Your De-Extinction Questions Answered

On Friday, I was down in Washington to speak at (and mostly watch) TEDxExtinction, a day-long meeting dedicated to exploring the possibility (and advisability) of bringing extinct species back into existence. The meeting coincided with the publication my story in the new issue of National Geographic on the subject. I invited readers to ask questions raised by either the story or the meeting, and then on Monday, National Geographic hosted a tweet chat on Twitter, which became an hour-long rapid-fire volley. So I’m only now getting a chance to write this long-promised post. Here are some answers to a few of the questions posted on the Loom and on Twitter–first on the logistics of de-extinction, and then the ethics.

This is an interesting question, because dodos were dinosaurs. Not to mention robins and hawks and other living birds. If your idea of Jurassic Park is being surrounded by dinosaurs, you are living the dream. If, on the other hand, you desire (or fear) the lineages of dinosaurs that became extinct 65 million years ago, such as tyrannosaurs, then you are out of luck. No viable cells or nuclei can survive 65 million years. And while scientists have recovered lots of DNA from species that became extinct tens of thousands of years ago, they can’t reach back tens of millions of years.


Peteykins said, “Too bad the dodo died out too long ago for viable DNA to survive. Now THAT I’d love to see.”

Dodos only became extinct less than 400 years ago. While there are no intact dodo cells left today, scientists have retrieved bits of dodo DNA from a specimen stored at the University of Oxford. If scientists could find a lot more dodo DNA, they might be able to identify the genetic variations that turned the ancestors of dodos–small, flying pigeons–into big flightless birds. Then they might be able to reverse engineer the genome of a stem cell from a closely related pigeon species and then turn that cell into eggs and sperm, which could produce dodos.

Size would present a problem, if a small pigeon had to lay a massive dodo egg. But you could imagine gradually developing dodos over several generations, getting bigger and bigger. Mind you, all this is just speculation from a few facts–the fact that we now have a little dodo DNA and that scientists are doing amazing research on cloning based on stem cell engineering. Lots of practical obstacles stand in the way, some of which might simply be insurmountable. For example, the home of the dodo, Mauritius, is a tropical island where conditions are terrible for preserving DNA. Ironically, scientists have reconstructed much more of the mammoth genome, despite the fact that the last mammoths became extinct 3700 years ago. That’s because cold permafrost is pretty good at storing DNA fragments.


When a population gets tiny, its genetic variation gets tiny, too. Thanks to the random shuffle of heredity’s dice, gene variants can disappear, leaving the organisms more and more similar to each other. That can be dangerous, because it can leave populations unable to reproduce as quickly and may leave them less capable of adapting to new challenges. If scientists created a dozen genetically identical dodos from a single egg, they’d face some serious problems with genetic diversity. This is just one of many practical challenges scientists would face in trying to truly revive a species, rather than getting one animal alive again just long enough to be photographed. But we should not assume these challenges are insurmountable. It might be possible to find variants of genes in ancient DNA from fossils or museum specimens, for example.



I agree that it is important to think about Deep Time when we think about extinction. Perhaps 99.99% of all species that ever existed are gone from this planet. But what’s happening now is unusual for two reasons.

One is the rate at which species are going extinct. In the past few centuries, the rate of extinction for some groups of species has jumped by roughly a factor of a thousand. That jump is due to us–to our hunting, logging, and other actions that leave species struggling to hold on to existence. If those actions continue into the future, and if we continue pumping carbon dioxide into the atmosphere at a rising rate, we could jack that extinction rate to levels that life has achieved only five times in the past half billion years. So we’re not in a “things come, things go” situation. It’s more like, “Things go, and a lot more things go after them.”

The other reason that what’s happening now is unusual is us. In no previous pulse of mass extinction did a single species consciously drive a number of other species extinct. I’m not saying that a bird hunter shooting into a flock of passenger pigeons 200 years ago realized he was part of an exercise that would drive the entire species of passenger pigeons extinct within 100 years. But as a people, we know it now. And we know that other species are on the ropes, because of what we are doing. Hence we can decide if we want to let this extinction crisis continue to balloon.

The whole conservation movement is organized around the proposition that biodiversity is something worth saving. When a species goes extinct, it can leave a hole. Its ecosystem may suffer because the species can no longer carry out some important task, such as pollinating plants or filtering water. We lose the opportunity to investigate its biology and discover some fascinating piece of natural history or even find a valuable molecule for curing infections or sequencing DNA. And we end up living in a world without Great Auks and gastric brooding frogs. Is de-extinction a tool for slowing or reversing this trend? That’s a good question. But one thing’s for sure. We’re not playing God. We’re coming to terms with our own powers, as well as the unexpected results of our actions.


Aaron asks, “Should we bring any animal back from extinction which could threaten human life?”

What constitutes a threat? We have a habit of perceiving threats where the risks are tiny or non-existent. In fact, some species, such as the thylacine, were eradicated because they were considered a threat to human life–specifically, that they were killing off herds of sheep. That was untrue, but it didn’t stop people from driving the species extinct. Bringing them back would not pose a threat either.

I’m not saying that no revived species would pose a risk. But we do have to make sure we aren’t letting emotions ride roughshod over our decisions. Scientists have already revived a very dangerous life form: the flu virus that killed 50 million people in 1918. But no one has died from it, because precautions have been taken. And scientists have learned a great deal about how influenza evolves and kills–information that could help us in the future. This was a de-extinction of sorts that presented both risks and benefits.



This is a point raised by many conservation biologists, both in my interviews for my article and at TEDx. “At this moment, brave conservationists are risking their lives to protect forest elephants from armed poachers,” David Ehrenfeld of Rutgers University said at the meeting. “And we’re talking in this safe auditorium about bringing back the woolly mammoth?”

If de-extinction really did make it harder to, say, pay guards to stop poaching, then I could definitely see a problem here. But where is the evidence of a zero-sum game at play? I don’t see it. No one at TEDx proposed cutting guard salaries to bring back a mammoth.

This concern could apply just as well to experimental research on animal reproduction–efforts to freeze cells of endangered species for research, assisted reproduction, and so on. They all cost money, they are not guaranteed success, and they all require people to do something other than guard against poaching. Yet some species have been introduced back to the wild, saved for now from extinction, thanks in large part to this kind of research.

These issues don’t just apply to extinct animals, but to the near extinct. There are four Red River giant softshell turtles left on Earth. They are not breeding with each other. We might be able to use stem cells to produce lots of new sperm and eggs and fertilize them to grow their population. Is this just a waste of resources, or will this end up saving the species? If we engineer frogs to resist chytrid fungus infections, is this just a simplistic technological fix, or the only way to keep them from going extinct?

My fellow Phenom blogger Brian Switek considers de-extinction little more than a slick marketing term. I disagree, if only because the issues that have emerged with its unveiling are going to stick around for a long time, even if no one tries to bring an extinct species back to life.


If you want to go deep into everything that would be required in bringing back Neanderthals, check out this piece by fellow Phenom Virginia Hughes. Do not worry about meeting a Neanderthal on the street tomorrow, or next year.

If we could bring them back, should we? I think not, for many reasons. Neanderthals were humans, and research on humans requires informed consent, which is hard to get from someone who belongs to an extinct lineage. It would be unethical to bring people back without a place where they could live with dignity, and we have no idea what such a place would be for a Neanderthal in the twenty-first century.




I am quite taken with the idea of bringing back Steller’s sea cow. The first scientist to describe it was Georg Wilhelm Steller, who was on a voyage across the Bering Sea in 1741. He and his crewmates were shipwrecked on an island there, where they discovered herds of these amazing animals. They were relatives of manatees, reaching 25 feet long or more and weighing six tons. Here’s a wonderful image of them by the great illustrator Carl Buell, which is now on display at the Smithsonian.

Steller's sea cow. Copyright Carl Buell
Stelle’s sea cow. Copyright Carl Buell
Steller sea cow. Copyright Carl Buell

Steller survived to write about the sea cows because his crew slaughtered some of the animals to eat on the voyage home. A single sea cow could feed a crew of 33 sailors for a month. Sailors on North Pacific ships killed so many sea cows that they vanished in 1768, just 27 years after Steller first described them.

Steller’s sea cow was part of the Pacific ecosystem for millions of years, and we are personally responsible for wiping it out. It would be quite something to figure out how put it back where it was just a couple centuries ago. But given the size of their potential surrogate mothers–not to mention many other obstacles–I’ll content myself with a daydream for now.

31 thoughts on “Your De-Extinction Questions Answered

  1. While I do think the term “de-extinction” itself is an unnecessary invention that has more to do with promotion than science, I didn’t say that the ideas behind it weren’t worth considering. My point is that “de-extinction” obscures that fact that advocates of bringing back mammoths aren’t *actually* reversing extinction, but creating slightly new animals that are close replicas of the originals. The distinct is slight, but it matters for how we approach the question of whether we should engage in such efforts. Are we really restoring mammoths, passenger pigeons, and the like to their original habitats? Or are we creating close proxy creatures that will interact with ecology in new ways? Those are questions worth asking and talking about, and I think “de-extinction” carries some baggage that obscures such details.

  2. Numerous knowledge gaps need to be filled in order to restore the phenotype of multicellular species using either complete or fragmented DNA. Many realms of research are involved, from biochemistry, genetics, embryology, zoology, and husbandry. It is no small endeavor. The effort stands upon a singularly focused objective which by its very nature will contribute to subsequent focused research and doubtless lead to new discoveries with broad application.

    If we are able to master this realm of science then we can represent an individual or entire species using data and algorithms. This has profound implications.

  3. One of the first pieces of science writing I ever wrote was when I was 11 years old – and it was a report on the plight of manatees in Florida. It makes my inner child super happy that you chose Steller’s sea cow 🙂

  4. I wrote my latest fiction novel, Chimera, on this topic … the creation of previously-extinct hunting trophies for wealthy collectors/poachers of illicit endangered species in 2011, thinking it would be an interesting but decidedly far-fetched sci-fi theme for many years to come. I found this idea comforting because I’m also the director of a federal crime lab devoted to protecting endangered and threatened species across the planet, and we’ve got plenty to do without trying to deal with genetically (re)created species. After reading your article, I’m no longer thinking “many years to come.” Sigh …

  5. Carl, I enjoyed your thoughtful commentary from this conference. One question I was hoping to hear more about: in the discussion about whether it’s ethical to de-extinct a species, why is the notion of a “species” considered ethically privileged?

    I mean, in the philosophical literature we assign special status to the notion of an individual. If an individual is killed, there is in some cases a moral imperative to undo that if we could. And I can see a utilitarian argument for trying to enrich food chains or simply study a long-dead organism.

    But did anyone discuss the rationale for assigning this special ethical status to a species?

    [CZ: Nobody talked about that explicitly. Kate Jones, a British conservation biologist, discussed the idea of resurrecting species that belonged to entire lineages that have mostly become extinct. Think about the few species of lungfish left on Earth. If they go, then we’ve just lost a 400-million-year-old lineage. Rodents wouldn’t get a high priority if we used this criterion for picking species to revive.]

  6. I would definitely like to see the resurrection of the Saber Toothed Salmon “Oncorhynchus (Smilodonichthys) rastrosus”.

    It would be a superior answer to increasing fish production than Frankenfish!

  7. Passenger Pigeon would have commercial potential; it is reported to have tasted better than chicken, and sold for more per pound in the markets of New York. Even a small “gourmet” market in its meat could support a decent-sized breeding population. But this raises the question of whether someone could patent an extinct species to secure exclusive rights upon de-extinction.

  8. There was a very interesting question that a conservationist had raised in an article on natgeo, will try and find that link, but the gist of it was that once we start bringing back extinct animals, or show that it is possible, how would it affect a conservationist’s efforts, in the sense that those who already lack any sensitivity when it comes to preservation of species & consequently the ecosystem, won’t they get even more brazen about their acts? Say those governments that promote & validate poaching and are in a way arm twisted by forums like CITES into conserving endangered species, wouldn’t they block such efforts altogether or refuse to co-operate once they realise that it might now be possible to bring back those species which have gone extinct? And won’t more and more people start losing all sanctity for life & various lifeforms once we start creating them in labs?

    Another point that merits consideration is the funds that come the way of science. With economies strained the world-over & governments spending ever-increasing amounts on defence systems, there is less and less money that is being set aside for scientific ventures. So in a way it really is an either-or situation when it comes to deciding between whether we want to bring back extinct species to life or if those funds won’t be better utilised in making the earth a more habitable place for those species that still exist, isn’t it?

  9. I know it’s impossible and would only be done for nothing more than human curiosity, plus it’s ethically wrong, but I would really like to see a living, breathing T. Rex.

  10. Regarding Church’s passenger pigeon resurrection idea; why use a rock pigeon if the closest living relative is actually the mourning dove (Zenaidura macroura)?

  11. I think it’s an awesome idea to bring back extinct species but with some terms and conditions:

    We should start with the animals we have recently extinct and work our way back – start with the golden toad, ivory – billed woodpecker, etc. Once we’ve learned their behavior and DNA sequence, we can return them back in the wild to try and restore their natural balance because it’s been only a short time that I’ve been “out of commission”.

    I’m a little more hesitant in bringing back the wooly mammoth, Smilodon, mastodons, and ground sloths because these animals wouldn’t survive in the modern world, especially with global warming since these animals were from the Ice Age. It would be cool to know their behavior and husbandry but where would we put these animals once we’re done with them? I have a feeling some people, after having brought them back to life, will either make them zoo attractions or, worse, kill them.

    All in all, I’m for “de-extinction” for animals we’ve killed in less than 10,000 years. Anything beyond that is a little precarious.

  12. I believe highly that we should bring back species in which have recently been extinct because of the fact that some of these animals maybe key factors in scientific research, but what about using this or cloning research or both to help figure out a solution to the decaying earth with the desertification process. Some of the species that we would benefit the most from bringing back would not survive in the earths rapid desertification path. Do you believe that this would help fix these issues?

  13. By De-Extinction can we prove Darwin’s theory about Human evolution wrong or Right? If we cannot revive our previous species from which we had evolved,then can we say that Darwin’s theory is nothing but a pseudo-Scientific theory?

  14. If we “resurrected” extinct species, where would they live? Would we place them into existing ecosystems and wish them luck? I don’t think so. Humans aren’t good at the whole live-and-let-live thing when it comes to other species. They’d most likely live in zoos (or something similar with a snazzier sounding name). We see how contemporary animals suffer even in the “best” situations of captivity in the world. What is ethical about bringing back these animals, who have given no consent, to live lives in captivity?

  15. I believe if we have the power to bring back a species that it is our duty to do so. In my eyes it is perfectly ethical to want to bring back what once was. I don’t really know where I would stand on bringing back a Neanderthal, but scientist always complain about finding missing links and such. Could be the answer to their problems. I’m guessing there is one scientist somewhere out there working on his own doing this very thing as we speak.

  16. Human is not so smart.
    Of course it would be nice to se Dodo, or some peacefull species, but no, do not do that.
    Nature done, what nature wanted.
    Scientists can make a mistake, and we will get prototype.
    The food chain could be rough, changed.

  17. I was thrilled to see the article in National Geographic about bringing back extinct Pleistocene megafauna like the Wooly Mammoth. But the letters in the next issue revealed that the public didn’t see the reasons that this was a good idea. As a rabid environmentalist myself, I’ve been promoting Pleistocene Re-wilding for years now, and in spite of raised eyebrows and shaken heads whenever I broach the subject I’ve become increasingly convinced that we need to do this for the sake of our own survival.

    The argument above doesn’t really cover the main reason I favor re-wilding, which is environmental restoration. The Pleistocene megafauna extinctions followed human migration around the globe. Africa, where humans co-evolved with large animals, is the only place that retained most of its megafauna, such as elephants, rhinos, lions, hyenas, giraffes, camels, etc. Elsewhere extinctions followed the arrival of humans swiftly. Within 1000 years of human arrival in the Western Hemisphere, the elephants, ground sloths, cave bears, lions, dire wolves, giant beavers, cheetahs, horses, camels, and many many other large mammals were gone. This mass extinction left a dangerously out-of-balance ecosystem.

    Elephants in Africa and Asia are important managers of the landscape, creating passages and clearings in forests from which many other species benefit. Large grazing animals maintain healthy grasslands, and browsers keep forests from becoming overgrown, while carnivores keep the herbivore populations in check. The web of life, plants and animals, co-evolve. Humans have changed that balance. We did it through our power and our ignorance.

    On this continent the aboriginal people learned over time to replace the management of the land that had been the domain of the megafauna by the use of fire. Virtually the entire continent was burned annually. This kept the forests open and parklike, with low, cool fires burning dropped branches and dry brush. It kept the grasslands open and filled with edible seed-producing grasses and flowers, rather than overgrown with dense scrub brush as so much of the land is now.
    When Europeans arrived, we did not learn the wisdom of this approach. We did the exact opposite, fighting fires, allowing the forests to become dense overgrown tinder boxes, the hills covered with impenetrable scrub. Today the West is burning uncontrollably. Fear of tick-born illnesses such as Lyme disease keep humans from enjoying the landscape. Human control of this situation is absolutely beyond imagining.

    To return to the Indians’ approach would mean first hand clearing immense amounts of fuel from the forest, so that fire could be safely applied. But fire means releasing carbon into the atmosphere. We can’t do that now. Hence my support of the idea of Pleistocene Re-wilding. What the land is crying out for is its lost megafauna, the true land managers. I haven’t even gone into the role of large herbivores in spreading seeds. To learn about that, read Connie Barlow’s “The Ghosts of Evolution”.

    Folks, it is clear that we have not yet really learned our place on this precious planet. I greatly fear that we will not learn it in time to prevent our own extinction. By reintroducing megafauna into the landscape, and allowing them to establish a balance in our unhealthy environment, I believe that, over time, there could be a return to Eden. Along with a voluntary reduction of human population through birth control, organic and Permacultural agricultural practices, and all the many other obviously necessary changes we need to make to protect the environment, re-wilding is an important and misunderstood piece of the puzzle. Thanks.

  18. I think we should bring back lots of the extinct animals, as long as they have a natural and safe habitat, it was not fair to the poor animals that they were hunted by humans and things so I do agree to bring the extinct animals back too life. for example the thylacine (Tasmanian tiger) never deserved to die the animal was mostly hunted so that is one of the many extinct animals I think should come back. So thank you and I hope we bring back those extinct animals. Thank you for you time.

  19. it would be so awesome to be able to bring back these animals and even me a 14 year old finds this amazing.

  20. this sounds amazing. though i have one question- How did you get the cells to de-extinct something like the wolly ma

  21. i am 12 and i think that they are worthy of the chance who here can honestly say that you have never thought of meeting the dead if they have to breed it with a asian elaphant to clone it who cares they are endangered this is EXTINCT and who knows this might save every animal and after they might be able to cross breed with humans think of it an atual centar or minotaur i say correct oor wrong doing and bring back the deadall those who want to eat it or make a coat of it are sick
    they shold be extinct instead of the mammoth and after this who knows they might bring back a saber toothed tiger or a gasp a neanderthal man this completly destroys darwins theroy why do you nee to evolve if you can be broth back from the dead in fact they could bring back darwin to show him this or show that every living person has the same dna rootand mutate more than one that would bring the endangerd spieces to a closewe will be more carful this time go teambringbackbuttercup

  22. Hello, I am Martin and I am in need of information about de extinction for a project. Can you please send me information ASAP

    Thank You

  23. Granted, I’m not on par with those who have commented on this article, but I would like to know if DNA/genome is being gathered from animals alive today, in case they are extinct tomorrow. I’m thinking specifically of the African Black Rhino, which was recently listed as extinct. I don’t know if there has been a successful breeding program of these animals in today’s more ecologically-minded zoos. Must I actually say goodbye to them for the rest of my life, and the lives of children and grandchildren to come?

  24. Well, animals are going extinct by the minute! I mean we already lost our black western rino and the dodo bird. But the dodo bird had no eniemies so it was kinda stupid. But people need to be better at that. I mean you dont know if an animal is extinct is you dont know how much are in the world!

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