We have triggered irreversible changes in our planet—which will have catastrophic effects on all that inhabit it. Since we can’t stop climate change, scientists are trying to alter the evolutionary course of animals—so they can survive it. But should we be playing God?
Researched by: Nirmal Bhansali
First, explain ‘assisted evolution’...
Defining evolution: The modern version we all study in school dates back to good old Charles Darwin and his seminal book ‘On the Origin of Species’—where he laid out the idea of ‘natural selection’. It claimed that all creatures produce more offspring than can survive. Those with traits best equipped to survive pass on their genes—which determines how that species evolves. But if you alter the environment, then the traits required to survive also change or evolve. Here’s a simple example:
If a creature with poor eyesight happens to produce offspring with slightly better eyesight, thanks to random mutations, then that tiny bit more vision gives them more chance of survival. The longer they survive, the more chance they have to reproduce and pass on the genes that equipped them with slightly better eyesight. Some of their offspring might, in turn, have better eyesight than their parents, making it likelier that they, too, will reproduce.
Redefining evolution: But we now live in the world of ‘unnatural selection’—aka the Anthropocene Era. Scientists agree that humans are now the most powerful evolutionary force on the planet. Every other species has to adapt to live alongside us. And we are changing the environment so quickly that many of them cannot adapt fast enough to survive—hence, their extinction rate is 1000X faster, due to human interference. As one scientist puts it: "There has never been another species that has so quickly changed the course of evolution."
Ergo, assisted evolution: This where humans actively intervene—in a variety of ways—to alter evolutionary change in a threatened species. They either may not possess the traits to avoid extinction—or may not be able to evolve in time. The aim is not to just change an individual creature—but also its descendants.
Ending the extinction vortex: Once we’ve reduced a species to a small number, even the best conservation efforts cannot save them. Take the example of the helmeted honeyeaters—there were only 50 left in 1989. As you can see, it’s a charming looking creature—greatly in need of saving:
Captive breeding programs were failing due to inbreeding:
In any small, closed breeding pool, harmful genetic mutations can build up over time, damaging animals’ health and reproductive success, and inbreeding exacerbates the problem. The helmeted honeyeater was an especially extreme case. The most inbred birds left one-tenth as many offspring as the least inbred ones, and the females had life spans that were half as long,
Species then develop “inbreeding depression”—the lack of diversity makes them more vulnerable to challenges in their environment. This is called the extinction vortex—where further breeding only brings a species closer to extinction. Assisted evolution becomes the only option at this point.
Ok, how do you ‘assist’ evolution?
There are many different ways to alter the evolutionary trajectory of a species—some are far more intrusive than others.
First, artificial selection: This is something humans have been doing for millennia. It’s how some wolves evolved into chihuahuas. We tinker with the environment of species—assisting the selection of certain traits that already exist within some members of a species. They survive—and so do their genes.
Example, the greater bilby: This is an Australian marsupial that is rapidly going extinct—and looks like this:
They have been decimated by feral cats—which have been responsible for the extinction of many Australian species. Typically, the solution would be to kill the cats—or transport the bilbies to a cat-free environment. Conservationists are, instead, trying a novel approach—encouraging the survival of bilbies that know how to survive cats. It looks something like this:
In one experiment, Moseby and her colleagues released five cats into a fenced-in paddock with a few hundred greater bilbies and left them there for two years. They then caught some of the surviving bilbies and as well as some bilbies from a “predator-free” paddock and attached radio transmitters to their tails.
The two groups of radio-tagged bilbies were transferred to another paddock with more cats. After 40 days, only a quarter of the “naïve” bilbies were still alive. By comparison, two-thirds of the “predator-exposed” bilbies had managed to avoid predation.
It’s a bloody process—but it works. The question is whether it will work fast enough to save the bilbies from extinction.
Up next, affecting the ‘gene flow’: Artificial selection only works when the species already possesses the desired genetic material. But when that is not an option, we change the genetic material that natural selection acts upon.
Example: the Florida panthers: By the 1970s, there were only 12-20 of these big cats in the United States. And simply protecting these remaining panthers would not save them from extinction:
Not only were their numbers dismal, but almost all of the male panthers showed signs of inbreeding depression, including undescended testicles, kinked tails and low sperm counts.
So conservationists brought in a subspecies of the panther to the rescue—eight female mountain lions. The effect was almost magical—and restored the panthers within a generation. Tails unkinked, testicles descended, and spirits revived—and the Florida panther was saved. But it was no longer the same.
Next, mutation: We are poised on the cusp of a global coral bleaching event—which threatens already endangered reefs. Studies show that 99% of the world's coral reefs are likely to die off by the end of the century—if the planet continues to heat up. At least some of that change is irreversible. So what are we going to do?
Engineering a better coral: Some researchers are trying methods of unnatural selection. They are teaching the algae that gives corals their colour—and nourishment—to endure hotter weather. Scientists are subjecting these algae to hotter temperatures over generations—“subjected to an accelerated version of survival-of-the-fittest.”
The other, more aggressive strategy involves using gene-editing tools like CRISPR. In a 2020 proof-of-concept study, researchers used CRISPR to alter the gene involved in heat tolerance in corals:
If, for instance, genes associated with better heat tolerance could be identified, then corals could, in theory at least, be gene edited to carry them. Using what’s known as “gene drive” they could also, potentially, be edited to pass that trait on to their offspring. (Gene drive is a form of gene editing that overrides the normal rules of heredity.)
Similar methods have been used to engineer frogs that are immune to a fungus that has already led to the extinction of 90 amphibian species. This ‘gene drive’ method could work just as well at killing species—as preserving them:
Scientists in New Zealand are researching the use of gene drive to eradicate invasive wasps, and scientists at Michigan State University are investigating the possibility of using gene drive to control invasive sea lampreys in the Great Lakes. In Australia, it’s been proposed that gene drive could be used to reduce or even eliminate feral cats.
Maybe those poor “naïve” bilbies are dying for no good reason.
Last but not least, cloning: The buzziest use of cloning for conservation focuses on reviving extinct species—for example, the woolly mammoth, Tasmanian tiger etc. However, clones can also help preserve species that have not been wiped out as yet. It solves the biggest problem facing dwindling populations—the lethal lack of genetic diversity.
Example, the black-footed ferret: This variety of ferrets has been endangered for the past 150 years—teetering on the edge of genetic oblivion. Finally, in 1986, US authorities made a last-ditch effort to save them. The eighteen remaining wild ferrets were captured—and became part of a captive breeding program. Of these, only seven reproduced—which means their descendants are terribly inbred.
Then in 2020, a female ferret named Elizabeth Ann was successfully cloned—from the preserved DNA of one of the ferrets who died in the 1980s. She isn’t a silver bullet—but she offers hope of saving species that have been reduced to a handful.
Surely, people must have problems with this…
Of course, any method that tampers with nature violates the core tenets of traditional conservation circles:
[A]nimals are autonomous beings, and any intervention into their lives or genomes must have “a very strong ethical and moral justification” — a bar that even many traditional conservation projects do not clear, said [environmental scientist] Adam Cardilini… Chris Lean, a philosopher of biology.. said he believed in the fundamental conservation goal of “preserving the world as it is for its heritage value, for its ability to tell the story of life on Earth.”
Also this: There is the law of unintended consequences. For example, saving pink pigeons by artificially selecting birds with genes that can resist a certain disease:
“You could end up breeding a population that is very successful at fighting off Trichomonas, but what you have done is accidentally decreased the amount of diversity in the immune system,” says [genomics researcher Matt] Clark. If that’s the case, he adds, a new disease that they weren’t prepared for could theoretically hit and wipe out the entire population.
All this holds even more true for genetic engineering, cloning etc. Playing God rarely ends well for humans.
And what’s the counter-argument?
To put it simply, we broke it. So we’ve got to fix it. Being a purist isn’t going to save these animals from human activity. Advocates of assisted evolution criticise what they call the “ethos of restraint”:
Despite aiming to make conservation science and practice more effective, many conservationists default to excessive precaution, advocating conservative actions—or even inaction. The field suffers from an understandable aversion to unintended consequences, especially for approaches involving biotechnology and “next-generation” interventions. We call this default precautionary attitude among conservationists the ethos of restraint and argue for replacing it with an ethos of responsible conservation action.
They say the traditionalists need to weigh the risk of intervention against the risk of doing nothing. Besides, it’s absurd to quibble about genetically engineering animals when we are busy using the same technology to save ourselves.
The bottom line: Right or wrong, assisted evolution may in the end be about embracing the inevitable:
In some ways, assisted evolution is an argument — or, perhaps, an acknowledgment — that there is no stepping back, no future in which humans do not profoundly shape the lives and fates of wild creatures. To Dr. Harley, it has become clear that preventing more extinctions will require human intervention, innovation and effort. “Let’s lean into that, not be daunted by it,” he said. “My view is that 50 years from now, biologists and wildlife managers will look back at us and say, ‘Why didn’t they take the steps and the opportunities when they had the chance?’”
Reading list
Elizabeth Kolbert in Yale 360 lays out the debate over assisted evolution—as do Smithsonian Magazine and the New York Times. We personally liked Ashley Braun’s thoughtful take in Long Reads the best. NPR and Cosmos look specifically at the attempt to save corals. For more on the critique of the ‘ethos of restraint’ read this paper in Conservation Science and Practice. This paper by John A Erwin in the Cornell Law Review makes the best case for genetic intervention.
