Dire wolves were among North America's dominant predators until quite recently, but most of what we thought we knew about them was wrong. In particular, far from being larger relatives of gray wolves, the two diverged 5-6 million years ago.
Dire wolves were once so common the bones of 4,000 of them have been found in the La Brea tar pits in Los Angeles. Yet research on their ancestry has been sparse. Now a large international team has compared dire wolf DNA from five locations dating back up to 50,000 years with that of modern canid species. The result, published in Nature is a shock. Dire wolves have no close living relatives. Instead, they separated from the line that includes gray wolves, dogs, and coyotes about the same time Eurasian jackals did. The ancestors of the dire wolf were probably in North America for a long time before the gray wolf and coyote arrived, but we know little about them.
When gray wolves crossed the Bering strait they shared a continent with dire wolves for at least 10,000 years, but there appears to have been no interbreeding. The authors think this indicates the two had evolved too far apart for successful mating to occur, something that modern canids manage even with jackals.
"Dire wolves are sometimes portrayed as mythical creatures – giant wolves prowling bleak frozen landscapes – but reality turns out to be even more interesting,” Dr Kieren Mitchell of the University of Adelaide said in a statement.
Mitchell told IFLScience he thinks the dire wolf's lineage was neglected in part because, “People were probably fairly confident they knew what the answer was,” given the similarities in the skeletons of the two wolves.
Moreover, Mitchell added, “Dire wolf fossils have mostly been found in tropical or subtropical environments, where DNA tends to be not that well preserved. We had to work a lot harder and spend a lot more money to extract the DNA.” Perhaps the dire wolf's habitat should have been a clue. The parts of the wolf that don't fossilize may have more in common with African wild dogs than the cold-loving gray wolf.
Mitchell told IFLScience they have no close living relatives. The only ancestor we can tie them to with confidence is the extinct Armbruster's wolf. “There are a lot of extinct species that were thought to be related to both the gray and dire wolf,” Mitchell added. Now scientists will need to work out whose line they are really on.
While the gray wolf line has diversified into several small species, there is no sign the dire wolves did this, which Mitchell thinks might be because in North America those niches were filled by members of the cat family. Once the last Ice Age finished a combination of rising temperatures, competition from humans, and the loss of prey species pushed dire wolves to extinction, along with saber-toothed cats and North American lions. A counterpart adapted to smaller prey might have survived.
This discovery means that dire wolves may need a new genus name, as they are no longer a member of Canis. Mitchell and colleagues suggest Aenocyon, meaning "terrible wolf", though it's likely Aenocyon dirus will still be called a dire wolf.
Mitchell told IFLScience he started studying dire wolves before George R.R. Martin's book series and the subsequent TV series Game of Thrones (#TeamStark) made them internationally beloved, but they certainly helped non-scientists understand his choice. “It's great when you are describing your work to people and they know the animal you're talking about,” he said, noting this is not always the case for specialists in extinct species.
Alas, Mitchell cannot say what the chances would have been of keeping a dire wolf as a pet or guardian against White Walkers.