- 9 months ago
Wiped off the face of the Earth by humans nearly a century ago, geneticists are now working on resurrecting the enigmatic Tasmanian Tiger.
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Whether you're a student, educator, policymaker, or simply curious about global education, you'll find valuable insights and compelling stories here.
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00:00Not long ago, a fierce predator rode the wilderness of Tasmania, the thylacine.
00:14Looking like a cross between a wolf and a big cat, they sported stripes on their backs,
00:19which gave rise to the nickname of Tasmanian tiger.
00:24Hunted to extinction on mainland Australia 3,000 years ago,
00:28a few survived on the island of Tasmania until the last one died in the Hobart Zoo in 1936.
00:38Dr. Andrew Pasch at the University of Melbourne wants to bring them back from the dead.
00:46These are just really amazing, unique, fantastic-looking animals, behaving animals,
00:52unlike anything we currently have on Earth, so who wouldn't want to see that?
00:58Drought and Aboriginal hunters caused the thylacine to disappear from the mainland of Australia.
01:15More than a thousand years later, the nearby population on the island of Tasmania was also wiped out.
01:21It was believed, wrongly so, that the thylacines were eating a lot of the sheep.
01:29And the Tasmanian government at the time actually offered a bounty for people to go out and cure specimens.
01:38From the nose to the tip of its tail, the creature stretched five feet long.
01:43And it weighed about 70 pounds, about the size of a German shepherd.
01:49They were not related to cats in any way.
01:52It has a body shape just like a dog, but it has stripes all over its back, like a tiger.
01:58And I think that's why the Tasmanian tiger, it's also known as the marsupial wolf,
02:02because of its dog-like appearance as well.
02:05And its scientific name actually means wolf-headed, pouched wolf.
02:12Like kangaroos, they carried their young in pouches.
02:20The world is still obsessed with this enigmatic predator.
02:26Some are convinced that thylazines are still alive, and sightings are common.
02:31People are always claiming to have had sightings of this animal in Tasmania, and even on the main lane.
02:40So we've got dogs running around, and they look extremely similar.
02:45So as much as I would love to believe that there are still thylacines running around in the wilderness in Tasmania,
02:51it's far more likely that these people are just seeing dogs.
02:56Scientists even collect scat.
02:58There's been many, many surveys using scat samples, so poo samples,
03:05and various other sort of hair traps and things to try and get any evidence of thylacines
03:10all across the entire island of Tasmania, and there's never been any physical evidence.
03:17Andrew Pask is an expert in developmental genetics in Australia.
03:21Developmental genetics is really looking at how all the genes in our genome
03:28give you a particular animal, a particular body shape, a particular form, and a particular physiology.
03:36His team made a huge breakthrough by sequencing the entire thylacine genome.
03:41But where did they get the thylacine DNA?
03:45Because people were going out and killing them on such a large scale,
03:48museums were really trying to collect specimens.
03:51They knew they were disappearing from the wild.
03:54And in some rare circumstances, there were females that were shot that still had babies in their pouch,
04:00and then those babies made it into museum collections.
04:03And that's what really enabled us to start looking into the biology of the thylacines.
04:07There were supposedly 13 preserved thylacine joeys worldwide.
04:14But Andrew discovered that 2 of the 13 were actually Tasmanian devils.
04:19And 10 of the genuine thylacines were preserved in formalin, which destroys DNA.
04:27We have to have good quality tissue for doing a genome.
04:32And formalin's actually very damaging to a DNA.
04:35But the 11th specimen had been stored in alcohol,
04:40and it happened to be walking distance from Andrew's lab.
04:44The specimen was a 4-week-old joey, taken from its dead mother's pouch in 1909.
04:50And the alcohol is actually really good at preserving that DNA.
04:57And so we're able to actually remove that DNA strand from the cells.
05:02And we could see immediately that we had a lot of DNA there.
05:06And that's what we really needed to start to embark on this sequencing project,
05:11is you need an awful lot of that DNA.
05:13But before they could move forward with their DNA samples,
05:17they needed to know how thylacines developed after birth.
05:21The team conducted CT scans on all 11 verified joey's worldwide to create 3D digital models.
05:31They wanted to determine when, during the creature's development,
05:36it began to change from a typical marsupial into something more like a wolf.
05:41And we were using a technique called micro-CT.
05:46This is very similar to when you go into a hospital and you have a break,
05:50and you can put your arm into a machine and it can look inside and look at the bones
05:53and all the different densities of tissue
05:55and give you a very high-resolution image of what that specimen looks like inside.
06:01And so we were able to do that for all of the pouching that were in existence.
06:07The data was used to construct three-dimensional images.
06:11When they reconstructed the thylacine's growth up to 12 weeks after birth,
06:16they discovered that the joey's started off with typical marsupial features.
06:23All marsupials, when they're born, basically look like a little pink jelly bean.
06:27They have extremely strong front arms, and the forearms are really muscly,
06:33and they need those because they need to be able to crawl
06:36from the position where they're born all the way up to get into the mother's pouch.
06:40The other thing that they need to have is a very well-developed head and mouth
06:44because they need to be able to latch onto that teat and start drinking milk immediately.
06:50By the time a thylacine was about 12 weeks old,
06:54it left the pouch to be partially independent.
06:57And it looked more like a dog or a wolf,
07:01with longer hind limbs than forelimbs.
07:05They were, like, exactly the same, actually.
07:08But the thing that sets them apart from the other groups of mammals
07:11is they were a marsupial, so they have a pouch,
07:13and their babies would have developed inside that pouch.
07:18The team wanted to identify the exact stage
07:21when the developing Tasmanian tiger began to take on the appearance of a dog.
07:27Because it looked so much like a dog,
07:29there's an awful lot we can learn by looking at its DNA
07:32about how animals evolve a particular body form.
07:37These animals, the dog and the thylacine,
07:39haven't shared an ancestor for over 160 million years.
07:43The 3D models enabled them to see
07:46when the joey's developing bones began to resemble dogs.
07:51I initially thought they would start to change very early on,
07:55and it would be very early events that made them look like a dog,
07:59but it was quite late in development
08:01before they started really taking on that dog-like appearance
08:04and having their limbs changed to have that really sort of paw shape
08:09and very un-marsupial, like, and much more like a wolf.
08:14The scientists now understood
08:16how thylacines physically developed after birth,
08:19but they needed to investigate
08:21how DNA played a role in the process.
08:25We can start to put those two bits of information together
08:28to understand which genes are important
08:31and at what time points to really give you that dog-like form.
08:36And that's starting to really answer that fundamental question then
08:39of how did this animal evolve to look like that
08:41and what specifically changed in its genome
08:45to give it that really unique body form.
08:49DNA from the Melbourne specimen
08:51had sequences long enough to recreate
08:53the entire three-bellion-letter genome of the thylacine.
08:58But Pask and his team
09:00needed to isolate specific genes from the DNA strings
09:04for the next phase of their research.
09:07De-extinction and trying to bring an animal back to life
09:10is very different from animal cloning.
09:12Animal cloning is something we're very good at today.
09:16In that process, you have to start with a living cell.
09:19And you can put that living cell into an embryo
09:22and you can use that living cell then
09:24to generate a whole other individual or clone
09:27of where that cell originally came from.
09:30The key thing for any of these sorts of technologies
09:32of bringing an animal back
09:33is you have to start with a living cell.
09:36So although we have the complete blueprint of a thylacine,
09:40this is letters on a computer screen.
09:43This is not a living cell.
09:45So you've got to start with that living cell template.
09:47You get then a living cell from a very closely related species.
09:59So quite a recent common ancestor.
10:02And then what you do is you sequence the DNA of that common ancestor
10:05and you compare it to the animal that's gone extinct.
10:09And then what you're going to do is you're going to take
10:12all of the differences from your extinct animal blueprints
10:15and edit them into the living cell that you've got
10:19from your existing live animal.
10:21Once you've done that, you've got a living cell now
10:25that has DNA or a blueprint that looks like the extinct animal.
10:29And then you can then transfer that cell into an embryo
10:33to generate a whole other living individual.
10:36The number of edits that you have to make
10:38is in the order of millions of edits.
10:41And each one of those edits has to be made very precisely
10:45and quadruple check that you've made that right change
10:48before you proceed to the next step.
10:50There's a new technology called CRISPR-Cas9 technology.
10:54It's a DNA editing tool that we now have
10:57that enables you to make those edits.
11:01After identifying and editing out the thylacine gene that creates bone,
11:06they inserted it into a mouse embryo with a chemical tag
11:10that made the gene glow blue when active.
11:14We can inject that piece of DNA into a very early mouse embryo
11:18and that piece of DNA will just get incorporated
11:20into the mouse genome or that mouse blueprint.
11:24And then from that, that gene will switch on and work
11:26whenever it would have during thylacine development.
11:30We're really trying to understand the parts of that genome
11:33that were important for giving it that thylacine-like form.
11:37So we're going to hook up a piece of thylacine DNA
11:40to what we call the reporter.
11:42So it's another bit of DNA that produces a particular colour.
11:45In this case, it was a blue dye.
11:47And that then helps us rebuild that picture of what that gene might be doing
11:52and which processes in development it might be affecting you.
11:56Blue patterns appeared in the mouse embryo's developing skeleton.
12:00This allowed them to pinpoint when thylacines diverged from normal mammals
12:06into pouch-using marsupials.
12:10The next step in Andrew Pask's journey through Jurassic Park Down Under
12:14will be to create a living thylacine genome
12:17by modifying the genome of a close-living relative.
12:21We can start to think about surrogate species
12:25that we would use to genome edit
12:28to make them look like a thylacine.
12:30But the really big problem with the thylacine then
12:32would be transferring that embryo
12:35into another marsupial surrogate mother
12:37that would then have to give birth to a thylacine pouch young.
12:44Pask thinks that Western Australia's Numbat
12:47might provide the best starting DNA blueprint.
12:51It's one of the thylacine's closest living relatives,
12:55last sharing a common ancestor 30 million years ago.
13:00The termite-eating creature also has stripes,
13:04but adults are only slightly bigger than a squirrel,
13:07where adult thylacines were much bigger.
13:12Numbats are the closest living relative to the thylacine.
13:17But unfortunately, these are insectivores,
13:20so they'd obviously have a very different digestive system.
13:24So they obviously have a huge amount of differences
13:26between their genomes.
13:28And that makes our job a lot harder
13:30because you would have to make many, many more of those edits
13:33to the blueprint to make our thylacine genome
13:37really come back to life.
13:39Still, 95% of the DNA sequences
13:44that make a species unique
13:46are shared between the thylacine and the Numbat.
13:50So although there's 5% difference or thereabouts
13:54between our Numbat DNA and the thylacine DNA,
13:58we know that not all of those changes
14:00are really important for making a thylacine.
14:02Why go to all this trouble
14:05to bring back an animal that's already extinct?
14:09It's one of the few animals that we know
14:11the exact moment that the last animal died
14:14and that species went completely extinct from our planet.
14:17And it's got this really sad story of extinction
14:20where we aggressively hunted this animal
14:22to extinction in the wild.
14:23The Tasmanian tiger's modern relatives
14:28are now in imminent danger.
14:31Tasmanian devils,
14:33eastern, northern and spotted quals
14:36are all in trouble.
14:39There's a number of other carnivorous marsupials
14:42which are on the endangered list.
14:45So rather than letting these animals go extinct
14:47now, we know what we can do to really protect
14:49and preserve those animals
14:50that we have an insurance population
14:52that can be used to repopulate them back after.
14:57The end goal of this de-extinction effort
14:59will be to reintroduce the thylacines
15:02to the wild reserves
15:03that cover about half of Tasmania today.
15:07With a thylacine,
15:08it's really a great example of a species
15:10that you could just pop back
15:12into the ecosystem in Tasmania
15:14and it certainly has everything it needs there
15:16in order to not just survive
15:18but also thrive in that environment.
15:22Most extinct creatures wouldn't survive today
15:25because too much has changed in their worlds.
15:30But Tasmania still has the same wilderness
15:33that the tigers called home
15:34and it still has their natural prey.
15:37The full habitat of this species
15:41is still in existence in the island of Tasmania
15:44for this animal once existed.
15:46That's a really important key piece
15:48that you need to have of your de-extinction puzzle
15:51if you really want to bring these animals back.
15:54You've got to have some place to put them.
15:57The habitat is the same
15:59and their prey is still there.
16:02Smaller marsupials
16:03like qualls,
16:05Tasmanian devils
16:06and wallabies
16:08are what thylacines ate.
16:11So there's no question
16:12thylacines could live in Tasmania's wilderness.
16:14There's a good reason to bring them back.
16:19For a good ecosystem to exist in harmony
16:23you really need these apex predators
16:25these animals that sit
16:26right at the top of the food chain
16:28and the thylacine was absolutely unique
16:31in marsupials
16:31in being the only apex predator
16:34that we have.
16:35As Tasmania's key carnivore
16:40the thylacine could re-establish
16:42the island's fragile ecosystems
16:44that are currently under threat.
16:47We have this huge diversity
16:49of life that we see
16:51in the marsupial mammals
16:52but none of them sit
16:54at the top of that food chain
16:55as these really apex predators.
16:57The thylacine was really
16:58the only one that we had.
17:01So bringing an animal like that
17:02back to life
17:03could really have a lot of potential
17:05benefits.
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