We may weep for the dodo, but could and should we bring this lovely bird back from the dead? De-extinction is the science of restoring lost species and it has been in the news, sporadically, for decades. The story in modern times began in 1990 when Michael Crichton published his science fiction novel Jurassic Park, in which he imagined a world where scientists were able to bring dinosaurs back to life. Crichton had trained as a biomedical scientist, so he was aware of the then new polymerase chain reaction (PCR) technology that was revolutionising life-sciences labs. PCR enabled molecular biologists to make millions or billions of copies of DNA very quickly meaning that only tiny samples were needed. Crichton imagined that PCR could be a way to amplify tiny quantities of dinosaur DNA and thus build a living embryo. The impact of the Jurassic Park movies, from the first in 1993 to the sixth in 2022, has been huge, although having seen them, any sane person would surely conclude that bringing dinosaurs back to the modern world would be a bad thing. Famously, the science imitated the art, and several encouraging papers were published in the 1990s that made it seem as though Crichton’s inspired guess would be borne out. Sadly, biologists soon realised that DNA in fact breaks down super-fast; even after 100 years, DNA from museum skins of dodos, quaggas, great auks and other recently extinct animals were decayed beyond repair. They could be sequenced using massive computational power, but then only with considerable uncertainty. And even if you capture a DNA sequence, there’s still the problem of how you get living cells to read that sequence and express the proteins that make the dinosaur or the dodo. Dolly the sheep, however, showed us that baby mammals could be created in the laboratory with only a mother sheep and a decent bit of DNA. So could we use the same technology for extinct species of sheep or other similar animals? Celia, the last surviving Pyrenean ibex, died in 2000. Using tissue samples taken from her a year before she died, the American firm Advanced Cell Technology applied the cloning tech used for Dolly in an attempt to bring Celia back to life. Of course they had no member of her own subspecies to act as surrogate mother, so they used a different kind of ibex. Of 285 cloned embryos, 54 were implanted, but none survived. In 2003, one clone was born alive but died after several minutes. Since then, the cloning-and-surrogate-mother concept has stalled and nobody talks about transferring the cells or cloned embryos of a deceased mammoth into a modern elephant any more. Instead the technology of choice now is genetic engineering. Last year, Colossal Biosciences, based in Dallas, Texas, raised $75m to support its efforts to bring the mammoth back to life, this time using genome editing. Genetic engineers can already insert cold-tolerant genes into plants to enable them to grow in cool conditions, and Colossal plans to do the same with modern Asiatic elephants. Their stated aim is “to see the woolly mammoth thunder upon tundra once again”. But why would anyone want to see mammoths, or something like them, roaming present-day Siberia? Well, they were undoubtedly amazing, mesmerising beasts. As well as hunting them, our distant ancestors painted their likenesses in caves across Europe. Fascinating as they may be, there’s some ecological justification for the project too. The plan is for the resurrected mammoths – OK, actually engineered Asiatic elephants – to help increase the biodiversity of the Siberian and Canadian tundra to levels not seen for millennia. Today most of the tundra, when not frozen in winter, is covered by short grasses, which represent a much poorer flora than existed at the time of the mammoths more than 10,000 years ago. Back then, they and other herbivores such as woolly rhinoceroses, mastodons and aurochs, the giant wild cattle of northern Eurasia, fed on a range of species of flowering plants collectively called forbs. As these large animals trampled about over the tundra snatching trunkfuls of vegetation, they left irregular gaps in the plant cover, allowing different species to thrive. Their hooves created deep prints in which plants could germinate, and their urine and dung provided richly nutritious islands of opportunity for germinating seeds. It was this diversity of land surface, broken up by heavy limbs and randomly fertilised by urine and faeces, that supported so much flora. Without the mammoths, that diversity disappeared. Return them and landscapes would once again thrum with an array of species, including flowers and bushes. True, it’s not de-extinction in the sense of bringing a long-dead species back to life. Instead it’s more like making a “dodo” by engineering a modern pigeon, its closest relative, to become huge and flightless. The result would be a big, fatty pigeon that, whether it looked like a dodo or not, would probably fulfil some of its ecological roles. The argument for repopulating the tundra with large mammals is fascinating and tracks the arguments for rewilding Britain with, say, beavers or wolves. These species restore the balance of nature and change the ecology of systems in ways that – according to your frame of reference – can be judged as either good or bad. Beavers build dams and flood upland plains, protecting lowland farms and villages. Wolves cull Highland deer and limit the damage they do to young trees. But they might also eat livestock. As a palaeontologist, I would of course love to see living dinosaurs, mammoths and dodos. In some ways, though, I am relieved that the optimistic claims for cloning and genetic technologies have not been borne out. The slowdown gives us time to consider the outcomes – and hopefully avoid some of Michael Crichton’s more fevered imaginings. Mike Benton is professor of vertebrate palaeontology at the University of Bristol. His book Extinctions will be published by Thames & Hudson in September. To buy a copy go to guardianbookshop.com Further reading How to Clone a Mammoth: The Science of De-Extinction by Beth Shapiro (Princeton University, £12.99) Resurrection Science: Conservation, De-Extinction and the Precarious Future of Wild Things by MR O’Connor (St Martin’s, £28). Rise of the Necrofauna: The Science, Ethics, and Risks of De-Extinction by Britt Wray (Greystone, £19.95)