Extinct animals scientists want to bring back to life

What if the thylacine once again roamed Tasmania’s forests and the dodo made Mauritius its home again? Cutting-edge science and modern technologies are making it possible to bring extinct animals back to life.

Although extinction is a natural process, human activity has dramatically accelerated it over the past 500 years. Many animals that once populated the Earth have vanished forever—often due to overhunting or invasive species. Using methods such as cloning, gene editing, and back-breeding, researchers are now attempting to reverse these losses. Here are seven fascinating examples.

Cloning: bringing animals back using living cells

Cloning involves using living cells from a species to create a genetically identical copy. This method requires intact cell nuclei and therefore only works for species from which tissue samples were cryopreserved before extinction. Long-extinct animals, for which only fragmented DNA from museum specimens exists, cannot be cloned—this is where gene editing comes into play.

Pyrenean ibex: the first cloned extinct animal

The Pyrenean ibex (Capra pyrenaica pyrenaica), a subspecies of the Iberian ibex, was the first extinct animal to be targeted for revival using modern biotechnology. The living cells came from Celia, the last known Pyrenean ibex, taken from a tissue sample shortly before her death in 2000 and cryopreserved.

Researchers used these cells to implant cell nuclei into enucleated goat egg cells. The resulting embryos were transferred into surrogate mothers, including hybrids of domestic and wild goats. Of 285 embryos, only one animal survived birth. On July 30, 2003, Celia’s clone was born, but it died a few minutes later due to a lung defect.

Despite its early death, the experiment marked an important breakthrough: it demonstrated that cloning extinct animals is fundamentally possible. The cloning of the Pyrenean ibex was intended to contribute to reintroducing the species into its original habitat in the Pyrenees and restoring the region’s ecological balance.

Gene editing: rewriting DNA

Conventional cloning is not an option for many extinct species. This is either because no living cells are available or, as in birds, because technical manipulation of their egg cells is not yet feasible. Bird egg cells are enormous compared to those of mammals, because the yolk of a bird’s egg is essentially the egg cell itself. The yolk is surrounded by several protective layers, including the egg white, membranes, and finally the hard calcium shell. This structure makes manipulation of the egg cell—necessary for cloning—extremely difficult.

Gene editing offers an alternative: using modern techniques such as CRISPR-Cas9, genetic information from extinct species can be integrated into the genome of living relatives to reconstruct their traits. This approach is used in both birds and mammals.

Dodo: the return of an iconic bird?

The dodo (Raphus cucullatus), a flightless bird from Mauritius, went extinct in the 17th century. Although its genome was decoded in 2022 from bone and museum remains, it is heavily damaged and incomplete. To fill these gaps, researchers compare the sequences with those of its closest relatives: the Nicobar pigeon (Caloenas nicobarica), the tooth-billed pigeon (Didunculus strigirostris), and the extinct Rodrigues solitaire (Pezophaps solitaria). The goal is to create the most complete possible reference genome to serve as a basis for gene editing. Targeted edits are intended to restore typical dodo traits such as body size and beak shape.

In September 2025, the US company Colossal Biosciences once again publicly presented its plans to resurrect the dodo. A key breakthrough is the long-term cultivation of primordial germ cells (PGCs) from pigeons—cells that later develop into sperm and eggs. This allows edited genes to be permanently introduced into the germ line. Using CRISPR, genes controlling dodo-typical traits (size, beak and body shape) are inserted into these cells. The edited germ cells are transferred into fertilized chicken eggs, which act as “surrogate mothers.” The chicks that hatch carry the modified germ line. Over further breeding cycles, the proportion of dodo traits is expected to increase.

According to Colossal, the first birds have already reached sexual maturity and are laying eggs. Over additional generations, animals that closely resemble the dodo are expected to emerge “within five to seven years.” However, these would not be true dodos, as the historical genome remains incomplete and must be supplemented with sequences from living species. What can emerge is only a genetically modified substitute bearing certain dodo traits, not the original genome in its entirety. Behavior and ecological role cannot be reconstructed either, as they depended on socialization and a long-changed environment.

The project is already facing criticism—particularly regarding Colossal’s communication strategy. The company is accused of packaging complex scientific advances in sensational headlines that promise more than the technology can deliver. Even the supposedly revived dire wolf turned out to be, in fact, a genetically modified gray wolf. The same applies to the “return” of the dodo. There is a real risk that media attention will flow into sensation rather than serious conservation work.

In parallel, scientists are testing an alternative approach: domestic chickens are genetically modified to produce germline cells of other species, such as the red junglefowl (Gallus gallus). This technique is considered a proof of concept for transferring extinct bird species into living hosts. If successful, it could eventually be applied to species such as the dodo or the passenger pigeon. Whether stable, ecologically viable populations could result remains uncertain.

South Island giant moa: a giant from New Zealand’s past

The South Island giant moa (Dinornis robustus) once lived in New Zealand’s forests until it likely went extinct in the 14th or 15th century due to human hunting.

In July 2025, Colossal Biosciences announced a new project in collaboration with the Ngāi Tahu Research Centre, the Canterbury Museum, and New Zealand filmmaker Peter Jackson: using genetic material from moa bones and modern gene editing, the first “moa-like” chicks are to be created within five to ten years—likely using genetically modified emus as surrogates. The goal is not only to revive the South Island giant moa but also to secure DNA from other moa species and eventually reintroduce these ratites into an ecotourism conservation area on Indigenous land.

Critics express doubts: the technology is not yet mature, and the result would not be a true moa but a genetically modified emu with some moa traits. Suitable habitat for a viable population is also currently lacking.

Passenger pigeon & ivory-billed woodpecker: reviving North America’s forests

The passenger pigeon (Ectopistes migratorius) was once the most abundant bird in North America, but overhunting drove it to extinction in the early 20th century. Scientists aim to reconstruct its genome using its closest living relative, the rock pigeon (Columba livia).

The revival of the passenger pigeon is intended to work in a similar way to the dodo project: researchers sequence DNA from museum specimens of the passenger pigeon and compare it with the genome of the rock pigeon. The passenger pigeon’s genetic traits are then integrated into the rock pigeon’s DNA to create birds that resemble the extinct species in appearance and behavior.

Reviving the passenger pigeon is likely to be significantly easier than reviving the dodo. The approximately 100-year-old DNA of the passenger pigeon is probably less fragmented and more complete than the 300-year-old dodo DNA, allowing a more precise and comprehensive reconstruction of the genome.

The outcome of gene editing could be genetically and functionally very close to a true passenger pigeon. After successful breeding in aviaries, these birds are intended to be released into the wild to restore the original passenger pigeon’s ecological role: they played a key role in forest regeneration in North America by dispersing seeds and naturally fertilizing the soil. Initial releases could take place in the 2030s.

The ivory-billed woodpecker (Campephilus principalis), last sighted in North America in 1944, is also slated for revival via gene editing. Which living bird species will serve as the basis for genetic reconstruction is still unclear. The aim is to breed the first individuals by 2025 and eventually reintroduce the species to the forests of the southern United States, where it once played an important ecological role.

Thylacine: the return of the Tasmanian tiger

The thylacine (Thylacinus cynocephalus), also known as the Tasmanian tiger, was Australia’s largest carnivorous marsupial until it was driven to extinction in 1936. Using its closest living relative, the fat-tailed dunnart (Sminthopsis crassicaudata), its revival could soon become reality. Researchers aim to genetically modify cells of this small marsupial so that they resemble those of the thylacine. These cells are then intended to develop into embryos carried by a larger marsupial surrogate.

The goal is to create an animal that is outwardly and functionally similar to the thylacine, even if it is not a true thylacine. The reconstruction is based on the thylacine genome decoded to 99.9%, supplemented by RNA analyses and modern sequencing technologies. The return of the thylacine could support Tasmania’s ecological balance, as a top predator it might help control invasive species such as foxes and rabbits.

Dire wolf: successful genetic reconstruction of a prehistoric hunter?

Colossal Biosciences made headlines in April 2025: the US company claimed to have successfully “cloned” three so-called dire wolves (Aenocyon dirus)—more precisely, genetically reconstructed them. These animals lived around 13,000 years ago in North and South America and were larger and more robust than modern wolves.

Using fossil DNA fragments and modern gene-editing techniques, scientists selectively altered 20 genes in the genome of the gray wolf (Canis lupus) to recreate traits of the extinct dire wolf. Embryos were created from the modified cells and carried by surrogate mothers. The three animals—two males and one female—were born between October 2024 and January 2025. Although they are not exact genetic copies, they closely resemble the dire wolf in appearance and behavior. Colossal describes this as a milestone on the path toward reviving lost species through gene editing.

Critics accuse the project of packaging a compelling story of scientific progress into sensational headlines that foster false hope and confusion among the public. Strictly speaking, the dire wolf was not brought back: the split between the dire wolf lineage and the gray wolf dates back about 5.7 million years—far more genetic differences than can be covered by 20 targeted gene edits. The result is therefore a genetically modified gray wolf with a few “prehistoric” traits rather than a true dire wolf. The newly created animal may resemble a dire wolf, but little more.

Back-breeding: recreating extinct animals

In back-breeding or re-creation breeding, scientists and breeders attempt to reproduce the traits of an extinct animal through targeted cross-breeding of living relatives. Animals with the desired characteristics are selectively bred over generations until the result comes as close as possible to the original.

Although this does not produce genetic copies, the recreations can restore many characteristics and functions of the extinct species. The method is not limited to appearance: behavior and ecological function can also be partially restored. A major challenge remains that these back-bred animals must survive in modern environments that may differ substantially from the original habitat of the extinct species.

Aurochs: will the landscape engineer return?

The aurochs (Bos primigenius), the wild ancestor of modern cattle, went extinct in 1627. Back-breeding projects use domestic cattle breeds that still retain typical aurochs traits to produce animals resembling the original. Examples include Sayaguesa cattle, Hungarian Grey cattle, and Chianina cattle.

Through targeted cross-breeding and selection, animals emerge that closely resemble the aurochs in size, horn shape, and behavior, with each generation breeding those individuals showing the strongest aurochs-like traits. Repeated crossings and strict selection over many generations produce animals that increasingly approximate the aurochs.

In the 1920s, back-breeding produced Heck cattle, which remained smaller and more compact than the aurochs. Modern projects such as the Tauros Programme or the Auerrind project have produced more robust animals with greater resemblance to the aurochs, including greater shoulder height and more pronounced horns. Back-bred aurochs-like cattle could help create open grazing landscapes, promote biodiversity, and revitalize degraded ecosystems.

Quagga: an unfinished zebra in South Africa

The quagga (Equus quagga quagga), a subspecies of the plains zebra, went extinct in 1883. Since 1987, the Quagga Project initiated by Reinhold Rau has aimed to create plains zebras with reduced striping through selective breeding, making them visually resemble the quagga. Particularly distinctive were the quagga’s fewer stripes—especially on the rear of the body—and its brownish coloration, traits that are recreated through careful selection of breeding animals.

With each generation, the animals’ stripes are further reduced, and by the fifth generation around 90 animals already closely resembled the historical quagga. By 2022, the population had grown to about 200 animals. Some of the bred “Rau quaggas” have been introduced into South Africa’s Karoo region to restore the ecological functions of the quagga.

Floreana giant tortoise: a return through genetic back-breeding

The Floreana giant tortoise (Chelonoidis niger niger) was a subspecies of the Galápagos giant tortoise endemic to Floreana Island in the Galápagos archipelago. It has been considered extinct since the mid-19th century. Whalers and early settlers killed the slow-growing animals in large numbers and used them as a food reserve aboard their ships. Within just a few decades, the population disappeared completely from Floreana.

In 2012, researchers made a surprising discovery on the slopes of the Wolf Volcano on Isabela Island: hybrid giant tortoises were found that had resulted from crosses between Chelonoidis niger niger and the Isabela subspecies, the Volcán Wolf giant tortoise (Chelonoidis niger becki). Genetic analyses revealed that some individuals still carried substantial portions of the genetic material of the extinct Floreana form. These hybrids likely descend from tortoises transported and released between islands by sailors in the 18th and 19th centuries.

In cooperation with the Galápagos National Park Directorate and the Charles Darwin Foundation, a breeding program was subsequently launched. The goal is to gradually establish a population that genetically resembles the original subspecies as closely as possible by selectively pairing individuals with a high proportion of Floreana ancestry. Unlike traditional back-breeding projects that focus primarily on external traits, this initiative is firmly based on molecular genetic analyses.

The tortoises bred today carry approximately 40 to 80 percent of the original Floreana genetic heritage, but they are not fully genetically “pure” representatives of the subspecies. It is a back-breeding project aimed at largely restoring the genetic identity, even though the historic genome cannot be completely reconstructed.

By 2025, around 400 juvenile tortoises had already hatched on Santa Cruz as part of this program. In 2026, 158 hybrid tortoises aged eight to thirteen were released on Floreana for the first time—more than 180 years after the original population disappeared. In the long term, approximately 700 individuals are planned to be reintroduced. As large herbivores, the tortoises are expected to gradually resume their ecological role: dispersing seeds, shaping vegetation structure, and contributing to the restoration of the island’s altered ecosystems.