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  • [TRACE] The passenger pigeon, the gastric brooding frog, the wooly mammoth, they all

  • 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 ishas 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...

  • You can Keep How Close Are We from going extinct too, by subscribing!

  • Just tap the Seeker symbol.

  • 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.

[TRACE] The passenger pigeon, the gastric brooding frog, the wooly mammoth, they all

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我们离灭绝物种有多近?(How Close Are We to Resurrecting Extinct Species?)

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    joey joey 發佈於 2021 年 04 月 16 日
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