Were ‘Game of Thrones' dire wolves real? Here's why the beasts went extinct and they looked way different
Scientists suggest that dire wolves were so different from other canine species like coyotes and grey wolves that they were not able to breed with each other
The iconic and terrifying dire wolf, made famous in the television series ‘Game of Thrones', prowled through North America until about 11,000 years ago or perhaps more, after which they went extinct. They were once believed to be closely related to living wolves. But research suggests that this is not true. Extinct dire wolves split off from other wolves nearly six million years ago and were only a distant relative of today’s wolves, according to a new study, which puts to bed a mystery that biologists have pondered for more than 100 years.
The ancestors of the gray wolf and the much smaller coyote evolved in Eurasia and are thought to have moved into North America less than 1.37M years ago, relatively recently in evolutionary time. An international team sequenced the ancient DNA of five dire wolf sub-fossils from Wyoming, Idaho, Ohio and Tennessee, dating back to over 50,000 years ago. The collaboration of 49 researchers across nine countries analyzed the genomes of dire wolves alongside those of many different wolf-like canid species. Their analyses indicates that unlike many canid species that apparently migrated repeatedly between North America and Eurasia over time, dire wolves evolved solely in North America for millions of years.
Even though dire wolves overlapped with coyotes and grey wolves in North America for at least 10,000 years before their extinction, the team found no evidence that they interbred with these species. Scientists suggest that dire wolves were so different from other canine species like coyotes and grey wolves that they were not able to breed with each other. Their deep evolutionary differences meant that they were likely ill-equipped to adapt to changing conditions at the end of the ice age, explains the report published in Nature.
“Dire wolves have always been an iconic representation of the last ice age in the Americas and now a pop culture icon thanks to ‘Game of Thrones', but what we know about their evolutionary history has been limited to what we can see from the size and shape of their bones and teeth. With this first ancient DNA analysis of dire wolves we have revealed that the history of dire wolves we thought we knew — particularly a close relationship to grey wolves — is much more complicated than we previously thought,” writes lead author, Dr Angela Perri from Durham University’s Archaeology Department.
Co-lead author, Dr Alice Mouton, who conducted the research as a University of California Los Angeles (UCLA) postdoctoral scholar in ecology and evolutionary biology, explains: “We have found the dire wolf is not closely related to the grey wolf. Further, we show that the dire wolf never interbred with the grey wolf. In contrast, grey wolves, African wolves, dogs, coyotes, and jackals can and do interbreed. Dire wolves likely diverged from grey wolves more than five million years ago, which was a great surprise that this divergence occurred so early. This finding highlights how special and unique the dire wolf was.”
A ‘lone’ wolf
The dire wolf is one of the most famous prehistoric carnivores from Pleistocene America. The Pleistocene, commonly called the Ice Age, ended roughly 11,700 years ago. “The terrifying dire wolf, a legendary symbol of Los Angeles and the La Brea Tar Pits (over 4,000 dire wolves have been excavated from here), has earned its place among the many large, unique species that went extinct at the end of the Pleistocene epoch,” says UCLA’s Robert Wayne, a distinguished professor of ecology and evolutionary biology and the study’s co-senior author.
Known scientifically as Canis dirus, meaning “fearsome dog", they preyed on large mammals like bison. The team notes the dire wolves’ stark evolutionary divergence from grey wolves places them in an entirely different genus — Aenocyon dirus (terrible wolf) — as first proposed by paleontologist John Campbell Merriam over 100 years ago.
Interbreeding is quite common among wolf lineages when their geographical ranges overlap. Modern gray wolves and coyotes, for example, frequently interbreed in North America. Yet the investigators, using a data set that included a Pleistocene dire wolf, 22 modern North American gray wolves and coyotes, and three ancient dogs, found that the dire wolf had not interbred with any of the others, likely because it was genetically unable to reproduce with those species.
“Our finding of no evidence for gene flow between dire wolves and gray wolves or coyotes, despite the substantial range overlap during the Late Pleistocene, suggests that the common ancestor of gray wolves and coyotes probably evolved in geographical isolation from members of the dire wolf lineage. This result is consistent with the hypothesis that dire wolves originated in the Americas,” says Wayne.
Co-lead author, Dr Kieren Mitchell, from the University of Adelaide, further explains that despite anatomical similarities between grey wolves and dire wolves — suggesting that they could perhaps be related in the same way as modern humans and Neanderthals — the genetic results show these two species of wolf are much more like distant cousins, like humans and chimpanzees. “All our data point to the dire wolf being the last surviving member of an ancient lineage distinct from all living canines,” adds Mitchell.
Author Laurent Frantz, a professor at Ludwig Maximillian University and the UK’s Queen Mary University, says that at the start of the study, they thought that dire wolves were just “beefed-up gray wolves". “So we were surprised to learn how extremely genetically different they were, so much so that they likely could not have interbred. This must mean that dire wolves were isolated in North America for a very long time to become so genetically distinct,” emphasizes Frantz.
Another hypothesis about the dire wolf — one untested in the current report — concerns its extinction. It is commonly thought that because of its body size — larger than gray 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 demise, states Mouton, now a postdoctoral researcher at Belgium’s University of Liege. “Perhaps the dire wolf’s inability to interbreed did not provide necessary new traits that might have allowed them to survive,” notes Mouton.