In a scientific milestone that sounds like it leapt from the pages of science fiction, Colossal Biosciences has announced the successful resurrection of the dire wolf (Aenocyon dirus), an Ice Age predator that vanished from Earth approximately 13,000 years ago. This achievement, described as “one of the wildest feats in modern science,” marks the world’s first successful de-extinction of an animal species and sets a new standard for genetic engineering.
From Ancient DNA to Living Wolves
The project’s success relied on an intricate multi-step process that began with extracting genetic material from dire wolf fossils. Colossal’s team sourced DNA from two remarkable specimens: a 13,000-year-old tooth from Sheridan Pit, Ohio, and a 72,000-year-old skull from American Falls, Idaho.
From these ancient remains, scientists sequenced and deciphered the dire wolf’s complete genome, assembling what amounts to a genetic blueprint of the extinct species. This was no small feat, as ancient DNA is typically highly fragmented and degraded. The team’s novel approach to iteratively improve their ancient genome reconstruction resulted in more than 500 times more coverage of the dire wolf genome than was previously available.
“Our novel approach to iteratively improve our ancient genome in the absence of a perfect reference sets a new standard for paleogenome reconstruction,” said Dr. Beth Shapiro, Colossal’s Chief Science Officer and a leading expert in ancient DNA.
The genomic analysis yielded several surprising discoveries. While earlier research couldn’t definitively determine the dire wolf’s closest living relative, Colossal’s high-quality genome revealed that gray wolves share 99.5% of their DNA with dire wolves. Interestingly, the analysis also revealed that dire wolves have a hybrid ancestry, emerging between 3.5 and 2.5 million years ago through hybridization between two ancient canid lineages.
Engineering the Past
After mapping the dire wolf genome, the team identified 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 distinctive vocalizations.
With this genetic roadmap in hand, Colossal’s scientists turned to modern technology to bring these ancient traits back to life. Rather than invasively harvesting tissue, they drew blood from living gray wolves and isolated endothelial progenitor cells (EPCs). Using CRISPR gene-editing technology, they precisely rewrote the DNA at the 14 target genes to install the 20 dire wolf variants.
This delicate step required significant care and foresight. For instance, when engineering the dire wolf’s white coat, the team had to work around a potential issue where coat-color gene variants linked to dire wolves might cause deafness in gray wolves. By adding compensatory genetic changes, they achieved the dire wolf’s characteristic white coat without harmful side effects.
The achievement 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 just 8 edits.
From Cells to Living Wolves
Once the cells were genetically modified into dire wolf cells, Colossal used somatic cell nuclear transfer (cloning techniques) to turn them 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 eggs were allowed to develop into embryos in the lab. When viable, they were implanted into surrogate mother animals for gestation. Domestic dogs (hound mixes) were chosen as surrogates given their genetic compatibility and proven success in related canid cloning.
Colossal transferred 45 edited embryos into two surrogate dogs in their first attempt. Two pregnancies took hold (one in each dog), leading to the birth of males Romulus and Remus after approximately 65 days of gestation. A few months later, a third surrogate carried another batch of edited embryos, resulting in the birth of female Khaleesi. All three pups were delivered via scheduled cesarean section to ensure safe delivery.
Remarkably, Colossal reported no miscarriages or stillbirths during these trials, indicating an unusually successful cloning process for this unprecedented de-extinction effort.
The Living Results
Today, three healthy dire wolf pups are thriving under careful supervision. 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, these snowy-white pups already display classic dire wolf traits.
Physically, the pups exhibit thick white fur, broad heads, and hefty builds, weighing approximately 80 pounds at just 6 months old. Their behavior also reflects their wild heritage—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 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.
“Colossal has achieved American Humane Society Certification, the prestigious designation ensuring excellence in animal welfare and care,” noted Robin Ganzert, Ph.D., CEO of American Humane Society. “The technology they are pursuing may be the key to reversing the sixth mass extinction and making extinction events a thing of the past.”
Beyond Resurrection: Conservation Applications
The technical breakthrough represented by the dire wolf’s resurrection extends far beyond the recreation of a single species. The same technologies that revived these Ice Age predators have immediate applications for endangered species conservation.
Alongside the dire wolf births, Colossal announced it had successfully cloned two litters of critically endangered red wolves (Canis rufus), producing four healthy red wolf pups using the same “non-invasive blood cloning” approach developed in the dire wolf work. With fewer than 20 red wolves remaining in North America, this achievement could significantly bolster recovery efforts for one of the world’s most endangered canids.
Harvard geneticist and Colossal co-founder Dr. George Church emphasized the broader implications: “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.”
As Colossal continues to monitor and study these revived dire wolves, the scientific community watches with great interest. Whether this achievement represents the beginning of a new era in conservation biology or simply an extraordinary one-off feat, it has unquestionably pushed the boundaries of what genetic science can accomplish.