The notion of bringing vanished species back to life—some call it de-extinction—has hovered at the boundary between reality and science fiction for more than two decades, ever since novelist Michael Crichton unleashed the dinosaurs of Jurassic Park on the world.
Though the revival of a mammoth or a passenger pigeon is no longer mere fantasy, the reality is still years away.
For another extinct species, the time frame may be much shorter.
The quest for de-extinction is the obsession of a group of Australian scientists led by Michael Archer, who call their endeavour the Lazarus Project.
Archer previously directed a highly publicised attempt to clone the thylacine, an iconic marsupial carnivore that went extinct in the 1930s. That effort managed to capture only some fragments of the thylacine’s DNA.
Bones from thylacine, the largest known carnivorous marsupial of modern times. It is commonly known as the Tasmanian tiger or the Tasmanian wolf [Image: Shutterstock]
Archer and his colleagues have now revealed they’re trying to revive two closely related species of Australian frog. Until their disappearance in the mid-1980s, the species shared a unique—and utterly astonishing—method of reproduction. The female frogs released a cloud of eggs, which the males fertilized, whereupon the females swallowed the eggs whole.
A hormone in the eggs triggered the female to stop making stomach acid; her stomach, in effect, became a womb. A few weeks later the female opened her mouth and regurgitated her fully formed babies.
This miraculous reproductive feat gave the frogs their common names: the northern (Rheobatrachus vitellinus) and southern (Rheobatrachus silus) gastric brooding frogs.
Unfortunately, not long after researchers began to study the species, they vanished. “The frogs were there one minute, and when scientists came back, they were gone,” says Andrew French, a cloning expert at the University of Melbourne and a member of the Lazarus Project.
To bring the frogs back, the project scientists are using state-of-the-art cloning methods to introduce gastric brooding frog nuclei into eggs of living Australian marsh frogs and barred frogs that have had their own genetic material removed. It’s slow going, because frog eggs begin to lose their potency after just a few hours and cannot be frozen and revived. The scientists need fresh eggs, which the frogs produce only once a year, during their short breeding season.
The matchless oddity of the gastric brooding frogs’ reproduction drives home what we lose when a species becomes extinct. But does that mean we should bring them back? Would the world be that much richer for having female frogs that grow little frogs in their stomachs? There are tangible benefits, French argues, such as the insights the frogs might be able to provide about reproduction—insights that might someday lead to treatments for pregnant women who have trouble carrying babies to term. But for many scientists, de-extinction is a distraction from the pressing work required to stave off mass extinctions.
“There is clearly a terrible urgency to saving threatened species and habitats,” says John Wiens, an evolutionary biologist at Stony Brook University in New York. “As far as I can see, there is little urgency for bringing back extinct ones. Why invest millions of dollars in bringing a handful of species back from the dead, when there are millions still waiting to be discovered, described, and protected?”
De-extinction advocates counter that the cloning and genomic engineering technologies being developed for de-extinction could also help preserve endangered species, especially ones that don’t breed easily in captivity. And though cutting-edge biotechnology can be expensive when it’s first developed, it has a way of becoming very cheap very fast. “Maybe some people thought polio vaccines were a distraction from iron lungs,” says George Church. “It’s hard in advance to say what’s distraction and what’s salvation.”
But what would we be willing to call salvation? Even if Church and his colleagues manage to retrofit every passenger pigeon–specific trait into a rock pigeon, would the resulting creature truly be a passenger pigeon or just an engineered curiosity? If Archer and French do produce a single gastric brooding frog—if they haven’t already—does that mean they’ve revived the species? If that frog doesn’t have a mate, then it becomes an amphibian version of Celia, and its species is as good as extinct. Would it be enough to keep a population of the frogs in a lab or perhaps in a zoo, where people could gawk at it? Or would it need to be introduced back into the wild to be truly de-extinct?
“The history of putting species back after they’ve gone extinct in the wild is fraught with difficulty,” says conservation biologist Stuart Pimm of Duke University. A huge effort went into restoring the Arabian oryx to the wild, for example. But after the animals were returned to a refuge in central Oman in 1982, almost all were wiped out by poachers. “We had the animals, and we put them back, and the world wasn’t ready,” says Pimm. “Having the species solves only a tiny, tiny part of the problem.”
Hunting is not the only threat that would face recovered species. For many, there’s no place left to call home. The Chinese river dolphin became extinct due to pollution and other pressures from the human population on the Yangtze River. Things are just as bad there today. Around the world frogs are getting decimated by a human-spread pathogen called the chytrid fungus. If Australian biologists someday release gastric brooding frogs into their old mountain streams, they could promptly become extinct again.
“Without an environment to put re-created species back into, the whole exercise is futile and a gross waste of money,” says Glenn Albrecht, director of the Institute for Social Sustainability at Murdoch University.
Even if de-extinction proved a complete logistical success, the questions would not end.
Passenger pigeons might find the rebounding forests of the eastern United States a welcoming home. But wouldn’t that be, in effect, the introduction of a genetically engineered organism into the environment? Could passenger pigeons become a reservoir for a virus that might wipe out another bird species? And how would the residents of Chicago, New York, or Washington, D.C., feel about a new pigeon species arriving in their cities, darkening their skies, and covering their streets with snowstorms of dung?
De-extinction advocates are pondering these questions, and most believe they need to be resolved before any major project moves forward. Hank Greely, a leading bioethicist at Stanford University, has taken a keen interest in investigating the ethical and legal implications of de-extinction. And yet for Greely, as for many others, the very fact that science has advanced to the point that such a spectacular feat is possible is a compelling reason to embrace de-extinction, not to shun it.
“What intrigues me is just that it’s really cool,” Greely says. “A saber-toothed cat? It would be neat to see one of those.”