Recently, Colossal Biosciences presented three animals to the public that appear to be wolves with thick, white fur. While these animals are the closest thing to a dire wolf seen on Earth in the last 10,000 years, they are not actually members of the extinct species.
So what exactly did the scientists do to bring back these wolves.
What were the dire wolves?
The dire wolf (Aenocyon dirus) was a species of the Canidae family that lived in the Americas about 250,000 years ago and went extinct around 10,000 years ago. It was closely related to the gray wolf (Canis lupus) we know today but was also related to the jackal and the African wild dog. Their lineage diverged from these species around 5.7 million years ago.
Dire wolves were larger than modern wolves and hunted large prey such as bison, early species of horses, and possibly even mammoths. At the end of the last Ice Age, many of these species, including the dire wolves, went extinct, likely due to a combination of climate change and human influence. Without their preferred prey, dire wolves could not compete with the gray wolves and eventually went extinct as well.
In 2021, scientists managed to sequence part of the DNA from dire wolf fossils. Among these scientists was Beth Shapiro, who later became Colossal's chief scientist. She and her team successfully extracted more dire wolf DNA from a 13,000-year-old tooth and a 72,000-year-old skull. This allowed them to compare the dire wolf’s DNA with that of the gray wolf. They found that the two species were very closely related but also identified significant differences in around 80 genes. They selected 20 genetic changes that seemed to affect the appearance and structure of the dire wolf—such as its size, fur color, and fur density. This was the foundation for creating the new "dire wolves" by Colossal.
The Jurassic Park of mammoths
Colossal Biosciences is a company focused on de-extinction, which is the process of bringing extinct animals back to life. This is similar to the concept in Jurassic Park, but Colossal's projects target animals that went extinct more recently, so their genetic material hasn't yet fully decomposed, allowing it to be extracted from fossils. Their most famous project, which gave the company its name, is the attempt to bring back the woolly mammoth. Other projects focus on the dodo, the symbol of extinct species, and the Tasmanian tiger, which went extinct in the 20th century.
How do they plan to achieve this? In theory, if we have the genetic material of an extinct animal, we could clone it by inserting its DNA into an egg cell (from which the nucleus has been removed) and implanting it into the womb of a surrogate mother. The first problem is that we don’t have mammoth or dire wolf eggs, nor do we have females that could serve as surrogates. To overcome this, scientists working on de-extinction plan to use the eggs and wombs of closely related species, such as the Asian elephant for the mammoth and dogs for the dire wolf.
The bigger issue is that, for cloning, we need more than just the DNA sequence—we need a live and functional cell nucleus that contains all the genetic material, as well as other necessary biological components for it to survive and replicate. The likelihood of finding a healthy and intact cell nucleus in animals that went extinct thousands of years ago is slim to none.
As a result, Colossal’s scientists are taking a different approach. They identify the genetic differences between the extinct animal and its closest living relative, then take DNA from the living species and modify it. They don’t attempt to make it identical to the extinct species but instead introduce enough genetic changes to create an animal that looks and behaves like the extinct one.
For the dire wolf, they took gray wolf DNA and made 20 modifications related to the animal's physical traits. Fifteen of these modifications came directly from the dire wolf’s genetic sequence, while five others were adjusted to prevent potential issues like deafness or blindness—problems observed in gray wolves. These 20 genetic changes affect the animal’s size, muscle structure, ear shape and fur.
Ramos, Romulus and Khaleesi
The modified DNA, with the 20 changes, was inserted into the eggs of a dog, and implanted into the wombs of large dogs. The scientists created dozens of such embryos, but only four developed successfully, with one pup dying after ten days due to complications unrelated to cloning. This left them with three wolf pups: two male pups, Ramos and Romulus, named after the legendary brothers who were suckled by a she-wolf and later founded Rome, and a female pup, Khaleesi, named after the character from "A Song of Ice and Fire" and the "Game of Thrones" series (since dire wolves feature prominently in the books and show). Some believe the pup should have been named after one of the Stark daughters, who had a closer connection to the dire wolves.
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The edited DNA was inserted into the eggs of a dog, which were then implanted into the wombs of large female dogs. The device from Colossal Biosciences was used to insert the nuclei containing the edited DNA into the eggs
(Photo: Colossal Biosciences)
Matt James, one of Colossal’s scientists who supervised the fertilization and births, told The New York Times that he knew the experiment had succeeded when he saw the wolf pup's white fur. "The first flash of white was like a slap in the face," he said. "I'll never forget that moment."
Already, the wolf pups are larger than gray wolf pups of the same age, with thick, dense and entirely white fur, a particularly furry tail, and the beginnings of a mane around their necks. It’s still unknown how large they will grow as adults. They currently live in an eight-square-kilometer enclosure somewhere in the northern United States, though the exact location is undisclosed.
The scientists are monitoring the pups' development and hope to observe any differences between them and gray wolves as they age. Unfortunately, we won’t learn much about their behavior compared to that of ancient dire wolves. "They don't grow up in packs of dire wolves where they could learn dire wolf behaviors," said American geneticist Adam Boyko.
Shapiro admitted that the unique circumstances of the pups' lives will affect their behavior. "I’d love to know what the natural behavior of a dire wolf was," she said, "but the pups live like the Carlton Ritz of wolves. They can't get a thorn in their paw without us knowing about it."
Dire Wolf or White Gray Wolf?
The key question raised by Colossal’s announcement is whether these are truly dire wolves.
According to Shapiro, there may be several answers, as different people define the concept of "species" differently. "You can use evolutionary proximity to decide what you call a species... we use a morphological concept of species and say, if it looks like the animal, then it’s the animal," she told New Scientist. In other words, if it looks like a dire wolf and acts like a dire wolf, it’s a dire wolf.
Other scientists are more cautious about this claim. Boyko told The New York Times that while it’s exciting to see a "living version of an extinct species," he doesn’t consider the three pups to be true dire wolves. They have 20 changes that give them the genes of dire wolves, but how many genes are truly responsible for the differences between the two species? "We don’t know what the number is," he concluded. "It could be 20, or it could be 2,000."
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Australian biologist Jeremy Austin was even more assertive. Shapiro's definition of species, he said in an interview with Science Alert, reminds him of the story of "The Emperor’s New Clothes." "If you say you've done something, and people believe you've done something, then you’ve done it," he said. "But I think many scientists will scratch their heads and say, 'Look, you’ve got a gray wolf with white fur.' This isn’t a dire wolf under any definition of species. I don’t think it represents de-extinction in any way."
Austin also questioned what the fate of the dire wolves would be. Could they return to the wild? After all, the environment they lived in more than 10,000 years ago no longer exists, nor does the large prey they fed on.
"Is there a place for dire wolves in the modern world?" Austin asked. "Or will they only live in zoos, displayed so people can pay to see them and say, ‘Hey, we saw a dire wolf today’?"
De-extinction vs. conservation
Austin's question touches on the broader issue of de-extinct animals. Is it ethical to clone animals just for our amusement? And is this really where we should be investing, considering so many species today are on the brink of extinction?
"If you have millions of dollars needed to bring a species back to life and you choose to invest it in that, you're making the ethical decision to revive one species and let others go extinct," Joseph Bennett, a conservation researcher, told The New York Times a few years ago. "It would be one step forward, three to eight steps back."
In the case of the dire wolves, if they were returned to the wild, they would compete with gray wolves for dwindling resources in the human-dominated territories that remain. Even gray wolves, though not considered an endangered species, face various threats. A proposal is expected to be voted on in the U.S. Congress soon to remove gray wolves from the list of protected species, opening the door for hunting. Competing with "dire wolves" would certainly not help them. There’s also a reasonable possibility that the two species might interbreed, leading to hybrids with unpredictable outcomes.
Julie Meachen, who was involved in the DNA research of dire wolves but not in Colossal's cloning project, told The New York Times she has mixed feelings about the pups. "The little girl inside me is excited and wants to see what they look like. But I have questions. We already have enough challenges with the wolves we have today."