de-extinction

File:Pyrenean ibex Cloning.svg. The tissue culture was taken from the last living, female Pyrenean ibex named Celia. The egg was taken from a goat (Capra hircus) and the nucleus removed to ensure the offspring was purely Pyrenean ibex. The egg was implanted into a surrogate goat mother for development.]]

Cloning is a commonly suggested method for the potential restoration of an extinct species. It can be done by extracting the nucleus from a preserved cell from the extinct species and swapping it into an egg, without a nucleus, of that species' nearest living relative.{{Cite journal |last=Shapiro |first=Beth |date=2016-08-09 |title=Pathways to de-extinction: How close can we get to resurrection of an extinct species? |journal=Functional Ecology |volume=31 |issue=5 |pages=996–1002 |doi=10.1111/1365-2435.12705 |doi-access=free |bibcode=2017FuEco..31..996S |issn=0269-8463 |s2cid=15257110}} The egg can then be inserted into a host from the extinct species' nearest living relative. This method can only be used when a preserved cell is available, meaning it would be most feasible for recently extinct species.{{cite news |title=Should we bring extinct species back from the dead? |last=Shultz |first=David |date=2016-09-23 |journal=Science |publisher=AAAS |url=https://www.science.org/content/article/should-we-bring-extinct-species-back-dead|access-date=2018-04-30}} Cloning has been used by scientists since the 1950s.{{Cite journal |last=Wadman |first=Meredith |year=2007 |title=Dolly: A decade on |journal=Nature |volume=445 |issue=7130 |pages=800–801 |doi=10.1038/445800a |doi-access=free |pmid=17314939 |s2cid=6042005}} One of the most well known clones is Dolly the sheep. Dolly was born in the mid-1990s and lived normally until the abrupt midlife onset of health complications resembling premature aging, that led to her death. Other known cloned animal species include domestic cats, dogs, pigs, and horses.

Genome editing has been rapidly advancing with the help of the CRISPR/Cas systems, particularly CRISPR/Cas9. The CRISPR/Cas9 system was originally discovered as part of the bacterial immune system.{{Cite journal|last1=Palermo|first1=Giulia|last2=Ricci|first2=Clarisse G.|last3=McCammon|first3=J. Andrew|date=April 2019|title=The invisible dance of CRISPR-Cas9. Simulations unveil the molecular side of the gene-editing revolution.|journal=Physics Today|volume=72|issue=4|pages=30–36|doi=10.1063/PT.3.4182|issn=0031-9228|pmc=6738945|pmid=31511751}} Viral DNA that was injected into the bacterium became incorporated into the bacterial chromosome at specific regions. These regions are called clustered regularly interspaced short palindromic repeats, otherwise known as CRISPR. Since the viral DNA is within the chromosome, it gets transcribed into RNA. Once this occurs, the Cas9 binds to the RNA. Cas9 can recognize the foreign insert and cleaves it. This discovery was very crucial because the Cas protein can now be viewed as a scissor in the genome editing process.

By using cells from a closely related species to the extinct species, genome editing can play a role in the de-extinction process. Germ cells may be edited directly, so that the egg and sperm produced by the extant parent species will produce offspring of the extinct species, or somatic cells may be edited and transferred via somatic cell nuclear transfer. The result is an animal which is not completely the extinct species, but rather a hybrid of the extinct species and the closely related, non-extinct species. Because it is possible to sequence and assemble the genome of extinct organisms from highly degraded tissues, this technique enables scientists to pursue de-extinction in a wider array of species, including those for which no well-preserved remains exist. However, the more degraded and old the tissue from the extinct species is, the more fragmented the resulting DNA will be, making genome assembly more challenging.

{{main|Breeding back}}

Back breeding is a form of selective breeding. As opposed to breeding animals for a trait to advance the species in selective breeding, back breeding involves breeding animals for an ancestral characteristic that may not be seen throughout the species as frequently.{{Cite journal|title=Pathways to de-extinction: how close can we get to resurrection of an extinct species?|journal=Functional Ecology|volume=31|issue=5|pages=996–1002|last=Shapiro|first=Beth|s2cid=15257110|doi=10.1111/1365-2435.12705|year=2017|doi-access=free|bibcode=2017FuEco..31..996S }} This method can recreate the traits of an extinct species, but the genome will differ from the original species. Back breeding, however, is contingent on the ancestral trait of the species still being in the population in any frequency. Back breeding is also a form of artificial selection by the deliberate selective breeding of domestic animals, in an attempt to achieve an animal breed with a phenotype that resembles a wild type ancestor, usually one that has gone extinct.{{citation needed|date=May 2025}}

{{main|Elvis taxon}}

A natural process of de-extinction is iterative evolution. This occurs when a species becomes extinct, but then after some time a different species evolves into an almost identical creature. For example, the Aldabra rail was a flightless bird that lived on the island of Aldabra. It had evolved some time in the past from the flighted white-throated rail, but became extinct about 136,000 years ago due to an unknown event that caused sea levels to rise. About 100,000 years ago, sea levels dropped and the island reappeared, with no fauna. The white-throated rail recolonized the island, but soon evolved into a flightless species physically identical to the extinct species.{{cite journal|last1=Hume|first1=Julian P.|last2=Martill|first2=David|date=2019-05-08|title=Repeated evolution of flightlessness in Dryolimnas rails (Aves: Rallidae) after extinction and recolonization on Aldabra|journal=Zoological Journal of the Linnean Society|volume=186|issue=3|pages=666–672|doi=10.1093/zoolinnean/zlz018|url=https://academic.oup.com/zoolinnean/article/186/3/666/5487031}}{{Cite web|last=Harris|first=Glenn|url=https://www.eurekalert.org/news-releases/715178|title=The bird that came back from the dead|website=EurekAlert!|date=2019-05-09}}

{{see also|List of longest-living organisms#Revived into activity after stasis}}

Not all extinct plants have herbarium specimens that contain seeds. Of those that do, there is ongoing discussion on how to coax barely alive embryos back to life.{{cite web|last1=Marinelli |first1=Janet |title=Back from the Dead: New Hope for Resurrecting Extinct Plants |url=https://e360.yale.edu/features/plant-de-extinctions-herbariums |website=Yale Environment 360 |date=12 July 2023|publisher=Yale School of the Environment}} See Judean date palm and tsori.

{{Main|In vitro fertilisation|Artificial insemination}}

In-vitro fertilisation and artificial insemination are assisted reproduction technology commonly used to treat infertility in humans. However, it has usage as a viable option for de-extinction in cases of functional extinction where all remaining individuals are of the same sex, incapable of naturally reproducing, or suffer from low genetic diversity such as the northern white rhinoceros, Yangtze giant softshell turtle, Hyophorbe amaricaulis, baiji, and vaquita. For example, viable embryos are created from preserved sperm from deceased males and ova from living females are implemented into a surrogate species.

The technologies being developed for de-extinction could lead to large advances in various fields:

• An advance in genetic technologies that are used to improve the cloning process for de-extinction could be used to prevent endangered species from becoming extinct.{{Cite web|url=https://e360.yale.edu/features/the_case_for_de-extinction_why_we_should_bring_back_the_woolly_mammoth|title=De-Extinction Debate: Should We Bring Back the Woolly Mammoth?|last=Brand|first=Stewart|date=2014-01-13|website=Yale Environment 360|language=en-US|access-date=2020-04-29}}
• By studying revived previously extinct animals, cures to diseases could be discovered.
• Revived species may support conservation initiatives by acting as "flagship species" to generate public enthusiasm and funds for conserving entire ecosystems.{{cite journal|last1=Bennett|first1=Joseph|date=25 March 2015|title=Biodiversity gains from efficient use of private sponsorship for flagship species conservation|journal=Proceedings of the Royal Society|volume=282|issue=1805|pages=20142693|doi=10.1098/rspb.2014.2693|pmc=4389608|pmid=25808885}}{{cite journal|last1=Whittle|first1=Patrick|display-authors=et al|date=12 Dec 2014|title=Re-creation tourism: de-extinction and its implications for nature-based recreation|journal=Current Issues in Tourism|volume=18|issue=10|pages=908–912|doi=10.1080/13683500.2015.1031727|s2cid=154878733}}

Prioritising de-extinction could lead to the improvement of current conservation strategies. Conservation measures would initially be necessary in order to reintroduce a species into the ecosystem, until the revived population can sustain itself in the wild.{{Cite web|url=https://www.labroots.com/trending/plants-and-animals/5579/pros-cons-reviving-extinct-animal-species|last=Bouchard|first=Anthony|date=2017-03-20|title=The Pros and Cons of Reviving Extinct Animal Species {{!}} Plants And Animals|website=LabRoots|access-date=2020-04-29}} Reintroduction of an extinct species could also help improve ecosystems that had been destroyed by human development. It may also be argued that reviving species driven to extinction by humans is an ethical obligation.{{Cite journal|last=Kasperbauer|first=T. J.|date=2017-01-02|title=Should We Bring Back the Passenger Pigeon? The Ethics of De-Extinction|journal=Ethics, Policy & Environment|volume=20|issue=1|pages=1–14|doi=10.1080/21550085.2017.1291831|s2cid=90369318|issn=2155-0085}}

The reintroduction of extinct species could have a negative impact on existing species and their ecosystem. The extinct species' ecological niche may have been filled in its former habitat, thus making them an invasive species. This could lead to the extinction of other species due to competition for food or other competitive exclusion. It could also lead to the extinction of prey species if they have more predators in an environment that had few predators before the reintroduction of an extinct species. If a species has been extinct for a long period of time the environment they are introduced to could be wildly different from the one that they can survive in. The changes in the environment due to human development could mean that the species may not survive if reintroduced into that ecosystem. A species could also become extinct again after de-extinction if the reasons for its extinction are still a threat. The woolly mammoth might be hunted by poachers just like elephants for their ivory and could go extinct again if this were to happen. Or, if a species is reintroduced into an environment with disease for which it has no immunity, the reintroduced species could be wiped out by a disease that current species can survive.

De-extinction is a very expensive process. Bringing back one species can cost millions of dollars. The money for de-extinction would most likely come from current conservation efforts. These efforts could be weakened if funding is taken from conservation and put into de-extinction. This would mean that critically endangered species would start to go extinct faster because there are no longer resources that are needed to maintain their populations.{{Cite web|url=https://e360.yale.edu/features/the_case_against_de-extinction_its_a_fascinating_but_dumb_idea|title=The Case Against De-Extinction: It's a Fascinating but Dumb Idea|website=Yale Environment 360|last1=Ehrlich|first1=Paul|last2=Ehrlich|first2=Anne H.|date=2014-01-13|language=en-US|access-date=2020-04-29}} Also, since cloning techniques cannot perfectly replicate a species as it existed in the wild, the reintroduction of the species may not bring about positive environmental benefits. They may not have the same role in the food chain that they did before and therefore cannot restore damaged ecosystems.{{Cite journal|last1=Richmond|first1=Douglas J.|last2=Sinding|first2=Mikkel-Holger S.|last3=Gilbert|first3=M. Thomas P.|date=2016|title=The potential and pitfalls of de-extinction|journal=Zoologica Scripta|language=en|volume=45|issue=S1|pages=22–36|doi=10.1111/zsc.12212|issn=1463-6409|doi-access=free}}

File:Woolly mammoth model Royal BC Museum in Victoria.jpg

{{main|Revival of the woolly mammoth}}

The existence of preserved soft tissue remains and DNA from woolly mammoths (Mammuthus primigenius) has led to the idea that the species could be recreated by scientific means. Two methods have been proposed to achieve this:

The first would be to use the cloning process;{{cite news|url=https://www.livescience.com/17386-woolly-mammoth-clone.html|author=Charles Q. Choi|date=December 8, 2011|title=Woolly Mammoths Could Be Cloned Someday, Scientist Says|work=Live Science}} however, even the most intact mammoth samples have had little usable DNA because of their conditions of preservation. There is not enough DNA intact to guide the production of an embryo.{{Cite web|url=https://www.nationalgeographic.com/news/2017/07/woolly-mammoths-extinction-cloning-genetics/|archive-url=https://web.archive.org/web/20190911152945/https://www.nationalgeographic.com/news/2017/07/woolly-mammoths-extinction-cloning-genetics/|url-status=dead|archive-date=September 11, 2019|title=We Could Resurrect the Woolly Mammoth. Here's How.|last=Worrall|first=Simon|date=2017-07-09|website=National Geographic News|language=en|access-date=2020-04-28}} The second method would involve artificially inseminating an elephant egg cell with preserved sperm of the mammoth. The resulting offspring would be a hybrid of the mammoth and its closest living relative the Asian elephant. After several generations of cross-breeding these hybrids, an almost pure woolly mammoth could be produced. However, sperm cells of modern mammals are typically potent for up to 15 years after deep-freezing, which could hinder this method.{{cite web|url=https://www.pbs.org/newshour/rundown/welcome-pleistocene-park-russian-scientists-say-high-chance-cloning-woolly-mammoth/|title=Welcome to Pleistocene Park: Russian scientists say they have a 'high chance' of cloning a woolly mammoth|last=Treu|first=Zachary|date=2014-03-14|work=PBS NewsHour|access-date=23 November 2014}} Whether the hybrid embryo would be carried through the two-year gestation is unknown; in one case, an Asian elephant and an African elephant produced a live calf named Motty, but it died of defects at less than two weeks old.{{cite journal | url= http://discovermagazine.com/1999/apr/cover | title= Cloning the Woolly Mammoth | first= R. | last= Stone | journal= Discover Magazine | year= 1999 | url-status= live | archiveurl= https://web.archive.org/web/20140729032746/http://discovermagazine.com/1999/apr/cover | archivedate= 29 July 2014 | df= dmy-all }}

In 2008, a Japanese team found usable DNA in the brains of mice that had been frozen for 16 years. They hope to use similar methods to find usable mammoth DNA.{{cite web|url=http://mammoth.psu.edu|title=Mammoth Genome Project|publisher=Pennsylvania State University|access-date=18 March 2013}} In 2011, Japanese scientists announced plans to clone mammoths within six years.{{cite news|url=http://news.blogs.cnn.com/2011/01/17/scientists-trying-to-clone-resurrect-extinct-mammoth/?hpt=T2|title=Scientists trying to clone, resurrect extinct mammoth|last=Lendon|first=B.|date=17 January 2011|access-date=22 May 2013|publisher=CNN|archive-date=14 May 2021|archive-url=https://web.archive.org/web/20210514024919/https://news.blogs.cnn.com/2011/01/17/scientists-trying-to-clone-resurrect-extinct-mammoth/?hpt=T2|url-status=dead}}

In March 2014, the Russian Association of Medical Anthropologists reported that blood recovered from a frozen mammoth carcass in 2013 would now provide a good opportunity for cloning the woolly mammoth. Another way to create a living woolly mammoth would be to migrate genes from the mammoth genome into the genes of its closest living relative, the Asian elephant, to create hybridized animals with the notable adaptations that it had for living in a much colder environment than modern day elephants.{{cite news|url=https://www.nationalgeographic.com/science/article/mammoth-elephant-hybrids-could-be-created-within-the-decade-should-they-be#:~:text=Don't%20expect%20pseudo%2Dmammoths,could%20take%20decades%20to%20establish.|author=Michael Greshko|date=September 13, 2021|title= Mammoth-elephant hybrids could be created within the decade. Should they be?|work=National Geographic}} This is currently being done by a team led by Harvard geneticist George Church. The team has made changes in the elephant genome with the genes that gave the woolly mammoth its cold-resistant blood, longer hair, and an extra layer of fat.{{cite web|url=https://www.vice.com/en/article/the-plan-to-turn-elephants-into-woolly-mammoths-is-already-underway/|title=The Plan to Turn Elephants Into Woolly Mammoths Is Already Underway|last=Koebler|first=Jason|date=2014-05-21|work=Motherboard|access-date=23 November 2014}} According to geneticist Hendrik Poinar, a revived woolly mammoth or mammoth-elephant hybrid may find suitable habitat in the tundra and taiga forest ecozones.{{cite web|url=https://www.ted.com/talks/hendrik_poinar_bring_back_the_woolly_mammoth|title=Hendrik Poinar: Bring back the woolly mammoth! - Talk Video - TED.com|author=Hendrik Poinar|date=30 May 2013 |publisher=Ted.com|access-date=23 November 2014}}

George Church has hypothesized the positive effects of bringing back the extinct woolly mammoth would have on the environment, such as the potential for reversing some of the damage caused by global warming.Church, George. "George Church: De-Extinction Is a Good Idea." Scientific American, 1 Sept. 2013. Web. 13 Oct. 2016. He and his fellow researchers predict that mammoths would eat the dead grass allowing the sun to reach the spring grass; their weight would allow them to break through dense, insulating snow in order to let cold air reach the soil; and their characteristic of felling trees would increase the absorption of sunlight. In an editorial condemning de-extinction, Scientific American pointed out that the technologies involved could have secondary applications, specifically to help species on the verge of extinction regain their genetic diversity.{{Cite web|url=https://www.scientificamerican.com/article/why-efforts-bring-extinct-species-back-from-dead-miss-point/|title=Why Efforts to Bring Extinct Species Back from the Dead Miss the Point|website=Scientific American|date=June 2013 |language=en|access-date=2021-03-11}}

In March 2025, Colossal Biosciences, a startup founded by George Church with funding from Ben Lamm announced the birth of woolly mice. These mice, while they do not contain almost any mammoth genetic information – most of the edited genes are known mice fur genetic variants, and not woolly mammoth variants{{cite bioRxiv |biorxiv=10.1101/2025.03.03.641227 |title=Multiplex-edited mice recapitulate woolly mammoth hair phenotypes |date=2025 |last1=Chen |first1=Rui |last2=Srirattana |first2=Kanokwan |last3=Coquelin |first3=Melissa L. |last4=Sampaio |first4=Rafael Vilar |last5=Wilson |first5=Raphael |last6=Ganji |first6=Rakesh |last7=Weston |first7=Jacob |last8=Ledesma |first8=Alba |last9=Beebe |first9=Jessie |last10=Sullivan |first10=Jacob |last11=Qin |first11=Yiren |last12=Chao |first12=J. Chris |last13=Papizan |first13=James |last14=Mastracci |first14=Anthony |last15=Bhide |first15=Ketaki |last16=Mathews |first16=Jeremy |last17=Oglesby |first17=Rorie |last18=Menon |first18=Mitra |last19=Van Der Valk |first19=Tom |last20=Bow |first20=Austin |last21=Cantarel |first21=Brandi L. |last22=James |first22=Matt |last23=Kehler |first23=James |last24=Dalén |first24=Love |last25=Lamm |first25=Ben |last26=Church |first26=George M. |last27=Shapiro |first27=Beth |last28=Abrams |first28=Michael E. }}{{cite web |title=Expert reaction to unpublished preprint on inducing loss of function of genes in mice to produce woolly mammoth- like hair phenotypes |url=https://www.sciencemediacentre.org/expert-reaction-to-unpublished-preprint-on-inducing-loss-of-function-of-genes-in-mice-to-produce-woolly-mammoth-like-hair-phenotypes/ |website=Science Media Centre |access-date=10 March 2025}} –, exhibit some of the key traits of the woolly mammoth, such as cold tolerance and long, shaggy, tawnt-toned fur, giving further credence to the feasibility of reviving the woolly mammoth through genome editing of the Asian elephant.{{Cite news |last=Davis |first=Nicola |date=2025-03-04 |title=Scientists aiming to bring back woolly mammoth create woolly mice |url=https://www.theguardian.com/science/2025/mar/04/genetically-modified-woolly-mice-mammoth |access-date=2025-03-09 |work=The Guardian |language=en-GB |issn=0261-3077}}

File:Taurus bull MBD.jpg

The aurochs (Bos primigenius) was widespread across Eurasia, North Africa, and the Indian subcontinent during the Pleistocene, but only the European aurochs (B. p. primigenius) survived into historical times.{{cite iucn |author=Tikhonov, A. |date=2008 |title=Bos primigenius |volume=2008 |page=e.T136721A4332142 |doi=10.2305/IUCN.UK.2008.RLTS.T136721A4332142.en |access-date=12 November 2021}} This species is heavily featured in European cave paintings, such as Lascaux and Chauvet cave in France,{{cite web|url=https://www.bbc.co.uk/nature/life/Aurochs#p00fc2yh|title=BBC Nature – Cattle and aurochs videos, news and facts|website=bbc.co.uk|access-date=23 November 2014|url-status=dead|archive-url=https://web.archive.org/web/20140411091101/https://www.bbc.co.uk/nature/life/Aurochs#p00fc2yh|archive-date=2014-04-11}} and was still widespread during the Roman era. Following the fall of the Roman Empire, overhunting of the aurochs by nobility caused its population to dwindle to a single population in the Jaktorów forest in Poland, where the last wild one died in 1627.{{cite journal |last1=Rokosz |first1=Mieczyslaw |year=1995 |title=History of the aurochs (Bos taurus primigenius) in Poland |journal=Animal Genetic Resources Information |volume=16 |pages=5–12 |doi=10.1017/S1014233900004582}}

However, because the aurochs is ancestral to most modern cattle breeds, it is possible for it to be brought back through selective or back breeding. The first attempt at this was by Heinz and Lutz Heck using modern cattle breeds, which resulted in the creation of Heck cattle. This breed has been introduced to nature preserves across Europe; however, it differs strongly from the aurochs in physical characteristics, and some modern attempts claim to try to create an animal that is nearly identical to the aurochs in morphology, behavior, and even genetics.{{cite web |last=Lawson |first=Kristan |title='Jurassic farm' can bring prehistoric barnyard animals back from extinction |date=2014-09-10 |website=Modern Farmer |url=http://modernfarmer.com/2014/09/jurassic-farm-can-bring-prehistoric-barnyard-animals-back-extinction/ |url-status=dead |access-date=23 November 2014|archive-url=https://web.archive.org/web/20150308174414/https://modernfarmer.com/2014/09/jurassic-farm-can-bring-prehistoric-barnyard-animals-back-extinction/|archive-date=2015-03-08}} There are several projects that aim to create a cattle breed similar to the aurochs through selectively breeding primitive cattle breeds over a course of twenty years to create a self-sufficient bovine grazer in herds of at least 150 animals in rewilded nature areas across Europe, for example the Tauros Programme and the separate Taurus Project.{{cite web |author=Pais, Bárbara |title=TaurOs Programme |website=Atnatureza.org |url=http://www.atnatureza.org/index.php/en/projects-hidder/2-uncategorised/125-programa-tauros-en |access-date=23 November 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141006134425/http://www.atnatureza.org/index.php/en/projects-hidder/2-uncategorised/125-programa-tauros-en |archive-date=2014-10-06}}

{{cite press release |title=TaurOs Programme fact sheet |date=2013-10-04 |website=Rewilding Europe |url=https://rewildingeurope.com/wp-content/uploads/2013/11/Tauros-programme.pdf |access-date=2023-03-24}} This organization is partnered with the organization Rewilding Europe to help revert some European natural ecosystems to their prehistoric form.{{cite web |title=Tauros Programme |website=Rewilding Europe (Rewildingeurope.com) |url=http://www.rewildingeurope.com/tauros-programme/ |access-date=23 November 2014}}

A competing project to recreate the aurochs is the Uruz Project by the True Nature Foundation, which aims to recreate the aurochs by a more efficient breeding strategy using genome editing, in order to decrease the number of generations of breeding needed and the ability to quickly eliminate undesired traits from the population of aurochs-like cattle.{{cite web |title=Aurochs |website=True Nature Foundation (truenaturefoundation.org) |url=http://www.truenaturefoundation.org/wildlife/aurochs |url-status=dead |access-date=2015-07-08 |archive-url=https://web.archive.org/web/20150116173809/http://www.truenaturefoundation.org/wildlife/aurochs |archive-date=2015-01-16}} It is hoped that aurochs-like cattle will reinvigorate European nature by restoring its ecological role as a keystone species and bring back biodiversity that disappeared following the decline of European megafauna, as well as helping to bring new economic opportunities related to European wildlife viewing.{{cite web |title=The Aurochs: Born to be wild |website=Rewilding Europe (Rewildingeurope.com) |url=http://www.rewildingeurope.com/publications/the-aurochs-born-to-be-wild/ |access-date=23 November 2014 |archive-date=7 May 2016 |archive-url=https://web.archive.org/web/20160507135555/https://www.rewildingeurope.com/publications/the-aurochs-born-to-be-wild/ |url-status=dead }}

Sometime in 2025, Tauros Programme and Rewilding Europe plan to release their aurochs into the wild in select areas of Europe and to have the species recognised as a protected wildlife species again.{{Cite web |date=2012-11-07 |title=The comeback of the European icon |url=https://rewildingeurope.com/news/the-comeback-of-the-european-icon/ |access-date=2025-01-23 |website=Rewilding Europe |language=en-GB}} In 2026, these animals will be reintroduced to parts of the Scottish Highlands.{{Cite web |date=2024-10-10 |title=The wild cattle to be 'brought back from the dead' in the Scottish Highlands |url=https://www.scotsman.com/news/the-wild-cattle-to-be-brought-back-from-the-dead-in-the-scottish-highlands-4817445 |access-date=2025-01-23 |website=The Scotsman |language=en}}

File:Quagga HIFI.jpg

The quagga (Equus quagga quagga) is a subspecies of the plains zebra that was distinct in that it was striped on its face and upper torso, but its rear abdomen was a solid brown. It was native to South Africa, but was wiped out in the wild due to overhunting for sport, and the last individual died in 1883 in the Amsterdam Zoo.{{cite web|url=http://animaldiversity.ummz.umich.edu/accounts/Equus_quagga/|last=Rodriguez|first=Debra L.|year=1999|title=Equus quagga|work=Animal Diversity Web|access-date=23 November 2014}} However, since it is technically the same species as the surviving plains zebra, it has been argued that the quagga could be revived through artificial selection. The Quagga Project aims to breed a similar form of zebra by selective breeding of plains zebras.{{cite web|url=http://www.quaggaproject.org/quagga-objectives.htm|title=OBJECTIVES :: The Quagga Project :: South Africa|publisher=Quaggaproject.org|url-status=dead|archive-url=https://web.archive.org/web/20141201150541/http://www.quaggaproject.org/quagga-objectives.htm|archive-date=1 December 2014|access-date=23 November 2014}} This process is also known as back breeding. It also aims to release these animals onto the western Cape once an animal that fully resembles the quagga is achieved, which could have the benefit of eradicating introduced species of trees such as the Brazilian pepper tree, Tipuana tipu, Acacia saligna, bugweed, camphor tree, stone pine, cluster pine, weeping willow and Acacia mearnsii.{{Cite journal|last1=Harley|first1=Eric H.|last2=Knight|first2=Michael H.|last3=Lardner|first3=Craig|last4=Wooding|first4=Bernard|last5=Gregor|first5=Michael|year=2009|title=The Quagga Project: Progress over 20 Years of Selective Breeding|journal=South African Journal of Wildlife Research|volume=39|issue=2|pages=155–163|citeseerx=10.1.1.653.4113|doi=10.3957/056.039.0206|s2cid=31506168}}

File:"Benjamin".jpg

The thylacine (Thylacinus cynocephalus), commonly known as the Tasmanian tiger, was native to the Australian mainland, Tasmania and New Guinea. It is believed to have become extinct in the 20th century. The thylacine had become extremely rare or extinct on the Australian mainland before British settlement of the continent. The last known thylacine died at the Hobart Zoo, on September 7, 1936. It is believed to have died as the result of neglect—locked out of its sheltered sleeping quarters, it was exposed to a rare occurrence of extreme Tasmanian weather: extreme heat during the day and freezing temperatures at night.Paddle (2000){{Broken anchor|date=2024-05-27|bot=User:Cewbot/log/20201008/configuration|target_link=#Paddle|reason= }}, p. 195.{{Cite news |last1=Dunlevie |first1=James |date=5 December 2022 |title=Stop calling the last thylacine Benjamin, Tasmanian tiger researcher says |url=https://www.abc.net.au/news/2022-12-06/benjamin-thylacine-tasmanian-tiger-naming-myth-persists/101734442 |url-status=live |archive-url=https://web.archive.org/web/20231216074150/https://www.abc.net.au/news/2022-12-06/benjamin-thylacine-tasmanian-tiger-naming-myth-persists/101734442 |archive-date=Dec 16, 2023 |newspaper=ABC News}} Official protection of the species by the Tasmanian government was introduced on July 10, 1936, roughly 59 days before the last known specimen died in captivity.{{cite web|url=http://www.environment.gov.au/biodiversity/threatened/ts-day/index.html|title=National Threatened Species Day|year=2006|publisher=Department of the Environment and Heritage, Australian Government|url-status=dead|archive-url=https://web.archive.org/web/20090709141827/http://www.environment.gov.au/biodiversity/threatened/ts-day/index.html|archive-date=July 9, 2009|access-date=21 November 2006}}

In December 2017, it was announced in the journal Nature Ecology and Evolution that the full nuclear genome of the thylacine had been successfully sequenced, marking the completion of the critical first step toward de-extinction that began in 2008, with the extraction of the DNA samples from the preserved pouch specimen.{{Cite news|url=https://news.nationalgeographic.com/2017/12/thylacine-genome-extinct-tasmanian-tiger-cloning-science/|archive-url=https://web.archive.org/web/20171211203647/https://news.nationalgeographic.com/2017/12/thylacine-genome-extinct-tasmanian-tiger-cloning-science/|url-status=dead|archive-date=December 11, 2017|title=Tasmanian Tiger Genome May Be First Step Toward De-Extinction|date=2017-12-11|access-date=2018-08-25}} The thylacine genome was reconstructed by using the genome editing method. The Tasmanian devil was used as a reference for the assembly of the full nuclear genome.{{Cite journal|last1=Feigin|first1=Charles Y.|last2=Newton|first2=Axel H.|last3=Doronina|first3=Liliya|last4=Schmitz|first4=Jürgen|last5=Hipsley|first5=Christy A.|last6=Mitchell|first6=Kieren J.|last7=Gower|first7=Graham|last8=Llamas|first8=Bastien|last9=Soubrier|first9=Julien|title=Genome of the Tasmanian tiger provides insights into the evolution and demography of an extinct marsupial carnivore|journal=Nature Ecology & Evolution|volume=2|issue=1|pages=182–192|doi=10.1038/s41559-017-0417-y|issn=2397-334X|pmid=29230027|year=2018|doi-access=free|bibcode=2017NatEE...2..182F }} Andrew J. Pask from the University of Melbourne has stated that the next step toward de-extinction will be to create a functional genome, which will require extensive research and development, estimating that a full attempt to resurrect the species may be possible as early as 2027.

In August 2022, the University of Melbourne and Colossal Biosciences announced a partnership to accelerate de-extinction of the thylacine via genetic modification of one of its closest living relatives, the fat-tailed dunnart.{{Cite press release |title=Lab takes 'giant leap' toward thylacine de-extinction with Colossal genetic engineering technology partnership |date=2022-08-16 |url=https://www.unimelb.edu.au/newsroom/news/2022/august/lab-takes-giant-leap-toward-thylacine-de-extinction-with-colossal-genetic-engineering-technology-partnership2 |access-date=2022-08-16 |publisher=The University of Melbourne |archive-url=https://web.archive.org/web/20220816184227/https://www.unimelb.edu.au/newsroom/news/2022/august/lab-takes-giant-leap-toward-thylacine-de-extinction-with-colossal-genetic-engineering-technology-partnership2 |archive-date=2022-08-16}} In October 2024, Colossal claimed to have reconstructed a 99.9% complete genome of the thylacine from a well-preserved skull estimated to be 110 years old;{{Cite web |title=MSN |url=https://www.msn.com/en-us/news/technology/most-complete-tasmanian-tiger-genome-yet-pieced-together-from-110-year-old-pickled-head/ar-AA1spMUf |access-date=2024-10-20 |website=www.msn.com}} however, the data has not yet been published.{{cite news |last1=Le Page |first1=Michael |title=De-extinction company claims it has nearly complete thylacine genome |url=https://www.newscientist.com/article/2452196-de-extinction-company-claims-it-has-nearly-complete-thylacine-genome/ |access-date=26 January 2025 |publisher=New Scientist |date=17 October 2024}} In January 2025, Colossal Biosciences and University of Melbourne claimed to have developed an artificial marsupial womb to further accelerate the de-extinction of thylacine and conservation for endangered marsupials.{{Cite web |date=2025-01-15 |title=Thylacine De-Extinction Achieves Mid-Gestation Marsupial Embryo Development In Artificial Uterus |url=https://www.iflscience.com/thylacine-de-extinction-achieves-mid-gestation-marsupial-embryo-development-in-artificial-uterus-77640 |access-date=2025-01-23 |website=IFLScience |language=en}}

File:Martha last passenger pigeon 1912.jpg, the last known passenger pigeon]]

The passenger pigeon (Ectopistes migratorius) numbered in the billions before being wiped out due to unsustainable commercial hunting and habitat loss during the early 20th century. The non-profit Revive & Restore obtained DNA from the passenger pigeon from museum specimens and skins; however, this DNA is degraded because it is so old. For this reason, simple cloning would not be an effective way to perform de-extinction for this species because parts of the genome would be missing. Instead, Revive & Restore focuses on identifying mutations in the DNA that would cause a phenotypic difference between the extinct passenger pigeon and its closest living relative, the band-tailed pigeon. In doing this, they can determine how to modify the DNA of the band-tailed pigeon to change the traits to mimic the traits of the passenger pigeon. In this sense, the de-extinct passenger pigeon would not be genetically identical to the extinct passenger pigeon, but it would have the same traits. In 2015, the de-extinct passenger pigeon hybrid was forecast ready for captive breeding by 2025 and released into the wild by 2030.{{Cite web |last=Journal |first=Amy Dockser Marcus Wall Street |title=Passenger Pigeon Project Update |url=https://reviverestore.org/projects/the-great-passenger-pigeon-comeback/progress-to-date/ |access-date=2024-09-01 |language=en-US}} In October 2024, Revive & Restore collaborated with Applied Ecological Institute to simulate forest disturbances in the American state of Wisconsin to see how trees would react to the reintroduced passenger pigeons. The original 2025 goal was not met, with the new goal for reviving the species for captive breeding set for between 2029 and 2032. However, it could take decades for the species to be reintroduced to the wild.{{Cite web |last=Cox |first=Lorin |date=2024-10-22 |title=With plan to revive extinct passenger pigeon species, researchers are testing Wisconsin trees |url=https://www.wpr.org/news/revive-extinct-passenger-pigeon-species-research-wisconsin-trees |access-date=2025-01-23 |website=WPR |language=en-US}}

File:Skeleton of little bush moa, Otago Museum, 2016-01-29-2.jpg

The bush moa, also known as the little bush moa or lesser moa (Anomalopteryx didiformis) is a slender species of moa slightly larger than a turkey that abruptly went extinct around 500–600 years ago following the arrival and proliferation of the Māori people in New Zealand, as well as the introduction of Polynesian dogs.{{Cite web |title=Little bush moa {{!}} New Zealand Birds Online |url=http://nzbirdsonline.org.nz/species/little-bush-moa |access-date=2021-02-19 |website=nzbirdsonline.org.nz}} Scientists at Harvard University assembled the first nearly complete genome of the species from toe bones, thus bringing the species a step closer to de-extinction.{{Cite web |date=2018-02-27 |title=Scientists reconstruct the genome of a moa, a bird extinct for 700 years |url=https://www.statnews.com/2018/02/27/moa-extinct-bird-genome/ |access-date=2021-02-19 |website=STAT |language=en-US}} Trevor Mallard, a New Zealander politician, has also previously suggested bringing back a medium-sized species of moa.{{cite web |date=10 July 2014 |title=Time to bring back... the moa |url=http://www.stuff.co.nz/national/10216641/Time-to-bring-back-the-moa |access-date=23 November 2014 |work=Stuff}} The proxy of the species will likely be the emu.{{Cite web |last=Begley |first=Sharon |date=2018-02-27 |title=With DNA from a museum specimen, scientists reconstruct the genome of a bird extinct for 700 years |url=https://www.statnews.com/2018/02/27/moa-extinct-bird-genome/ |access-date=2024-10-24 |website=STAT |language=en-US}}

File:MusMacleariSmit.jpg

The Maclear's rat (Rattus macleari), also known as the Christmas Island rat, was a large rat endemic to Christmas Island in the Indian Ocean. It is believed Maclear's rat might have been responsible for keeping the population of Christmas Island red crab in check. It is thought that the accidental introduction of black rats by the Challenger expedition infected the Maclear's rats with a disease (possibly a trypanosome),Pickering J. & Norris C.A. (1996). "New evidence concerning the extinction of the endemic murid Rattus macleari from Christmas Island, Indian Ocean". Australian Mammalogy. 19: 19–25. which resulted in the species' decline.Wyatt KB, Campos PF, Gilbert MT, Kolokotronis SO, Hynes WH, et al. (2008). "Historical mammal extinction on Christmas Island (Indian Ocean) correlates with introduced infectious disease" The last recorded sighting was in 1903.Flannery, Tim & Schouten, Peter (2001). A Gap in Nature: Discovering the World's Extinct Animals. Atlantic Monthly Press, New York. ISBN 978-0-87113-797-5. In March 2022, researchers discovered the Maclear's rat shared about 95% of its genes with the living brown rat, thus sparking hopes in bringing the species back to life. Although scientists were mostly successful in using CRISPR technology to edit the DNA of the living species to match that of the extinct one, a few key genes were missing, which would mean resurrected rats would not be genetically pure replicas.{{Cite journal |vauthors=Lin J, Duchêne D, Carøe C, Smith O, Ciucani MM, Niemann J, Richmond D, Greenwood AD, MacPhee R, Zhang G, Gopalakrishnan S, ((Gilbert MTP)) |date=11 April 2022 |title=Probing the genomic limits of de-extinction in the Christmas Island rat |journal=Current Biology |volume=32 |issue=7 |pages=1650–1656.e3|doi=10.1016/j.cub.2022.02.027 |pmid=35271794 |pmc=9044923 |bibcode=2022CBio...32E1650L |hdl=11250/3052724 |hdl-access=free }}

File:Dodo 1.JPG]]

The dodo (Raphus cucullatus) was a flightless bird endemic to the island of Mauritius in the Indian Ocean. Due to various factors such as the inability to feel fear caused by isolation from significant predators, predation from humans and introduced invasive species such as pigs, dogs, cats, rats, and crab-eating macaques, competition for food with invasive species, habitat loss, and the birds naturally slow reproduction, the species' numbers declined rapidly.{{Cite book |last=Hume |first=Julian P. |title=Extinct birds |date=2017 |publisher=Christopher Helm |isbn=978-1-4729-3744-5 |edition=Second |location=London New York}} The last widely accepted recorded sighting was in 1662. Since then, the bird has become a symbol for extinction and is often cited as the primary example of man-made extinction.{{Cite journal |last1=Turvey |first1=Samuel T. |last2=Cheke |first2=Anthony S. |date=June 2008 |title=Dead as a dodo: the fortuitous rise to fame of an extinction icon |url=https://www.tandfonline.com/doi/full/10.1080/08912960802376199 |journal=Historical Biology |language=en |volume=20 |issue=2 |pages=149–163 |doi=10.1080/08912960802376199 |bibcode=2008HBio...20..149T |issn=0891-2963|url-access=subscription }} In January 2023, Colossal Biosciences announced their project to revive the dodo alongside their previously announced projects for reviving the woolly mammoth and thylacine in hopes of restoring biodiversity to Mauritius and changing the dodo's status as a symbol of extinction to de-extinction.{{Cite web |last=Snider |first=Mike |title=Scientists are trying to resurrect the dodo – centuries after the bird famously went extinct |url=https://www.usatoday.com/story/news/nation/2023/01/31/genetics-company-wants-bring-back-dodo-along-woolly-mammoth/11141047002/ |access-date=2024-08-11 |website=USA TODAY |language=en-US}}{{Cite web |date=2023-01-31 |title=Dodo {{!}} Reviving the Dodo |url=https://colossal.com/dodo/ |access-date=2024-08-11 |website=Colossal |language=en}}

File:The Model of Steller's sea cow (Hydrodamalis gigas).jpg

The Steller's sea cow was a sirenian endemic to Bering Sea between Russia and the United States but had a much larger range during the Pleistocene. First described by Georg Wilhelm Steller in 1741, it was hunted to extinction 27 years later due to its buoyancy making it an easy target for humans hunting it for its meat and fur in addition to an already low population caused by climate change. In 2021, the nuclear genome of the species was sequenced.{{Cite journal |last1=Sharko |first1=Fedor S. |last2=Boulygina |first2=Eugenia S. |last3=Tsygankova |first3=Svetlana V. |last4=Slobodova |first4=Natalia V. |last5=Alekseev |first5=Dmitry A. |last6=Krasivskaya |first6=Anna A. |last7=Rastorguev |first7=Sergey M. |last8=Tikhonov |first8=Alexei N. |last9=Nedoluzhko |first9=Artem V. |date=2021-04-13 |title=Steller's sea cow genome suggests this species began going extinct before the arrival of Paleolithic humans |journal=Nature Communications |language=en |volume=12 |issue=1 |page=2215 |doi=10.1038/s41467-021-22567-5 |pmid=33850161 |issn=2041-1723|pmc=8044168 |bibcode=2021NatCo..12.2215S }} In late 2022, a group of Russian scientists funded by Sergei Bachin began their project to revive and reintroduce the giant sirenian to its former range in the 18th century to restore its kelp forest ecosystem. Arctic Sirenia plans to revive the species through genome editing of the dugong, but they need an artificial womb to conceive a live animal due to lack of an adequate surrogate species.{{Cite web |title=Arctic Sirenia |url=https://www.arcticsirenia.com/#project |access-date=2024-11-18 |website=www.arcticsirenia.com}} Ben Lamm of Colossal Biosciences has also expressed desire to revive the species once his company develops an artificial womb.{{Cite web |last1=Writer |first1=Anna Skinner Senior |last2=Assignment |first2=General |date=2023-12-01 |title=Extinct animals could suddenly be brought back to life |url=https://www.newsweek.com/extinct-animals-could-suddenly-brought-back-life-1848552 |access-date=2024-11-18 |website=Newsweek |language=en}}

File:Sudan, Northern White Rhino.jpg, the final male northern white rhinoceros was euthanised due to age-related illnesses on the Ol Pejeta Conservancy in 2018]]

The northern white rhinoceros or northern white rhino (Ceratotherium simum cottoni) is a subspecies of the white rhinoceros endemic to East and Central Africa south of the Sahara. Due to widespread and uncontrollable poaching and civil warfare in their former range, the subspecies' numbers dropped quickly over the course of the late 1900s and early 2000s.{{Cite web |date=2007-10-23 |title=Northern White Rhino |url=http://www.rhinos-irf.org/rhinoinformation/whiterhino/subspecies/northern.htm |access-date=2024-08-11 |archive-url=https://web.archive.org/web/20071023203029/http://www.rhinos-irf.org/rhinoinformation/whiterhino/subspecies/northern.htm |archive-date=2007-10-23 }}{{Cite journal |last=Smith |first=Kes Hillman |date=July–December 2001 |title=Status of northern white rhinos and elephants in Garamba National Park, Democratic Republic of Congo, during the wars |url=http://www.rhinoresourcecenter.com/pdf_files/125/1255075757.pdf |journal=Pachyderm Journal}} Unlike the majority of the potential candidates for de-extinction, the northern white rhinoceros is not extinct, but functionally extinct and is believed to be extinct in the wild with only two known female members left, Najin and Fatu who reside on the Ol Pejeta Conservancy in Kenya.{{Cite web |title=Just two northern white rhinos are left on Earth. A new breakthrough offers hope |url=https://www.cnn.com/interactive/2024/01/world/rhino-ivf-pregnancy-scn-cnnphotos/ |access-date=2024-08-11 |website=www.cnn.com}} The BioRescue Team in collaboration with Colossal Biosciences plan to implement 30 northern white rhinoceros embryos made from egg cells collected from Najin and Fatu and preserved sperm from dead male individuals into female southern white rhinoceros by the end of 2024.{{Cite magazine |last1=Kluger |first1=Jeffrey |last2=Vitale |first2=Photos by Ami |date=2024-01-25 |title=An Inside Look at the Embryo Transplant That May Help Save the Northern White Rhino |url=https://time.com/6588316/breakthrough-white-rhino-embryo-implantation-photos/ |access-date=2024-08-11 |magazine=TIME |language=en}}{{Cite web |date=2024-02-07 |title=Colossal Biosciences Joins BioRescue in Its Mission to Save the Northern White Rhino From Extinction {{!}} BioSpace |work=BioSpace |url=https://www.biospace.com/article/colossal-biosciences-joins-biorescue-in-its-mission-to-save-the-northern-white-rhino-from-extinction/ |access-date=2024-08-11 |archive-url=https://web.archive.org/web/20240207142414/https://www.biospace.com/article/colossal-biosciences-joins-biorescue-in-its-mission-to-save-the-northern-white-rhino-from-extinction/ |archive-date=2024-02-07 }}

File:Ivory-billedWoodpeckerNHMLondon.jpg]]

The ivory-billed woodpecker (Campephilus principalis) is the largest woodpecker native to the United States, with an endemic subspecies in Cuba. The species numbers have declined since the late 1800s due to logging and hunting.{{Cite book |title=Recovery Plan for the Ivory-billed Woodpecker (Campephilus Principalis) |publisher=U.S. Fish and Wildlife Service, Southeast Region |year=2010 |url=https://www.fws.gov/ivorybill/pdf/IBWRecoveryPlan2010.pdf |url-status=dead |archive-url=https://web.archive.org/web/20200808014921/https://www.fws.gov/ivorybill/pdf/IBWRecoveryPlan2010.pdf |archive-date=2020-08-08 }} Similarly to the northern white rhinoceros, the ivory-billed woodpecker may not be completely extinct, but rather functionally extinct, though the evidence suggests that the species is 'very likely extinct'.{{Cite web |title=Ivory-billed Woodpecker (Campephilus principalis) - BirdLife species factsheet |url=https://datazone.birdlife.org/species/factsheet/ivory-billed-woodpecker-campephilus-principalis/details |access-date=2024-08-26 |website=datazone.birdlife.org}} In October 2024, Colossal Biosciences announced their non-profit Colossal Foundation, a foundation dedicated to conservation of extant species with their first projects being the Sumatran rhinoceros, vaquita, red wolf, pink pigeon, northern quoll, and ivory-billed woodpecker. Colossal plans to revive or rediscover the species through genome editing of its closest living relatives, such as the pileated woodpecker and using drones and AI to identify any potential remaining individuals in the wild.{{Cite web |last=Jacobo |first=Julia |date=2024-10-01 |title=How the process of de-extinction will be used to restore this fabled species |url=https://abcnews.go.com/US/ivory-billed-woodpecker-extinct-genetic-engineering-company-aims/story?id=114352833 |access-date=2024-10-02 |website=ABC News |language=en}}{{Cite web |date=2024-10-01 |title=The Colossal Foundation Aims to Save Threatened Species with De-Extinction Science |url=https://www.yahoo.com/entertainment/colossal-foundation-aims-save-threatened-203640641.html |access-date=2024-10-02 |website=Yahoo Entertainment |language=en-US}}

File:AlfredOttoGross1.jpg holding Booming Ben, the last known heath hen ]]

The heath hen (Tympanuchus cupido cupido) was a subspecies of greater prairie chicken endemic to the heathland barrens of coastal North America. It is even speculated that the pilgrims' first Thanksgiving featured this bird as the main course instead of wild turkey.{{Cite web |title=The Original "Thanksgiving Turkey" is Now Extinct |url=https://www.idausa.org/campaign/farmed-animal/latest-news/the-original-thanksgiving-turkey-is-now-extinct/ |access-date=2024-09-01 |website=IDA USA |language=en}} Due to overhunting caused by its perceived abundancy, the population became extinct in mainland North America by 1870, leaving a population of 300 individuals left on Martha's Vineyard. Despite conservation efforts, the subspecies became extinct in 1932 following the disappearance and presumed death of Booming Ben, the final known member of the subspecies. In the summer of 2014, non-profit organisation, Revive & Restore held a meeting with the community of Martha's Vineyard to announce their project to revive the heath hen in hopes of restoring and maintaining the sandplain grasslands.{{Cite web |title=The Heath Hen Could Come Back |url=https://reviverestore.org/projects/heath-hen-project/ |access-date=2024-09-01 |language=en-US}}{{Cite web |title=Heath Hen Debate Contains Vineyard DNA |url=https://vineyardgazette.com/news/2014/07/24/heath-hen-debate-contains-vineyard-dna?k=vg53ebfb1806549 |access-date=2024-09-01 |website=The Vineyard Gazette - Martha's Vineyard News |language=en}} On April 8, 2020, germs cells were collected from greater prairie chicken eggs at Texas A&M.{{Cite web |title=Heath Hen Project: Progress to Date |url=https://reviverestore.org/progress-to-date/ |access-date=2024-09-01 |language=en-US}}{{Cite AV media |url=https://www.youtube.com/watch?v=f_0SpjiUGlM |title=Greater Prairie Chicken In Mating Call and Stamping |date=2020-04-08 |last=Revive & Restore |access-date=2024-09-01 |via=YouTube}}

File:Rùa Đồng Mô.jpg, Vietnam]]

The Yangtze giant softshell turtle (Rafetus swinhoei) is a softshell turtle endemic to China and Vietnam and is possibly the largest living freshwater turtle. Due to various factors such as habitat loss, wildlife trafficking, trophy hunting, and the Vietnam War, the species population has been reduced to only three male individuals, rendering it functionally extinct similar to the northern white rhinoceros and ivory-billed woodpecker.{{Cite journal |last1=Department of Animal Science and Fishery, Faculty of Agricultural and Forestry Sciences, Universiti Putra Malaysia, Bintulu Sarawak Campus, 97008 Bintulu, Sarawak, Malaysia |last2=Al-Asif |first2=Abdulla |date=2022 |title=A ray of hope in the darkness: What we have learned from Yangtze giant soft-shell turtle Rafetus swinhoei (Gray, 1873) conservation? |url=http://ajcb.in/journals/full_papers_dec_2022/Editorial_AJCB-Vol11-No2-Al-Asif%20et%20al.pdf |journal=Asian Journal of Conservation Biology |volume=11 |issue=2 |pages=167–168 |doi=10.53562/ajcb.EN00022}}{{Cite web |date=2006-12-14 |title=Rafetus swinhoei field guide - Asian Turtle Conservation Network |url=http://www.asianturtlenetwork.org/field_guide/Rafetus_swinhoei.htm |access-date=2024-12-06 |archive-url=https://web.archive.org/web/20061214052701/http://www.asianturtlenetwork.org/field_guide/Rafetus_swinhoei.htm |archive-date=14 December 2006 }} There is one captive individual in Suzhou Zoo in China, and two wild individuals at Dong Mo Lake in Vietnam. Efforts to save the species from extinction through various means of assisted reproduction in captivity have been ongoing since 2009 by the Suzhou Zoo and Turtle Survival Alliance.

Despite efforts to breed the turtles naturally, the eggs laid by the final known female were all infertile and unviable. In May 2015, artificial insemination was performed for the first time in the species.{{Cite web |date=2015-05-26 |title=Scientists Make Novel Attempt to Save Giant Turtle Species - NYTimes.com |website=The New York Times |url=https://www.nytimes.com/2015/05/26/science/yangtze-giant-softshell-turtle-artificial-insemination.html?hp&action=click&pgtype=Homepage&module=mini-moth®ion=top-stories-below&WT.nav=top-stories-below |access-date=2024-12-06 |archive-url=https://web.archive.org/web/20150526055239/https://www.nytimes.com/2015/05/26/science/yangtze-giant-softshell-turtle-artificial-insemination.html?hp&action=click&pgtype=Homepage&module=mini-moth®ion=top-stories-below&WT.nav=top-stories-below |archive-date=26 May 2015 }} In July of the same year, the female laid 89 eggs, but like all previous natural attempts, they were all unviable.{{Cite web |date=2015-09-10 |title=First Artificial Breeding Attempt for World's Rarest Turtle Unsuccessful {{!}} Turtle Survival Alliance (TSA) |url=http://www.turtlesurvival.org/blog/1/368#.VfDxS6DP32d |access-date=2024-12-06 |archive-url=https://web.archive.org/web/20150910025553/http://www.turtlesurvival.org/blog/1/368#.VfDxS6DP32d |archive-date=10 September 2015 }} In April 2019, the female individual at the zoo died after another failed artificial insemination attempt.{{Cite web |title=1 of world's 4 remaining giant softshell turtles dies – DW – 04/14/2019 |url=https://www.dw.com/en/death-of-rare-yangtze-giant-softshell-turtle-leaves-3-remaining-in-the-world/a-48321971 |access-date=2024-12-06 |website=dw.com |language=en}} In 2020, a female was discovered in the wild, reigniting hope for the survival of the species.{{Cite web |title=World's Most Endangered Turtle Gets Some Good News In 2020 |url=https://newsroom.wcs.org/News-Releases/articleType/ArticleView/articleId/15641/Worlds-Most-Endangered-Turtle-Gets-Some-Good-News-In-2020.aspx |access-date=2024-12-06 |website=newsroom.wcs.org |language=en-US}} However, this individual was found dead in early 2023.{{Cite magazine |last=Hanoi |first=Chris Humphrey / |date=2023-04-28 |title=Rare, Revered Reptile on Brink of Extinction After Last Female Dies |url=https://time.com/6275373/giant-yangtze-softshell-turtle-female-dies/ |access-date=2024-12-06 |magazine=TIME |language=en}} Several searches across China and Vietnam are currently underway to locate female individuals to breed with the final known males, or to undergo artificial insemination.{{Cite web |date=2019-04-12 |title=Interview surveys in northern Vietnam look for remaining Swinhoe's softshell turtles in the wild |url=http://www.asianturtleprogram.org/pages/other_pages/2018-10-Lai_Chau_interview_survey/2018-Lai_Chau_interview_survey_EN.htm |access-date=2024-12-06 |archive-url=https://web.archive.org/web/20190412151414/http://www.asianturtleprogram.org/pages/other_pages/2018-10-Lai_Chau_interview_survey/2018-Lai_Chau_interview_survey_EN.htm |archive-date=12 April 2019 }}{{Cite web |date=2019-04-18 |title=The Yangtze Softshell Turtle – TURTLE ISLAND |url=http://www.turtle-island.at/en/projekte/the-yangtze-softshell-turtle/ |access-date=2024-12-06 |archive-url=https://web.archive.org/web/20190418195242/http://www.turtle-island.at/en/projekte/the-yangtze-softshell-turtle/ |archive-date=18 April 2019 }}{{Cite web |last=Price |first=Katie |date=2024-11-13 |title=There are Only 2 of These Turtles Left in the Wild |url=https://a-z-animals.com/articles/endangered-efforts-yangtze-giant-softshell-turtle/ |access-date=2024-12-06 |website=A-Z Animals |language=en-US}}

{{main|Romulus, Remus, and Khaleesi}}

There have been attempts to recreate the dire wolf (Aenocyon dirus) in modern times. The first is a project called the Dire Wolf Project, a project begun in 1988 that aims to revive the species through backbreeding of domestic dogs, similar to the Quagga project. However, this project is not based in scientific method.{{Cite web |title=Find out about the Dire Wolf Project {{!}} Dire Wolf Project |url=https://direwolfproject.com/about-us/ |access-date=2025-04-07 |website=direwolfproject.com |language=en}}

In April 2025, it was announced that Colossal Biosciences used cloning and gene-editing to birth three genetically modified wolf pups with the characteristics of the dire wolf, six-month-old males Romulus and Remus and two-month-old female Khaleesi. In-house scientists at Colossal analyzed the dire wolf genome, extracted from two ancient samples – a 13,000-year-old tooth and a 72,000-year-old ear bone. After comparing the genomes of gray wolves and dire wolves to identify the genetic differences responsible for the dire wolf's distinctive features, Colossal made edits to the genetic code of the gray wolf to replicate those traits. Domestic dogs were used as surrogate mothers for the pups.{{Cite magazine|url=https://time.com/7274542/colossal-dire-wolf/|author=Jeffrey Klinger|title=The Return of the Dire Wolf|date=April 7, 2025|magazine=Time|access-date=April 7, 2025|archive-date=April 7, 2025|archive-url=https://web.archive.org/web/20250407144101/https://time.com/7274542/colossal-dire-wolf/|url-status=live}}{{Cite magazine|url=https://www.newyorker.com/magazine/2025/04/14/the-dire-wolf-is-back|author=D. T. Max|title=The Dire Wolf is Back|date=April 7, 2025|magazine=The New Yorker|access-date=April 7, 2025|archive-date=April 7, 2025|archive-url=https://web.archive.org/web/20250407131025/https://www.newyorker.com/magazine/2025/04/14/the-dire-wolf-is-back|url-status=live}}{{cite magazine|url=https://time.com/7275439/science-behind-dire-wolf-return/|author=Jeffrey Kluger|date=April 7, 2025|title=The Science Behind the Return of the Dire Wolf|magazine=Time}} Colossal claims that these minor genetic modifications effectively revive dire wolves as a species, though "no ancient dire wolf DNA was actually spliced into the gray wolf's genome".

File:Maharajah Ramanuj Pratap Singh Deo with cheetah kill 1948 BNHS.jpg shot three of the final Indian cheetahs in 1948, leaving a lone female who was last spotted in 1951.]]

The Indian cheetah was a population of the Asiatic cheetah (Acinonyx jubatus venaticus) that was endemic to India. The Asiatic cheetah was extirpated from the region due to trapping by Indian royalty to aid in coursing since the 16th century, and later poaching, habitat loss, and loss of prey in the 20th century, leading to being declared extinct by the Indian government in 1952.Divyabhanusinh (1999). The End of a Trail: the Cheetah in India. Banyan Books, New Delhi. In 2022 and 2023, African cheetahs have been imported to India to act as an ecological proxy for the locally extinct subspecies. In April 2025, Birbal Sahni Institute of Palaeosciences in collaboration with Zoological Survey of India announced plans to revive and rewild the Indian cheetah through the same methods as Colossal Biosciences' dire wolf project, editing the genome of the African cheetah to reflect that of the Indian cheetah with an African cheetah acting as a surrogate.{{Cite news |date=2025-04-21 |title=Scientists set to bring back extinct Indian cheetahs with gene technology after reviving dire wolves |url=https://timesofindia.indiatimes.com/science/scientists-set-to-bring-back-extinct-indian-cheetahs-with-gene-technology-after-reviving-dire-wolves/articleshow/120480666.cms |access-date=2025-04-22 |work=The Times of India |issn=0971-8257}}{{Cite web |date=2025-04-18 |title=Can the Indian cheetah be 'revived' with gene tech? |url=https://www.firstpost.com/explainers/can-the-indian-cheetah-be-revived-with-gene-tech-13880985.html |access-date=2025-04-22 |website=Firstpost |language=en-us}}

A "De-extinction Task Force" was established in April 2014 under the auspices of the Species Survival Commission (SSC) and charged with drafting a set of Guiding Principles on Creating Proxies of Extinct Species for Conservation Benefit to position the IUCN SSC on the rapidly emerging technological feasibility of creating a proxy of an extinct species.IUCN SSC (2016). IUCN SSC Guiding principles on Creating Proxies of Extinct Species for Conservation Benefit. Version 1.0. Gland, Switzerland: IUCN Species Survival Commission

• Giant moa – The tallest birds to have ever lived. Both the northern and southern species became extinct by 1500 due to overhunting by the Māori in New Zealand.
• Elephant bird – The heaviest birds to have ever lived, the elephant birds were driven to extinction by the early colonization of Madagascar. Ancient DNA has been obtained from the eggshells but may be too degraded for use in de-extinction.{{cite news|url=https://www.telegraph.co.uk/news/science/science-news/7405923/Extinct-elephant-bird-of-Madagascar-could-live-again.html|title=Extinct elephant bird of Madagascar could live again|date=10 March 2010|work=Telegraph.co.uk|last1=Alleyne|first1=Richard}}

File:Conuropsis carolinensis (Carolina parakeet).jpg

• Carolina parakeet - One of the few native parrots to the United States, it was driven to extinction by destruction of its habitat, overhunting, competition from introduced honeybees, and persecution for crop damages and declared extinct following the death of its final known member, Incas in 1918. Hundreds of specimens with viable DNA still exist in museums around the world, making it a prime candidate for revival. In 2019, the full genome of the Carolina parakeet was sequenced.{{Cite web |last=Dodgson |first=Lindsay |title=25 animals that scientists want to bring back from extinction |url=https://www.businessinsider.com/animals-scientists-bring-back-de-extinction-2017-1 |access-date=2021-02-19 |website=Business Insider}}{{Cite web |last=Smith |first=Kiona N. |title=Scientists Sequenced The Genome Of The Carolina Parakeet, America's Extinct Native Parrot |url=https://www.forbes.com/sites/kionasmith/2019/12/13/scientists-sequenced-the-genome-of-the-carolina-parakeet-americas-extinct-native-parrot/ |access-date=2024-09-19 |website=Forbes |language=en}}
• Great auk - A flightless bird native to the North Atlantic physically similar to penguins. The great auk went extinct in the 1800s due to overhunting by humans for food. The last two known great auks lived on an island near Iceland and were clubbed to death by sailors. There have been no known sightings since.{{Cite web|date=2013-04-01|title=Bringing Them Back to Life|url=https://www.nationalgeographic.com/magazine/article/species-revival-bringing-back-extinct-animals|archive-url=https://web.archive.org/web/20210219193125/https://www.nationalgeographic.com/magazine/article/species-revival-bringing-back-extinct-animals|url-status=dead|archive-date=February 19, 2021|access-date=2021-02-18|website=Magazine|language=en}} The great auk has been identified as a good candidate for de-extinction by Revive and Restore, a non-profit organization. Because the great auk is extinct it cannot be cloned, but its DNA can be used to alter the genome of its closest relative, the razorbill, and breed the hybrids to create a species that will be very similar to the original great auks. The plan is to introduce them back into their original habitat, which they would then share with razorbills and puffins, who are also at risk for extinction. This would help restore the biodiversity and restore that part of the ecosystem. Colossal Biosciences has also expressed interest in reviving the species.{{Cite web|title=Can the great auk return from extinction? {{!}} Conservation {{!}} Earth Touch News|url=https://www.earthtouchnews.com/conservation/conservation/can-the-great-auk-return-from-extinction|access-date=2021-02-18|website=Earth Touch News Network|language=en}}
• Imperial woodpecker – The largest woodpecker to have ever lived. Endemic to Mexico and possibly extinct, it has not been seen since 1956 due to habitat destruction and hunting. The Federal government of Mexico has considered the species extinct since 2001, 47 years after the last widely accepted sighting. However, they have conservation plans if the species is rediscovered or attempts at de-extinction are made.{{Cite web |title=CONSIDERATION OF PROPOSALS FOR AMENDMENT OF APPENDICES I AND II |url=https://cites.org/sites/default/files/eng/cop/16/prop/E-CoP16-Prop-21.pdf |website=cites.org}}
• Cuban macaw – A colourful macaw that was endemic to Cuba and Isla de la Juventud, it was the only macaw species of the Antilles. It became extinct in the late 19th century due to overhunting, pet trade, and habitat loss.
• Labrador duck – A duck native to North America. it became extinct in the late 19th century due to colonisation in their former range combined with an already naturally low population. It is also the first known endemic North American bird species to become extinct following the Columbian Exchange.{{Cite web |last=Renko |first=Amanda |title=EXTINCT: Seeking a bird last seen in 1878 |url=https://www.stargazette.com/story/news/local/2016/09/09/searching-last-labrador-duck/90118798/ |access-date=2024-08-27 |website=Star-Gazette |language=en-US}}

File:Huia Buller.jpg

• Huia – A species of Callaeidae native to New Zealand. It became extinct in 1907 due to overhunting from both the Māori and European settlers, habitat loss, and predation from introduced invasive species. In 1999, students of Hastings Boys' High School proposed the idea of de-extinction of the huia, the school's emblem through cloning.{{Cite web |date=2008-06-12 |title=NZSM OnLine -- Ten years of New Zealand Science Monthly magazine |url=http://nzsm.webcentre.co.nz/article2371.htm |archive-url=https://web.archive.org/web/20080612131328/http://nzsm.webcentre.co.nz/article2371.htm |url-status=dead |archive-date=2008-06-12 |access-date=2024-08-27 }} The Ngāti Huia tribe approved of the idea and the de-extinction process would have been performed by the University of Otago with $100,000 funding from a Californian-based internet startup.{{Cite journal |last=Dorey |first=Emma |date=1999-08-01 |title=Huia cloned back to life? |url=https://www.nature.com/articles/nbt0899_736c |journal=Nature Biotechnology |language=en |volume=17 |issue=8 |pages=736 |doi=10.1038/11628 |pmid=10429272 |issn=1546-1696}} However, due to the poor state of DNA in the specimens at Museum of New Zealand Te Papa Tongarewa, a complete huia genome could not be created, making this method of de-extinction improbable to succeed.{{Cite web |date=2014-08-26 |title=The last huia - Health - Science - The Listener |url=http://www.listener.co.nz/current-affairs/science/the-last-huia/ |archive-url=https://web.archive.org/web/20140826162224/http://www.listener.co.nz/current-affairs/science/the-last-huia/ |url-status=dead |archive-date=2014-08-26 |access-date=2024-08-27 }}
• Moho – An entire family and genus of songbirds that were endemic to the islands of Hawaii. The genus and family became extinct in 1987 following the extinction of its final living member, the Kauaʻi ʻōʻō. The reasons for the genus' decline were overhunting for their plumage, habitat loss caused by colonization of Hawaii, natural disasters, mosquito-borne diseases, and predation from introduced invasive species.

• Caribbean monk seal – A species of monk seal that was native to the Caribbean. It became extinct in 1952 due to poaching and starvation caused by overfishing of its natural prey.
• Bluebuck – A species of antelope that was native to Africa. The species was hunted to extinction by 1799 or 1800 by Europeans, and the species had a naturally low population similar to the Labrador duck. In 2024, the nuclear genome of the species was sequenced by University of Potsdam and Colossal Biosciences.{{Cite web |date=2024-04-18 |title=Genetic Puzzles Solved: Why European Colonization Drove the Blue Antelope to Extinction |url=https://scitechdaily.com/genetic-puzzles-solved-why-european-colonization-drove-the-blue-antelope-to-extinction/#:~:text=An%20international%20team%20of%20researchers,Dr. |access-date=2025-01-02 |website=SciTechDaily |language=en-US}} Colossal Biosciences has also expressed interest in reviving the species in the future.{{Cite web |date=2023-01-31 |title=Our Species |url=https://colossal.com/species/ |access-date=2025-01-02 |website=Colossal |language=en}}
• Pyrenean ibex – A subspecies of ibex that was native to the Pyrenees, the subspecies was declared extinct in the early 2000 following the death of Celia, the endling of the subspecies after two centuries of overhunting and competition with livestock and introduced species. Celia was successfully cloned by Spanish scientists in 2003, but the clone died shortly after its birth due to a lung defect. 10 years later, The Aragon Hunting Federation in collaboration with CITA (Centre for Research and Food Technology of Aragon) began a second attempt to potentially revive the subspecies by verifying if Celia's frozen cells were still viable for future cloning attempts. As of April 2025, no further statements have come out from this project.{{cite news |last1=Rincon |first1=Paul |date=2013-11-22 |title=Fresh effort to clone extinct animal |url=https://www.bbc.com/news/science-environment-25052233 |access-date=23 November 2014 |website=BBC News}}{{Cite web |last=Elcacho |first=Joaquim |date=2013-11-26 |title=¿Es posible clonar el bucardo, la cabra extinguida del Pirineo? |url=https://www.lavanguardia.com/natural/20131126/54394554030/clonar-bucardo-cabra-extinguida-pirineo.html |access-date=2024-04-11 |website=La Vanguardia |language=es}}
• Vaquita – The smallest cetacean to have ever lived; endemic to the upper Gulf of California in Mexico. The vaquita is not completely extinct, but functionally extinct with an estimate of 8 or less members left due to entanglement in gillnets meant to poach totoabas, a fish with a highly valued swim bladder on Asian black markets due to its perceived medicinal values.{{Cite web |last=Stickney • • |first=R. |date=2013-04-24 |title=Multi-Million Dollar Fish Bladder Factory Uncovered in Calexico |url=https://www.nbcsandiego.com/news/local/totoaba-smuggling-san-diego-fish-bladder-factory-uncovered-calexico/2057730/#ixzz2RYWZ9VDD |access-date=2024-10-07 |website=NBC 7 San Diego |language=en-US}}{{Cite web |last=devon11 |date=2024-06-11 |title=Vaquita Survey 2024 - Executive Summary |url=https://seashepherd.org/2024/06/11/executive_summary/ |access-date=2024-10-07 |website=Sea Shepherd Conservation Society |language=en-US}} In October 2024, Colossal Biosciences launched their Colossal Foundation, a non-profit foundation dedicated to conservation of extant species with one of their first projects being the vaquita. In addition to using technology to monitor the final remaining individuals, they aim to collect tissue samples from vaquitas in order to revive it if it does become extinct in the near future.{{Cite web |last1=Innovates |first1=Dallas |last2=Murray |first2=Lance |date=2024-10-01 |title=Colossal Launches The Colossal Foundation with $50M for 'BioVault' Biobanking, Genetic Rescues, and More |url=https://dallasinnovates.com/colossal-launches-the-colossal-foundation-with-50m-for-biovault-biobanking-genetic-rescues-and-more/#:~:text=Colossal,%20in%20partnership%20with%20the%20Vaquita%20Monitoring%20Group%20and%20in |access-date=2024-10-07 |website=Dallas Innovates |language=en-US}}

• Irish elk – The largest deer to have ever lived, formerly inhabiting Eurasia from present day Ireland to present day Siberia during the Pleistocene. It became extinct 5–10 thousand years ago due to suspected overhunting from humans.
• Cave lion – A species of Panthera related to the modern lion found throughout the Holarctic during the Pleistocene. It is estimated that the species died out 14-15 thousand years ago due to climate change and low genetic diversity. The discovery of well-preserved cubs in the Sakha Republic, Russia ignited a project to clone the animal.{{Cite web |title=South Koreans kick off efforts to clone extinct Siberian cave lions |url=http://siberiantimes.com/science/casestudy/news/n0606-south-koreans-kick-off-efforts-to-clone-extinct-siberian-cave-lions/ |access-date=2021-02-19 |website=siberiantimes.com}}{{cite web |date=5 March 2016 |title=Scientists to clone Ice Age cave lion |url=http://www.news.com.au/technology/science/animals/scientists-trying-to-clone-ice-age-cave-lion-after-finding-two-nearperfectly-preserved-cubs/news-story/2cd211fb23f944aa63e08862d564625e |work=NewsComAu}}
• Cave hyena – A species or subspecies of hyena that was endemic to Eurasia during the Pleistocene. It is estimated that the species died out 31 thousand years ago due to competition with early humans and other carnivores and decreased availability of prey.
• Castoroides – An entire genus of giant beavers endemic to North America during the Pleistocene. It is unknown how the species died out, but some suggest that climate change and competition are factors. Beth Shapiro of Colossal Biosciences has expressed interest in reviving a species from this genus.{{Cite news |date=2024-10-05 |title=First it was the dodo – now scientists want to resurrect the giant bear and jumbo beaver |url=https://www.telegraph.co.uk/news/2024/10/05/dodo-giant-bear-beaver-extinction-resurrect/?msockid=39772c7a47306cd30e26381c46796d8a |access-date=2024-10-25 |work=The Telegraph |language=en-GB |issn=0307-1235}}
• Steppe bison – The ancestor species of all modern American bison, formerly endemic to Western Europe to eastern Beringia in North America during the Late Pleistocene. The discovery of the mummified steppe bison of 9,000 years ago could help people clone the ancient bison species back, even though the steppe bison would not be the first to be "resurrected".{{cite web |date=6 November 2014 |title=9,000-year-old bison found mummified in Siberia |url=http://www.techtimes.com/articles/19666/20141106/9-000-year-old-bison-found-mummified-in-siberia.htm |work=techtimes.com}} Russian and South Korean scientists are collaborating to clone steppe bison in the future using DNA preserved from an 8,000-year-old tail{{Cite web |last=Surugue |first=Léa |date=2016-12-02 |title=Cloning ancient extinct bison sounds like sci-fi, but scientists hope to succeed within years |url=https://www.ibtimes.co.uk/cloning-ancient-extinct-bison-sounds-like-sci-fi-scientists-hope-succeed-within-years-1594574 |access-date=2021-03-09 |website=International Business Times UK |language=en}}{{Cite web |title=The remains of an 8,000 year old lunch: an extinct steppe bison's tail |url=http://siberiantimes.com/science/casestudy/news/n0804-the-remains-of-an-8000-year-old-lunch-an-extinct-steppe-bisons-tail/ |access-date=2021-03-09 |website=siberiantimes.com}} and wood bison as a surrogate species, which themselves have been introduced to Yakutia to fulfil a similar niche.
• Longhorn bison – Also known as the giant bison, a species of bison native to North America from Southern Canada to Mexico during the Late Pleistocene. It is estimated that the species died out 13,000 years ago, possibly due to pressure from early humans and overhunting.
• Ground sloths – An extremely diverse group of sloths native to the Americas during the Pleistocene with some growing to the size of modern elephants. Ground sloths died out on the mainland 11 thousand years ago, but relict populations in the Caribbean survived until about 4 thousand years ago like the final populations of woolly mammoths on Wrangel island. Ground sloths died out primarily due to climate change and some suspect that their size and slowness made them easy targets for early humans. The insular Caribbean populations were likely driven to extinction through overhunting.
• Woolly rhinoceros – A species of rhinoceros that was endemic to Northern Eurasia during the Pleistocene. It is believed to have become extinct as a result of both climate change and overhunting by early humans. In November 2023, scientists managed to sequence the woolly rhinoceros's genome from faeces of cave hyenas in addition to the existence of mummified specimens.{{Cite web |last=Starr |first=Michelle |date=2023-11-02 |title=Europe's Wooly Rhino Genes Reconstructed From DNA in Predator Poop |url=https://www.sciencealert.com/europes-wooly-rhino-genes-reconstructed-from-dna-in-predator-poop |access-date=2024-09-12 |website=ScienceAlert |language=en-US}}{{Cite web |last=Cassella |first=Carly |date=2021-01-02 |title=A Freakishly Well-Preserved Woolly Rhino Was Plucked From Siberia's Melting Tundra |url=https://www.sciencealert.com/a-freakishly-well-preserved-woolly-rhino-has-been-plucked-from-siberia-s-melting-tundra |access-date=2024-09-12 |website=ScienceAlert |language=en-US}}
• Miracinonyx – Also known as American cheetahs, an entire genus of felines that were native to North America during the Pleistocene. It is unknown how the genus went extinct, but some suggest that they died out for the same reasons as other North American megafauna; climate change, loss of prey, and competition with early humans and other carnivores.{{Cite web |title=Evolution of Speed: How Has the Clever Pronghorn Outlived The American Cheetah? |url=https://www.discovermagazine.com/planet-earth/evolution-of-speed-how-has-the-clever-pronghorn-outlived-the-american |access-date=2025-01-06 |website=Discover Magazine |language=en}}

File:Homotherium cub mummified head.png

• Machairodontinae – Commonly referred to as sabre-tooth cats or sabre-tooth tigers, an entire subfamily of feline apex predators that were widespread globally with the exceptions of Oceania and Antarctica from the middle Miocene to early Holocene. The final two genera of this subfamily, Smilodon and Homotherium, are estimated to have become extinct during the Quaternary extinction event 10–13 thousand years ago for the same reasons as other carnivorous megafauna. Despite one of their common names, the biggest challenge in the restoration of any species belonging to this subfamily is that they are too genetically distinct from modern big cats, such as tigers. In 2020, a mummified Homotherium latidens cub was discovered in Yakutia, Russia.{{Cite journal |last1=Lopatin |first1=A.V. |last2=Sotnikova |first2=M. V. |last3=Klimovsky |first3=A. I. |last4=Lavrov |first4=A. V. |last5=A. V. |first5=Protopopov |last6=Gimranov |first6=D. O. |last7=Parkhomchuk |first7=E. V. |date=14 November 2024 |title=Mummy of a juvenile sabre-toothed cat Homotherium latidens from the Upper Pleistocene of Siberia |journal=Scientific Reports |volume=14 |issue=1 |page=28016 |doi=10.1038/s41598-024-79546-1 |issn=2045-2322 |pmc=11564651 |pmid=39543377|bibcode=2024NatSR..1428016L }}
• Columbian mammoth – A species of mammoth that was endemic to North America across what are now the United States and northern Mexico. The species became extinct 12 thousand years ago during the Quaternary extinction event due to climate change, overhunting from early humans, and habitat loss.
• Mastodon – An entire genus of proboscideans that were native to North America from the Miocene to the early Holocene. Like the Columbian mammoth, the species became extinct about 11,795 to 11,345 years ago due to climate change, overhunting from early humans, and habitat loss.
• Arctodus – An entire genus of short-faced bears endemic to North America during the Pleistocene. It is estimated that they became extinct 12 thousand years ago following the death of its final member, Arctodus simus due to climate change and low genetic diversity. Beth Shapiro of Colossal Biosciences has expressed interest in reviving one of the two species from the genus.

• Gastric-brooding frog – A genus of ground frogs that were native to Queensland, Australia. They became extinct in the mid-1980s primarily due to chytridiomycosis. In 2013, scientists in Australia successfully created a living embryo from non-living preserved genetic material, and hope that by using somatic-cell nuclear transfer methods, they can produce an embryo that can survive to the tadpole stage.{{Cite web | url=https://www.treehugger.com/natural-sciences/scientists-successfully-create-living-embryo-extinct-species.html | title=Scientists successfully create living embryo of an extinct species | access-date=2017-11-15 | archive-date=2017-11-16 | archive-url=https://web.archive.org/web/20171116032551/https://www.treehugger.com/natural-sciences/scientists-successfully-create-living-embryo-extinct-species.html | url-status=dead }}

File:Glaucopsyche xerces.jpg, an extinct butterfly]]

• Xerces blue – A species of butterfly that was native to the Sunset District of San Francisco in the American state of California. It is estimated that the species became extinct in the early 1940s due to urbanization of their former habitat. Similar species to the Xerces blue, such as Glaucopsyche lygdamus and the Palos Verdes blue, have been released into the Xerces blue's former range to substitute its ecological role. On April 15, 2024, non-profit organisation Revive & Restore announced the early stages of their plans to potentially revive the species.{{Cite web|date=2017-02-08|title=Candidate species {{!}} Revive & Restore|work=Revive & Restore |url=http://reviverestore.org/candidates/|access-date=2021-02-20|archive-url=https://web.archive.org/web/20170208075406/http://reviverestore.org/candidates/|archive-date=2017-02-08}}{{Cite web |last=Tuff |first=Kika |title=Relative of extinct butterfly helps fill ecological void |url=https://reviverestore.org/relative-of-extinct-butterfly-helps-fill-ecological-void/ |access-date=2024-09-12 |language=en-US}}

File:Barthel 067 Glyph.JPGs of Paschalococos, an extinct genus of palm trees native to Easter Island]]

• Paschalococos – A genus of coccoid palm trees that were native to Easter Island, Chile. It is believed to have become extinct around 1650 due to overharvesting for its edible nuts and its subsequent disappearance from the pollen records.
• Hyophorbe amaricaulis – A species of palm tree from the Arecales family that is native to the island of Mauritius. Unlike the majority of potential candidates, this palm is not completely extinct, but functionally extinct and is believed to be extinct in the wild with only one known specimen left in the Curepipe Botanic Gardens. In 2010, there was an attempt to revive the species through germination in vitro in which Isolated and growing embryos were extracted from seeds in tissue culture, but these seedlings only lived for three months.{{Cite journal |last=Sarasan |first=Viswambharan |date=2010-12-01 |title=Importance of in vitro technology to future conservation programmes worldwide |url=https://link.springer.com/article/10.1007/s12225-011-9250-7 |journal=Kew Bulletin |language=en |volume=65 |issue=4 |pages=549–554 |doi=10.1007/s12225-011-9250-7 |bibcode=2010KewBu..65..549S |issn=1874-933X|url-access=subscription }}

{{Main|List of resurrected species}}

File:Methuselah-Ketura-2018-10.jpg excavations in the 1960s]]

The Judean date palm is a species of date palm native to Judea that is estimated to have originally become extinct around the 15th century due to climate change and human activity in the region.{{Cite book |last=Issar |first=Arie S. |url=https://books.google.com/books?id=ZPTYf5x-rzIC&pg=PA28 |title=Climate Changes during the Holocene and their Impact on Hydrological Systems |date=2004-08-05 |publisher=Cambridge University Press |isbn=978-1-139-43640-3 |language=en}} In 2005, preserved seeds found in the 1960s excavations of Herod the Great's palace were given to Sarah Sallon by Bar-Ilan University after she came up with the initiative to germinate some ancient seeds.{{Cite web |last=Zhang |first=Sarah |date=2020-02-05 |title=After 2,000 Years, These Seeds Have Finally Sprouted |url=https://www.theatlantic.com/science/archive/2020/02/how-to-grow-a-date-tree-from-2000-year-old-seeds/606079/ |access-date=2024-08-18 |website=The Atlantic |language=en}} Sallon later challenged her friend, Elaine Solowey of the Center for Sustainable Agriculture at the Arava Institute for Environmental Studies with the task of germinating the seeds. Solowey managed to revive several of the provided seeds after hydrating them with a common household baby bottle warmer along with average fertiliser and growth hormones.{{Cite journal |last1=Sallon |first1=Sarah |last2=Cherif |first2=Emira |last3=Chabrillange |first3=Nathalie |last4=Solowey |first4=Elaine |last5=Gros-Balthazard |first5=Muriel |last6=Ivorra |first6=Sarah |last7=Terral |first7=Jean-Frédéric |last8=Egli |first8=Markus |last9=Aberlenc |first9=Frédérique |date=2020-02-05 |title=Origins and insights into the historic Judean date palm based on genetic analysis of germinated ancient seeds and morphometric studies |journal=Science Advances |volume=6 |issue=6 |pages=eaax0384 |doi=10.1126/sciadv.aax0384 |issn=2375-2548 |pmc=7002127 |pmid=32076636|bibcode=2020SciA....6..384S }} The first plant grown was named after Lamech's father, Methuselah, the oldest living man in the Bible. In 2012, there were plans to crossbreed the male palm with what was considered its closest living relative, the Hayani date of Egypt to generate fruit by 2022. However, two female Judean date palms have been sprouted since then.{{Cite web |last=Kresh |first=Miriam |date=2012-03-25 |title=Ancient 2000-year old date pit sprouts - Green Prophet |url=https://www.greenprophet.com/2012/03/2000-year-old-date-pit-sprouts-in-israel/ |access-date=2024-08-18 |language=en-US}} By 2015 Methuselah had produced pollen that has been used successfully to pollinate female date palms. In June 2021, one of the female plants, Hannah, produced dates. The harvested fruits are currently being studied to determine their properties and nutritional values.{{Cite web |date=2021-06-23 |title=Extinct tree from the time of Jesus rises from the dead - BBC Reel |url=https://www.bbc.com/reel/playlist/the-worlds-rarest?vpid=p09m0v51 |access-date=2024-08-18 |archive-url=https://web.archive.org/web/20210623012805/https://www.bbc.com/reel/playlist/the-worlds-rarest?vpid=p09m0v51 |archive-date=2021-06-23 }} The de-extinct Judean date palms are currently at a Kibbutz located in Ketura, Israel.{{Cite web |title=Dr. Elaine Solowey |url=https://arava.org/arava-research-centers/arava-center-for-sustainable-agriculture/csa-staff/dr-elaine-solowey/ |access-date=2024-08-18 |website=Arava Institute for Environmental Studies |language=en-US}}

File:Rastreadora Brasileira Gaya.jpg]]

The Rastreador Brasileiro (Brazilian Tracker) is a large scent hound from Brazil that was bred in the 1950s to hunt jaguars and wild pigs. It was originally declared extinct and delisted by the Fédération Cynologique Internationale and Confederação Brasileira de Cinofilia in 1973 due to tick-borne diseases and subsequent poisoning from insecticides in attempt to get rid of the ectoparasites.{{Cite web |date=2011-07-06 |title=DESENVOLVIMENTO E RECONHECIMENTO |url=http://rastreador.urrador.vilabol.uol.com.br/historico.htm |access-date=2024-10-07 |archive-url=https://web.archive.org/web/20110706154951/http://rastreador.urrador.vilabol.uol.com.br/historico.htm |archive-date=2011-07-06 |language=Brazilian Portuguese}} In the early 2000s, a group named Grupo de Apoio ao Resgate do Rastreador Brasileiro (Brazilian Tracker Rescue Support Group) dedicated to reviving the breed and having it relisted by Confederação Brasileira de Cinofilia began work to locate dogs in Brazil that had genetics of the extinct breed to breed a purebred Rastreador Brasileiro.{{Cite web |date=2011-07-06 |title=Materia Revista Mania de Bicho |url=http://rastreador.urrador.vilabol.uol.com.br/materias.htm |access-date=2024-10-07 |archive-url=https://web.archive.org/web/20110706155004/http://rastreador.urrador.vilabol.uol.com.br/materias.htm |archive-date=2011-07-06 |language=Brazilian Portuguese}} In 2013, the breed was de-extinct through preservation breeding from descendants of the final original members and was relisted by the FCI.{{Cite web |date=2023-08-15 |title=The Brazilian Tracker |url=https://academichound.com/the-brazilian-tracker/#:~:text=The%20Brazilian%20Tracker%20was%20originally%20recognized%20by%20the%20FCI%20in |access-date=2024-10-07 |website=The Academic Hound |language=en-US}}{{Cite web |title=RASTREADOR BRASILEIRO |url=https://www.fci.be/en/nomenclature/BRAZILIAN-TRACKER-275.html |access-date=2024-10-07 |website=www.fci.be}}

The Floreana giant tortoise (Chelonoidis niger niger) is a subspecies of the Galápagos tortoise endemic to Floreana Island, Ecuador that is believed to have become extinct by 1850 due to overexploitation, predation, and habitat degradation by sailors and invasive species such as feral livestock, rodents, and stray dogs and cats. A deliberate wildfire started by Thomas Chappel, a crew member of the Essex in 1820 is also cited as a reason for the subspecies initial decline.{{Cite web |last=Conrad |first=Cyler |title=Moby-Dick and the Galápagos Tortoises |url=https://www.scientificamerican.com/article/moby-dick-and-the-galapagos-tortoises/ |access-date=2025-01-02 |website=Scientific American |language=en}} In 2012, Floreana and Volcán Wolf tortoise hybrids were discovered Isabela Island.{{cite journal |last1=Poulakakis |first1=N. |last2=Glaberman |first2=S. |last3=Russello |first3=M. |last4=Beheregaray |first4=L. B. |last5=Ciofi |first5=C. |last6=Powell |first6=J. R. |last7=Caccone |first7=A. |date=2008-10-07 |title=Historical DNA analysis reveals living descendants of an extinct species of Galápagos tortoise |journal=Proceedings of the National Academy of Sciences |volume=105 |issue=40 |pages=15464–15469 |bibcode=2008PNAS..10515464P |doi=10.1073/pnas.0805340105 |pmc=2563078 |pmid=18809928 |doi-access=free}} Allegedly, these tortoises were imported or abandoned on the island in the early 19th century, allowing them to hybridise with the native subspecies. In 2017, a breeding programme was established to revive the subspecies through back breeding the hybrids to regain their genetic purity.{{Cite web |title=Reptiles of Ecuador book |url=https://www.reptilesofecuador.com/index.html |access-date=2025-01-02 |website=www.reptilesofecuador.com}} As of 2025, 400 Floreana giant tortoises have been hatched on Santa Cruz Island with plans to release them into the wild on Floreana Island after the successful extirpation of invasive species.{{Cite web |title=12 missing species set to return to Floreana, Galápagos |url=https://www.islandconservation.org/12-galapagos-species-for-floreana/ |access-date=2025-01-02 |website=Island Conservation |language=en-US}}{{Cite web |last=Nicholls |first=Henry |date=2024-04-12 |title=The return of the Floreana giant tortoise |url=https://galapagosconservation.org.uk/floreana-giant-tortoise-reintroduction/ |access-date=2025-01-02 |website=Galapagos Conservation Trust |language=en}} However, IUCN has yet to update the status of the subspecies due to lack of a genetically pure specimen at the time of the 2017 evaluation and the de-extinct subspecies has yet to reproduce naturally in the wild.{{cite web | url=https://www.iucnredlist.org/species/9023/3149101 | title=IUCN Red List of Threatened Species: Chelonoidis niger | work=IUCN Red List of Threatened Species | date=25 January 2017 }}

In 2010, Sarah Sallon of Arava Institute for Environmental Studies grew a seed found in excavations of a cave in the northern Judean desert in 1986. The specimen, Sheba reached maturity in 2024 and is believed to be an entirely new species of Commiphora with many believing that Sheba may be the tsori or Judean balsam, plants that are said to have healing properties in the Bible.{{Cite journal |last1=Sallon |first1=Sarah |last2=Solowey |first2=Elaine |last3=Gostel |first3=Morgan R. |last4=Egli |first4=Markus |last5=Flematti |first5=Gavin R. |last6=Bohman |first6=Björn |last7=Schaeffer |first7=Philippe |last8=Adam |first8=Pierre |last9=Weeks |first9=Andrea |date=2024-09-10 |title=Characterization and analysis of a Commiphora species germinated from an ancient seed suggests a possible connection to a species mentioned in the Bible |journal=Communications Biology |language=en |volume=7 |issue=1 |page=1109 |doi=10.1038/s42003-024-06721-5 |pmid=39256474 |issn=2399-3642|pmc=11387840 }}{{Cite web |title=MSN |url=https://www.msn.com/en-us/news/world/mystery-tree-grown-from-1-000-year-old-seed/ar-AA1rRbwQ?ocid=BingNewsSerp |access-date=2024-10-11 |website=www.msn.com}}

The York groundsel is a species of Senecio that was first discovered in York, England in 1979 and last seen in the wild in 1991.{{Cite news |last=Barkham |first=Patrick |date=2023-05-27 |title=York groundsel blooms again in Britain's first-ever de-extinction event |url=https://www.theguardian.com/environment/2023/may/27/york-groundsel-bloom-again-britain-first-ever-de-extinction-event-natural-england |access-date=2023-05-27 |work=The Guardian |language=en-GB |issn=0261-3077}} A survey by UK government advisory body Natural England found it was driven to extinction by 2000, partly due to the use of weedkiller.{{Cite web |date=2010-03-12 |title=Weedkiller blamed for loss of York Groundsel |url=https://www.yorkpress.co.uk/news/5057471.weedkiller-blamed-for-loss-of-york-groundsel/ |access-date=2023-05-27 |website=York Press |language=en}} Seeds of the plant were stored at the Millennium Seed Bank, successfully germinated, and reintroduced to York in 2023, marking the first time an extinct species has been revived and successfully reintroduced into its native range.

File:Muskmelon, the largest in cultivation (extract).jpg

The Montreal melon, also known as the Montreal market muskmelon, Montreal nutmeg melon, and in French as melon de Montréal (Melon of/from Montreal) is a cultivar of melon native to Canada and traditionally grown around the Montreal area. Despite its status as a delicacy on the east coast of North America, the Montreal melon disappeared from farms and was presumed extinct by the 1920s due to urbanisation in the region and being ill-suited for agribusiness. In 1996, seeds of the lost melon were discovered in a seed bank in the American state of Iowa. Since then, the plant has been reintroduced to its former range by local gardeners.{{Cite web |date=2011-10-11 |title=Missing melon: Abstract- Canadian Geographic Magazine |url=http://canadiangeographic.ca/magazine/back_issues/article.asp?article=1759 |access-date=2024-10-30 |archive-url=https://web.archive.org/web/20111011115526/http://canadiangeographic.ca/magazine/back_issues/article.asp?article=1759 |archive-date=2011-10-11 }}{{Cite web |title=Montreal melon, once thought to be all but gone, makes long-awaited comeback {{!}} Globalnews.ca |url=https://globalnews.ca/news/10724842/montreal-melon-comeback/ |access-date=2024-10-30 |website=Global News |language=en-US}}

{{div col|colwidth=30em}}

• Arava Institute for Environmental Studies
• Breeding back
• Colossal Biosciences
• Cryoconservation of animal genetic resources
• Endangered species
• Endling
• Functional extinction
• Holocene extinction
• List of introduced species
• Pleistocene Park
• Pleistocene rewilding{{div col end}}

{{Reflist|colwidth=30em}}

• {{cite book|last1=O'Connor|first1=M.R.|title=Resurrection Science: Conservation, De-Extinction and the Precarious Future of Wild Things|date=2015|publisher=St. Martin's Press|location=New York|isbn=9781137279293|url=http://us.macmillan.com/resurrectionscience/mroconnor|archive-url=https://archive.today/20160704211818/http://us.macmillan.com/resurrectionscience/mroconnor|url-status=dead|archive-date=2016-07-04}}
• {{cite book|last1=Shapiro|first1=Beth|title=How to Clone a Mammoth: The Science of De-Extinction|date=2015|publisher=Princeton University Press|location=Princeton, NJ|isbn=9780691157054|url=https://archive.org/details/howtoclonemammot0000shap|url-access=registration}}
• Pilcher, Helen (2016). [https://www.bloomsbury.com/uk/bring-back-the-king-9781472912251/ Bring Back the King: The New Science of De-extinction] {{Webarchive|url=https://web.archive.org/web/20210507013317/https://www.bloomsbury.com/uk/bring-back-the-king-9781472912251/ |date=2021-05-07 }}. Bloomsbury Press {{ISBN|9781472912251}}

• [http://tedxdeextinction.org/ TEDx DeExtinction] March 15, 2013 conference sponsored by Revive and Restore project of the Long Now Foundation, supported by TEDx and hosted by the National Geographic Society, that helped popularize the public understanding of the science of de-extinction. Video proceedings, [http://longnow.org/revive/events/tedxdeextinction/tedxdeextinction-2013/ meeting report], and [http://longnow.org/revive/events/tedxdeextinction/media/ links to press coverage] freely available.
• [https://web.archive.org/web/20130513035532/http://www.nationalgeographic.com/deextinction/ De-Extinction: Bringing Extinct Species Back to Life] April 2013 article by Carl Zimmer for National Geographic magazine reporting on 2013 conference.

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