Learn how Colossal brought back dire wolves extinct for 12,000 years with CRISPR

A groundbreaking scientific achievement has resurrected the dire wolf, a species extinct for over 12,500 years, famous for inspiring the fearsome canines in HBO’s “Game of Thrones.” Colossal Biosciences, a Dallas-based biotech firm, unveiled on April 7 the birth of three dire wolf pups—Romulus, Remus, and Khaleesi—created using DNA from fossils up to 72,000 years old, combined with cutting-edge cloning and CRISPR gene-editing techniques. Born between October 2024 and January 2025, these pups emerged from a process that altered 20 variants across 14 genes of the gray wolf, their closest living relative, to mimic traits like white fur, larger size, and a stronger jaw. Now housed in a 2,000-acre enclosure surrounded by a 10-foot-high, zoo-grade fence at an undisclosed U.S. location, the wolves are under constant watch via drones, cameras, and security teams. Hailed as the world’s first successfully de-extinct animal, this milestone sparks both awe and debate about the boundaries of bringing ancient species back to life.

The pups owe their existence to ancient DNA extracted from a 13,000-year-old tooth found in Ohio and a 72,000-year-old skull unearthed in Idaho. Scientists at Colossal mapped these genomes against those of modern canids, pinpointing unique dire wolf traits, then edited gray wolf cells to express them before transferring the resulting embryos into mixed-breed domestic dogs serving as surrogates. Romulus and Remus, two males, arrived on October 1, 2024, followed by the female Khaleesi on January 30, 2025, all delivered via C-section to protect the surrogate mothers, who were later adopted. This success marks a leap forward for Colossal, a company founded in 2021 by Ben Lamm and Harvard geneticist George Church with over $435 million raised to revive species like the woolly mammoth and dodo, though the dire wolf project had remained under wraps until now.

Beyond the dire wolves, Colossal’s technology shows promise for conservation. The same methods produced four red wolf pups, a critically endangered species, hinting at broader applications. The 2,000-acre habitat, certified by the American Humane Society and registered with the U.S. Department of Agriculture, underscores the firm’s focus on animal welfare. Yet, questions linger: with a genome 99.9% identical to the gray wolf, are these truly dire wolves or sophisticated hybrids? As Romulus, Remus, and Khaleesi grow, monitored in their vast enclosure, the scientific community weighs the implications of this feat, achieved with DNA dormant for millennia.

• Pup names: Romulus, Remus, and Khaleesi, nods to mythology and pop culture.
• Ancient DNA: Sourced from fossils aged 13,000 and 72,000 years.
• Secure habitat: 2,000 acres monitored by drones and security teams.

How Colossal crafted the dire wolf pups

Reviving the dire wolf started with fossils locked in time. A 13,000-year-old tooth from Ohio and a 72,000-year-old skull from Idaho provided the DNA that Colossal’s team used to reconstruct two high-quality genomes of the Aenocyon dirus. By comparing these to living canids like gray wolves and jackals, scientists identified 20 genetic variants across 14 genes tied to traits such as thick white fur and a robust build. Using CRISPR, they edited gray wolf cells, inserting these ancient variants before extracting the nuclei and placing them into donor eggs stripped of their own genetic material. The resulting embryos were implanted into large, mixed-breed domestic dogs, chosen for their genetic closeness to wolves, ensuring a viable interspecies pregnancy.

The gestation lasted 65 days, culminating in carefully planned C-sections. Romulus and Remus debuted on October 1, 2024, while Khaleesi followed on January 30, 2025, all born healthy and displaying the expected dire wolf traits. The surrogate dogs, cared for throughout the process, found adoptive homes afterward, reflecting Colossal’s attention to ethical standards. The gene edits avoided risky mutations linked to issues like deafness, ensuring the pups—now housed in a 2,000-acre secure site—thrive as they grow. This meticulous approach, blending ancient DNA with modern biotech, showcases a new frontier in science.

A leap forward in de-extinction

Editing a living species to resurrect traits of an extinct one pushes biotechnology into uncharted territory. Colossal Biosciences, launched in 2021 with a $435 million war chest, had been chasing the woolly mammoth, dodo, and Tasmanian tiger, but the dire wolf pups stole the spotlight as their first triumph. Romulus and Remus, at six months, already tip the scales at around 80 pounds and are projected to reach 140 pounds as adults, outpacing gray wolves by up to 25%. Khaleesi, at two months, follows suit, her white coat and sturdy frame echoing fossils of the Aenocyon dirus, a top predator of Ice Age North America until its extinction 12,500 years ago.

This breakthrough isn’t without contention. Colossal touts it as the first functional de-extinction, yet the pups’ genomes remain 99.9% gray wolf, with only 20 edits distinguishing them. For some, this makes them hybrids rather than true dire wolves, though their physical traits—larger heads, thicker fur—mirror the ancient species. The technology’s potential shines beyond nostalgia: Colossal also cloned four red wolves, a species teetering on the brink with fewer than 20 left in the wild, proving its tools can bolster conservation efforts alongside reviving the past.

Scientific debate over the dire wolf revival

Reviving an extinct species sparks a philosophical clash among scientists. Colossal claims Romulus, Remus, and Khaleesi, born between October 2024 and January 2025, are dire wolves due to their edited traits—white fur, bigger frames, and stronger jaws—drawn from DNA of fossils aged 13,000 and 72,000 years. Housed in a 2,000-acre fenced area, these pups embody a phenotype lost for millennia, achieved through 20 edits in 14 genes using CRISPR. The company sees this as a triumph of de-extinction, a term they’ve championed since raising over $435 million since 2021.

Not all agree. With 99.9% of their DNA matching gray wolves, some argue these are advanced hybrids, not authentic Aenocyon dirus, which split from gray wolves millions of years ago. The 20 edits—out of roughly 19,000 genes—recreate the dire wolf’s look, but not its full genetic identity. Still, the leap is undeniable: expressing ancient genes in living animals opens new possibilities, from studying lost species to aiding endangered ones like the red wolves cloned in parallel, blending science fiction with practical impact.

• Edited genes: 20 variants in 14 genes for dire wolf traits.
• Hybrid debate: 99.9% gray wolf DNA with ancient tweaks.
• Conservation link: Red wolf cloning shows broader potential.

Life in the 2,000-acre sanctuary

Romulus and Remus, six months old, and Khaleesi, two months, roam a 2,000-acre enclosure somewhere in the U.S., surrounded by a 10-foot fence built to zoo standards. Born on October 1, 2024, and January 30, 2025, respectively, these dire wolf pups thrive under round-the-clock surveillance from drones, live camera feeds, and on-site teams. Certified by the American Humane Society, the site ensures their safety and comfort, with space to grow into their projected 140-pound adult frames. Their white coats and distinct howls, captured in footage released by Colossal, hint at their ancient lineage.

The pups’ names blend lore and pop culture: Romulus and Remus nod to Rome’s mythical founders, raised by a she-wolf, while Khaleesi echoes “Game of Thrones,” where dire wolves gained fame. Once apex predators hunting bison across North America, their real ancestors vanished 12,500 years ago. Today, these hybrids live in isolation, studied for how ancient genes behave in a modern world, offering a living window into a lost era.