By Erin Cashion and David Dyer

On April 7, the story in Time magazine was posted everywhere: we had brought the extinct Ice Age Dire Wolf, Aenocyon dirus, back from the dead. Alongside this unbelievable headline came the video of two adorable white, fluffy canines in the hands of a human caregiver.

These two pups were Romulus and Remus, the culmination of years of work by the U.S.-based biotechnology company Colossal Biosciences. (This company made headlines in March 2025 with the news that they’d produced gene-edited “woolly mice”, which did not actually have any woolly mammoth DNA.) The pups alongside their sister Kahleesi represent the first of what is likely to be a series of “de-extinctions”, in which extinct animals are brought back to life using gene editing technology.

So, did Colossal Biosciences really de-extinct the Dire Wolf?

For quite a long time it was thought that dire wolves were simply a larger version of today’s Gray Wolf (Canus lupus) due to how similar their bones are. The dire wolf is thought to be about the size of today’s largest gray wolves, which are found in Alaska and northwest Canada. In some cases, it’s impossible to tell dire wolf remains from Ice Age gray wolf remains by physical comparison alone. One major difference is that the dire wolf had much larger carnassial teeth, the enlarged lower molar and upper premolar pair found in some carnivores that function to shear flesh.

However, recent genetic analyses indicate that the dire wolf represents a distinct lineage of canines that evolved in isolation from other canids in the Americas. The ancestors of today’s Gray Wolf and the Dire Wolf branched off from each other 5.7 million years ago. (For context, humans and our closest living relatives, chimpanzees, split from a common ancestor 7 million years ago.) The North American Gray Wolf evolved in Europe and migrated to North America during an interglacial period 16,000 – 13,000 years ago, some time after humans arrived on the continent around 30,000 years ago. The branch that includes the Gray Wolf is also ancestral to Cape Hunting Dogs (Lycaon pictus), dholes, jackals, and coyotes. The gray wolf and dire wolf are different enough genetically that interbreeding would have been impossible, and they very likely would not have recognized each other as kin.

Bear in mind that, like our own lineage, the Dire Wolf and Gray Wolf did not spring fully formed from their shared common ancestor and remain unchanged in the intervening time – for both animals, there were many intermediate steps along the way, and many evolutionary dead ends.

The last Dire Wolf lived around 10,000 years ago. Remains have been found all over the Americas and as far south as Peru, with a startling number from the La Brea Tar Pits in California. The oldest remains have been dated to 125,000 years old, although some canid remains with an inconclusive identity (meaning they may be Dire Wolf or a Dire Wolf ancestor) have been dated to over 200,000 years old.

The beautiful, unusually large (and now half-grown) canids roaming Colossal’s  2000 acre ecological preserve are Gray Wolves (Canis lupus) that had 14 specific genes edited to match DNA collected from the remains of two specimens of Dire Wolf – one from Ohio, and one from Oregon. These genes are responsible for 20 traits including coat color, size, and growth rate “thought to be” characteristic of the Dire Wolf. No actual Dire Wolf DNA was spliced into their wolf genomes. Moreover, the difference between the two species is far more than just 14 genes. Also not taken into account is Dire Wolf mitochondrial DNA, which so far no research team has been able to retrieve.

So are they Dire Wolves, or not? That is a philosophical debate that boils down to the ultimate question with no single answer that lies at the heart of modern biology: what is a species?