The dire wolf, a species that went extinct some 12,500 years ago but was made famous by the Game of Thrones series, has been brought back to life, according to Texas-based biotech firm Colossal Biosciences.
The company has described the dire wolf as the “world’s first successfully de-extinct animal”.
On Monday, the company announced that its research had led to the birth of three pups — Romulus, Remus and Khaleesi.
But the recently born wolves have DNA which is very close to that of the grey wolf, leading to criticism of the company’s claims.
So are Romulus, Remus and Khaleesi truly dire wolves? Here is what we know about them:
What is a dire wolf?
The dire wolf, the real-life inspiration behind the wolves in HBO’s Game of Thrones, was once a dominant predator across North America.
Fossils suggest that dire wolves were built for strength, not speed. They had more muscle and a heavier build than other ancient or modern wolves.
But despite their size, fossils show that the dire wolf could still move well through different environments, Colossal Biosciences said. It could hunt big animals and live alongside other species. Their powerful bodies made dire wolves strong predators.
These carnivores hunted large Ice Age animals like bison, horses and possibly mammoths.
As many of their prey species disappeared, likely in part due to human hunting, dire wolves may have been driven to extinction, paving the way for the grey wolf to move down from northern Canada and Alaska to take over its ecological role.
SOUND ON. You’re hearing the first howl of a dire wolf in over 10,000 years. Meet Romulus and Remus—the world’s first de-extinct animals, born on October 1, 2024.
The dire wolf has been extinct for over 10,000 years. These two wolves were brought back from extinction using… pic.twitter.com/wY4rdOVFRH
— Colossal Biosciences® (@colossal) April 7, 2025
“Many people view dire wolves as mythical creatures that only exist in a fantasy world, but in reality, they have a rich history of contributing to the American ecosystem,” said Game of Thrones author George RR Martin, who is also an investor and cultural adviser to Colossal.
“I get the luxury to write about magic, but [they] have created magic by bringing these majestic beasts back to our world.”
How are dire wolves different from more common wolves?
According to Colossal, at first glance, dire wolves — their formal, scientific name is Aenocyon dirus — appeared more heavily built, with thicker legs, broader heads and shoulders, a stockier frame, and a more pronounced snout.
Although they look alike, dire wolves are not closely related to grey wolves and are not their ancestors. Genetic studies reveal that the two species diverged millions of years ago and evolved separately in the Americas.
How did scientists bring a dire wolf ‘back’?
Scientists extracted and sequenced DNA from two ancient dire wolf specimens — a 13,000-year-old tooth and a 72,000-year-old ear bone. This analysis identified 20 key genetic differences between dire wolves and their closest living species, grey wolves.
Using CRISPR technology, a kind of molecular scissors to cut DNA at a specific spot, researchers edited the genomes of grey wolf cells to incorporate these 20 specific genetic variants associated with dire wolf traits, such as larger size, broader heads and thicker fur.
The genetic material was inserted into an egg cell from a domestic dog. Once the embryos were developed, they were implanted into surrogate dogs. Sixty-two days later, the genetically engineered pups were born.
What do we know about Romulus, Remus and Khaleesi?
Romulus and Remus, both males, were born on October 1, 2024, while Khaleesi, a female, was born on January 30, 2025.
Romulus and Remus, at six months old, each measure nearly 4 feet (122cm) in length and weigh approximately 80 pounds (36kg), with projections to reach 6 feet (183cm) and 150 pounds (68kg) at full maturity. Khaleesi, at three months, is developing similarly.
The wolves exhibit physical characteristics such as white coats, larger body sizes, and broader heads.
When the first dire wolf pup was delivered by Caesarean section, Colossal’s chief animal officer, Matt James, recalled gently rubbing the newborn between two towels to stimulate its first breath. “Good lord, this thing is huge,” he remembered thinking.
Are dire wolves really back?
While Colossal Biosciences referred to these animals as “de-extincted” dire wolves on Monday, some experts argue that they are genetically modified grey wolves rather than true representations of the extinct species.
“We call them dire wolves,” Ben Lamm, founder and CEO of the Dallas-based startup, said.
Love Dalen, a professor in evolutionary genomics based at the Centre for Palaeogenetics at Stockholm University and adviser to Colossal, also argued this is more of a philosophical question.
“There’s no secret that across the genome, this is 99.9 percent grey wolf. There is going to be an argument in the scientific community regarding how many genes need to be changed to make a dire wolf, but this is really a philosophical question,” Dalen said.
“It carries dire wolf genes, and these genes make it look more like a dire wolf than anything we’ve seen in the last 13,000 years. And that is very cool,” he added.
The two newly born baby Dire Wolves, brought back from extinction by genetic engineering, seated on the Iron Throne. 🐺
George R.R. Martin serves as a Colossal Biosciences cultural advisor and investor, with Peter Jackson loaning his Iron Throne prop for the photoshoot. pic.twitter.com/Yax9WjCp7a
— westerosies (@westerosies) April 7, 2025
Why bringing it back?
According to Colossal, the project helps push the boundaries of genetic engineering and could provide tools for conservation, especially for species with shrinking genetic pools. The dire wolf also served as a high-profile case to demonstrate these capabilities.
“This project demonstrates the awesome potential for advances in genetic engineering and reproductive technologies to recreate lost diversity,” Andrew Pask, Colossal advisory board member, said.
“This work underpins pioneering research that seeks to stabilise ecosystems to prevent further biodiversity losses and to create new methods to actually restore lost biodiversity,” he added.
We’re Colossal Biosciences, the de-extinction company responsible for bringing back the first animals from extinction. Our dire wolf pups, Romulus and Remus, were born on October 1, 2024. Watch these pups grow up on our YouTube channel. Link in bio.
These two wolves were… pic.twitter.com/hbk1wFQ3lf
— Colossal Biosciences® (@colossal) April 7, 2025
Some in the conservation world are optimistic, while others view the efforts by Colossal and similar companies as a risky diversion from more urgent conservation priorities. Still, other experts argue that we may not yet understand the full implications of these changes.
“We can’t protect what we already have,” said Dan Ashe, president and CEO of the Association of Zoos and Aquariums in Canada, in an interview with the Toronto Star.
So far, investors have committed $435m to the company, boosting its valuation to $10.2bn.
What’s next?
Colossal plans to monitor the pups’ growth, health, and behaviour, and may pursue further projects, including de-extinction of other species like the woolly mammoth.
The broader goal is to apply the tech to real-world conservation.
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