A species of wolf that vanished thousands of years ago is walking the earth once more. Dire wolves (scientific name Aenocyon dirus), iconic Ice Age predators long thought lost to time, have been brought back from extinction by Colossal Biosciences.

Dallas-based biotech startup Colossal announced on April 8, 2025, that it has successfully produced living dire wolf pups — the first-ever de-extinct animals created through advanced genetic engineering. Once known only from fossils (and pop culture like Game of Thrones), the dire wolf’s return marks a historic milestone in science. Media coverage has described the achievement as “one of the wildest feats in modern science” and possibly “the most bonkers science story of the year”, underscoring how this real-world breakthrough reads like science fiction made real.

Colossal’s announcement revealed the birth of three healthy dire wolf pups named Romulus, Remus, and Khaleesi — nods to legend and fantasy befitting these “mythical” wolves. The two males, Romulus and Remus, were born in October 2024, and the younger female, Khaleesi, was born in January 2025. Now about 6 months and 3 months old respectively, the snowy-white pups are thriving. Observers note that these are “not dogs, or even modern-day wolves. They’re dire wolf pups, back from extinction after some 12,000 years.”

Physically, they already exhibit classic dire wolf traits — thick white fur, broad heads, hefty builds — and weigh ~80 lbs at just 6 months old. Their behavior is also notably wild: unlike domestic puppies, Romulus and Remus keep their distance from humans, flinching or retreating even from familiar caretakers, demonstrating true wild lupine instincts.

The dire wolf pups are being raised in a dedicated, secure wildlife facility. According to Colossal, the wolves reside on a 2,000+ acre protected reserve under round-the-clock care and monitoring. The site — certified by the American Humane Society — includes naturalistic habitats and on-site veterinary support to ensure the animals’ well-being.

Robin Ganzert, Ph.D., CEO of the American Humane Society, praised Colossal for its high standards of animal welfare in raising the wolves, calling the company “a shining example of excellence in humane care.” She stated that “the technology they are pursuing may be the key to reversing the sixth mass extinction and making extinction events a thing of the past.”

Bringing back the dire wolf required a fusion of cutting-edge gene editing, cloning, and reproductive technology. Colossal did not find any frozen dire wolf to clone directly — instead, the company recreated the dire wolf genome and engineered living animals to match it.

The process involved several key steps: First, researchers obtained genetic material from dire wolf fossils — notably a 13,000-year-old tooth and a 72,000-year-old skull. From these remains, Colossal’s scientists sequenced and deciphered the dire wolf’s genome, assembling a genomic blueprint of the extinct species.

Next, the dire wolf’s genome was compared to that of its closest living relative, the gray wolf. The team pinpointed 14 important genes (with 20 distinct genetic variants) that give dire wolves their characteristic features. These included genes influencing the dire wolf’s larger size, more muscular build, wider skull, bigger teeth, thick light-colored coat, and even its unique howling vocalizations.

Using CRISPR genome editing, Colossal edited living cells from a modern canid to carry dire wolf genes. Rather than invasively harvesting tissue, scientists drew blood from living gray wolves and isolated endothelial progenitor cells (EPCs) from the blood. They then applied CRISPR gene-editing to the nuclei of those cells, precisely rewriting the DNA at the 14 target genes to install the 20 dire wolf variants.

Once the cells were genetically modified into “dire wolf” cells, Colossal used cloning techniques to turn those cells into embryos. Scientists removed the nucleus from domestic dog/wolf egg cells and replaced it with the nucleus of an edited cell — essentially tricking the egg into thinking it was a fertilized zygote. These reconstructed ova were allowed to develop into embryos in the lab.

The viable embryos were implanted into surrogate mother animals for gestation. In this case, domestic dogs (hound mixes) were chosen as surrogates, given their genetic compatibility and proven success in related canid cloning. Colossal transferred a total of 45 edited embryos into two surrogate dogs in the first attempt. Two pregnancies took hold (one in each dog), leading to the birth of Romulus and Remus after ~65 days of gestation. A few months later, a third surrogate carried another batch of edited embryos, resulting in the birth of Khaleesi. All three pups were delivered via scheduled cesarean section to ensure a safe delivery.

Notably, Colossal reported no miscarriages or stillbirths during these trials, indicating a remarkably successful cloning process for an unprecedented de-extinction effort.

This combined approach of ancient DNA + CRISPR editing + cloning is what allowed Colossal to accomplish what was once the stuff of science fiction. The company effectively “rewrote the genetic code of the common gray wolf to match” that of a dire wolf, bringing back traits absent for millennia. The achievement also set a scientific record: 20 precise genetic edits were made to create the dire wolf — the highest number of deliberate genome edits in any animal to date.

(By comparison, Colossal’s previous feat, the “woolly mouse” with mammoth genes, had 8 edits.) This showcases a leap forward in precision germline engineering, proving that complex ancient traits can be resurrected in a living, breathing creature.

Ben Lamm, CEO of Colossal, stated: “I could not be more proud of the team. This massive milestone is the first of many. Our team took DNA from a 13,000 year old tooth and a 72,000 year old skull and made healthy dire wolf puppies. It was once said, ‘any sufficiently advanced technology is indistinguishable from magic.’ Today, our team gets to unveil some of the magic they are working on and its broader impact on conservation.”

Harvard geneticist and co-founder of Colossal, Dr. George Church, added: “Preserving, expanding, and testing genetic diversity should be done well before important endangered animal species like the red wolf are lost. Another source of ecosystem variety stems from our new technologies to de-extinct lost genes, including deep ancient DNA sequencing, polyphyletic trait analyses, multiplex germline editing, and cloning. The dire wolf is an early example of this, including the largest number of precise genomic edits in a healthy vertebrate so far — a capability that is growing exponentially.”

The successful resurrection of the dire wolf has wide-ranging implications for conservation and biotechnology. First and foremost, it proves that the dream of “de-extinction” — bringing vanished species back to life — can move from theory to reality. This achievement validates Colossal’s de-extinction platform, boosting confidence that more ambitious targets are within reach.