can we really push the undo extinction button?

Biotech company Colossal keeps promising to return extinct creatures from the dead. But could they actually do it? And most importantly, should they?

For five million years, mammoths roamed the Earth. While we used to be taught that humans hunted them down to extinction, the reality is that climate change wiped out their main source of food and the giant animals couldn’t adapt quickly enough. Now, on the other hand, the thylacine, a marsupial predator that roamed Tasmania for two million years, was our victim. Since they kept on threatening sheep, we kept shooting them until a farmer in 1930 killed the last known wild specimen. And about 300 years prior to that, we doomed the dodo, making us two for three in the extinction games.

But a company called Colossal Biosciences wants to fix our mistakes, as well as bring back the wooly mammoth just in case we did happen to push some populations over that edge. That’s right, they not only want to resurrect mammoths and thylacines, in a recent announcement, the company is claiming that they can also return the dodo to Mauritius. Aside from the philosophical implications which we’ll put aside for now, the idea of de-extinction comes with numerous caveats because it’s dependent on using the creatures’ DNA samples, filling in missing genetic data from relatives, engineering an embryo, then hoping that a similar modern animal can gestate it to term.

In mammoths’ case, you would use an Asian elephant. For new Tasmanian tigers, tiny carnivores called dunnarts could serve as a bridge between embryo and an artificial pouch in which a joey would be nursed until it’s strong enough to be autonomous. For the dodo, the process would edit the germ lines of a Nicobar pigeon, combining them with the DNA of a dodo and a Rodrigues solitaire, then having a chicken hatch the end result, which should look just like a dodo bird. All three of these are wildly complicated experiments which come with an extremely high risk of failure. Even a successful birth would still be no guarantee of survival, much less a stable population.

If that sounded very Jurassic Park to you, it is. The only real difference is that dinosaur genes preserved in amber have a half-life of roughly 1.5 million years while DNA from mammoths is only thousands of years old by comparison, dodo specimen date back roughly 350 years, and thylacine samples were collected barely a century ago. If we’d really want to hatch a viable velociraptor, no amount of frog genes would suffice, and we’d have to resort to reverse-engineering birds. If we wanted complete genomes for thylacines, dodos, and wooly mammoths, well, we more or less have them. The catch is that we’d only have a handful of individuals’ genes, which is a big problem.

why you can’t rewind time in nature

For just a moment, let’s push past all the caveats and imagine a world where there’s a baby mammoth, a dodo chick, and a thylacine joey in a Colossal lab. All of them are healthy, happy, and growing. Now what? Introducing a single animal into the wild is an absurd idea, of course. You’d need at least a few thousand individuals for the species to have any chance to survive again, and with a very limited sample pool, there will be an extremely high risk of inbreeding that could easily wipe out the species again when disease and environmental changes strike. Just as importantly, there’s the question of exactly how well an extinct animal would fare in today’s world.

While Colossal says it selected animals that would benefit today’s ecosystems, plenty of zoologists remain very skeptical. The last mammoth died 4,000 years ago, but their numbers had been dwindling for hundreds of thousands of years. In the 90 years that the thylacine was gone, dingoes, foxes, and other predators filled its ecological niches and are probably not going to give them up without a vicious turf war. And if the dodo couldn’t handle humans introducing rats and pigs to their island some 400 years ago, how well would their resurrected descendants handle the same island now full of the same species that drove them to extinction in the first place today?

It may make us feel warm and fuzzy to think that we could one day atone for our sins and bring back species we killed off, but nature seldom shows any mercy. De-extinct animals will now be an invasive species in a different, rapidly changing world. It’s also at this point that we should mention climate change and how it’s drastically reshaping habitats around the world and creating the precursors of a mass extinction. It seems like it should be a far more pressing concern to save today’s endangered biodiversity before we start bringing back long dead animals through an extremely expensive and uncertain effort in genetic engineering no one asked to undertake.

Even if we did have the technology and could artificially generate sustainable genetic diversity, raise at least 5,000 individuals from an extinct species, and introduce them back into the wild, all we would do is disrupt ecological niches with what will amount to invasive pests. As cruel as it sounds, it seems that once a species has been gone for several generations, it’s gone for good as far as nature is concerned. Throw in the aforementioned challenges posed by climate change, and it becomes very likely that these de-extinct species would quickly die out once again, making the whole thing an exercise in futility at best.

big promises, flashy articles, few results

It seems like Colossal wants to achieve mastery of genetic engineering, which would allow it to license its technology to develop the kinds of cures and treatments that we only see in science fiction today, and it’s gambling on attracting investors with flashy projects like resurrecting extinct species. Even if there are no thylacines roaming the wild by 2075, maybe there are breakthroughs we could use to treat cancers and offer new kinds of gene therapy, goes the thinking. Unfortunately, biology is known to be a very finicky field where promising discoveries often don’t scale or translate between species the way we think it should based on what we know.

Of course, this is not to say that genetic engineering is impossible, or that there’s no way these de-extinction projects won’t provide useful insights no matter what. There would be no way to know that but to try. But we need to be realistic. Impressive feats with a few specimen often end up more as a parlor trick than a gateway to something as profound as we think it will. Cloning still fails roughly half the times it’s tried, clones often don’t look or act like the donor animal, and we have not been able to use cloned cells to 3D print replacement organs by manipulating these cells’ development, as we were originally promised shortly after the reveal of Dolly the sheep.

Again, this is not to say that Colossal is lying, or the biotechnology is filled with hordes of fabulists making promises they can’t keep. Biology is known as the squishy science because it’s so unpredictable and full of so many exceptions and surprises that what seems like a sure bet often ends with frustration and head-scratching problems when research gains enough steam to scale up exploratory experiments to test populations. It’s simply not possible to meet a goal made to the public even after years of very real, verified, replicated data, and biologists today are very aware of this fact. Much of the biotech hype you see in the media today is really little more than clickbait.

This is why it seems so odd that Colossal keeps running around making one amazing claim after another. Today, they’ll bring back the wooly mammoth. Tomorrow, they’re going to resurrect the Tasmanian tiger. Are you suddenly pining to see a real life dodo in its natural environment? No worries, they have that covered too according to their latest press release. Maybe they’ll announce plans to return Steller's sea cow as their next project. And yet, we know all of this is likely not possible or responsible. If it was, we’d already have baby mammoths in a lab or a zoo. So, next time you see an article about extinct species being brought back to life, take it with a huge heap of salt.

note: This post borrows from a piece originally published on 09.01.2022 for the old blog, expands on its main points, and updates the analysis with the recent news that Colossal is claiming they can resurrect the dodo from extinction.