De-extinction: a revival for conservation? - Veterinary Practice
Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now



De-extinction: a revival for conservation?

ROBIN FEARON reports that efforts to resurrect extinct species using newly developed genetic technologies are creating a stir in the natural sciences – and may lead to some startling revivals

OPTIMISM is a curious thing. Without it we would be condemned to repeat past mistakes and with it we can see the positive in almost any situation, however hopeless. Take that mindset and apply it to species survival and you create a curious situation where extinction does not mean “forever”.

Biotechnology and genetics have now reached the stage where convergent technologies could provide a DNA databank for threatened species and even reintroduction for species long extinct.

This is the central premise of the Revive and Restore project set up by entrepreneur Stewart Brand and his wife Ryan Phelan.

Working on principles established by Nobel Prize-winning biologist Svante Paabo, miner of mammoth and neanderthal DNA, the pair – Brand the ideas man and Phelan a biotechnologist – have already started work on reviving the passenger pigeon, whose “final” demise came at the hands of the US military in 1914.

Prior to its untimely end as canned product for hungry soldiers, the passenger pigeon had been the most abundant bird in North America. Its weakness for settling in one huge flock and the advent of the telegraph proved historical circumstances too weighty for the species to bear.

So using DNA from a zoo specimen preserved in Cincinnati, the project will give wings to what some would call wildly optimistic hopes to reintroduce a viable population to the US.

Incredible breakthroughs

In Revive and Restore’s corner are two incredible technological breakthroughs: the first is two genetic technologies (CRISPR and TALENs) that allow highly targeted genome editing and the second is even more astounding – the ability to allow one species to give birth to another.

Mike McGrew’s work at the Roslin Institute, in collaboration with the Central Veterinary Research Laboratory of Dubai, showed that germ cells from a chicken could be placed in a duck’s embryo, birthing offspring that then produced chicken sperm. This is then only a short gene knockout step away from duck matings producing chickens.

Revive and Restore has taken these surprising developments as the green light for its ambitions. Using the passenger pigeon’s nearest genetic relative, the band-tailed pigeon, the group wants to “de-extinct” an entire species. Science author and self-labelled “rational optimist” Matt Ridley is a supporter.

“They asked why we could not just investigate this problem and in particular that it could be made to work correctly and not cause more problems,” he said at the recent Thinking Digital conference. “For example, that it did not make people complacent about extinction or it did not bring species back in a form where they could not survive except in a zoo. Until five years ago I would have said that was a ridiculous pipe dream.”

He disagrees with the view that this generation is overseeing mass extinction events across the globe. “Globally we have [only] driven six species extinct continentally,” he explained.

The role of pests

“If we look at groups like birds and mammals it looks like it peaked around the end of the nineteenth century. Most of the species extinctions we have caused, another 123, have been on islands where we have introduced rats, cats or other pests.”

Brand and Phelan have recruited graduate student Ben Novak to sequence the passenger pigeon’s DNA, sampled from the toepad of a preserved male bird. An almost complete sequence was the result, but after piecing together the entire code using the band-tailed pigeon’s DNA as a guide there are greater challenges ahead.

How will the offspring be reared? Passenger pigeons have been classified as an unusually social species so, supposing parental guidance from a bandtailed pairing, we can only create a crude estimate of species behaviour. Then there is the change in habitat, in eco-systems, intervention by man and other species.

As one astute MIT Technology reviewer points out, the billion strong flocks of passenger pigeons that were said to cover the sky for hours would pose a unique threat to aircraft.

Mistakes and mutations

Technology becomes secondary in this discussion. Possessing the genome and the means to replicate it are the bare bones. “When you see it you just have it in the computer, you don’t have it in biology,” said Matt. “So how do you get it into biology? It is not going to be easy. It will take years.

“There will be mistakes and mutations, there will be chicks that fail to hatch and other problems, but it is no longer impossible or even unlikely that this will happen in the next five, 10 or 15 years.”

David Ehrenfeld, a conservation biologist at Rutgers University, has publicly disagreed with the project’s aims. Thriving populations of reintroduced passenger pigeons are nothing but a pipe-dream. “The birds will live in a cage labelled “passenger pigeon” but they won’t be, not really,” he said.

At a National Geographic forum he pointed out the irony of discussing reintroduction when conservationists are outgunned in their battle to save African elephants from armed poachers.

“So why are we sitting in this auditorium talking about bringing back the woolly mammoth? Think about it.”

Reintroducing species

Matt Ridley acknowledges the struggle. “There is time to save a lot of these creatures. Many are hanging on, largely thanks to the efforts of conservationists. But wouldn’t it be great to get some of those 129 extinct species back?”

The excitement about reintroducing species like the Tasmanian tiger, the gastric brooding frog or the mammoth guarantees headlines, but privately the doubts linger even among the most optimistic.

“I have a dream that the Farne Islands with their huge populations of guillemots, razorbills and puffins will one day have a huge colony of great auks on it,” said Matt. “There are ecological issues with this. Is the habitat still there?

“Can we do this in a way that there will be wild creatures that can plug back into their ecosystems and not just zoo animals? Guillemots train their young how to feed and great auks probably did too.

“There are all sorts of issues. People are even saying ‘maybe it deserved to go extinct’. I don’t buy that, but we have to think very carefully about whether it is the right thing to do, whether it is sending the wrong message that extinction is not forever.

“Nonetheless it is an exciting new project and one worth pursuing.”


  • TALENs –
  • CRISPR –
  • Central Veterinary Research Laboratory, Dubai –

Have you heard about our
IVP Membership?

A wide range of veterinary CPD and resources by leading veterinary professionals.

Stress-free CPD tracking and certification, you’ll wonder how you coped without it.

Discover more