Thousands of years ago, as the Earth’s last ice age began its transition into the Holocene epoch, massive land mammals that once populated the world underwent widespread extinctions, significantly reducing the global megafaunal density.
While echoes of the large creatures that once walked the Earth are preserved in the fossil record, none of these long extinct species have been seen by human eyes for thousands of years—until now.
The dire wolf (aenocyon dirus), a massive extinct canine that last hunted Pleistocene-era forests and plains of North America thousands of years ago, has now been resurrected in a remarkable achievement by Texas-based biotechnology company Colossal Biosciences, making it “the world’s first successfully de-extincted animal.”
“The successful birth of three dire wolves is a revolutionary milestone of scientific progress that illustrates another leap forward in Colossal’s de-extinction technologies and is a critical step on the pathway to the de-extinction of other target species,” the company said in a statement revealing the achievement.
Speaking with The Debrief in advance of the historic announcement, Ben Lamm, CEO of Colossal, said his company was able to obtain remarkably well-preserved samples of the extinct canine’s remains, which provided enough quality genetic material to restore the ancient species.
“We took a 13,000-year-old tooth, and a 74,000-year-old skull, and we made puppies,” Lamm told The Debrief.
America’s Ancient Megafaunal Canine
Often mistaken for a creature of fantasy from its famous portrayal in the HBO series Game of Thrones based on the fantasy novels of George R. R. Martin, the dire wolf was one of many ancient megafaunal animals that thrived in North and South America during the Pleistocene, with some disputed evidence that may suggest their migration into parts of China across Beringia.
The species was first discovered in the early 1850s and formally recognized in 1858, with the largest collection of dire wolf remains having been recovered from the famous La Brea Tar Pits in Los Angeles, California.
Roughly comparable in size to the largest known gray wolves today, the dire wolf was believed to possess several unique characteristics—many of them adaptations that enabled it to prey on other megafaunal mammals of its era—that have never been observed in a living specimen until now.
The Dire Wolf is Reborn
After scientists at Colossal successfully reconstructed the complete genome of the dire wolf using DNA from the ancient samples they obtained, it was determined that the ancient species split from other similar ancestors as far back as 4.5 million years ago, later interbreeding with another species, resulting in two distinct ancestral groups.
Further genetic analysis revealed several unique adaptations that contributed to the dire wolf’s large size and several other distinctive characteristics, including its facial features and the species’ unique vocalizations. The samples used to sequence the dire wolf genome produced 500 times more paleogenomic coverage than any previously available data.
Employing an advanced multiplex gene editing technique, the Colossal science team undertook precision gene editing across 14 genes, modifying the genome to bring the once extinct species back to life using cutting-edge CRISPR-based editing.
“This unprecedented level of extinct DNA restoration in a living canid not only sets a new benchmark in de-extinction science but also redefines what is possible in species restoration,” the company said in a statement, “demonstrating the power of synthetic biology to reverse extinction and reshape the future of conservation.”
The dire wolves created by Colossal include a pair of male pups born last October named Romulus and Remus, inspired by the twin brothers of Roman mythology who were raised by wolves, and young female named Khaleesi—a feminine title from the fictional Game of Thrones universe meaning “queen”—who was born in January.
“They’re super healthy,” Lamm told The Debrief. “Our puppies—they’re five months old—they’re 80 pounds.”
Lamm said that although dire wolves were known to be larger and stronger than modern wolves, it was unknown precisely how they might differ in appearance. Images Lamm shared with The Debrief before the company’s announcement revealed the quickly growing dire wolf pups to be larger than modern wolf varieties. They also possess unique characteristics, including a thick, mane-like coat area along their necks.
From De-Extinction to Conservation
Founded in 2021 by Lamm and Harvard University professor and geneticist George Church, Colossal set out with more in mind than just reviving extinct species like the woolly mammoth, the thylacine, and the dodo. A crucial part of their mission includes conservation efforts, the restoration and preservation of ecosystems, and how modern gene-editing and de-extinction technology can help us understand evolutionary change.
Now, in addition to the first successful de-extinction of an ancient “lost” species, Lamm told The Debrief that Colossal has used a newly invented cloning process to birth two litters of red wolves, linking Colossal’s de-extinction science with ongoing efforts to support conservation and protection for extant but critically endangered species.
“We want to pair every single de-extinction with a species preservation moment,” Lamm told The Debrief. “We picked a red wolf because it’s our only endemic wolf in America, that’s only in America. It’s critically endangered—there are only 12 left in the wild.”
Lamm said the company’s new process for cloning the red wolf litters differs from those used in the past, which normally rely on invasive tissue sampling processes that endangered any prospective donor. By contrast, Colossal’s new process allows for the extraction of rare cell types, including pericytes and Endothelial Progenitor Cells (EPCs), which are obtained directly from blood samples that can be safely sourced from a living donor.
“It’s awesome,” Lamm said of Colossal’s conservation efforts, while acknowledging the historic nature of what his company has achieved now with the first successful use of its innovative de-extinction technology.
The resurrection of dire wolves followed the company’s announcement earlier this year that it had created a woolly mouse using genetic engineering to produce mice with thick, bushy hair similar to that which extinct Pleistocene mammals—namely the woolly mammoth—once possessed.
“I mean look, the woolly mouse was great. We were very excited about it,” Lamm told The Debrief. “We watched all the excitement around the woolly mouse, and we’re like, people are this excited about our mouse. Wait until they see our wolves.”
Some experts remain divided over whether the dire wolves created by Colossal can be considered true representations of their extinct forbears. Describing the process she and her colleagues used to engineer the wolf pups genetically, Beth Shapiro, Ph.D., a Professor of Ecology and Evolutionary Biology at UC Santa Barbara and a scientist at Colossal, explained in a statement that “we targeted DNA sequences that lead to dire wolf traits and then edited grey wolf cells,” noting that grey wolves are close living relatives to the extinct species.
Several scientists have also pointed to differences between the two species, arguing that the genetic modification of traits in an entirely separate genus to give it dire wolf-like traits is different from using valid ancient DNA to clone one of the extinct creatures. While Colossal’s achievement has led to some controversy, the company has nonetheless demonstrated that genetic modifications can recreate, at very least, a near approximation of ancient species that were once considered entirely lost. With their advancements in cloning added into the mix, Colossal’s current efforts to revive more recent extinctions like the dodo and the thylacine could generate very promising results in the near future.
An Ancient Species and a Pop Culture Icon
Beyond its innovations in de-extinction technology, Lamm says that Colossal has also helped to restore to life an enigmatic species that has become a favorite in pop culture, thanks to its appearances in series like HBO’s Game of Thrones.
“We’ve de-extincted this pop culture icon,” Lamm said. “The mouse proves our end-to-end process works and produces healthy animals. This proves that our end-to-end process works, and we’re using ancient DNA.
“It’s never been done before,” Lamm added. “It’s crazy. We started this project a little over 18 months ago.”
“We really do care about conservation, as well as ensuring what’s best for the animals,” Lamm told The Debrief. “So we brought animals to term that we knew had the ancient DNA in them, where the cells were healthy, and there was nothing negative in the off-target effects from the geoengineering.”
“This is the most precision-edited germ-line engineered animal on the planet,” Lamm said.
Over the last several months, as the Colossal team has nurtured the dire wolf pups on a secure property where they are currently being raised, Lamm says his personal interactions with these enigmatic canines have been life-changing, providing a window through time and a surreal look into North America’s ancient past.
“I still get chills looking at them,” Lamm said.
This article was updated on April 8, 2025.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.