The dire wolf, scientifically known as Aenocyon dirus was an impressive predator that lived in North and South America during the Late Ice Age and went extinct approximately 10,000 years ago.
Its extinction coincided with the demise of many other large mammals (megafauna) at the end of the last Ice Age. Despite its long-ago extinction, the dire wolf has maintained a place in popular consciousness, not least through its prominent role in the fantasy series Game of Thrones, where they are portrayed as loyal and powerful companions.
In April 2025, the Texas-based biotechnology company Colossal Biosciences announced that it had successfully “resurrected” the dire wolf by breeding three pups created using ancient DNA and genetic engineering.4 The company claimed this was the “first successful resurrection of an extinct species”.9 This sensational news garnered significant attention and fascination, but also raised questions about what this “resurrection” actually means from a scientific perspective. The stark contrast between the fictionalized image of the dire wolf and the scientific reality necessitates a careful and nuanced explanation to avoid spreading misconceptions.
The purpose of this article is to examine this claim more closely and present a scientifically grounded analysis of the research behind the claim, the methods used, the credibility of the claim, and the potential consequences.
What is a Dire Wolf?
The dire wolf was about the same size as the largest modern gray wolves, with an average weight of 60-68 kg for the subspecies A. d. guildayi and 68 kg for A. d. dirus. However, some individuals could weigh up to 150 lbs (approximately 68 kg). Colossal Biosciences reported that their six-month-old pups already weighed around 36 kg and were expected to reach about 63 kg as adults. The dire wolf had a more massive skull and larger teeth than modern gray wolves, suggesting an adaptation to hunting larger prey and possibly crushing bones. Colossal Biosciences found genetic variants suggesting dire wolves had a white coat color.
The scientific classification of the dire wolf has evolved. It was originally named Canis dirus in 1858. In 1918, paleontologist John Campbell Merriam proposed placing it in its own genus, Aenocyon (meaning “terrible dog” in Greek).
A groundbreaking genetic study published in Nature in 2021 led by researchers such as Dr. Angela Perri showed that the dire wolf was not closely related to modern gray wolves (Canis lupus). The study analyzed ancient DNA from five dire wolf fossils and found that their evolutionary lineage diverged from the one leading to modern wolves and coyotes approximately 5.7 million years ago. This means they could not interbreed with gray wolves. The results supported the reintroduction of the genus name Aenocyon for the dire wolf. This significant genetic difference underscores that any attempt to “resurrect” a dire wolf would require much more than minor genetic adjustments to a closely related species. The evolutionary distance suggests substantial differences in their entire genome and biological makeup.
Table: Comparison between Dire Wolf (Aenocyon dirus) and Gray Wolf (Canis lupus)
| Characteristic | Dire Wolf (Aenocyon dirus) | Gray Wolf (Canis lupus) |
| Scientific Name | Aenocyon dirus | Canis lupus |
| Size/Weight | Similar or slightly larger, more robust (up to approx. 68 kg) | Smaller, more slender (average approx. 45 kg) |
| Skull | More powerful, broader head | Narrower head |
| Teeth | Larger, stronger bite | Smaller teeth |
| Coat Color | Likely light/white | Variable (gray, black, white, brown) |
| Genetic Relationship | Distant relative (diverged approx. 5.7 million years ago) | Closer relative to coyotes and African wild dogs |
| Time Period | Late Pleistocene – Early Holocene (approx. 125,000 – 10,000 years ago) | Currently living |
| Distribution | North and South America | Northern Hemisphere |
News Reporting on the “Resurrection”
News outlets worldwide reported on Colossal Biosciences’ announcement with headlines suggesting a complete resurrection of the dire wolf. The three genetically modified pups were named Romulus and Remus (males born in October 2024) and Khaleesi (female born in January 2025), alluding to mythology and popular culture. The company’s CEO, Ben Lamm, described the birth of the pups as a “massive milestone” and the “world’s first successful resurrection of an extinct species”. The media coverage, while generating excitement, often simplified the complex science involved and may not have accurately reflected the scientific consensus on what constitutes de-extinction. The use of terms like “resurrected” can be misleading.
The Alleged Research and Methods
Colossal Biosciences used ancient DNA extracted from an approximately 13,000-year-old tooth from Sheridan Pit in Ohio and an approximately 72,000-year-old inner ear bone from American Falls in Idaho to reconstruct the dire wolf genome. The researchers compared the reconstructed dire wolf genome with that of the gray wolf and identified approximately 20 key genetic differences in 14 genes believed to be responsible for the dire wolf’s unique characteristics, such as larger size, white coat, and more powerful jaws. These differences were then introduced into gray wolf cells using CRISPR-Cas9 gene-editing technology. The nuclei from the genetically modified gray wolf cells were then transferred to enucleated egg cells from domestic dogs. The resulting embryos were implanted in surrogate dogs, and three healthy pups were born: two males (Romulus and Remus) in October 2024 and a female (Khaleesi) in January 2025. The process involved creating a hybrid genome by editing a small number of genes in gray wolf cells to match those assumed for the dire wolf. This differs from true cloning with intact ancient DNA, which is currently impossible for species that have been extinct for thousands of years.
Table: Colossal Biosciences’ “Resurrection” Method in Brief
| Step | Description |
| Ancient DNA Source | 13,000-year-old tooth from Ohio, 72,000-year-old skull from Idaho |
| Donor Species for Genetic Material | Gray Wolf (Canis lupus) |
| Number of Genetic Modifications | Approximately 20 in 14 genes |
| Surrogate Species | Domestic Dog (Canis lupus familiaris) |
| Number of Pups Born | Three (two males: Romulus and Remus; one female: Khaleesi) |
The Definition of “Resurrected”: What Does it Really Mean?
Despite Colossal Biosciences successfully reconstructing a significantly larger portion of the dire wolf genome than previous studies 18, the 20 genetic changes in 14 genes represent only a very small fraction of the total genome. The dire wolf and the gray wolf share approximately 99.5% of their DNA. The created pups are essentially genetically modified gray wolves that express certain phenotypic traits resembling those of the dire wolf, such as larger size and white fur. They do not possess the entire genetic makeup or the evolutionary history of a true dire wolf. The scientific community generally agrees that it is currently not possible to create an exact genetic copy of an extinct species. The term “de-extinction” in this context refers to creating an animal with some of the extinct species’ characteristics. Colossal Biosciences is also working on trying to recreate other extinct species such as woolly mammoths, dodos, and Tasmanian tigers using similar genetic engineering methods. These projects face similar challenges and debates surrounding the definition of “resurrection.” The term “resurrected” is misleading in this context. A more accurate description would be “genetically modified to resemble” or “dire wolf phenotype recreated in a gray wolf.”
Credibility and Scientific Review
At the time of this analysis, Colossal Biosciences has not published its research on the dire wolves in a peer-reviewed scientific journal. Peer review is a crucial process in science where experts review research results before publication to ensure quality, accuracy, and validity. The absence of this makes it difficult to assess the full scientific weight of the research. Several independent researchers have expressed skepticism towards Colossal Biosciences’ claim of “resurrection.” Jeremy Austin, director of the Australian Centre for Ancient DNA, believes that what has been created is a genetically modified gray wolf, not a dire wolf by any definition. Vincent Lynch, a biologist at the University at Buffalo, states that the only thing that can be done now is to create something that superficially looks like something else, not fully revive extinct species. Dr. Julie Meachen, a paleontologist, considers it scientifically inaccurate to call these animals dire wolves due to the large genetic difference between dire wolves and gray wolves. Experts believe that it would likely require thousands, if not hundreds of thousands, of genetic changes to create a genetically accurate dire wolf.9 The 20 changes made to the gray wolves’ genome are likely insufficient to recreate all the complex characteristics of an extinct species that evolved over millions of years.68 Researchers emphasize that although the genetically modified gray wolves may exhibit certain phenotypic similarities to dire wolves, such as size and coat color, it does not mean they are genetically or evolutionarily identical. The genotype, the complete genetic makeup, is what defines a species. The scientific community’s cautious reaction highlights the difference between a sensational claim and the rigorous standards of scientific validation. The current project is more accurately described as an attempt to recreate certain aspects of the dire wolf’s phenotype in a living relative.
Potential Consequences
Introducing a large predator like the dire wolf (or a close relative) into modern ecosystems could have unpredictable consequences. It is uncertain how they would compete with existing predators for resources and how their hunting behavior would affect prey populations. There is a risk that the “resurrected” animals could become invasive species and negatively impact the biodiversity of the areas where they are introduced. History shows examples of species introduced into new environments with devastating consequences for native species. The dire wolf preyed on megafauna such as horses, bison, and camels.1 Many of these prey animals are now extinct, raising the question of what the “resurrected” dire wolves would eat and how they would adapt to modern prey animals.
There is an ethical debate about whether resources used for de-extinction projects could not be better used to protect and preserve currently living endangered species and their habitats. Ethical questions regarding the welfare of the animals in the process of genetic manipulation and cloning, including risks to surrogate mothers and potential health problems in the “resurrected” animals, must also be considered. Some argue that de-extinction could be a way to compensate for human impact on species extinction, while others believe that the focus should be on preventing further extinctions. The potential ecological disruptions and ethical dilemmas associated with the “resurrection” of dire wolves underscore the need for careful scientific evaluation and public discourse before any attempts at reintroduction are made.
What is the Research Really About?
It is important to emphasize that Colossal Biosciences has not resurrected a genetically identical dire wolf. Instead, they have used genetic engineering to modify gray wolves to express certain characteristics reminiscent of the dire wolf. No ancient dire wolf DNA has been directly inserted into the gray wolves’ genome. Colossal Biosciences highlights that their work with dire wolves also aims to develop techniques that can be used to preserve and increase the genetic diversity of currently living endangered species. For example, they have also used similar methods to clone the red wolf, a critically endangered species. Colossal Biosciences also has ambitious plans to try to “resurrect” other extinct species, including woolly mammoths, dodos, and Tasmanian tigers, through similar genetic engineering methods. The project, while not a true resurrection, represents a significant advancement in genetic engineering and the analysis of ancient DNA. The potential to apply these techniques to conserve endangered species offers a more immediate and tangible benefit.
Conclusion
In summary, Colossal Biosciences has created three pups that are genetically modified gray wolves with certain dire wolf-like characteristics. The claim that the dire wolf has been fully resurrected is not supported by the current scientific understanding. Rather, it is an advanced biotechnology project aimed at recreating certain extinct traits in a living species. While the idea of bringing extinct animals back to life captures the imagination, it is crucial to ground such claims in scientific accuracy and have thoughtful discussions about the consequences of these technologies. The case of the “resurrected” dire wolf serves as a compelling example of the complexities and nuances involved in de-extinction projects. It is important to distinguish between sensational news reporting and the underlying scientific reality. The research conducted by Colossal Biosciences certainly represents progress in genetic engineering and the analysis of ancient DNA, but it is important to be aware of the limitations and the fact that a true resurrection of an extinct species with current technology is not possible. The potential ecological and ethical consequences of such projects also require careful consideration.
Works cited
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