The return of the dead to life has long fascinated storytellers, appearing in myths like Orpheus and Eurydice, festivals like Mexican Dia del Muerte, at Mary Shelley’s Frankenstein and of course, jurassic park. The idea continues to cast its spell. As we describe in our book Strange natures, the “de-extinction” or “resurrection” of extinct species is the idea of using new genetic technologies that most excites conservation commentators.
The best established approach to de-extinction is cloning. In 2003, Spanish scientists cloned the Pyrenean ibex, a subspecies of the Iberian ibex that became extinct in 2000. The animal only lived for seven minutes, but was hailed as the first species to be brought back from extinction. De-extinction continues to produce surprising headlines and graphics: Attempts to bring back mammoths even made the cover of the April 2013 issue of National geography.
Unfortunately, maybe you can’t clone a mammoth. At least that’s the conclusion of Beth Shapiro in her fascinating book How to clone a mammoth (despite its title). It turns out that the DNA in all mammoth samples will always be too degraded to make cloning possible. And the same goes for velociraptors or tyrannosaurs, condemning jurassic park in all its forms to remain a delicious exercise in science fiction.
But there is another approach to de-extinction. It uses gene editing techniques to restructure parts of the genome of an extant, closely related species to match that of its extinct parent. Before you begin, you will need a complete genome sequence of both the extinct species and a relatively closely related living species. Working to create the new life form requires the use of new gene editing technologies (in particular CRISPR, for which Jennifer Doudna and Emmanuelle Charpentier received the Nobel Prize in Chemistry in 2020).
The woolly mammoth is now the subject of a serious project, led by the charismatic figure of George Church of Harvard University and the American NGO Revive & Restore. They sequenced the DNA of semi-conserved mammoths in arctic permafrost and that of their closest living relative, the Asian elephant.
Gene editing is used to rewrite genes in Asian elephant cell lines, generating more and more mammoth-like cells (controlling hemoglobin, hair growth and production of fat) in each edition. In theory, these synthesized strands of “mammoth” DNA could be inserted into the egg of an Asian elephant and implanted into an elephant host. If a fetus were brought to term and born alive, it would bear the features of a woolly mammoth – not exactly a mammoth but more like a mammoth than anything since the last one died out about 4,000 years ago.
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There are about 1.4 million differences between the genomes of mammoths and Asian elephants, so they hardly look alike. Bridging this gap to create an elephant resembling a mammoth will allow the project to focus for years on the scientific complexities of the genetic basis of cellular protein production. It’s best understood as an eye-catching biological experiment, an engine of scientific discovery, and an advertisement for gene editing.
While the science of de-extinction obviously excites those who practice it, it is less clear whether de-extinction should be a priority for environmentalists. De-extinction certainly has its supporters beyond the coterie of synthetic biologists in their laboratories. Charismatic species already exert a strong fascination for environmentalists and the public.
Some conservationists also point out that extinct species could promote ecosystem recovery by restarting lost ecological processes (a sort of extreme view of “rewilding”). From this point of view, it is not the fact that the species is alive that is important, but what it does and the resulting ecological interactions..
On the other hand, as scientifically or culturally intriguing as it is, the conservation benefits of de-extinction are far from clear. First, all laboratory experimentation could create an organism that looks like an extinct species, but it will be a genetic hybrid with the modern species. It would only contain part of the genetic diversity of the whole of the old species. The International Union for the Conservation of Nature suggests the term “proxy of extinct species” and not “extinct species” for such creatures, if they were to be created.
And where would such a species live? Many (perhaps most) ‘resuscitated’ species (notably the mammoth) would struggle to find a space to live outside of laboratory or zoo conditions, let alone have the chance to establish viable populations. in freedom – like the Russian tundra proposed for novo – the mammoths. A single extinct species would be just as lonely as the last original individual, likely living their life in a zoo enclosure. He may be alive, but he would still be on the verge of re-extinction.
There are many more questions about any organism that has been genetically modified to look like an extinct species. Taxonomists would have to decide how it should be classified, and lawyers should decide whether the genetic modification could be patented. There are also obvious and important ethical issues regarding the implications of animal testing for animal welfare in the name of de-extinction.
All applications of synthetic biology to conservation are new and untested. Their use in laboratory experiments aimed at the eventual extinction of species is fascinating, complicated, expensive, ethically cumbersome and speculative. Overall, it is unlikely to be an important conservation strategy. Indeed, as critics have pointed out, the possibility that extinct species could be “brought back from the dead” could distract attention from the challenges of tackling the drivers of extinction today.
Despite its brilliance and appeal, de-extinction is not the most developed, important, or potentially controversial application of synthetic biology to conservation. As we discuss in Strange natures, scientists discuss many ways to modify genes in wildlife for conservation purposes, from using gene drive to control invasive species to gene editing to improve survival in the face of wildlife disease or change climate.
These raise fundamental questions about the distinction between what is natural and what is made by man. The idea of bringing extinct species back from the dead is bizarre and exciting, but the greatest opportunities and challenges in the power to edit the genes of wildlife do not lie in the resurrection of the past, but in the shaping of the past. future of conservation.
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Strange Natures: Conservation in the Age of Synthetic Biology by Kent H Redford and William M Adams is now available (£ 25, Yale Books).