Scientists are actively working to bring back at least half a dozen extinct species, with the woolly mammoth, the thylacine (Tasmanian tiger), and the dodo bird leading the pack. These aren’t hypothetical projects. Multiple labs and biotech companies are editing genes, developing surrogate animals, and planning reintroduction sites right now. The field has moved well beyond theory, though no fully de-extinct animal is walking around yet.
The Woolly Mammoth
The woolly mammoth is the flagship project of Colossal Biosciences, a Texas-based biotech company that has attracted hundreds of millions in funding. The approach involves taking living cells from the Asian elephant, the mammoth’s closest relative, and using gene-editing tools to swap in mammoth DNA sequences responsible for key traits like dense hair, cold tolerance, and fat metabolism. Restoring these complex traits may require editing tens of thousands of individual DNA bases, making this one of the most technically ambitious genetic engineering projects ever attempted.
Researchers have already made progress on understanding which genes control woolly hair and cold adaptation. A 2025 study created mice with multiple mammoth-related gene edits to test whether those changes actually produce the expected physical traits. Think of it as a dress rehearsal: if the edits work in mice, there’s stronger reason to believe they’ll work in elephant cells. The ultimate goal is an animal that looks and behaves enough like a mammoth to fill the same ecological role in Arctic tundra environments, even if it’s technically a heavily modified Asian elephant.
The Thylacine (Tasmanian Tiger)
The last known thylacine died in a Tasmanian zoo in 1936. Now, the TIGRR Lab at the University of Melbourne is working to bring it back. Their research focuses on three core problems: mapping the full thylacine genome from preserved specimens, creating and maintaining marsupial stem cells, and developing assisted reproductive techniques that work for marsupials, which reproduce very differently from placental mammals.
Colossal Biosciences is also involved in this project, partnering with the Melbourne team. The work has a practical side benefit: every advance in marsupial stem cell science and reproduction helps conserve living marsupial species that are currently threatened. Australia has one of the worst mammal extinction rates in the world, so the technology being developed for the thylacine could end up saving animals that are still alive.
The Dodo
The dodo, which vanished from Mauritius around 1681, is further along than many people realize. Scientists at Colossal have developed gene-edited chickens that will serve as surrogates for dodo reproduction. The process works like this: chickens are injected with primordial germ cells from Nicobar pigeons, the dodo’s closest living relative. Over time, with additional gene edits to recreate the dodo’s distinctive body and head shape, these surrogates would produce offspring that are functionally dodos.
Colossal’s CEO has estimated the timeline at five to seven years, not twenty. The company is already working with wildlife groups to identify rat-free sites in Mauritius where dodos could eventually be released. The goal isn’t to produce a couple of novelty birds. The stated aim is to breed thousands of dodos with enough engineered genetic diversity to sustain a wild population. Beth Shapiro, a lead geneticist on the project, has emphasized that any reintroduction would be slow and carefully managed rather than a mass release.
The Dire Wolf
Colossal added the dire wolf to its roster more recently. Dire wolves went extinct roughly 13,000 years ago and once roamed the plains, grasslands, and forests of North America. The plan involves using CRISPR to edit gray wolf cells, then transferring the resulting embryo into a domestic dog surrogate. This project is earlier-stage than the mammoth or dodo efforts, and it raises some of the sharpest ecological questions of any de-extinction attempt, since reintroducing a former apex predator into modern landscapes is far more disruptive than reintroducing a flightless bird to an island.
The Passenger Pigeon and Heath Hen
The passenger pigeon, once so abundant it darkened North American skies in flocks of billions, went extinct in 1914. The nonprofit Revive & Restore is leading the effort to bring it back by editing genetic material recovered from museum specimens into the genome of the band-tailed pigeon, its closest living relative. One of the more surprising aspects of this project is that researchers believe they can engineer enough genetic diversity from museum samples to avoid the inbreeding problems you’d expect from starting with preserved tissue. By designing genetically distinct individuals from the start, they could theoretically produce a founding population with near-zero inbreeding.
The heath hen, a bird that disappeared from coastal New England in 1932, is a quieter project using similar techniques. The plan involves editing prairie chicken germ cells to express heath hen traits, following the same surrogate-based playbook as the dodo project.
The Aurochs: A Different Approach
Not every de-extinction effort involves gene editing. The Tauros Programme, led by Rewilding Europe, is trying to recreate the aurochs, a massive wild ox that was the ancestor of modern cattle and went extinct in 1627. Instead of editing DNA, they’re using “back-breeding,” which means crossing existing cattle breeds that each retain certain aurochs-like traits until the offspring resemble the original animal in body shape, behavior, and genetics.
The program currently has about 500 animals. Of those, roughly 160 are founding-generation cattle, 150 are first-generation crossbreeds, 130 are second-generation, 50 are third-generation, and 15 have reached the fourth generation. Each generation gets closer to an animal that can fill the ecological role aurochs once played: large-scale natural grazing that keeps European landscapes open and biodiverse.
How De-Extinction Actually Works
Most modern de-extinction projects rely on a tool called CRISPR, which lets scientists precisely cut and edit DNA sequences. The basic workflow has three steps. First, researchers sequence the extinct animal’s genome from preserved remains. Second, they compare it to the genome of the closest living relative and identify the specific differences that made the extinct species unique. Third, they use CRISPR to introduce those edits into living cells from the modern relative.
Newer techniques go beyond simple single-gene edits. Tools now exist that can insert gene-sized fragments of DNA or replace entire sections of a genome at once, which is essential when you’re trying to recreate traits controlled by many genes working together. After the cells are edited, the next challenge is turning them into a living animal, typically through cloning into a surrogate mother from a related species.
Why It’s Harder Than It Sounds
The first (and so far only) animal to be technically “de-extincted” was a Pyrenean ibex in 2003. A cloned female was born from a surrogate goat, making history as the first extinct species brought back to life. She died minutes after birth. Even if she had survived, there were no males to breed with, and any population grown from a single female’s tissue would have suffered from severe inbreeding, low disease resistance, and high rates of genetic disorders.
That cautionary example highlights the challenges every current project faces. Surrogate mothers from related species may not perfectly replicate the womb environment the extinct animal evolved in. Diet, social behavior, and upbringing are nearly impossible to reconstruct for a species no one has ever observed alive. An engineered mammoth-like elephant, for instance, faces unknown risks from its edited genome: susceptibility to diseases it has no evolutionary defenses against, social needs that researchers can only guess at, and a rapidly changing Arctic climate that looks nothing like the mammoth’s original habitat.
Ecological Risks of Bringing Species Back
Reintroducing engineered species into modern ecosystems is not the same as traditional wildlife conservation. A dire wolf proxy, for example, could put significant pressure on prey species and disrupt ecological relationships that have had thousands of years to stabilize without it. The ecological niche a dire wolf once filled may simply no longer exist in today’s heavily developed North American landscapes. Even if an engineered predator were released into a wilderness area, it might spread more easily than expected because its natural enemies and competitors are long gone.
There’s also the question of unintended consequences. An engineered species could act as a carrier for diseases it was never vaccinated against, or outcompete native species that currently occupy similar roles. These cascading effects are difficult to predict and could ultimately harm the biodiversity that de-extinction projects claim to support. For less ecologically disruptive species like the dodo, the risks are lower, but careful, staged reintroductions remain essential.