Game of Thrones may have ended in what can only be described as a creative disaster, but fans still hold a special place in their hearts for many of the show's iconic characters — including the sigil of House Stark: the dire wolf.
Dire wolves are no mere fantasy dreamt up by GoT author George R.R Martin, but very real creatures that roamed the Earth during the Late Pleistocene period. Ancient remains chart their presence in North America, showing they lived on the continent between 13,000-250,000 years ago.
Bigger than today's gray wolves, they also had larger teeth and jaws than these canines do today. It's no surprise that dire wolves are classified under the genus Aenocyon, which means 'terrible' or 'dreadful' wolf.
Despite their relatively recent past, we still know very little about the evolution — and extinction — of these ferocious predators. Research published Wednesday in the journal Nature provides crucial genetic information about dire wolves' relationship to living canines, along with information about their sad, lonely demise.
Kieren Mitchell is a leading co-author on the study and a postdoctoral researcher from the University of Adelaide. He tells Inverse that the dire wolf's end likely came as a result of its sheer isolation. Despite their depiction in GoT as loyal companions, in truth these were lonely creatures.
"While inability to hybridize with other species may not ultimately have driven the dire wolf extinct, it certainly removed one possible way they might have adapted to changes in their environment," he says.
How they did it — The scientists identified five dire wolf DNA samples dating between some 13,000-50,000 years ago for their study.
From those specimens, they identified a type of collagen found in dire wolves known as COL1.
They then compared the dire wolf DNA to the genetic data of eight living canines, ranging from the gray wolf to the African wild dog (Lycaon pictus). They also generated a phylogenetic tree, which allowed them to compare the species in greater detail.
What they found — Through their research, Mitchell and his colleagues came up with three primary canine lineages: dire wolves, African jackals, and a lineage that includes all other living wolf-like canids.
But these different canine lineages also rapidly diverged from each other, charting their own evolutionary path.
From the data, the researchers realized the dire wolf's last common ancestor with living wolves dates back to 5.7 million years ago. Not long after, the jackal diverged from that common ancestral path, too.
The researchers found no excess shared DNA between dire wolves or any living wolf species — which you would expect if dire wolves shared ancestry with living canines. Ultimately, dire wolves are not closely related to gray wolves, coyotes, African wolves, or dogs. They are truly their own kind. There was no genetic signal indicating interbreeding between dire wolves and living wolf species, the study shows. This was surprising — gray wolves and dire wolves are visually alike, and share similar features.
"Something important to highlight though is that the similarities we see are mainly in the shape and size of their bones, we actually know very little about how dire wolf behavior, physiology, and external appearance would have compared to grey wolves," Mitchell says.
The study does show, however, that an ancient ancestor of dire wolves bred with the shared ancestor of wolves and coyotes around 3 million years ago.
Taken together, the results reveal two divergent evolutionary paths — one which ended in the dire wolves, and the other which gave rise to modern gray wolves and coyotes.
Digging into the details — Interestingly, the study adds a twist to the GoT depiction of these creatures. There is an assumption GoT is based off European civilizations and mythologies — but the dire wolf is an American species.
Again, the result distinguishes dire wolves from coyotes and gray wolves, which originated in Europe and came to the Americas fairly recently in evolutionary terms.
The researchers base their reasoning for this finding on the lack of intermixing or "hybridization" between species in similar ranges. The dire wolf may have shared a similar range with gray wolves and coyotes, but it still wasn't closely related to them.
"Whenever we look at the genomes of living wolf-like species, we almost always find evidence of hybridization between species with overlapping geographical ranges; and... we didn't find any evidence for hybridization in the dire wolf genome," Mitchell says.
Why it matters — For far too long, we've known too little about the dire wolf's history. This creature may be extinct, but it lives on in popular culture as the ultimate wolf, an apex predator unlike any other.
It's not due to a lack of available specimens. More than 4,000 dire wolf remains have been excavated from the La Brea tar pits in California alone.
Through this research, Mitchell and his team put together a more complete genetic picture of the dire wolf than ever before.
Their research can help scientists better understand the dire wolf's evolution and demise, and how this predator relates to modern-day wolves. For example, scientists had previously assumed some genetic relationship between dire wolves and gray wolves due to their similar body composition.
But now that we know that dire wolves have a different evolutionary trajectory than living wolves, we can likely chalk these similarities up to a scientific phenomenon known as convergent evolution, which describes how unrelated animals evolved similar traits.
But it's not totally clear how that convergent evolution happened with dire wolves.
"We didn't delve too much into the possible drivers of convergence between dire wolves and grey wolves, but I think follow-up studies will help get to the bottom of this," Mitchell says.
Now that we know the dire wolf's evolution, we can speculate more about why the dire wolf went extinct — while gray wolves did not, Mitchell says.
"Our results raise the possibility that the two species may have been very different in these respects. It's an exciting hypothesis that may help us to better understand the extinction of the dire wolf," Mitchell says.
Having evolved independently from the ancestor of modern-day wolves, the dire wolf developed specific functions that allowed it to hunt more specialized prey.
But as those prey went extinct, the dire wolf didn't adapt to preying on other food sources — essentially, it may have starved to death as a result. The dire wolf also could not interbreed with gray wolves or coyotes, which may have helped it develop traits to adapt to its changing circumstances.
Mitchell says dire wolves likely "had no opportunity for hybridization, because they were geographically isolated until relatively recently, and by the time they encountered grey wolves and coyotes they were probably different enough that hybridization was impossible."
What's next — There may be other reasons why gray wolves and coyotes could better adapt to changing environments compared to dire wolves — two deserve special consideration.
First: wolves and coyotes may have had more flexible diets compared to dire wolves from the get-go, which helped them survive.
Second: gray wolves and coyotes likely bred with other animals — like dogs — giving them evolutionary advantages, including a better immune response, and a coat color that allowed them to blend in with their environment.
But it's hard to know which theory holds more merit. Further research is required.
"It's very hard to make a call based on the evidence that we have, it could be one or the other or even both," Mitchell says.
"We know that hybridization can sometimes result in beneficial traits being passed from one species to another," he adds.
Mitchell cites the example of modern-day Tibetans, who possess genetic variants that their "ancestors inherited through hybridization with Denisovans — an extinct relative of modern humans." These genetic traits may have helped Tibetans' ancient ancestors survive at high altitudes.
Ultimately, much like its fictional counterparts — of all the Game of Thrones' dire wolves, only two survived — the real-life dire wolf had a tragic end, too.
Abstract: Dire wolves are considered to be one of the most common and widespread large carnivores in Pleistocene America1, yet relatively little is known about their evolution or extinction. Here, to reconstruct the evolutionary history of dire wolves, we sequenced five genomes from sub-fossil remains dating from 13,000 to more than 50,000 years ago. Our results indicate that although they were similar morphologically to the extant grey wolf, dire wolves were a highly divergent lineage that split from living canids around 5.7 million years ago. In contrast to numerous examples of hybridization across Canidae2,3, there is no evidence for gene flow between dire wolves and either North American grey wolves or coyotes. This suggests that dire wolves evolved in isolation from the Pleistocene ancestors of these species. Our results also support an early New World origin of dire wolves, while the ancestors of grey wolves, coyotes and dholes evolved in Eurasia and colonized North America only relatively recently.