If extinct animals could be brought back from the dead, should we do it? – Science News
Posting pictures of your newborn baby on social media isn’t unusual.
But Ben Novak’s baby photos are a little stranger than most.
The biologist, a recent first-time father of twins, has taken to tweeting pictures of pigeon hatchlings instead.
The birds are likely the world’s first transgenic or genetically engineered pigeons — and Mr Novak hopes they’ll help him bring an extinct bird back from the dead.
An expat American — now PhD student at Monash University and CSIRO — Mr Novak works with the global conservation initiative Revive and Restore.
Co-founded by a green philanthropist and a genomics entrepreneur, Revive and Restore’s controversial mission is to use biotechnology to “genetically rescue” extinct or endangered animals.
But other teams are exploring the possibility of bringing back extinct aurochs (a wild ancestor of domesticated cows), a Galapagos tortoise, the quagga (a South African zebra) and a giant flightless bird once common in New Zealand, the bush moa.
Some wonder if Australia’s iconic meat-eating marsupial, the Tasmanian tiger, might even get to roam again one day too.
Why bring back the passenger pigeon?
A pigeon seems like a distinctly unsexy species to start with. But Mr Novak has made it his life’s quest to bring back the passenger pigeon by 2025.
The bird was once endemic to the north-eastern United States, and part of Canada.
“150 years ago, there were 5 billion passenger pigeons,” Mr Novak said.
“It was probably the most abundant bird on the planet.”
The species behaved uniquely. Its entire population amassed together in just two or three giant flocks, sweeping across the sky in staggering formations.
They had a dramatic impact wherever they descended, stripping trees bare, and exposing the forest floor to sunlight and mounds of rich fertiliser in the form of guano — that is, poo.
This promoted the regeneration and renewal of forests as a healthy habitat for other animals.
“They essentially did the same as a hurricane and a forest fire might,” Mr Novak told a Science Friction audience at the Melbourne Museum — which holds five passenger pigeon specimens in its collection.
But American’s love of pigeon pie eventually wiped the species out altogether.
The last passenger pigeon, known as Martha, died in captivity at the Cincinnati Zoo in 1914.
Mr Novak believes the environmental impact of the pigeon’s demise has been substantial.
“In eastern United States … there is more forest habitat than there has been in 150 years, in some places, 400 years.
“The forest is coming back [but] most of the species living in the forest are still declining.”
What’s missing, his investigations suggest, is the pigeon’s unique role in the ecosystem.
“It turns out that passenger pigeons were likely the major driver of that regeneration process for … possibly the last million years.”
Mr Novak and colleagues point to what happened when wild wolves, a so-called apex predator, were intentionally returned to Yellowstone National Park in 1995. Their 70-year absence had caused the elk population to explode and overgraze, destroying habitat for other animals.
When the wolves came back, that changed, with a positive flow-on effect for biodiversity in the park: “The beavers came back.”
Mr Novak believes de-extinction and so-called “re-wilding” projects must carefully consider what species to target, and not just seek to fulfil a fantastical desire to bring back lost icons.
“[The focus should be] to bring back animals that we know have really important roles that completely transform habitats and ecosystems,” he said.
The science of resurrection
The starting point for scientists is to sequence the genome of the extinct animal they want to try to bring back.
In the case of the passenger pigeon, old specimens preserved in museum collections have made this possible.
“You take a little chunk off of its toe, about the size of a pinhead,” Mr Novak said.
The next step will be to use the tools of biotechnology to recreate the ancient genome in a living animal.
“This is pretty far out. We’re not there yet,” he said.
If a frozen specimen exists with intact healthy tissue, its cells could potentially be used to create a direct clone of the extinct creature, using the same technique that made Dolly the sheep.
In reproductive cloning — like that used for Dolly — the DNA from a donor’s body cell is inserted into the evacuated nucleus of an egg cell, which is then triggered to develop into an embryo and implanted into a mother’s womb.
Mr Novak’s approach will be to take a species that is genetically similar to the passenger pigeon, the band-tailed pigeon, and use it as a living template.
The gene editing technique known as CRISPR-Cas9 can then be used to cut, snip and sculpt its genome to resemble its long-lost ancestor.
It’s early days, but Mr Novak is developing the technique in pigeons, starting with domesticated rock pigeons.
“Band-tailed pigeons are rather rare in captivity,” he said.
“Rock pigeons live in higher densities and are easier to work within research settings.”
This year he has successfully bred a small number of genetically modified pigeons (16 in total across three batches). They contain the Cas9 gene in their reproductive or germ cells.
This means when they breed they’ll pass the gene onto their offspring.
Cas9 is an enzyme that acts like a pair of molecular scissors to cut DNA. It can be used to help delete, edit or insert specific DNA sequences in a genome.
Animal behaviour: it’s about more than genes
Recreating an extinct genome is only part of the story. We are all much more than our genes. What about replicating the complex behaviours of extinct animals?
Band-tailed pigeons don’t gather in vast, dense flocks as passenger pigeons did, but Mr Novak thinks gene editing could help with that.
“We can edit the DNA of a band-tailed pigeon so that they become hyper-social.”
Mr Novak said they are currently mining the genomes to identify mutations for specific traits — for instance, “those that support social breeding behaviour.
“Then we have a species capable of resuming [the passenger pigeon’s] role in nature, as long as we nurture it. It’s not just about DNA.”
A successful result would be a proxy or doppelganger of the extinct passenger pigeon, not a faithful replica.
But that’s a long way off — if it ever happens at all.
The de-extinction controversy
Many scientists see de-extinction efforts as fanciful, even maverick work, and a distraction from the real crisis.
“We’re living in the middle of an extinction crisis,” said Euan Ritchie, a wildlife ecologist at Deakin University.
Professor Ritchie and others point to evidence suggesting we’re experiencing the sixth mass extinction event in the Earth’s history — on par with what wiped out the dinosaurs 65 million years ago.
But an asteroid isn’t responsible this time — we are.
“We are in a stage where humans are really the strongest kind of engineering force in nature, rather than nature itself,” said Christy Hipsley, an evolutionary biologist and palaeontologist at the Melbourne Museum.
“A single species having that impact is something that has never happened in all of time.”
De-extinction science can never replicate the wonder of evolution, nor how long it takes for species to evolve, Professor Ritchie said.
“That’s what we’re doing.
“We’re losing species every day all over the world.”
Critics of de-extinction projects share Professor Ritchie’s concern that limited resources would be better spent on effective strategies to conserve critically endangered species.
“Don’t get me wrong — I would love to see a thylacine [Tasmanian tiger]. Nothing would make me happier,” he said.
“[But] we should be focusing on what we have now and asking why species went extinct in the first place.”
Would extinct animals be happy in the 21st century?
Some argue we have a moral duty to bring back extinct animals if we had the technology to do so, especially if our actions caused their original demise.
Mr Novak, however, says he isn’t motivated by a sense of moral obligation.
Other scientists have significant concerns about animal welfare consequences of de-extinction efforts.
Even if an animal could be genetically engineered back into existence, would it thrive in the 21st century — especially if its habitat has been destroyed and food sources depleted?
There is a risk a species would be returned only to face extinction again. Or, perhaps worse, become an invasive species itself and cause others to disappear.
“The communities that currently exist have now evolved and adapted in the absence of those species. You’re introducing something completely novel to them,” Professor Ritchie said.
“There are a whole range of really complex ecological arguments and problems to think about.”
Other benefits of de-extinction efforts
Accusations of scientific hubris or maverick research aside, some scientists think investment in de-extinction science might have other benefits.
The techniques that Mr Novak and colleagues are pioneering — for example, gene-editing wild species — may help pull threatened animals back from the brink.
Dr Hipsley was part of the team that published the genome of the extinct Tasmanian tiger study earlier this year.
She wonders whether the science might offer hope for the Tasmanian devil. Populations of this distant relative of the Tasmanian tiger are being wiped out by a deadly facial tumour disease.
“You could insert resistant genes into a population … [and] … release populations of the Tasmanian devil that are resistant to the disease.
“I think there are so many applications that often aren’t factored into the cost.”
A bleak future without biodiversity
According to recent modelling by Danish researchers, published in the Proceedings of the National Academy of Sciences, it would take 5 to 7 million years to restore biodiversity levels to what they were before humans evolved, and 3 to 5 million years to recover the species expected to disappear over the next 50 years.
If Mr Novak succeeds in resurrecting the passenger pigeon, could this technological fix foster a sense of complacency about saving endangered species?
If biotechnology can bring them back, why should we care about what’s being lost?
“Many people have said that conservation needs extinction because without extinction there’s no argument for conservation,” Professor Ritchie said.
Mr Novak believes we have a vital choice to make.
“We live on this planet in such a dominating way that we get to choose how we live here,” he said.
“Do we want trees and prairies to clean our air, or do we want giant atmospheric scrubbers made out of steel and concrete?
“Do we want to live on a planet that’s impoverished for the entire duration of our existence or do we want to live in one that is … rich and diverse?”