The last Tasmanian tiger died in a zoo in 1936, killed off by bounty hunters who earned a pound per pelt. The passenger pigeon, once numbering in the billions, vanished from North American skies in 1902. The woolly mammoth disappeared roughly 4,000 years ago. But what if these losses weren't permanent? What if we could bring them back?

Scientists are now using CRISPR gene editing to do exactly that. And they're not just trying to resurrect extinct animals for the spectacle. They're attempting to heal broken ecosystems that never recovered from these disappearances.

What Makes De-Extinction Possible Now

CRISPR works like molecular scissors with a GPS system. A guide RNA directs the Cas9 enzyme to a precise spot in the genome. There, it cuts the DNA, allowing scientists to delete, insert, or change genetic material.

This technology emerged shortly after 2000, alongside two other crucial breakthroughs: next-generation genomics that can sequence ancient DNA, and reproductive technologies that can transmit edited genes through germlines. Together, these three innovations made resurrection biology possible for the first time in human history.

But there's an important caveat. The International Union for the Conservation of Nature clarified in 2016 that "de-extinction" is somewhat misleading. We can't resurrect extinct species in their complete genetic, behavioral, and physiological form. What we're actually creating are modern hybrids—close cousins engineered to fill the ecological roles their ancestors once played.

The Woolly Mammoth: Engineering Cold-Resistant Elephants

Colossal Biosciences leads the charge in de-extinction. Founded by Harvard geneticist George Church, the company focuses on species whose return could restore damaged ecosystems.

Their flagship project targets the woolly mammoth. Scientists are using the Asian elephant—the mammoth's closest living relative—as their starting point. They're editing elephant DNA to add mammoth traits: thick fur, small ears, subcutaneous fat, and cold tolerance.

The breakthrough came in March 2024 when Colossal created elephant induced pluripotent stem cells. These iPSCs are crucial building blocks for developing mammoth embryos. The team is now exploring both African and Asian elephants as potential surrogate mothers, with African elephants offering advantages due to their larger size.

But this isn't just about creating a museum curiosity. George Church explains: "What's more important is the impact it has on restoring habitats for carbon absorption and sequestering, like the Woolly Mammoth and Arctic grasslands."

Here's how it would work: Mammoths once maintained vast Arctic grasslands by knocking down trees, trampling snow, and exposing the soil. Without them, those grasslands transformed into forests and moss-covered tundra. The thick vegetation and snow insulate the permafrost, which now holds massive amounts of trapped carbon. Resurrected mammoths could reverse this process, potentially slowing climate change.

As a bonus, the project generated the world's first mRNA vaccine against elephant endotheliotropic herpesvirus—the leading killer of baby Asian elephants. The de-extinction work is already helping save living species.

The Tasmanian Tiger: Restoring an Apex Predator

Benjamin, the last Tasmanian tiger, died on September 7, 1936—just two months after the species finally received protected status. By then, it was far too late. Bounty hunters had systematically eliminated the striped marsupial carnivore from Tasmania.

The Tasmanian government had paid one pound per thylacine since 1888. Before that, private companies offered bounties starting in 1830. Humans drove this apex predator to extinction through deliberate extermination.

The ecological consequences cascaded through Tasmania's ecosystems. Without this top predator, disease proliferated—including the devastating Tasmanian devil facial tumor disease. Invasive species flourished unchecked. Wildfires became more severe. Carbon sequestration declined.

Scientists call this "trophic downgrading"—when removing a top predator destabilizes an entire ecosystem. Restoring the thylacine could reverse this damage.

Colossal is using the dunnart, a small marsupial, as the genetic foundation. They're editing thylacine genes into the dunnart genome, working toward an animal that looks and behaves like the extinct predator.

The Dodo: Second Chances on Mauritius

The dodo became the poster child for extinction—a cautionary tale about human carelessness. The flightless bird lived only on Mauritius island and disappeared around 1690.

Humans didn't hunt dodos to extinction directly. Instead, we introduced rats, pigs, goats, deer, and macaques to the island. These invasive species devoured dodo eggs. Since dodos laid only one egg per year, they couldn't reproduce fast enough to survive.

Beth Shapiro, Colossal's Chief Science Officer, led the team that sequenced the dodo genome from DNA extracted from a skull. They achieved approximately 50X coverage—enough detail to identify the genes that made dodos unique.

The closest living relative is the Nicobar pigeon. Scientists are now editing its genome to recreate the dodo's distinctive characteristics.

In October 2024, "Lord of the Rings" director Peter Jackson invested in the project. His support highlights growing public interest in resurrection biology.

If successful, reintroduced dodos could return to Mauritius, where conservation efforts have already begun restoring native habitats. The bird's presence could help disperse native plant seeds and rebalance the island's ecology.

The Passenger Pigeon: From Billions to Zero to Rebirth

In 1860, passenger pigeons were the most abundant bird on Earth. Flocks of 3 to 5 billion birds darkened American skies. Their massive numbers shaped eastern forest ecosystems.

Then commercial hunting began. Market hunters killed them by the millions for cheap meat. The last wild passenger pigeon died in 1902. The extinction shocked western civilization and helped spark the modern conservation movement.

Revive & Restore, a nonprofit organization, aims to hatch the first new passenger pigeons by 2032. They're using the band-tailed pigeon as their starting point, writing passenger pigeon genes into its genome.

Lead scientist Ben Novak frames the work as redemption: "The extinction of the passenger pigeon is a tragedy of human avarice, but that doesn't have to be the end of their story. As we rewrite their genome back into being, we are writing a future chapter—one of ecological restoration, cultural reclamation, and human redemption."

Passenger pigeons were keystone species. Their enormous flocks created forest disturbances that promoted regeneration cycles. They knocked down dead trees, cleared underbrush, and fertilized the soil with their droppings. Their absence left eastern woodlands ecologically impoverished.

Returning them could restore these natural forest dynamics and increase biodiversity across millions of acres.

Beyond the Headlines: Dire Wolves and Great Auks

In April 2025, Colossal announced progress on dire wolf de-extinction. They're creating grey wolves with genes altered to match dire wolf characteristics. These Ice Age predators could potentially help manage prey populations in rewilded landscapes.

The Great Auk project moves forward more quietly. This flightless seabird went extinct around 1844 when hunters killed the last one on an island off Iceland. Scientists have sequenced its genome and identified the razorbill as its closest living relative.

Each project faces unique challenges. Some are harder than others.

The Limits of Playing God

A 2022 study on the Christmas Island rat revealed CRISPR's limitations. Scientists found they could edit a living relative's genome to resemble the extinct rodent, but they couldn't recover important genes that had been completely lost. The result would be an approximation, not a true resurrection.

This applies to all de-extinction projects. We're not actually bringing back extinct species. We're creating new animals engineered to fill old ecological niches.

Conservationists have embraced the term "deep ecological enrichment" to describe this work. The goal isn't perfect genetic recreation. It's restoring lost ecosystem functions to increase biodiversity and resilience.

The Bigger Picture

De-extinction technology raises obvious questions. Should we resurrect species humans destroyed? Do we have the right to create new life forms? What happens if resurrected species can't survive in modern ecosystems?

But these questions miss a crucial point. Asian elephants are endangered, with populations declining 50% over three generations. African forest elephants are critically endangered. The technologies developed for mammoth de-extinction are already helping save their living cousins.

The same pattern repeats across projects. Each attempt to resurrect an extinct species generates tools, knowledge, and techniques that help conserve endangered ones.

And the ecosystems themselves desperately need repair. We didn't just lose individual species. We lost the ecological functions they performed. Forests that once cycled through regeneration now stagnate. Grasslands that sequestered carbon now release it. Predator-prey relationships that maintained balance now spiral into dysfunction.

De-extinction offers a path toward healing these wounds. It acknowledges that some damage can be reversed, that extinction doesn't have to be forever, and that humans can restore what we destroyed.

The first woolly mammoth hybrid won't lumber across the Arctic tundra for years. The first passenger pigeon won't take flight until the 2030s at the earliest. But the work is already changing how we think about conservation, extinction, and our responsibility to the living world.

We broke these ecosystems. Now we're learning to fix them—one edited gene at a time.