♪ 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."

♪ 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: 1,200 years is nothing 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 illegal?"

♪ 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 65 million years ago.

(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 rifle, 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 "War 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 "War 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 2,000 other organisms, 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 400 parts per million 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.

♪ ♪ ♪