De-extinction (also known as resurrection biology, or species revivalism) is the process of generating an

organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...

that either resembles or ''is'' an

extinct species This page features lists of extinct species, organisms that have become Extinction, extinct, either in the wild or completely disappeared from Earth. In actual theoretical practice, a species not definitely located in the wild in the last fifty ...

. There are several ways to carry out the process of de-extinction.

Cloning Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, c ...

is the most widely proposed method, although genome editing and

selective breeding Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant ...

have also been considered. Similar techniques have been applied to certain

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

, in hopes to boost their

genetic diversity Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species. It is dis ...

. The only method of the three that would provide an animal with the same genetic identity is cloning. There are benefits and malefits to the process of de-extinction ranging from technological advancements to ethical issues.

Methods

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. The egg can then be inserted into a host from the extinct species' nearest living relative. It is important to note that this method can only be used when a preserved cell is available, meaning it would be most feasible for recently extinct species. Cloning has been used in science since the 1950s. One of the most well known clones is Dolly the sheep. Dolly was born in the mid 1990s and lived a normal life until she experienced health complications that led to her death. Other animal species known to have been cloned include dogs, pigs, and horses.

Genome editing

Genome editing Genome editing, or genome engineering, or gene editing, is a type of genetic engineering in which DNA is inserted, deleted, modified or replaced in the genome of a living organism. Unlike early genetic engineering techniques that randomly inserts ...

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. 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 now the Cas protein can 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.

Back breeding

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. 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. Breeding back is not to be confused with dedomestication.

Iterative evolution

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 white-throated rail was a flightless bird that became extinct about 136,000 years ago due to an unknown event that caused sea levels to rise. The species "reappeared" about 100,000 years ago when sea levels dropped, allowing the bird to evolve once again as a flightless species on the island of

Aldabra Aldabra is the world's second-largest coral atoll, lying south-east of the continent of Africa. It is part of the Aldabra Group of islands in the Indian Ocean that are part of the Outer Islands of the Seychelles, with a distance of 1,120 ...

, where it is found to the present day.The bird that came back from the dead
/ref>
/ref>This Bird Went Extinct and Then Evolved Into Existence Again
/ref>

Advantages of de-extinction

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. *By studying revived previously extinct animals, cures to diseases could be discovered. *Revived species may support conservation initiatives by acting as "

flagship species In conservation biology, a flagship species is a species chosen to raise support for biodiversity conservation in a given place or social context. Definitions have varied, but they have tended to focus on the strategic goals and the socio-economi ...

" to generate public enthusiasm and funds for conserving entire ecosystems. 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. 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.

Disadvantages of de-extinction

The reintroduction of extinct species could have a negative impact on extant species and their ecosystem. The extinct species' ecological niche may have been filled in its former habitat, making it 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

elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantida ...

s for their

ivory Ivory is a hard, white material from the tusks (traditionally from elephants) and teeth of animals, that consists mainly of dentine, one of the physical structures of teeth and tusks. The chemical structure of the teeth and tusks of mammals i ...

and could go extinct again if this were to happen. Or, if a species is reintroduced into an environment with disease it has no immunity to 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. 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.

Current candidates for de-extinction

Woolly mammoth

The existence of preserved soft tissue remains and DNA from

woolly mammoth The woolly mammoth (''Mammuthus primigenius'') is an extinct species of mammoth that lived during the Pleistocene until its extinction in the Holocene epoch. It was one of the last in a line of mammoth species, beginning with '' Mammuthus s ...

s 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, 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. 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 The Asian elephant (''Elephas maximus''), also known as the Asiatic elephant, is the only living species of the genus '' Elephas'' and is distributed throughout the Indian subcontinent and Southeast Asia, from India in the west, Nepal in t ...

. 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. 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. In 2011, Japanese scientists announced plans to clone mammoths within six years. 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

, to create hybridized animals with the notable adaptations that it had for living in a much colder environment than modern day elephants. 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. According to geneticist Hendrik Poinar, a revived woolly mammoth or mammoth-elephant hybrid may find suitable habitat in the tundra and taiga forest ecozones. 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 In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

.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 ''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many famous scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it. In print since 1845, it ...

'' pointed out that the technologies involved could have secondary applications, specifically to help species on the verge of extinction regain their

Pyrenean ibex

The Pyrenean ibex was a subspecies of Spanish ibex that lived on the Iberian peninsula. While it was abundant through

medieval times In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...

, over-hunting in the 19th and 20th centuries led to its demise. In 1999, only a single female named Celia was left alive in Ordesa National Park. Scientists captured her, took a tissue sample from her ear, collared her, then released her back into the wild, where she lived until she was found dead in 2000, having been crushed by a fallen tree. In 2003, scientists used the tissue sample to attempt to clone Celia and resurrect the extinct subspecies. Despite having successfully transferred nuclei from her cells into domestic goat egg cells and impregnating 208 female goats, only one came to term. The baby ibex that was born had a lung defect, and lived for only seven minutes before suffocating from being incapable of breathing oxygen. Nevertheless, her birth was seen as a triumph and is considered the first de-extinction. In late 2013, scientists announced that they would again attempt to resurrect the Pyrenean ibex. A problem to be faced, in addition to the many challenges of reproduction of a mammal by cloning, is that only females can be produced by cloning the female individual Celia, and no males exist for those females to reproduce with. This could potentially be addressed by breeding female clones with the closely related

Southeastern Spanish ibex The Southeastern Spanish ibex or Beceite ibex (''Capra pyrenaica hispanica'') is a goat that is Endemism, endemic to Spain. CapraPyrenaicaHispanicaMontCaro

The

aurochs The aurochs (''Bos primigenius'') ( or ) is an extinct cattle species, considered to be the wild ancestor of modern domestic cattle. With a shoulder height of up to in bulls and in cows, it was one of the largest herbivores in the Holocene ...

was widespread across Eurasia, North Africa, and the Indian subcontinent during the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

, but only the European aurochs ('' Bos primigenius primigenius'') survived into historical times. This species is heavily featured in European cave paintings, such as

Lascaux Lascaux ( , ; french: Grotte de Lascaux , "Lascaux Cave") is a network of caves near the village of Montignac, in the department of Dordogne in southwestern France. Over 600 parietal wall paintings cover the interior walls and ceilings of t ...

and Chauvet cave in France, and was still widespread during the

Roman era In modern historiography, ancient Rome refers to Roman civilisation from the founding of the city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD. It encompasses the Roman Kingdom (753–509 BC ...

. Following the fall of the

Roman empire The Roman Empire ( la, Imperium Romanum ; grc-gre, Βασιλεία τῶν Ῥωμαίων, Basileía tôn Rhōmaíōn) was the post-Roman Republic, Republican period of ancient Rome. As a polity, it included large territorial holdings aro ...

, 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. 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 The H. J. Heinz Company is an American food processing company headquartered at One PPG Place in Pittsburgh, Pennsylvania Pittsburgh ( ) is a city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, United States, and the co ...

and

Lutz Heck Ludwig Georg Heinrich Heck, called Lutz Heck (23 April 1892 in Berlin, German Empire – 6 April 1983 in Wiesbaden, West Germany) was a German zoologist, animal researcher, animal book author and director of the Berlin Zoological Garden where he s ...

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. 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 The Tauros Programme, formerly known as TaurOs Project, is a cooperation between the Dutch foundation Stichting Taurus and universities such as the Wageningen University and Research Centre. It is an international effort to breed a type of cat ...

and the

Taurus Project The Taurus Project of the German aims to re-create the extinct aurochs, the wild ancestor of domestic cattle, by cross-breeding Heck cattle (themselves bred in the 1920s and 1930s in an attempt to replicate the aurochs) with aurochs-like cat ...

. This organization is partnered with the organization Rewilding Europe to help restore balance to European nature. A competing project to recreate the aurochs is the

Uruz Project The Uruz Project had the goal of breeding back the extinct aurochs (''Bos p. primigenius''). Uruz is the old Germanic word for aurochs. The Uruz Project was initiated in 2013 by the True Nature Foundation and presented at TEDx DeExtinction, a d ...

by the True Nature Foundation, which aims to recreate the aurochs through a more efficient breeding strategy and through genome editing, in order to decrease the number of generations of breeding needed and the ability to quickly eliminate undesired traits from the aurochs-like cattle population. 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.

Quagga

The quagga (''Equus quagga quagga'') is a subspecies of the

plains zebra The plains zebra (''Equus quagga'', formerly ''Equus burchellii''), also known as the common zebra, is the most common and geographically widespread species of zebra. Its range is fragmented, but spans much of southern and eastern Africa south o ...

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 South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

, but was wiped out in the wild due to overhunting for sport, and the last individual died in 1883 in the Amsterdam Zoo. However, since it is technically the same species as the surviving

Plains zebra The plains zebra (''Equus quagga'', formerly ''Equus burchellii''), also known as the common zebra, is the most common and geographically widespread species of zebra. Its range is fragmented, but spans much of southern and eastern Africa south o ...

, it has been argued that the quagga could be revived through artificial selection. The

Quagga Project The Quagga Project is an attempt by a group in South Africa to use selective breeding to achieve a breeding lineage of Burchell's zebra (''Equus quagga burchellii'') which visually resemble the extinct quagga (''Equus quagga quagga''). History ...

aims to breed a similar form of zebra by selective breeding of plains zebras. 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 An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...

trees In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are u ...

such as the

Brazilian pepper tree ''Schinus terebinthifolia'' is a species of flowering plant in the cashew family, Anacardiaceae, that is native to subtropical and tropical South America. Common names include Brazilian peppertree, aroeira, rose pepper, broadleaved pepper tree, ...

Tipuana tipu ''Tipuana tipu'', also known as tipa, rosewood and pride of Bolivia, is a South American tree. It is the only member of the genus ''Tipuana''. It was recently assigned to the informal monophyletic ''Pterocarpus'' clade within the Dalbergieae ...

Acacia saligna ''Acacia saligna'', commonly known by various names including coojong, golden wreath wattle, orange wattle, blue-leafed wattle, Western Australian golden wattle, and, in Africa, Port Jackson willow, is a small tree in the family Fabaceae. Nativ ...

Bugweed ''Solanum mauritianum'' is a small tree or shrub native to South America, including Northern Argentina, Southern Brazil, Paraguay and Uruguay. Its common names include earleaf nightshade (or "ear-leaved nightshade"), woolly nightshade, flannel we ...

Camphor tree ''Camphora officinarum'' is a species of evergreen tree that is commonly known under the names camphor tree, camphorwood or camphor laurel. Description ''Camphora officinarum'' is native to China south of the Yangtze River, Taiwan, southe ...

, Stone pine, cluster pine,

Weeping willow ''Salix babylonica'' (Babylon willow or weeping willow; ) is a species of willow native to dry areas of northern China, but cultivated for millennia elsewhere in Asia, being traded along the Silk Road to southwest Asia and Europe.Flora of Chin ...

and Acacia mearnsii.

Thylacine

The

thylacine The thylacine ( , or , also ) (''Thylacinus cynocephalus'') is an extinct carnivorous marsupial that was native to the Australian mainland and the islands of Tasmania and New Guinea. The last known live animal was captured in 1930 in Tasma ...

, commonly known as the Tasmanian Tiger, was native to the

Australian mainland Mainland Australia is the main landmass of the Australian continent, excluding the Aru Islands, New Guinea, Tasmania, and other Australian offshore islands. The landmass also constitutes the mainland of the territory governed by the Commonwea ...

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

and

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torres ...

. It is believed to have become

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

in the 20th century. The thylacine had become extremely rare or extinct on the

before British settlement of the continent. The last known thylacine, named Benjamin, died at the Hobart Zoo, on September 7, 1936. He is believed to have died as the result of neglect—locked out of his sheltered sleeping quarters, he was exposed to a rare occurrence of extreme Tasmanian weather: extreme heat during the day and freezing temperatures at night. Paddle (2000), p. 195. 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. In December 2017 it was announced in

Nature Ecology and Evolution ''Nature Ecology and Evolution'' is an online-only monthly peer-reviewed scientific journal published by Nature Publishing Group covering all aspects of research on ecology and evolutionary biology. It was established in 2017. Its first and curre ...

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. The Thylacine genome was reconstructed by using the genome editing method. The

Tasmanian devil The Tasmanian devil (''Sarcophilus harrisii'') ( palawa kani: purinina) is a carnivorous marsupial of the family Dasyuridae. Until recently, it was only found on the island state of Tasmania, but it has been reintroduced to New South Wales ...

was used as a reference for the assembly of the full nuclear genome. Andrew J. Pask from the

University of Melbourne The University of Melbourne is a public research university located in Melbourne, Australia. Founded in 1853, it is Australia's second oldest university and the oldest in Victoria. Its main campus is located in Parkville, an inner suburb ...

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 Colossal Biosciences is a biotechnology and genetic engineering company working to genetically resurrect the woolly mammoth, the Tasmanian tiger, and the Dodo. It has claimed to have the first woolly mammoth hybrid calves by 2027 and will reint ...

announced a partnership to accelerate de-extinction of the thylacine.

Passenger pigeon

The

passenger pigeon The passenger pigeon or wild pigeon (''Ectopistes migratorius'') is an extinct species of pigeon that was endemic to North America. Its common name is derived from the French word ''passager'', meaning "passing by", due to the migratory habits ...

numbered in the billions before being wiped out due to 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 The band-tailed pigeon (''Patagioenas fasciata'') is a medium-sized bird of the Americas. Its closest relatives are the Chilean pigeon and the ring-tailed pigeon, which form a clade of ''Patagioenas'' with a terminal tail band and iridescent p ...

. 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. The de-extinct passenger pigeon hybrid is expected to be ready for captive breeding by 2024 and released into the wild by 2030.

Maclear's Rat

The

Maclear's rat Maclear's rat (''Rattus macleari'') is an extinct large rat Endemism, endemic to Christmas Island in the Indian Ocean. It was one of two species of rat native to Christmas Island, alongside the bulldog rat. Abundant, unfamiliar with and seemingly ...

(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 The ''Challenger'' expedition of 1872–1876 was a scientific program that made many discoveries to lay the foundation of oceanography. The expedition was named after the naval vessel that undertook the trip, . The expedition, initiated by Wi ...

infected the Maclear's rats with a disease (possibly a trypanosome), which resulted in the numbers of the species declining. The last recorded sighting was in 1903. In March 2022, researchers discovered the Maclear's Rat shared about 95 percent of its genes with the living Norway 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.

Future potential candidates for de-extinction

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.

Birds

* Little bush moa – a slender species of moa, slightly larger than a

turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a transcontinental country located mainly on the Anatolian Peninsula in Western Asia, with a small portion on the Balkan Peninsula ...

that went extinct abruptly, around 500-600 years ago following the arrival and proliferation of the Maori people in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island coun ...

, as well as the introduction of Polynesian dogs. Scientists at

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of highe ...

assembled the first nearly complete genome of the species from toe bones, thus bringing the species a step closer to being "resurrected". New Zealand politician

Trevor Mallard Trevor Colin Mallard (born 17 June 1954) is a New Zealand politician and member of the Labour Party. First elected to Parliament in 1984, he was Speaker of the New Zealand House of Representatives from 2017 until 2022. Mallard was a Cabinet m ...

had previously suggested bringing back a medium-sized species of moa. *

Heath hen The heath hen (''Tympanuchus cupido cupido'') is an extinct subspecies of the greater prairie chicken (''Tympanuchus cupido''), a large North American bird in the grouse family. It became extinct in 1932. Heath hens lived in the scrubby heat ...

– this subspecies of the prairie chicken became extinct on

Martha's Vineyard Martha's Vineyard, often simply called the Vineyard, is an island in the Northeastern United States, located south of Cape Cod in Dukes County, Massachusetts, known for being a popular, affluent summer colony. Martha's Vineyard includes the ...

in 1932 despite conservation efforts; however, the availability of usable DNA in museum specimens and protected areas in its former range makes this bird a possible candidate for de-extinction and reintroduction to its former habitat. *

Dodo The dodo (''Raphus cucullatus'') is an extinct flightless bird that was endemic to the island of Mauritius, which is east of Madagascar in the Indian Ocean. The dodo's closest genetic relative was the also-extinct Rodrigues solitaire. ...

– this large, flightless ground bird endemic to

Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label= Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It ...

was last sighted in the 1640s and was most likely extinct by 1700, due to exploitation by humans and due to

such as rats and pigs, which ate their eggs. It has since become a symbol of extinction in popular culture. Due to a wealth of bones and some tissues, it is possible that this species may live again as it has a close relative in the surviving

Nicobar pigeon The Nicobar pigeon (''Caloenas nicobarica'', Car: ') is a bird found on small islands and in coastal regions from the Andaman and Nicobar Islands, India, east through the Malay Archipelago, to the Solomons and Palau. It is the only living membe ...

. *

Elephant bird Elephant birds are members of the extinct ratite family Aepyornithidae, made up of flightless birds that once lived on the island of Madagascar. They are thought to have become extinct around 1000-1200 CE, probably as a result of human activity. ...

– One of the largest birds to have ever existed, the elephant bird was 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. * Carolina parakeet - One of the only indigenous

parrot Parrots, also known as psittacines (), are birds of the roughly 398 species in 92 genera comprising the order Psittaciformes (), found mostly in tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittacoide ...

s to North America, it was driven to extinction by destruction of its

deciduous forest In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals ...

habitat. Hundreds of specimens with viable DNA still exist in museums around the world, making them a prime candidate for revival. *

Great auk The great auk (''Pinguinus impennis'') is a species of flightless alcid that became extinct in the mid-19th century. It was the only modern species in the genus ''Pinguinus''. It is not closely related to the birds now known as penguins, wh ...

- A flightless bird similar to the penguin. The great auk went extinct in the 1800s due to humans hunting them 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. 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 a razorbill bird’s genome 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. * Imperial Woodpecker *

Ivory-billed Woodpecker The ivory-billed woodpecker (''Campephilus principalis'') is a possibly extinct woodpecker that is native to the bottomland hardwood forests and temperate coniferous forests of the Southern United States and Cuba. Habitat destruction and hunting ...

Cuban macaw The Cuban macaw or Cuban red macaw (''Ara tricolor'') is an extinct species of macaw native to the main island of Cuba and the nearby Isla de la Juventud. It became extinct in the late 19th century. Its relationship with other macaws in its genu ...

Labrador duck The Labrador duck (''Camptorhynchus labradorius'') was a North American bird; it has the distinction of being the first known endemic North American bird species to become extinct after the Columbian Exchange, with the last known sighting occurri ...

Huia The huia ( ; ; ''Heteralocha acutirostris'') is an extinct species of New Zealand wattlebird, endemic to the North Island of New Zealand. The last confirmed sighting of a huia was in 1907, although there was a credible sighting in 1924. It ...

* Moho

Mammals

* Caribbean monk seal * Irish elk * Cave lion – The discovery of two preserved cubs in the

Sakha Republic Sakha, officially the Republic of Sakha (Yakutia),, is the largest republic of Russia, located in the Russian Far East, along the Arctic Ocean, with a population of roughly 1 million. Sakha comprises half of the area of its governing Far E ...

ignited a project to clone the animal. *

Steppe bison The steppe bisonSeveral literatures address the species as ''primeval bison''. or steppe wisent (''Bison'' ''priscus'')
– Y ...

– 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". Russian and South Korean scientists are collaborating to clone steppe bison in the future, using DNA preserved from a 8,000 year old tail, in wood bison (morphologically similar), which themselves have been reintroduced to

Yakutia Sakha, officially the Republic of Sakha (Yakutia),, is the largest republic of Russia, located in the Russian Far East, along the Arctic Ocean, with a population of roughly 1 million. Sakha comprises half of the area of its governing Far E ...

. *

Tarpan The term tarpan (''Equus ferus ferus'') refers to free-ranging horses of the Russian steppe from the 18th to the 20th century. It is generally unknown whether those horses represented genuine wild horses, feral domestic horses or hybrids. The las ...

– A population of free-ranging horses that went extinct in 1909. Much like the aurochs, there have been many attempts to breed tarpan-like horses, the first being by the Heck brothers, creating the

Heck horse The Heck horse is a horse breed that is claimed to resemble the tarpan (''Equus ferus ferus''), an extinct equine. The breed was created by the German zoologist brothers Heinz Heck and Lutz Heck in an attempt to breed back the tarpan. Al ...

as a result. Though it is not a genetic copy, it is claimed to bear many similarities to the tarpan. Other attempts were made to create tarpan-like horses. A breeder named Harry Hegardt was able to breed a line of horses from American

Mustang The mustang is a free-roaming horse of the Western United States, descended from horses brought to the Americas by the Spanish. Mustangs are often referred to as wild horses, but because they are descended from once-domesticated animals, the ...

s. Other breeds of supposedly tarpan-like horse include the

Konik The Konik or Polish Konik, pl, konik polski, is a Polish breed of pony. There are semi- feral populations in some regions. They are usually mouse dun or striped dun in color. The Bilgoray, pl, konik biłgorajski, of south-eastern Poland is ...

and Strobel's horse. *

Baiji The baiji (; IPA: ; ''Lipotes vexillifer'', ''Lipotes'' meaning "left behind" and ''vexillifer'' "flag bearer") is a possibly extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolph ...

Steller's sea cow Steller's sea cow (''Hydrodamalis gigas'') is an extinct sirenian described by Georg Wilhelm Steller in 1741. At that time, it was found only around the Commander Islands in the Bering Sea between Alaska and Russia; its range extended across ...

Woolly rhinoceros The woolly rhinoceros (''Coelodonta antiquitatis'') is an extinct species of rhinoceros that was common throughout Europe and Asia during the Pleistocene epoch and survived until the end of the last glacial period. The woolly rhinoceros was a me ...

Cave bear The cave bear (''Ursus spelaeus'') is a prehistoric species of bear that lived in Europe and Asia during the Pleistocene and became extinct about 24,000 years ago during the Last Glacial Maximum. Both the word "cave" and the scientific name ...

Reptiles

Floreana Island tortoise Floreana Island (Spanish language, Spanish: ''Isla Floreana'') is an island of the Galápagos Islands. It was named after Juan José Flores, the first President (government title), president of Ecuador, during whose administration the governmen ...

– In 2008, mitochondrial DNA from the Floreana tortoise species was found in museum specimens. In theory, a breeding program could be established to "resurrect" a pure Floreana species from living hybrids.

Amphibians

Gastric-brooding frog The gastric-brooding frogs or platypus frogs (''Rheobatrachus'') is a genus of extinct ground-dwelling frogs native to Queensland in eastern Australia. The genus consisted of only two species, both of which became extinct in the mid-1980s. The ...

– 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.

Insects

* Xerces blue

Plants

Rapa Nui palm ''Paschalococos disperta'', the Rapa Nui palm or Easter Island palm, formerly ''Jubaea disperta,'' was the native cocoid Arecaceae, palm species of Easter Island. It disappeared from the pollen core, pollen record circa AD 1650. Taxonomy It is no ...

References

External links

TEDx DeExtinction
March 15, 2013 conference sponsored by Revive and Restore project of the Long Now Foundation, supported by

TEDx TED Conferences, LLC (Technology, Entertainment, Design) is an American-Canadian non-profit media organization that posts international talks online for free distribution under the slogan "ideas worth spreading". TED was founded by Richard Sa ...

and hosted by the

National Geographic Society The National Geographic Society (NGS), headquartered in Washington, D.C., United States, is one of the largest non-profit scientific and educational organizations in the world. Founded in 1888, its interests include geography, archaeology, ...

, that helped popularize the public understanding of the science of de-extinction. Video proceedings
meeting report
an
links to press coverage
freely available.
De-Extinction: Bringing Extinct Species Back to Life
April 2013 article by

Carl Zimmer Carl Zimmer (born 1966) is a popular science writer, blogger, columnist, and journalist who specializes in the topics of evolution, parasites, and heredity. The author of many books, he contributes science essays to publications such as ''The ...

for ''National Geographic'' magazine reporting on 2013 conference. {{Portal bar, Biology, Technology Cloning Conservation biology Emerging technologies Evolution of the biosphere Extinction