Is this really a dire wolf? Here’s how the ‘de-extinct’ pups compare to the real thing.
Genetics and behavior complicate efforts to bring back extinct species.
For over 200,000 years, dire wolves roamed across North America—from southern Alberta, Canada to Florida, and even down into Chile. The ancient animals were megafauna hunters, ultimately disappearing with the last giant ground sloths and mastodons about 13,000 years ago. Yet last week, Time proclaimed their second coming with a white wolf on its cover.
The private company Colossal Biosciences claims to have resurrected dire wolves through genetic editing. The resulting trio, named Romulus, Remus, and Khaleesi, are better understood as slightly-modified gray wolves rather than true dire wolves. The company’s researchers extracted and studied ancient dire wolf DNA from a pair of fossils, and then made 20 edits to the genomes of modified modern gray wolf embryos to make the resulting clones seem more dire-wolf-like, similar to their fictional representations in the Game of Thrones series.
From woolly mammoths to dodos, Colossal aims to bring a menagerie of ancient species back—an effort that faces serious scientific hurdles and ethical concerns. The company presents their wolves as a victory for “de-extinction,” but such efforts are complicated by the fact that paleontologists are still assembling an understanding of how dire wolves evolved and the role they played on the prehistoric landscape.
Dire wolves weren’t just super-sized gray wolves
Paleontologists first recognized dire wolves (Aenocyon dirus) in 1858. In overall size, dire wolves are comparable to large gray wolves (Canis lupus) living in Alaska today. The obvious differences, notes La Brea Tar Pits and Museum paleoecologist Emily Lindsey, are seen in their skulls. “Dire wolves have large sagittal crests on their skulls,” or a flange of bone for increased jaw muscle attachments, “and more robust teeth, which suggest they had a stronger bite force,” Lindsey says.
The prehistoric predators evolved to hunt large-bodied prey species, which paleontologists have narrowed down to horses, young mammoths, and other herbivores like the Shasta ground sloth. Although, Lindsey notes, “As any dog owner knows, dogs will eat anything,” perhaps explaining the abundance of dire wolves at the famed La Brea site in Los Angeles, California where many different species were trapped in oozing asphalt. Bones from thousands of dire wolves spanning thousands of years have been found in the tar pits.
Despite their rich fossil record, exactly where dire wolves fit in the canid or dog family tree has only recently become clear from ancient DNA. For a long time, researchers thought that modern gray wolves were their closest relatives based on overall skeletal similarity. But a 2021 study of dire wolf DNA found that dire wolves emerged from a canid lineage that was closer to African jackals around 5 million years ago. The prehistoric dogs eventually evolved into larger sizes and independently evolved some traits similar to those of gray wolves, leading to the origin of dire wolves around 230,000 years ago.
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(Read more about the surprises scientists found in dire wolf DNA.)
In fact, the Colossal team posted a preliminary pre-print paper on bioRxiv April 11 that outlines their analysis of fossil dire wolf DNA (and includes Colossal investor and Game of Thones scribe George R. R. Martin as a coauthor). Bolstering the results of the 2021 study, the team proposes that the dire wolf lineage emerged about 4.5 million years ago when a species of early canid, perhaps similar to today’s bush dogs, interbred and hybridized with a canid closer to the group containing jackals, dholes, and wolves. “Dire wolves are not simply an ancient version of today’s gray wolves,” Colossal Biosciences concluded in a prepared statement, though the company’s website still brands their genetically modified gray wolves as de-extinct dire wolves as of this publication.
How dire wolves lived
The new picture of how dire wolves evolved, and their relationships to other prehistoric canids, is set against decades of research into where the carnivores lived and how they hunted.
During their thousands of years in North America, dire wolves lived in a wide range of environments. “It certainly seems that dire wolves inhabited a variety of different habitats,” says Canadian Museum of Nature paleontologist Ashley Reynolds, ranging from chilly, open steppe to scrubby woodlands. Paleontologists are even still finding where dire wolves once roamed.
This week, Pennsylvania State University paleontologist Chris Widga and colleagues reported on new records of dire wolves from Iowa and Arkansas. “In the Ozarks of Missouri and Arkansas, dire wolves are often found in caves and associated with flat-headed peccaries,” Widga says, likely the wolves’ favored prey in the region.
Wherever they ranged, though, dire wolves lived among a broader diversity and number of large creatures that are entirely missing from our landscape today, not only giant ground sloths and mastodons but vast herds of familiar animals like bison, as well extinct horses and camels. As Widga puts it, “It was a wild time!”
In addition to big herbivores, dire wolves were part of a vast carnivore guild that more closely resembled the diversity of carnivores seen in eastern Africa today than modern North America. “The Pleistocene was a whole different beast, pun very much intended,” Reynolds said.
Dire wolves competed with a broad variety of other large carnivores, including sabertoothed cats like Smilodon, the ancient hyena Chasmaporthetes, the American lion Panthera atrox, and larger individuals of familiar species such as grizzly bears and jaguars. “Dire wolves were not necessarily the apex predator in their environments,” Reynolds says, and in addition to taking down ancient horses the wolves could have bullied cougars, coyotes, and even gray wolves off their kills.
The ancient canids likely lived in packs, coordinating with each other to take down large herbivores and share the spoils. While reconstructing the behavior of fossil species is always challenging, Reynolds notes, the sheer number of dire wolf individuals found at asphalt seep sites strongly hints that the canids lived in social groups. Beyond La Brea’s fossil collection, a site in Peru called Talara—literally “the tar” —has yielded more than 4,500 dire wolf fossils from dozens upon dozens of individuals.
What we still don’t know about dire wolves
Living in packs meant that young dire wolves would have learned from the adults around them—something that can’t be recreated with Colossal’s modern clones. “Colossal’s genetically modified wolves won’t necessarily act like dire wolves just because they have dire wolf genes,” Reynolds says, noting that “because these wolves are being raised without contact with dire wolves, and apparently no contact with any other canids, they don’t have the opportunity to learn important wolf skills from others.”
The finding that dire wolves were not close relatives of gray wolves at all, but independently evolved into a similar niche, raises questions about what modern models are best for comparing dire wolves. “For a long time, we thought that the dire wolf’s closest living relative was the gray wolf,” Reynolds says, “but now we need to add jackals, painted dogs, dholes, and more to the mix” in order to study dire wolf behavior and biology.
African wild dogs and dholes, for example, tend to form large social groups that stay in contact almost constantly as opposed to gray wolf pack structures that split and come back together as individuals forage for food, and jackals tend to be either solitary or live in small social groups of two to four. The social lives of dire wolves could have resembled those of these other canids, or perhaps something entirely unique that is now lost to time. “If dire wolves weren’t actually social, as scientists think, or even if they lived in smaller or larger social groups than expected, these behaviors might have different effects on prey species,” Reynolds notes, which is critical for understanding the role dire wolves played in Ice Age ecology.
The fact dire wolves evolved in North America, and had a deep, different history on the continent, shifted expert perspectives. “It was a wolf that was well-adapted to native ecosystems on this continent and its ancestors evolved alongside other American originals like camels and horses,” Widga says. Unlike gray wolves, dire wolves did not travel over the Bering land bridge. The animals evolved to be part of a now-vanished ecosystem, one in which many beasts lived large.
Why dire wolves went extinct around 13,000 years ago is also largely unknown beyond the disappearance of their preferred prey. Ancient DNA evidence hints that dire wolves didn’t interbreed with gray wolves or otherwise leave a genetic legacy.
“Dire wolves disappeared during a massive, global wave of extinctions that dramatically altered how Earth’s ecosystems had been structured for tens of millions of years,” Lindsey notes, as humans were spreading across the planet as the climate was rapidly warming.
Rather than wolf clones, modern canid species may be the true heirs of dire wolf knowledge. If paleontologists can understand the fate of the dire wolf, they could give today’s canids, from bush dogs to gray wolves, a better shot at survival.
