Michael Crichton’s "Jurassic Park" series popularized the notion that it might be possible to bring extinct animals back to life; yet as with much science fiction, the 1990 book (and subsequent movies) were far ahead of the state of the science. While dinosaurs will likely never be brought back from extinction — at least, not in their original un-spliced genetic form, as no DNA strand can feasibly survive 65 million years or more — we are at a point where it is possible that scientists may soon resurrect recently-extinct species like the passenger pigeon, the Pyrenean ibex, and even Ice Age megafauna like the woolly mammoth.
But just because bringing extinct animals back from the dead is possible does not mean that it is a good idea. Again, "Jurassic Park" was ahead of its time here: In the 1993 film, Jeff Goldblum’s character, Dr. Ian Malcolm, tells the park’s CEO, “your scientists were so preoccupied with whether or not they could that they didn’t stop to think if they should.” Indeed, there are many things that are scientifically possible, but perhaps murky ethically or morally.
Which brings us back to bringing extinct animals back, a process sometimes called “de-extincting.” Imagine the loneliness of being the only member of your entire species, created in a lab and born from another species’ womb. Some argue that we have a moral obligation to bring back species in the name of restoring ecological balance; yet even in the case of animals that occupied an ecological niche that is now missing, it is difficult to say with any foresight whether or not de-extincting them would actually fix anything.
Britt Wray, a science writer and PhD candidate in science communications, has spend years studying the thorny issue of de-extinction, and its myriad social, ethical and biological implications. Wray has a new book out, titled “Rise of the Necrofauna: The Science, Ethics, and Risks of De-Extinction.” I spoke with her about the brave new world of biology that we’ve only just entered.
In your book, you wrote that despite the idea of de-extinction ranking high in popular consciousness thanks to movies like "Jurassic Park," there aren't really that many scientists around the world who are attempting de-extinction. Why is this?
Britt Wray: First, there's not a lot of funding for de-extinction. There's not scientific agreement that it is a necessary conservation tool, and therefore we should be working on it. Yet some people are working on it. They're generally donating their own funds from side laboratory projects, and getting private donations and support from the nonprofit Revive and Restore. [Editor’s note: Revive and Restore is a nonprofit, part of the Long Now Foundation, that is working on funding de-extinction efforts.]
Also, [de-extinction] is simply experimental to the greatest degree that you can imagine. People have only done de-extinction once before successfully, and it's a relatively fringe activity inasmuch that we don't have a lot of precedent of it working. Now, there's a time where people are trying to collect themselves and turn what were once a scattering of fringe science projects into an evolving field, a movement, and it's just the early days of that.
What animals are scientists interested in de-extincting?
Wray: In terms of the projects that are underway already, we've got the woolly mammoth revival project happening in George Church's lab at Harvard Medical School. There's also a history of teams in Japan and South Korea trying to clone a mammoth back to life by using cells that they take from frozen carcasses that are pulled out of places like Siberia. However, in order to use cloning as a method, you need a perfectly intact cell with its DNA wrapped up nice and neatly in the nucleus, and that has never been found because when animals die thousands of years ago, contamination from other organism sets in and their DNA decays. Basically, perfect intact cells have been impossible to retrieve from those dead mammoths. That's why George Church's team at Harvard are using a different approach, gene editing.
Then there are also other animals like the passenger pigeon… the Tasmanian tiger has been approached before as a project. If they get more funding, they might reboot it. The same team led by Michael Archer in Australia is also working on cloning the extinct gastric brooding frog back to life. That was a really special frog that gave birth out of its mouth — it could turn its stomach into a uterus on demand, which is pretty amazing.
There are other projects that are in the beginning stages, such as the heath hen. We've also got back-breeding of the aurochs, which is the extinct ancestor of all of today's living cattle. We've got a project called the Quagga Project, which is using artificial selection to recreate the extinct subspecies of zebra known as a quagga. [Quaggas] had a bare backside and mocha color under their stripes, instead of this dark white that we know zebras to have.
Of these projects underway, which is most likely to succeed?
Wray: Maybe the gastric brooding frog. They've already been able to take the nucleus with the DNA of the extinct frog and insert that into the egg cell of its closest living relative, which is the great barred frog, then see that transfer of the extinct nucleus into the donated egg, [and] get stimulated to start [its cells] dividing. They have one chance a year to try this because of the breeding season of the great barred frog. Although they haven't yet been able to grow those into tadpoles, this year again, in February or March, they're going to try it and see if they get further than they did before.
The woolly mammoth project is really interesting because George Church is a wildly talented writer of genetic technologies, and [a] scientist who just works in a variety of fields that touch on bioengineering. He predicts that perhaps they’ll be able to recreate the woolly mammoth embryo [via] an Asian elephant embryo [by] about 2019. That's pretty soon. That's just the embryo, so it'll take a lot longer to actually gestate that, grow an animal that would be successful, et cetera. But there's reason to believe that it would definitely be possible within the next decade from a team like his.
Then, there's the Passenger Pigeon Project. Ben Novak is working on gene-editing the band-tailed pigeon's genome, which is the closest living relative to the extinct passenger pigeon, which disappeared only 103 years ago now. He predicts that by 2022, he might be able to show the world some of the engineered birds that he's produced this way. We'll just have to wait and see, but it's not unbelievable that this could happen.
The passenger pigeon example is really interesting to me because, as you've written about, there were huge numbers of passenger pigeons.
Wray: Billions.
Billions! What led to their demise, and also, how would our world be different if they were still around? Presumably, they were an important part of the ecosystem in some way.
Wray: Right. It's really difficult to imagine how colossal this species was, because we have never seen anything like it since their disappearance. It's said to be the most populous avian species that humans ever interacted with. In 1914, the last passenger pigeon, named Martha, died in the Cincinnati Zoo, but between that point and 50 years prior is really when the bulk of their crash occurred, because humans found them to be a tasty and cheap source of protein and we developed a whole market trade around capturing them.
There are records of a single flock of passenger pigeons taking about 14 hours to pass over a single spot in Southern Ontario, and there are also records of one bullet being fired up into the sky, making as many as 25 to 99 birds come down, because they were flying in layers that thick. It’s just unbelievable, [an] almost mythical scale. They definitely acted as a superorganism because of how many they were — so they had an important functional role to play in the eastern forest of North America.
Now, what happens today in those forests where they once were? [They] often have a closed canopy, meaning that the branches of the trees up high prevent sunlight from coming in and hitting the forest floor. If the sunlight reached the floor, it would cause regeneration of different species and vegetation down there.
The advocates of passenger pigeon de-extinction, especially Ben Novak, who studies them and is trying to recreate them now, say that if we could bring hundreds of thousands, maybe a few million passenger pigeons back, when they come in, they would mimic what the extinct bird did, which was weigh down the tree branches when they would come to roost and nest. They would make bark chip off the trees. They would destroy young saplings or old trees and cause that closed canopy to break down, and the sun would then be able to come through the trees, hit the forest floor.
Because they were such a disturbance, forests, as we see today around the world, generally are able to build the next successive forest after a lot of disruptions. Things like forest fires and hailstorms cause forests to regenerate, and similarly, the argument here is that billions of passenger pigeons caused the forest to create new shoots that would sprout up after the disturbance. People who believe in this project [think] it would be a natural and desirable way to regenerate forests that haven't been regenerated at that scale since the passenger pigeon went extinct.
In the history of de-extinction, there has actually been one successful instance of an animal being de-extincted, although it only lasted about 10 minutes. Can you talk about this case a little bit?
Wray: That happened in the early 2000s with the bucardo, also known as the Pyrenean ibex, which is a type of mountain goat that lived in the Spanish Pyrenees mountain range. Celia, the last living bucardo, was this female who was monitored in a conservation program, and she was all that was left after humans hunted her and her species out of the wild. One day, her radio collar sent out a signal that something was amiss. The scientists and the conservationists rushed out to see what had happened, and they discovered that she had been crushed to death by a branch that fell from a tree. They couldn't save her from that, and they knew enough beforehand to try and preserve some of her tissue just in case anything beneficial could be done down the line. They'd already taken some cells from her ear and from her flank and quickly frozen them in liquid nitrogen so that they would be perfectly preserved and intact. Then, a couple of years after she died, they did what's called somatic cell nuclear transfer — this is the same method of cloning that was used to make Dolly the sheep.
They got one success after many, many attempts — they had to create 57 embryos in order to get one success this way. They took the DNA in the nucleus of one of the cells from the extinct bucardo, transferred it into the egg cell that came from a living goat, stimulated it with a shock, which started it dividing, and planted it in a surrogate goat mom. I think they were able to make seven goats pregnant after 57 embryos were made this way. One baby lived for 10 minutes, but then died due to a deformity on its lung. That's pretty common with cloning. There's a lot of failure rates and there's a lot of congenital diseases that they can be born with.
The whole case of that Pyrenean ibex kind of makes me wonder about the ethical or moral questions driving whether or not humans should de-extinct animals. Given that humans are generally the main driver of extinction on Earth, do you think that we have a moral obligation to be involved in de-extincting animals? What are the ethics of this?
Wray: There are some people who say we have a moral obligation to use whatever tools we have available to us now to bring some of these species back in whatever way, shape, or form that we can if we cause their extinction; that we owe them this, that there are holes in nature we ripped open and now we should fill them in. But I find that there's a logical disjuncture there, because if we really felt that responsible, and guilty, and motivated by this moral argument, we'd be doing a lot more to help the threatened species that are currently facing extinction than we are. We have a rich opportunity to make a greater impact by concentrating our efforts there than saying that it's morally just to try and de-extinct animals that we killed for whatever reason there might be.
I think that there are potentially interesting conservation benefits of having aspects of extinct biodiversity back in the world, but that doesn't necessarily mean cloning extinct animals. Endangered species that can use the tools being applied in de-extinction — for instance, gene editing with tools like CRISPR to put biodiversity into endangered populations right now that have low fecundity, that can't really make it on their own because they have really, really small amounts of biodiversity in their population. For example, black-footed ferrets… although there's quite a few of them, they're really badly inbred. Some of the people who are working on supporting de-extinction projects have also turned their attention to this species to try and figure out how they can bioengineer living ferrets to have more genetic diversity in them, by taking the DNA of long-dead ferrets that used to be more diverse that we have, stored in liquid nitrogen.
Or, take the northern white rhino; there are only three of them left living in Kenya. These types of bioengineering tools are now being applied to help them. They're effectively a dead species walking. They can't reproduce between themselves. They're also all very closely related, so it would be a bad idea. Now, there are a variety of different approaches to resuscitate them with methods that look a lot like de-extinction, and I think that that's really cool. But it's challenging to say where do we draw the line. Is it really that much better to help a species when there's only three left and they're functionally extinct in the wild? Is that a lot better in moral terms compared to trying to de-extinct them after the last rhino died?
So you're saying that we could put our efforts towards stopping endangered animals from going extinct in the first place, and that's easier and probably less resource-intensive than bringing back to life some of the extinct ones?
Wray: Well, I am, but I'm also just pointing out that it becomes really foggy as to where the moral reasoning should sit, because it will be probably just as resource-intensive to [try to stop] the northern white rhino from going extinct, [as] there's only three of them left. I mean, we need to look at each case individually, I think, and then judge from there.
But most importantly, for animals being de-extincted, we need to know: is there a good habitat that's available where they could live? Where they could thrive? Where they have all the factors that they need to be able to do well? Otherwise, they'll just go extinct a second time.
Portions of this interview have been edited and condensed for clarity.
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Britt Wray is the author of "Rise of the Necrofauna: The Science, Ethics, and Risks of De-Extinction."
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