,

and they find a really beautiful
piece of amber,

inside of which they can see
this fantastic insect

that looks perfectly preserved.

They take a big needle, and
they stick it into the insect,

and they draw out blood,
presumably from a dinosaur.

And then they take
that blood to the lab,

and they do some magic

that for some reason
involves frogs,

even though we already
knew at the time

that birds were the closest
living ancestor of dinosaurs.

And then more magic
happens and, uh,

dinosaurs are back to life!

But we now know a lot
more about DNA than we used to.

And everything we know
tells us, no question about it,

that this molecule just doesn't
stick around

for millions
and millions of years.

Dinosaurs have been extinct
for more than 65 million years.

We will never get dinosaur DNA.

"Jurassic Park"
is not going to happen.

I'm sorry.

♪

Getting DNA out of
things that are alive is easy.

This is because modern DNA,
DNA from living organisms,

is in fantastic condition.

Long strands of DNA,
if you can think of it

kind of as party streamers.

♪

Ancient DNA
is more like confetti.

The reason that modern DNA
party streamers get chopped up

into the confetti
that is ancient DNA

is because of random processes
that happen outside the body.

Mostly things like UV
radiation from the sun.

When we walk outside,
UV hits our skin

and it gets into our cells,
and it damages our DNA.

But when we're alive,
we have proofreading enzymes

that will come along

and fix those damages.

Otherwise, we would get cancer

every time we walked outside.

But proofreading and fixing DNA,

this is an energy-requiring
process.

And after you're dead,
there is no more energy.

♪

RAGHAVAN:
With ancient DNA,

it's always been a
needle in the haystack problem.

This is a fragile molecule.

So, even when we first
understood

that DNA could stick around
after death,

the question was,
how much and where?

Early on, we thought

only in soft tissue--

so, a human mummy
or a frozen mammoth.

In about 1990,

we had the huge insight
that fossil bones

and teeth could
protect DNA like time capsules.

But well-preserved
fossils are rare.

And fossils that contain DNA,
they're even rarer.

So, in our field, that has been
one of the biggest challenges.

We're all chasing
these precious time capsules.

♪

NARRATOR:
Three decades ago,

Eske was determined
to join the hunt.

But the odds were against him.

WILLERSLEV:
In 1995,
I was a biology student

and I wanted to do

my research on ancient DNA.

But I had no fossils.

I wasn't famous, so nobody
wanted to give me fossils.

That was a bit of a problem.

You want to do ancient DNA,
but you have no fossils.

I remember I was in my flat,

it was an awful day.

[thunder rumbling]
The rain was just coming down,

and leaves were
falling from the trees.

And I saw this woman
out walking her dog.

And she stops.

The dog squats, takes a poop.

It's funny,

inspiration sometimes comes out
of the strangest times.

[chuckles]

I'm looking
at that miserable wet dog,

thinking, "Well, there's DNA
in the dog.

"So, there's DNA
in the dog poop, right?

But will it survive?"

We know there's
DNA in the leaves,

but we also do know that
these things will disappear.

After next rainfall,
the dog poop will disappear.

After a few years,
the leaves will be gone.

The question I asked myself was,
"What will happen to the DNA?

Will that be gone, too? Or will
that be preserved in the soil?"

Because if it's
preserved in the soil,

we don't need any fossils,
problem solved.

So, I remember I went into
the coffee room

in the Department of Zoology,

where all the professors
were sitting,

you know, having their lunch.

And I came with this
idea saying, "Well, what about

looking in, in the soil
for DNA of animals and plants?"

[laughter]
And they were laughing.

And my, my
supervisor turned around,

he was head of department,
saying,

[speaking Danish]

[laughter]

"I never heard
anything as stupid in my life."

No one had ever thought
to recover DNA from dirt.

And why would it be there?

The idea is that DNA is,
is kind of known to be

such an unstable
molecule in general.

If you're working in
a molecular biology lab

and you don't look after your
DNA, it's gone very fast.

So yeah,
it was a completely crazy idea

that, that it would
even be found.

I mean, that DNA enters
the environment is obvious

if an animal
urinates or defecates.

But that DNA stays in the
environment, completely crazy.

SHAPIRO:
So, early on, we didn't know

how long ancient
DNA could survive.

But there was a second
really big hole

in our understanding:
contamination.

♪

Ancient DNA getting
mixed up with modern DNA.

Well, the trouble is
that DNA is everywhere.

My DNA is now on
this chair and on my hands

and on my shirt,

and DNA is coming out of
my mouth as I talk.

And there is microbial
DNA absolutely everywhere.

So, when people were
sequencing these bones,

they were getting DNA.

And they were saying, "Wow,
there's DNA in these bones.

It must be dinosaur DNA."

I think there
was some dinosaur DNA

that was published that they
were really excited about

because it closely matched
a bird.

Well, turns out
the field excavation team

was having
a chicken dinner one night.

[chicken clucking]

[typing]

WILLERSLEV: In those early days,
when I was still a student,

we were all struggling with
the problem of contamination.

Which was the big downfall

of the dinosaur DNA guys
of the '90s.

And I decided, well,

somehow, we are going to solve
that problem.

I was working
on this with another student,

Anders Hansen.

So, we had this room that were
basically our clean laboratory.

But we had a problem
with a mold contamination.

And in the end,
we became so desperate,

we decided, okay,
we will basically clean

the entire room down
with very strong bleach.

♪

We knew, well,
it wasn't really allowed,

and we didn't have
money for gas masks.

[scrubbing]

♪

Anders got,
got dizzy and threw up.

[retching]

And the security guard
was coming,

saying, "What the [bleep]
is going on here?"

It's smelling like a swimming
pool in the entire building."

And Monday morning,
we were, had to stand in front

of the professor
and the lab director.

And they were furious, right?

I mean,
"What are you guys doing?

I mean, do you know this
is totally ill*gal?"

♪

But the good news was even
though we, we got all this heat,

the fungi contamination
were gone!

NARRATOR:
Finally, Eske had a mold-free
lab.

He first tried getting
DNA out of 2,000-year-old ice.

WILLERSLEV:
We got ice cores from Greenland,

and we showed we could
recover ancient fungi DNA

trapped in the ice
without contamination.

And that was big.

So, then we knew,
we were ready to move

to the next step--
searching for DNA in the dirt.

So, I really believed
in this idea

of environmental DNA
or dirt DNA.

And more than that,

that it could survive in the
environment as ancient DNA.

But I had to prove it.

So, I set out to retrieve
ancient DNA from the dirt.

And at that point,
no one had done that.

NARRATOR:
Eske was searching for DNA

from the Ice Age,
which ended 12,000 years ago.

It kept our planet in
a frigid grip

for about two-and-a-half
million years.

WILLERSLEV:
The Ice Age,
it's an amazing period.

It's the time
of the big mammals.

You have giant wolves,
giant beavers,

mammoth, mastodons, right?

[animals growling]

So, I thought,

imagine how much poop and urine

these big mammals had
been producing over time, right?

That is in the soil,
in the surrounding,

frozen in time in the arctic.

So, my idea was to bring back

that Ice Age world
by retrieving DNA

directly from the permafrost.

And that permafrost
I got from Siberia.

[drilling]

So, while everyone else

was looking for DNA
in fossil bone and teeth,

and discovering
one species at a time,

I was looking in
the dirt for everything.

♪

NARRATOR:
It's one thing
to recover ancient DNA,

but it's a far more
daunting challenge

to read those tiny fragments
of genetic confetti.

That is, to decode what kind
of ancient life they come from.

The shorter the fragment,

the harder it is to identify.

A genome is like
a twisted ladder.

So, if you think of
a long ladder,

every rung is a base pair.

And a base is a single
molecule-- A, T, G and C.

A human genome
is incredibly long.

It has three billion base pairs.

So, that's three
billion rungs on the ladder.

That's a big number.

But when we're
working with ancient DNA,

we're working with short pieces,

pieces just a few rungs long.

And we have to hope that those
little pieces

contain enough
unique information

that we can match
them to known DNA.

NARRATOR:
Some of Eske's Siberian
permafrost

was 400,000 years old.

If he could identify species

from ancient DNA frozen inside
it, he would set a new record.

♪

WILLERSLEV:
So, it's Christmas Eve,
and I'm, I'm sitting

alone in the lab,

everybody have already gone
home, right, for, for Christmas.

And I'm, I'm basically checking
the DNA sequences

that we got out of the dirt
and comparing those

to all known DNA
sequences in the world.

And when I see the results,

the hairs on
my back are just rising.

It was-- bang!-- woolly mammoth.

It was-- bang!-- bison.

It was-- bang!-- reindeer.
It was-- bang!-- hare.

It was-- bang, bang, bang!--

different types of plants.

It worked better than
I could even have imagined.

NARRATOR:
Eske had matched the ancient DNA
in his Siberian dirt

to known species,
whose genetic sequences

were collected
in a vast catalogue.

And sure enough,
he found dozens of matches,

including extinct species.

Eske was the first to show

that enough DNA can survive in
the dirt

to paint a picture of the past.

Still a student,

he'd just sparked
a new field of science--

ancient environmental DNA.

The reason the technique
of environmental DNA works

is that DNA is everywhere.

It is raining DNA.

The very problem we had
with DNA contaminating samples--

that DNA is falling off of me
and coming out of my mouth

and floating in the air
around me--

that is exactly the opportunity
we have with environmental DNA.

So I realized
it's not the scarcity

of DNA that is limiting us.

Environmental DNA is everywhere;
the limit is time.

And this is really
when I started thinking,

"Well, how far back in time
can we really push this?"

♪

SHAPIRO:
So today we are in the
Holocene.

That's about
the last 12,000 years.

♪

Before that,
it was the Pleistocene,

a period of lots
of ice ages, more than 20,

lasted about two-and-a-half
million years.

And before that
was the Pliocene,

when it was much warmer
than the Pleistocene.

[horse neighs, camel grunts]

Yeah, it was a really
weird place,

you would not
recognize that world.

When you go
back three million years,

you're in a way warmer climate.

Earth was just hotter.

[insects buzzing]

And it had been that way
for a very long time,

since before the extinction

of the dinosaurs


[birds calling]

I'm a vertebrate paleontologist.

I study the animals that lived

in the Arctic
before the Ice Age.

Mammals of the Pliocene Arctic.

The reality is
we don't know very much.

The time before
the Ice Age began, the Pliocene,

it's kind of a lost world.

We don't have full skeletons
of any Pliocene mammals.

We just have fragments,
shards of bone,

evidence of maybe 13 species.

♪

I still have so many questions.

For a paleontologist like me,
it's really frustrating.

NARRATOR:
So, where fossils are lacking,
could DNA help us?

Could genetic traces

really endure for millions
of years?

Everything we knew about DNA
had told us that was impossible.

WILLERSLEV:
The oldest DNA is the coldest
DNA.

DNA is fragile,

so it falls apart over time,

but cold slows
that process down.

♪

No one has ever succeeded

in getting DNA older
than one million years.

But our tools
are getting better.

So I think
the limits might change.

NARRATOR:
Twenty years ago,
recovering 400,000-year-old DNA

from Siberian permafrost was
an impressive leap back in time.

The student
was suddenly a professor--

the youngest in Denmark.

But Eske's quest had just begun.

WILLERSLEV:
So, I just happened to get

this invitation from a group of
geologists

to go up to
northeastern Greenland.

And this is a remarkable place.

I mean, there you have,
uh, something called

the Kap Kobenhavn Formation.

And it's a super dry
and a super cold place.

Naturally,

I thought, northern Greenland
would hold the answer.

If really old DNA is going to be
preserved anywhere, it's here.

♪

Northeastern Greenland--

it's one of the most hostile
places on Earth, extremely cold.

But even more important,
this is an Arctic desert.

It was too dry
for glaciers to form.

No glaciers
to grind away the landscape.

The sediments up there
are perfectly preserved.

In Kap Kobenhavn,

you're literally walking on dirt

from before the Ice Age.

It's incredible.

This place that is almost
barren ground today, right,

in the sediments, we discovered
chunks of trees of wood

that are three million years old

but is still preserved there.

I mean, you can basically

take them up and use them
as fuel in your campfire.

So this told me two things.

First, Kap Kobenhavn

must have looked very
different in the past.

And secondly, this must be among

the best places in the world for
long-term preservation of DNA.

[waves lapping shore]

This gave me an idea.

A naughty idea.
[laughs]

♪

What if we could just dig
in the dirt

and recover DNA
millions of years old?

SHAPIRO:
If your goal is

to get the oldest sample,

then you go where that
oldest sample is likely to be.

It reckons back to the age
of exploration, right?

I mean, th... think about my,
my kids are in fourth grade,

uh, so they're learning about

the explorers that went
around the world.

And this is kind of, I think,
how Eske sees himself a bit.

He's like, "Oh, you know what?
There's an Arctic desert.

I'm gonna go there, and
I'm gonna get DNA from that."

And he will because he's Eske.

And that's how Eske works.

[laughing]

In 2005, I published
this review paper

where we basically
claimed, well,

ancient DNA cannot survive
for more than one million years.

That's the absolute limit.

But in the back of my head,

I was still wondering

is that really true, right?

Could DNA survive longer
than one million years

in a place like
the Kap Kobenhavn Formation?

So, on that
same expedition, I thought,

"Hey! I mean, we're here!
Why not sample the sediments?

You never know, we just
might be able to find DNA."

♪

I remember it was
pretty miserable up there.

We were working in
the freezing Arctic desert,

where it rained anyway.

Still, we cored
into the frozen ground,

and I got my crazy samples.

[helicopter blades whirring]

So, I took the sediment samples
back to my lab in Copenhagen.

And, uh, to be honest,

this was the beginning of
a very frustrating project.

NARRATOR:
Those Greenland
samples would tease

and torment Eske and his team

for the next 15 years.

In the early days, Astrid
Schmidt was a doctoral student

in Eske's lab.

When Eske offered her
the Greenland samples,

she jumped on them.

ASTRID SCHMIDT:
At that time,

Eske was a, a star in
the scientific community,

and I was inspired
by Eske's enthusiasm.

We had a hypothesis that, if the
environment had been kept cold,

and the temperatures had
not been moving up and down,

fluctuated,
then we would have had

at least a possibility
of finding

ancient DNA.

So, we were, uh,
being optimistic,

knowing it was a long shot, but
also knowing that we could get

ground-breaking results
from this.

And there was DNA
in the samples.

We could see it.

But it was super degraded.

♪

RAGHAVAN:
It's not enough

to see that your samples
contain ancient DNA.

You have to be able
to identify that DNA

and to know what forms
of life it came from.

To do that, the fragments
need to be long enough.

You need a certain number
of base pairs in a fragment.

You need enough rungs
on your ladder.

NARRATOR:
When Astrid started,

scientists needed
at least 100 base pairs.

SCHMIDT:
We did everything we could

with the technology
that existed,

but we just couldn't overcome
the central problem.

The Greenland DNA
was just too old,

the fragments were too short.

It was very frustrating.

The DNA, after one million year,
was just total garbage.

With, you can say, the
technology in hand at the time,

uh, the DNA
was completely unreadable.

Well, Astrid, uh,

was one of many people in my lab

that tried the Kap Kobenhavn
samples and basically failed.

In retrospect...

[clicks tongue]
I was probably not

a very good supervisor, right?

Because I, I kind of pushed
for people to do these samples

every time we had improvements
of our methodology,

in a hope, "Well, this time,
they will work."

If that happened,
it would be a career booster.

But the...

the risk associated with
this project was huge, right?

So it was failure after failure.

Kap Kobenhavn project was,
um, yeah, a bit sensitive.

As a postdoc,
if you decided to invest

your time in this,
it was the case of

having only so many years

to be able to produce
excellent research.

If you're not able
to produce research

because the technology
doesn't allow it,

not because
you're a bad researcher,

you still end up with
nothing to show for it.

SCHMIDT:
In 2013,
I left research science,

and I didn't pursue science,
um, since then.

I took a big risk,
and I paid a price.

[student speaking indistinctly]

WILLERSLEV: Yeah, but again...
the thing is, just like with...

NARRATOR:
In Eske's lab,
students began calling

the Greenland samples cursed.

[Willerslev speaking
indistinctly]

But Eske and his team
kept returning to Greenland,

hoping to find DNA
in better condition.

Meanwhile, four more students
suffered under the curse,

failing to recover DNA
long enough to identify.

They all changed careers.

But as they left, new ones
stepped into their shoes.

MIKKEL PEDERSEN:
So, you, you can imagine
what I felt

when this, these samples
landed on my table.

So, I was a PhD student

in Eske Willerslev's lab.

This was my last option,
also, to succeed in a project

that I was given
as a PhD student.

I was coming to...
[laughs]

the final tries of, of
actually making this a success.

Back in the day, we needed

almost hundred base pair
fragments to survive in a sample

in order to retrieve
any DNA whatsoever.

But the technology was changing.

And I had a student, Mikkel,
who came to me with an idea.

I was immediately excited.

I thought,
"Yes, this could work."

Mikkel suggested we use

a powerful technique
called shotgun sequencing.

Shotgun sequencing
itself wasn't new,

but no one had ever used it
on dirt DNA.

I don't know why, in retrospect.

It seemed kind of obvious.

NARRATOR:
First, Mikkel proved
that the shotgun technique

could work on dirt DNA
several thousand years old.

It really showed us
that we could actually

get ancient environmental DNA

even from
the very shortest threads

that, that were
preserving in the samples.

And the obvious next step
would actually be

to take on the most
challenging project of them all.

What we refer to as the curse,

the Kap Kobenhavn Formation.

RAGHAVAN: In the early years
of ancient DNA,

we had to decide which part

of the genome to look at.

Those are the giveaway parts
of the genome

that we call barcodes.

They reveal the identity

of an organism.

We matched those barcodes

to our reference catalog,

but those barcode fragments
had to be long enough.

RAGHAVAN:
We know that DNA fragments
over a hundred base pairs

just don't survive
millions of years,

even frozen,
high up in the Arctic.

So, shotgun sequencing
was a revolution.

Now, instead of targeting
a specific part of the genome

with precision, like with
a r*fle, we're using a shotgun.

A shotgun hits everything.
[shotgun fires]

WILLERSLEV:
With the shotgun method,

we just sequence
all the DNA we can find.

Then we look for matches
with every genome sequence

for every organism
that we know of.

It takes immense computing
power, billions of operations.

And only now are computers
powerful enough

to work with fragments
down to 30 base pairs.

♪

Imagine shredding
"w*r and Peace."

All you have are short phrases,
not even sentences.

And you walk into
the Library of Congress,

and you start looking
for a match

for each one of those phrases,

book by book by book.

There's another "w*r and Peace"
in there somewhere,

but you need to work through
millions of other books

before you find a match.

And once you do,
your job is to reconstruct

as many pages
of that novel as you can.

So we were the first to use
shotgun sequencing on dirt.

And when we did,

man, it was powerful.

In science,

moments like this
actually feels like magic.

I have no other way
of putting it.

It was just like
that Christmas Eve 25 years ago.

As if by magic, we were seeing
the genetic signatures

of these plants
and animals appear.

Bang, bang, bang.

But it's different this time.

Now, there's hundreds--

fleas, lemmings,
arctic hare, geese, caribou.

A whole forest ecosystem:

larch, poplar, willow, spruce,

ash, cedar trees.

We're looking at a long list

of organisms from a place
that today is an Arctic desert.

♪

NARRATOR:
Eske's team had recovered

the genetic fingerprints
of a lost world--

nine land and sea animals, from
horseshoe crabs to big mammals;

over a hundred plants,
from mosses to forest trees;

and nearly


including bacteria and plankton,

some of them extinct
and many of them

never detected in the Arctic.

But this incredible breakthrough

created another problem.

If you're claiming
to have recovered

the world's oldest DNA,

you'd better be
very sure about the date.

♪

[Willerslev speaking
indistinctly]

WILLERSLEV:
We knew we were going
to get hammered.

Extraordinary claims demand
extraordinary evidence, right?

We had to be very sure about
the dates from Kap Kobenhavn.

That took two more years
of hard work.

♪

Eske.

[voiceover]:
We used a whole set

of different methods.

We looked for organisms
in the sediments

that we knew lived on Earth

for a known period of the past.

We used the biological clock

based on
how DNA mutates over time.

NARRATOR:
And Eske's team used
three more independent methods

to date the sediment
from Greenland.

When their work was done, they
had made a remarkable discovery.

The Cape Copenhagen DNA is
at least two million years old.

WILLERSLEV:
It's important to understand

that this is
the minimum possible age.

Taking all the lines of
the dating evidence as a whole,

the most likely age
of the Kap Kobenhavn DNA

is actually 2.5 million years.

This puts us
into the late Pliocene,

which is the period just before
we start having glaciations.

If Eske's DNA is that old,

if it is Pliocene,
then that is huge.

NARRATOR:
Eske had his hands on DNA

from before the last Ice Age.

WILLERSLEV:
Finally, we are catching sight

of the living world
that existed in Greenland

before the world grew cold.

That was the moment.

That was when we knew we had
something to tell the world.

NARRATOR:
Sixteen years

after Eske began collecting dirt
in Greenland,

the breakthrough was published
in "Nature" magazine.

It was covered by over 400
newspapers around the world.

It even landed on the front page
of "The New York Times."

This was one of the biggest
science stories of the year.

Until this day,
the record for the oldest DNA

was from a single fossil,

a mammoth that lived just over
one million years ago,

during the Ice Age.

Using dirt DNA
instead of fossils,

Eske's team
shattered that record,

opening a window on
an unknown living world

more than twice as old
as that mammoth.

SHAPIRO:
It feels almost magical
to be able to infer

such a complete picture
of an ancient ecosystem,

from tiny fragments
of preserved DNA.

♪

When I first heard
about the results

from Kap Kobenhavn...
[inhales]

I just said to myself,
"What?!"

What we're talking about

is pushing the record back

to at least two million years,

and I believe
much longer than that.

It was a complete tour de force.

What are my feelings
when I first saw this paper,

is, uh, stunned.

I think we just never really
thought it would be possible,

after years of trying,

to get DNA from
these ancient ecosystems.

We never thought
we'd see such a rich

and diverse ecosystem
in Greenland.

We're seeing
the very last Arctic forests

from a hotter world
before the Ice Age.

And these forests are unique.

We have nothing like them today.

[geese honking]

♪

WILLERSLEV:
I always knew

that there was forest
in the High Arctic.

I touched the wood
of ancient trees up there.

But when we looked at
the sequences from Greenland,

there was one
that completely shocked me,

shocked everyone.

[mastodon roars]

To hear that there was mastodon
DNA from Kap Kobenhavn,

this just struck me as,
"Whoa. How can that be?

That is so far north."

NARRATOR:
Relatives of
the modern elephant,

mastodons were forest creatures

that died out
at the end of the Ice Age.

The closest to Cape Copenhagen
their remains have been found

is almost 3,000 miles to
the south, in North America.

It comes completely
out of the blue.

And it was the first time
that we found

such a large animal
in Greenland.

♪

WILLERSLEV:
So, after all those years,
we broke the curse

of the Greenland samples.

I guess you can say
it was a breakthrough

that immediately
became a problem.

The big question, of course, is

how do such DNA survive

beyond
the one-million-year-old limit?

That was the mystery
we had to solve.

♪

It turns out, DNA survived

such an incredible long time

because of minerals in the soil.

DNA is electrically charged.

And many mineral particles
that you find in the soil

is also electrically charged.

So, therefore, DNA fragments
will basically bind itself

around such sediment particles.

And this will reduce
the rate of degradation,

of the spontaneous reaction

that are attacking the DNA
and breaking it up.

So, yes,
it will still be degraded,

it will still be destroyed,

but the rate by which this is
happening is heavily reduced.

It turned out that
particularly certain minerals

of clay and quartz
binds the DNA very strong.

If bound to clay and quartz,
DNA is basically frozen in time.

What is super cool about
the Greenland breakthrough,

is the discovery
that certain minerals

can freeze DNA in time.

Because this means
that everything we thought

about the limits of DNA
preservation are out the window.

NARRATOR:
Not back to
the age of dinosaurs,

but far beyond the old
one-million-year limit.

♪

WILLERSLEV [voiceover]:
So, these cores

that no one believed in

turned out to contain

the most amazing treasure.

It just took us 15 years
to find out how to get it out.

...amazing to...

[voiceover]:
To be honest,
I never really lost faith

because every limit
we have ever set, we broke.

[birds chirping]

NARRATOR:
Until now, what we knew
of the living world

before the Ice Age,
we learned from fossils.

At the
Canadian Museum of Nature,

Natalia Rybczynski only
has fragments of bone to study.

But with the spectacular
discovery of DNA from Greenland,

finally a detailed portrait

of this lost world is emerging.

And it's even stranger
than scientists expected.

WILLERSLEV: This was
a really weird environment.

You had a forest where
half the year it was dark.

And the other half the year
it was sunshine all day around.

This means that all
the organisms we are uncovering

had to survive
half the year in darkness.

[footsteps on vegetation]

[snuffling, light growling]

♪

RYBCZYNSKI:
I think the thing
that really blew our minds

from the Pliocene is the camel.

NARRATOR:
How could this camel, known only

by a few fragments of bone,

survive so far north?

The living world revealed
by the Greenland DNA

gives us some clues.

RYBCZYNSKI:
When you think
about camels today,

it's really easy to imagine

that they evolved
to live in the desert.

And this is where the finding
of the High Arctic camel

is so mind-blowing, right?

Because it's not in a desert.

It's living a complete
opposite to a desert.

It's in a forest.

Ever notice how huge
a camel's eye is?

Well, it turns out
they have incredible vision,

including night vision.

That's pretty useful when it's
dark six months of the year.

[camel grunting]

One of the, uh,
most dramatic features

of the camel, it's the hump.
[camel gurgles]

It's actually
a specialized fat deposit.

And when you think about
the importance of fat,

energy storage,

this is something that's
also very important

for animals that survive
through harsh winters.

The wide feet of camels,

you know, it's listed
as one of the traits

that helps them walk over sand,

also would function well
in soft snow.

WILLERSLEV:
We haven't found camel DNA

from before the Ice Age.

Not yet.

♪

But we have now

recreated the forest world

they were living in,
and Natalia's fossils

tells us they were there.

This is a forest that stretched

from Greenland to Canada
on solid land without barriers.

♪

SHAPIRO:
We used to believe that
ancient DNA could take you back

a few thousand years.

Today, we know we can see
millions of years back in time.

NARRATOR:
Back to a hotter time,

before the Ice Age,

the Pliocene:

a long-lost epoch
that climate scientists

believe may hold
a lesson for us today.

MAUREEN RAYMO:
The Pliocene's a big

red flashing light, right?

The Pliocene was the last time
atmospheric CO2 levels

were the same as today.

You would have to go back

three million years to find
a climate equivalent to

what we're doing right now.

That is a CO2 level of about


in the atmosphere.

♪

The new Pliocene has begun.

It's called the Anthropocene.

We've already altered
Earth's climate.

We're living in a climate that

is about one degree C warmer
globally than it should be.

♪

The climate of the Pliocene
is where we're going.

It's like our instruction
manual for what's coming.

[insects buzzing]

RYBCZYNSKI:
When the Pliocene ended,

and the Ice Age began,
that was a big blow.

But it didn't end life on Earth.

All life around us
has its evolutionary roots

in a hotter world, including us.

NARRATOR:
And that hotter world
could hold lessons

for our own survival.

Greenland proves

we can go much deeper in time

than what we thought we would.

♪

We now have the technology

to go even farther back in time,

potentially
many millions of years.

SHAPIRO:
We have access
to the genetic codes

of plants and animals
that survived

in different climates,

hotter climates, drier climates.

If we can sequence the genomes

of those ancient organisms,
maybe they can help us.

And I think
we're gonna need help.

NARRATOR:
The rescue effort
has already started.

♪

Scientists in Copenhagen
have identified a gene

from the Greenland DNA
that helped

poplar trees grow in the extreme

light conditions
of the High Arctic.

And they've put that gene
into a modern barley plant.

One day, when our climate
is much warmer,

this barley might thrive
at the top of the world,

just as those
ancient poplar trees did.

WILLERSLEV:
This is a food plant

engineered for a hot future.

♪

We are stealing
genetic secrets of the past

so we can rescue the future.

I want to do my part
to rescue the future.

♪
[woman vocalizing]

We are going to sequence

thousands, millions
of ancient genomes

from sediment samples
all over the world.

Because we are now using robots

across the entire pipeline,

we can do 200 samples a week.

We are starting
an industrial revolution

in ancient DNA sequencing.

♪

NARRATOR:
Arctic barley
could be just the beginning.

Scientists are gearing up to put
ancient genes into rice, wheat,

and other foods to help
them thrive in a warming world.

♪

Today we take for granted

that all organisms are shedding
DNA around in the environment.

But, once, this was a new idea.

It all started with
that dog pooping in the rain.

And that is why we can do this,

where a little bit of dirt
contains an entire living world.

♪

♪

♪