have one thing in common, they're extinct.... dead as a dodo, if you will.

In fact, scientists estimate that 5 billion species have come and gone off this planet.

But what if we could bring them back?

What if extinction didn't have to be a permanent thing?

Right now scientists are using revolutionary new genetic techniques to try to bring back

some of these species.

For example the wooly mammoth could roam the Northern Tundra.

[TRACE] It sounds like a science fiction, but it could happen.

So how close are we to de-extinction?

[TRACE] The woolly mammoth is an impressive specimen.

It was the king of the tundra for millions of years.

Then it rather suspiciously disappeared around the same time that humans appeared.

Most scientists think it's likely that they were hunted to extinction.

[JACK DUMBACHER] Most of the species that have gone extinct in recent years is because

we destroyed the habitat, we've introduced species, or we've killed them outright, like

the passenger pigeons.

It was hard to imagine, at the time, that this bird species that's so abundant could

actually be hunted to extinction.

But we managed to do that.

[TRACE} While it's normal for species to die out over time because of evolution or

a cataclysmic event some scientists think the Earth is now entering a new age of mass

extinction, called the Anthropocene or Holocene extinction, caused by, you guessed it, us.

Animals, plants and insects are dying out at a rate of 1,000 to 10,000 times faster

than ever before, with dozens of species going extinct every single day.

Some scientists estimate that as many as 30 to 50 percent of all species could be headed

towards extinction by end of the century!

But again, what if extinction didn't have to be a thing?

What if we could bring species back at will?

To do that, we'd need DNA, an egg cell, and a birthing Mom.

Which is why Jurassic Park will never be a thing.

[JACK DUMBACHER] The dinosaurs are so old, that all those chemicals, have been turned

to rock.

There's no source of DNA that we have right now for dinosaurs, There's no way that we

could create a dinosaur, because we don't know what it's genome looked like.

[BEN NOVAK] We can't get dinosaur DNA so no Jurassic Park on the bench, but we can

get DNA dating from tissue and fossils from organisms from 10,000 years ago to 100,000

years ago so the woolly mammoth is an active project.

[TRACE] That's right.

The wooly mammoth could be a thing again!

[JACK DUMBACHER] Mammoths are very different than dinosaurs because scientists are able

to go up to the Arctic, and find thawing chunks of earth that still have frozen mammoths in

them and those have DNA.

And that's where scientist are going to get the DNA from the mammoth in order to reconstruct

its genome.

That's why mammoths are different than dinosaurs, because we have that DNA.

[TRACE] And they're closer than you think to bringing them back..

[BEN NOVAK] So right now .. there are cells dividing and living in a little Petri dish

at Harvard that have mammoth mutations.

We have a mammoth genome.

We have mammoth habitat, we have a good motivation for doing it.

We just need the filler in between who's making the mammoth.

[TRACE] Woah woah, Ben.

We're not quite there yet.

We've got the DNA, but it's not exactly perfect.

DNA degrades over time, it has a half-life of about 521 years.

Meaning we need to fix any mammoth DNA before we can clone it.

Cloning is the closest thing we have to reviving extinct animals right now.

And we're not bad at it!

Remember Dolly the sheep?

Now we regularly clone cattle, pigs, camels, frogs, lab rats, and even your pet dog!

Now, even with perfect DNA cloning is really hard, but they can make DNA even more perfect

by editing it.

[BEN NOVAK] The revolutionary technology that made considering de-extinction possible which

also opens up all those new genetic rescue capabilities is what's known as precise

genome editing.

It's using things like CRISPR Cas9, or talens, or megaTALs.

[TRACE] In case you haven't heard of it, CRISPR Cas9 is an editing tool for DNA.

It's able to go through millions of strands of DNA, locate a specific genome and remove

or add to it.

In de-extincting the Mammoth - scientists are using the DNA of an Asian Elephant and

replacing parts with a mammoth's DNA.

To make a 'mammophant'.

A name I hate.

So, we have cloning technology, we've got elephant and mammoth DNA that we can edit

together, and the plan is to try to artificially inseminate an Asian Elephant mom to carry

the baby.

But, just because you bring back one mammoth that doesn't mean de-extinction.

De-extinction by definition, is bringing back a whole species.

And just because we can bring the wooly mammoth back ... should we?

[JACK DUMBACHER] I think sometimes people think about de-extinction like, oh you wouldn't

it be cool to have a passenger pigeon, or a California grizzly, or some other species?

But, it's not just about that species and it being cool.

Sometimes it's about, those species have a role in the ecosystem, which is now empty.Jack:

A great example, that a lot of people are aware of, is wolves in Yellowstone...we've

seen huge changes in the ecosystem in Yellowstone, that people are attributing to the wolves,

[TRACE] So if we do put a mammoth back into the world, what would happen?

Where would it go?

What would it eat?

If mammoths ate up all the grasses, what would happen to other herbivores in the Tundra?

If the wolves of Yellowstone can change the course of a river, what would a herd of mammoths

do?

[JACK DUMBACHER] I'm not sure I'm comfortable with releasing weird, hairy Asian elephants

into the tundra.

[BEN NOVAK] Once you have your animals, breed them up in captivity, condition them for the

wild, put them back into the wild and that's where you start getting into all of your ethical

questions of whether or not we should or should not be doing this.

[JACK DUMBACHER] Wooly mammoths have been extinct and one question is “has that ecosystem

already become something different?”

And when you put wooly mammoths back are you gonna end up having detrimental impacts on

things that are living there now.

[TRACE] there are other animals that we might bring back first.

Like the humble passenger pigeon.

We hunted it to extinction, and changed the forests of North America.

Oak trees need the pigeon for regeneration as well as controlling the underbrush, which

is a major fire hazard.

If we de-extinct them we fill a hole in the ecosystem -- a hole that we put there.

[JACK DUMBACHER] There's a portfolio of extinct animals that you could potentially bring back.

The challenge is trying to figure out which of those is going to have the biggest positive

impacts, and then working on those first.

[TRACE] So, in less than ten years we could de-extinct the passenger pigeon, maybe someday

we'll have Wooly mammoths roaming the tundra or even see dodo birds waddling around.

How close are we to de-extinction?

REALLY REALLY close.

But just because we can, doesn't mean we should...

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Extinction doesn't have to be forever, but that doesn't mean we should encourage it.

Did you know the Border Wall between Mexico and the U.S. is causing extinction too?

Yeah.

Find out more here.

And thanks a lot for watching Seeker.