DNA sequencing has revealed that dire wolves, previously thought to be closely related to grey wolves, diverged from other species almost 6m years ago.
Grey Wind, Ghost, Lady, Nymeria, Summer and Shaggydog – these names might sound familiar if you’re a Game of Thrones fan. They’re what the Stark children called the dire wolves gifted to them in the first book of George RR Martin’s renowned fantasy series.
The canine characters also appeared in the HBO TV adaptation of the books, which recruited Northern Inuit dogs, an arctic wolf and green-screen technology to portray them on the small screen.
In reality, dire wolves were ice-age predators that went extinct around 13,000 years ago. Their scientific name, Canis dirus, translates to ‘fearsome dog’. Until now, dire wolves were thought to be closely related to grey wolves because of similarities in their physical forms, such as the size and shape of their teeth and bones.
However, new DNA research led by a team at Durham University, alongside researchers from the University of Oxford, Ludwig Maximilian University, the University of Adelaide and the University of California Los Angeles, has revealed new information about the species.
— Durham University (@durham_uni) January 13, 2021
The research, published in Nature, states that dire wolves diverged from other wolves almost 6m years ago. This makes them a distant relative of today’s wolves. They were common in North America until they went extinct, according to the paper, but were unable to interbreed with grey wolves and other canine species such as coyotes.
Dr Angela Perri of Durham University’s Department of Archaeology, a lead author on the paper, said: “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 actually much more complicated than we previously thought.”
Analysing the ancient DNA of dire wolves
The findings were made by sequencing the ancient DNA of five dire wolf sub-fossils. These had been excavated in Idaho, Ohio, Tennessee and Wyoming in the US and dated back to more than 50,000 years ago.
This is the first time ancient dire wolf DNA has been analysed and through collaborations between 49 researchers, the complex history of the species became clearer.
Taking the genomes and comparing them with different wolf-like species, the researchers found that while other canine species seemingly migrated between North America and Eurasia over time, dire wolves stayed in North America for millions of years.
Here, they evolved and overlapped with both coyotes and grey wolves for at least 10,000 years before they went extinct. However, there was no evidence that the dire wolves had interbred with coyotes or grey wolves.
This surprised researchers as similar species, including African wolves and jackals, can and do interbreed. The researchers concluded that “deep evolutionary differences” meant that dire wolves were likely “ill-equipped to adapt to changing conditions at the end of the ice age”, causing them to go extinct.
A ‘special and unique’ species
A co-lead author on the paper, Dr Alice Mouton of the University of California Los Angeles, said the findings “highlight how special and unique the dire wolf was”.
University of Adelaide’s Dr Kieren Mitchell, another co-lead author, added: “Dire wolves are sometimes portrayed as mythical creatures – giant wolves prowling bleak frozen landscapes – but reality turns out to be even more interesting.
“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 – our genetic results show these two species of wolf are much more like distant cousins, like humans and chimpanzees.
“While ancient humans and Neanderthals appear to have interbred, as do modern grey wolves and coyotes, our genetic data provided no evidence that dire wolves interbred with any living canine species. All our data point to the dire wolf being the last surviving member of an ancient lineage distinct from all living canines.”