The University of Melbourne has just received $5 million in funding to establish a new research lab dedicated to resurrecting the thylacine (Tasmanian tiger), as well as marsupial conservation.
The new lab, the Thylacine Integrated Genetic Restoration Research (TIGRR) Lab, will be headed up by biosciences professor Andrew Pask.
In the past, says Pask, “we could never propose to do something as big as bringing back a Tassie tiger, simply because we wouldn’t have had the funding or the longevity of funding to achieve such a big goal”.
“But this philanthropic donation has now given us that scope that we can actually really have a bloody good go at trying to achieve this.”
But how will it work? And what are the risks?
The thylacine: an Aussie icon
The Tasmanian tiger is a tragic allegory for the ravaging effects of European settlement on Australia.
Once abundant on the island, the creatures were hunted to extinction because they were thought to kill sheep, a staple of the colonial economy. Later research revealed that tigers weren’t sheep predators at all, but by then it was too late. The last known Tassie tiger, named Benjamin, died in Hobart Zoo on 7 September 1936.
The thylacine also lived on the Australian mainland until some 3,000 years ago. Its iconic striped and gape-jawed image can be found on ancient rock-art all over the continent, and especially in Western Australia and the Northern Territory. Skeletal remains have been found in western New South Wales.
Though its ghost still stalks the hills of Tasmania in the form of tantalising alleged sightings and local folklore, it seems likely that the real thylacine has been lost to time – but for how long?
How do you build a Tassie tiger from scratch?
Bringing a creature back from oblivion may seem more Jurassic Park than actual science, but the researchers in the new laboratory have more than a simple idea: they have a plan to make the living thylacine a reality.
“The first thing you need is a really good genome from your extinct species,” says Pask. “It’s like the blueprint of how to build a Tasmanian tiger, in their DNA.”
In fact, that step is already complete.
“We were fortunate enough to stumble upon a preserved pouch specimen,” says Pask. “So this is a baby that was taken from his mother’s pouch when she was shot, as part of the bounty they had in Tasmania to wipe out the tigers.
“And they took these little babies from the parents and dropped them in alcohol, and those specimens that were sitting in alcohol actually preserved the DNA much better.”
Pask and a team of researchers released an assembly of the thylacine genome in 2017.
The next step involves identifying the extinct species’ closest living relative. “We can’t create life from extinct tissue or dead DNA, we have to start off with something that’s living,” Pask explains. “And then we can use that as our template to create the thylacine.”
In this case, the closest living relative to a Tasmanian tiger turned out to be the dunnart, a marsupial mouse.
“The next step is to compare those two blueprints, and look to find all the places [on the genome] where the thylacine is different from the marsupial mouse,” Pask says. “Then we go into a living cell from a marsupial mouse, and we start editing in all of those changes.”
This kind of gene editing is only possible due to the revolutionary CRISPR-Cas9 technology. CRISPR-Cas9 was adapted from a naturally occurring function present in bacteria: it allows us to, in layman’s terms, ‘snip’ out certain target segments of DNA and replace them with others.
With the help of this gene-editing technology, the team believe they can effectively turn a marsupial mouse cell into a thylacine cell – though some of the science will need to be refined in the next ten years (the length of time the current funding will last).
“Once you’ve got that living cell – that is, a Tasmanian tiger engineered cell – it’s just a matter of going through the sort of standard cloning process that we use almost every day for other mammals, to turn that cell into a whole organism,” Pask says.
And the lab’s work won’t just be about reviving the tiger: they will create a ‘biobank’ of diversity in at-risk marsupial populations, which they could then use to breed and reintroduce endangered or disappeared species.
What are the risks?
There are a few obvious and troubling questions raised here, of course. For example, if you’re creating a thylacine based on one particularly well-preserved specimen, how do you prevent the new population from forming a genetic bottleneck? How do you create a robust, diverse population that can thrive?
“What we strive to do is not just recreate one, but to have a population that can actually thrive back in its native environment,” Pask stresses. “To do that, we need to understand what the variation was between animals in that population.”
With that in mind, the research team hopes to apply these techniques to the genomes derived from multiple specimens.
“Once we’ve got that one blueprint down pat for one thylacine – which is what we were able to get from that specimen – we can sequence all of those other specimens in museums around the world,” explains Pask. “Because even though the DNA is broken up into lots of little pieces, we can match it back to where it should sit.”
That means that should they succeed in ‘building’ a thylacine and raising it to maturity, they can then do the same for other thylacines with different genes. That’s important, because lack of genetic diversity in a population can create dangerous risks, including diseases and defects.
Another key issue is that we don’t know how much of the Tassie tiger’s behaviours, for example hunting abilities, were learned rather than innate.
“Unless somebody goes down the pathway of bringing the animal back, we don’t know what that impact will be,” agrees Pask. There may be some potential avenues around this, though they sound like the stuff of a children’s book.
“There are ways that you can teach that behaviour,” he muses. “Maybe we put it in with Tassie devils as surrogates, maybe you put it with a wolf or something that hunts so it can learn, there are ways that you can surmount these issues.”
But Pask notes the most pressing ethical conundrum will rear its head when and if a thylacine population is successfully bred: “Then people will be thinking about whether we want to introduce these animals back in the wild, and what impacts that might have.”
It’s an important question. Humans have a jaded history of introducing animals to environments they aren’t currently living in (see: cane toad). To some, that kind of decision looks a bit like playing God. This kind of work, playing around with genes and bringing creatures back from the brink, is deeply controversial – and not everyone in the scientific community is comfortable with it.
“To play the Goldblum in this scenario,” wrote University of Tasmania conservation ecologist David Hamilton on Twitter, “I’m personally of the view that we should prioritise protecting the ecosystems we currently have in Tasmania – plenty [of] species are struggling, and we can have no idea what the impacts of throwing an apex predator back into the mix would be.”
But Pask points out it was the removal of tigers from the island that jeopardised the ecosystem, not the other way around.
“It’s a very recent extinction event, and completely human-driven,” he says. “So, if we could recreate [the thylacine] we could put it straight back into its natural habitat, and it should be able to reoccupy the same position in the food chain there.”
The extinction of the Tassie tiger, Pask says, robbed the island of its one, sole apex predator.
“Marsupials are really odd in that we don’t have any examples of apex predators in marsupials except for the Tassie tiger,” Pask says. “And they are really important animals for stabilising the ecosystem beneath them.”
The loss of an apex predator can cause all sorts of mayhem in the prey populations of an ecosystem, according to Pask.
“A great example of this is the Tasmanian Devil Facial Tumour disease,” Pask says. The disease, which was first described in 1996, has wiped out an estimated 50% of the Tasmanian devil population.
“But if you’ve got a Tassie tiger there, they eat those sick animals and weak animals in the population, and so they remove those sick animals and prevent the spread of disease,” Pask says. “So that’s a great example of how if the tiger was still in place, we probably wouldn’t have seen that disease spread through the whole population.”
Mike Archer, a professor in the life sciences at UNSW Sydney, is another prominent advocate for de-extinction. He pioneered early work exploring the possibility of cloning Tassie tigers by working with preserved DNA at the Australian Museum, of which he was director from 1999 to 2004. Nowadays, his de-extinction research with colleagues at UNSW is focused on trying to resurrect the extinct gastric-brooding frog, which disappeared in the 1980s.
Archer has an easier time of it than Pask in his current research: they already have preserved cells from the frog, so it’s possible for them to transplant those into the egg of a different species in the hopes of producing a “100%, completely authentic gastric-brooding frog”. The team have already produced early-stage embryos of the frog.
Archer believes, along with Pask, that restoring an apex predator to the ecosystem will do more good than harm.
Archer draws a parallel with the North American experience in Yellowstone National Park: wolves disappeared from the park around the 1920s thanks to predator control.
“When wolves were eliminated from Yellowstone, the ecosystem began to collapse,” he says. “The elk numbers got out of control, they began to overeat vegetation, rivers were beginning to erode because the vegetation wasn’t stabilising the banks anymore.
“When [wolves] were returned, the ecosystem stabilised again, and it’s back to normal.”
From both Archer’s and Pask’s perspectives, this work is thus more about righting the wrongs of the past than playing God.
“When we wiped them from the face of the Earth, we created this massive imbalance in Tasmania, and if we have the technology to bring them back I think we owe it to that species and everything else in Tasmania,” says Pask.
Archer agrees: “We played God when we inappropriately exterminated the thylacine, that’s when humans did a terrible inexcusable thing. I would like to think now…we can undo the damage we did.”
Archer acknowledges, though, that there are some troubling ethical conundrums associated with de-extinction.
“One of the things that has plagued all of us who have been interested in de-extinction has been some concern by ecologists that we would end up extincting extinction,” he says.
“In other words, why would anybody concern themselves any more with conserving endangered species if there’s the possibility of bringing a species back from extinction?”
But Archer has a response to those fears.
“It’s much, much easier to look after an endangered species, and reduce the risks of extinction for that species, than it is to try to bring something back after it’s become extinct.
“So, in terms of economics, energy, finances and so on, we’d be far better off looking at the species before they become extinct.”
For Archer, the imperative is to do as much as possible to reverse the ravaging effects of human-driven extinction events – both before and after they happen.
“When you get beyond frankly fairly facile arguments about playing God, every person in the world has an inarguable responsibility to stop the massive rate of things going extinct in the world.”
And that, he says, involves deploying all the tools in our arsenal.
“I’ve often said it’s a bit like playing a game of golf: when a golfer goes out to play a game of golf, if they only have one club in their bag they’re probably not going to play a particularly good game of golf.
“But if they’ve got a range of different clubs, for all sorts of different purposes, they’re more likely to play a good game.
“I think conservation is much like this. If we just go with the assumption that we can keep wildlife safe on the other side of the fence, and try to stop people from messing over in that area, we’re not going to do a very good job of conservation.
“But if we use all these additional strategies, including de-extinction, including translocation, including even conceivably synthetic biology, then we’re more likely to play a much more effective game of conserving the precious biodiversity, the global genome, that underpins our own survival.”