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categories: ["genetics"]categories: ["genetics"]tags: ["conservation", "genome editing", "cloning", "ancient dna", "biodiversity", "proxy species"]tags: ["conservation", "genome editing", "cloning", "ancient dna", "biodiversity", "proxy species"]summary: "The attempt to recreate extinct organisms, in practice by editing a close living relative to carry some of the extinct animal's traits rather than restoring the species itself."summary: "The attempt to recreate extinct organisms, in practice by editing a close living relative to carry some of the extinct animal's traits rather than restoring the species itself."updated: "2026-07-27"updated: "2026-10-29"humanEvidence: "Nothing here has been applied to people; the only extinct animal ever brought to term was a cloned Pyrenean ibex that died within minutes of birth in 2003."humanEvidence: "Nothing here has been applied to people; the only extinct animal ever brought to term was a cloned Pyrenean ibex that died within minutes of birth in 2003."access: "Nothing to obtain: no restored species exists, and the work runs inside a small number of venture-funded and academic programmes."access: "Nothing to obtain: no restored species exists, and the work runs inside a small number of venture-funded and academic programmes."reversibility: "irreversible"reversibility: "irreversible"lines 35–41 → 35–4120 unchanged lines not shown
**Back-breeding** selectively breeds living descendants for traits resembling the ancestral form. The Heck cattle of the 1920s and the later Tauros programme aimed at something aurochs-like; the Quagga Project in South Africa breeds plains zebras for reduced striping. These produce animals that look the part and are genomically ordinary.**Back-breeding** selectively breeds living descendants for traits resembling the ancestral form. The Heck cattle of the 1920s and the later Tauros programme aimed at something aurochs-like; the Quagga Project in South Africa breeds plains zebras for reduced striping. These produce animals that look the part and are genomically ordinary. **Cloning by somatic cell nuclear transfer** requires intact cells, which extinction usually precludes. The one success remains the bucardo, a Pyrenean ibex whose last individual was tissue-sampled before her death in 2000; a cloned kid was born in 2003 and died within minutes from a lung malformation.[^folch2009] The same technique is used productively for species that are endangered rather than extinct, as in the cloning of a black-footed ferret and a Przewalski's horse from cell lines cryopreserved decades earlier. That is genetic rescue, and it works. The mechanics are covered in [[human-cloning]].**Cloning by somatic cell nuclear transfer** requires intact cells, which extinction usually precludes. The one success remains the bucardo, a Pyrenean ibex whose last individual was tissue-sampled before her death in 2000; a cloned kid was born in 2003 and died within minutes from a lung malformation.[^folch2009] The same technique is used productively for species that are endangered rather than extinct, as in the cloning of a black-footed ferret and a Przewalski's horse from cell lines cryopreserved decades earlier. That use, genetic rescue, works. The mechanics are covered in [[human-cloning]]. **Genome editing of a close relative** is the route every current headline project takes. It exists because ancient DNA is fragmentary. Even exceptionally preserved permafrost specimens yield short, chemically damaged fragments rather than chromosomes, and there are no living cells to clone from.[^vandervalk2021] Sequencing a mammoth is therefore possible; growing one from mammoth cells is not. The workaround is to sequence the extinct genome, compare it with a living relative, identify variants underlying traits of interest, and install those variants in the relative's cells with [[crispr-cas9]] or its derivatives.**Genome editing of a close relative** is the route every current headline project takes. It exists because ancient DNA is fragmentary. Even exceptionally preserved permafrost specimens yield short, chemically damaged fragments rather than chromosomes, and there are no living cells to clone from.[^vandervalk2021] Sequencing a mammoth is therefore possible; growing one from mammoth cells is not. The workaround is to sequence the extinct genome, compare it with a living relative, identify variants underlying traits of interest, and install those variants in the relative's cells with [[crispr-cas9]] or its derivatives. lines 53–67 → 53–6711 unchanged lines not shown
The 2025 canid announcement is the clearest case study. Three grey wolf pups were produced carrying, on the company's account, about twenty edits across fourteen genes, selected from a dire wolf genome assembled from ancient specimens, and presented as the return of a species that has been extinct for roughly ten thousand years. Specialists pointed out that dire wolves are not closely related enough to grey wolves for a small edit set to reconstitute them, that the edited traits were largely morphological, and that the resulting animals are grey wolves with alterations. The company's own scientific framing has been more careful than its announcements, using a functional definition under which an animal counts if it performs the extinct species' ecological role; the exchange is set out under [[colossal-biosciences]].The 2025 canid announcement is the clearest case study. Three grey wolf pups were produced carrying, on the company's account, about twenty edits across fourteen genes, selected from a dire wolf genome assembled from ancient specimens, and presented as the return of a species that has been extinct for roughly ten thousand years. Specialists pointed out that dire wolves are not closely related enough to grey wolves for a small edit set to reconstitute them, that the edited traits were largely morphological, and that the resulting animals are grey wolves with alterations. The company's own scientific framing has been more careful than its announcements, using a functional definition under which an animal counts if it performs the extinct species' ecological role; the exchange is set out under [[colossal-biosciences]]. Mammoth work is further from an animal and technically more interesting. It requires elephant pluripotent stem cells, which were reported only recently and remain hard to work with; multiplex editing of many loci; and gestation. The last is the binding problem. An elephant pregnancy runs close to two years, the only available surrogate species is itself endangered, and the alternative is an [[artificial-womb]] for a several-hundred-kilogram fetus, which is a much harder problem than the neonatal work described in [[ectogenesis]].Mammoth work is further from an animal. It requires elephant pluripotent stem cells, which were reported only recently and remain hard to work with; multiplex editing of many loci; and gestation. The last is the binding problem. An elephant pregnancy runs close to two years, the only available surrogate species is itself endangered, and the alternative is an [[artificial-womb]] for a several-hundred-kilogram fetus, which is a much harder problem than the neonatal work described in [[ectogenesis]]. Marsupials invert the difficulty. The thylacine programme uses the fat-tailed dunnart, a mouse-sized relative, because marsupial gestation is very short and development continues in the pouch. The size difference between host and target is extreme, and the germline route requires deriving and editing marsupial stem cells with tools that were developed for mice. Birds are harder still: avian de-extinction depends on culturing and editing primordial germ cells, which works reliably in chickens and poorly in pigeons, the group containing the dodo's relatives. All three programmes are gated on reproductive biology, not on editing, and the field's dependence on [[induced-pluripotent-stem-cells]] and on [[in-vitro-gametogenesis]]-adjacent techniques is more decisive than its dependence on nucleases.Marsupials invert the difficulty. The thylacine programme uses the fat-tailed dunnart, a mouse-sized relative, because marsupial gestation is very short and development continues in the pouch. The size difference between host and target is extreme, and the germline route requires deriving and editing marsupial stem cells with tools that were developed for mice. Birds are harder still: avian de-extinction depends on culturing and editing primordial germ cells, which works reliably in chickens and poorly in pigeons, the group containing the dodo's relatives. All three programmes are gated on reproductive biology rather than on editing: progress depends more on [[induced-pluripotent-stem-cells]] and on [[in-vitro-gametogenesis]]-adjacent techniques than on nucleases. ## What "de-extinct" would have to mean## What "de-extinct" would have to mean A species is not a list of variants. It is a genome, a developmental environment, a gut microbiome, a set of learned behaviours transmitted between generations, and an ecological context. An edited elephant would have elephant mitochondria unless those were replaced, elephant epigenetic inheritance, an elephant microbiome and no mammoths to learn from. Beth Shapiro, an ancient-DNA specialist who later became chief science officer at [[colossal-biosciences]], argued before joining the company that the honest target is a functional proxy rather than a resurrection.[^shapiro2015]A species is more than a list of variants. It is a genome, a developmental environment, a gut microbiome, a set of learned behaviours transmitted between generations, and an ecological context. An edited elephant would have elephant mitochondria unless those were replaced, elephant epigenetic inheritance, an elephant microbiome and no mammoths to learn from. Beth Shapiro, an ancient-DNA specialist who later became chief science officer at [[colossal-biosciences]], argued before joining the company that the honest target is a functional proxy rather than a resurrection.[^shapiro2015] The IUCN's guidance takes the same line, treating any such organism as a proxy to be evaluated on whether it delivers conservation benefit and on what risks its release carries.[^iucn2016] Under that standard the interesting question about a cold-adapted elephant is not whether it is a mammoth but whether releasing it into Arctic tundra does what proponents claim, which is to convert moss and shrub tundra to grassland, raise surface albedo and slow permafrost thaw. That hypothesis is contested among ecologists and has never been tested at scale.The IUCN's guidance takes the same line, treating any such organism as a proxy to be evaluated on whether it delivers conservation benefit and on what risks its release carries.[^iucn2016] Under that standard the question about a cold-adapted elephant is what releasing it into Arctic tundra would do, rather than whether it is a mammoth. Proponents claim it would convert moss and shrub tundra to grassland, raise surface albedo and slow permafrost thaw. That hypothesis is contested among ecologists and has never been tested at scale. > [!debate] Restoration or distraction> [!debate] Restoration or distraction> Proponents argue that de-extinction develops genetic-rescue tools with immediate use for endangered species, and that the publicity funds conservation science that would otherwise go unfunded. Critics reply that resources spent on proxies could conserve more biodiversity if spent on habitat, and that the promise of reversal weakens the case for prevention.[^bennett2017]> Proponents argue that de-extinction develops genetic-rescue tools with immediate use for endangered species, and that the publicity funds conservation science that would otherwise go unfunded. Critics reply that resources spent on proxies could conserve more biodiversity if spent on habitat, and that the promise of reversal weakens the case for prevention.[^bennett2017]removed, struck through added, underlinedLine numbers count the serialised markdown of each revision, frontmatter included.
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