Dire wolves: the first of their name and the last of their kind. That phrase might sound more than a little familiar to fans of the hit HBO TV series Game of Thrones.
But here’s something that might not be so familiar: Direwolves existed and hunted in packs across the prehistoric world.
That’s right. Dire wolves, those great big hairy beasts so beloved by the Stark family in Game of Thrones, were real. Like many who loved both the original books and the TV series, I too believed that dire wolves were just a wonderful figment of author George R. R. Martin’s superb imagination.
But no. Dire wolves were, in fact, every bit the massive, snarling and savagely primitive beasts that they were depicted as in Game of Thrones but probably without the ethereal connection to humans.
Dire wolves, known scientifically as Canis dirus, meaning ‘fearsome dog’, preyed on large mammals like bison. They roamed the wilds of North America from 50,000 years ago to more than 11, 000 years ago.
More than that, scientists have now managed to map the dire wolf’s genome and, according to their research, the dire wolf was a class above in the wild wolf world. For more than 100 years, scientists have assumed that the dire wolf was in fact just a larger version of the grey wolf, a smaller species of wolf that lived at the same time as the dire wolf, but which has survived into the 21st Century.
But this latest investigation by an international team of scientists from the United Kingdom, Germany, Australia, and the United States has revealed that it was so genetically different from the grey wolf that the two species were unlikely to have been able to interbreed.
“The terrifying dire wolf has earned its place among the many large, unique species that went extinct at the end of the Pleistocene epoch,” said UCLA’s Robert Wayne, a distinguished professor of ecology and evolutionary biology and the study’s co-senior author. The Pleistocene epoch, commonly called the Ice Age, ended roughly 11,700 years ago.
More than 4,000 dire wolves have been excavated from the La Brea Tar Pits in California, but scientists have known little about their evolution or the reasons for their ultimate disappearance. Grey wolves, also found in the fossil-rich pits, still roam the wild and remote forests of North America.
“Dire wolves have always been an iconic representation of the last ice age in the Americas, but what we know about their evolutionary history has been limited to what we can see from the size and shape of their bones,” says co-lead author Angela Perri of Durham University.
Those bones are now revealing much more. Using cutting-edge molecular approaches to analyse five dire wolf genomes from fossil bones dating back 13,000 to 50,000 years ago, the researchers were able to reconstruct the evolutionary history of the long-extinct carnivore for the first time.
Significantly, they found no evidence for the flow of genes between dire wolves and either North American grey wolves or coyotes. The absence of any genetic transference indicates that dire wolves evolved in isolation from the Ice Age ancestors of these other species.
“We have found the dire wolf is not closely related to the grey wolf. Further, we’ve shown that the dire wolf never interbred with the grey wolf,” said co-lead author Alice Mouton, who conducted the research as a UCLA postdoctoral scholar in ecology and evolutionary biology.
The ancestors of the grey wolf and the much smaller coyote evolved in Eurasia and are thought to have moved into North America less than 1.37 million years ago, a comparatively recent event in evolutionary time. The dire wolf, on the other hand, based on its genetic difference from those species, is now believed to have originated in the Americas.
“When we first started this study, we thought that dire wolves were just beefed-up grey wolves, so we were surprised to learn how extremely genetically different they were, so much so that they likely could not have interbred,” said the study’s last author, Laurent Frantz, a professor at Ludwig Maximillian University and the U.K.’s Queen Mary University. “This must mean that dire wolves were isolated in North America for a very long time to become so genetically distinct.”
“Dire wolves are sometimes portrayed as mythical creatures — giant wolves prowling bleak frozen landscapes — but reality turns out to be even more interesting,” said Kieren Mitchell of the University of Adelaide in South Australia, a co-lead author.
“Our finding of no evidence for gene flow between dire wolves and grey wolves or coyotes, despite the substantial range overlap during the Late Pleistocene, suggests that the common ancestor of grey wolves and coyotes probably evolved in geographical isolation from members of the dire wolf lineage.” The results, says Kieren, supports the theory that dire wolves originated in the Americas.
Another theory about the dire wolf concerns its ultimate demise. It is commonly thought that because of its body size — larger than grey wolves and coyotes — the dire wolf was more specialized for hunting large prey and was unable to survive the extinction of its regular food sources. A lack of interbreeding may have hastened its extinction, says Alice Mouton.
“Perhaps the dire wolf’s inability to interbreed did not provide necessary new traits that might have allowed them to survive,” Alice says.“ The ancestors of dire wolves likely diverged from those of grey wolves more than 5 million years ago — it was a great surprise to discover that this divergence occurred so early. This finding highlights how special and unique the dire wolf was.”
Feature image: Artwork depicting two grey wolves confronting a pack of dire wolves (by Mauricio Antón)