Dirty wolves (red) fight down gray wolves for dibs on a bison kill in this artist’s reconstruction.
Mauricio Antón
By David Grimm
One of North America’s most famous ancient predators – and a favorite of Game of Thrones fans – emerged just as mysteriously when it disappeared. Dirty wolves, which became extinct at the end of the last ice age with mammoths and saber-toothed cats, have long been thought to be close cousins of gray wolves. The first analysis of the poor wolf DNA found that they had rather walked a lonely evolutionary path: they differed so much from other wolves, coyotes, and dogs that they did not belong to the genus that included these animals. Instead, researchers claim, they need a whole new scientific classification.
“This is a fascinating study” that reveals how terribly distressed wolves were, says Robert Dundas, a vertebrate paleontologist and animal expert at California State University, Fresno, who was not involved in the work.
Archaeologists know that fierce wolves lived in North America about 250,000 to 13,000 years ago. They were about 20% larger than the gray wolves of today – the size of their skeletons often gives them away – and, like other wolves, they probably traveled in packs, on bison, old horses and maybe even small mammoths and mastodons. Many followed their prey into the sticky asphalt of present-day La Brea Tar Pits in Los Angeles, where they were trapped for centuries. Hundreds of horrible wolf skulls lie along the walls of the California Museum.
But this is where most knowledge stops. Because the skeletons of distressed wolves are similar to those of gray wolves, the two animals were considered closely related. Scientists have long classified serious wolves as Canis dirusand place them in the same species as gray wolves, coyotes, and dogs. But the one thing that could have concluded the deal – serious wolf DNA – was broken down by the tar of the pits.
In the new study, researchers searched North America to retrieve genetic samples from dozens of cruel remains at universities and museums. They recovered about a quarter of the nuclear genome and complete mitochondrial DNA in five individuals, ranging from about 13,000 to more than 50,000 years old.
The genetic material has unveiled a new evolutionary tree and a surprise: Dirty wolves occupy their own genus, apart from those that gave rise to African foxes, gray wolves, coyotes and dogs for almost 6 million years, the team reported today in Earth. “Even though they look like wolves, serious wolves have nothing to do with wolves,” said Angela Perri, a zoologist at Durham University and one of the study’s lead authors.
Perri and her colleagues also obtained proteins from the collagen of a wolf from La Brea, which supports the cleavage between the species. The growing evidence has convinced the team to recommend taking serious wolves out of the country Canis genus completely and place it elsewhere in the larger Canid family, which – in addition to wolves and prairie birds – includes foxes, foxes and other canine carnivores. Dire wolves would become Aenocyon dirus, a name proposed in 1918, but largely ignoring scientists.
“The Aenocyon genus has been left in the historical dustbin, but it may be revived, ”said Xiaoming Wang, a vertebrate paleontologist and expert on ancient dogs at the Natural History Museum in Los Angeles County. “Based on the genetic data this team provides, I will support the reclassification.”
It can also mean a re-imagining of how bad wolves look. Artists – and Game of Thrones creators – often depicted the predators as large wooden wolves: bulky, gray and wild. But Perri says that on the warmer latitudes in North America, they can give their characteristics more common to dogs and other animals in this climate, such as red fur, a bushy tail and more rounded ears. As such, she says, serious wolves may have looked like a giant, reddish coyote.
Genetic analysis further shows that predators probably evolved in the Americas, where they were the only wolf-like species for hundreds of thousands – or perhaps millions of years. When gray wolves and coyotes, probably about 20,000 years ago, arrived from Eurasia, serious wolves apparently could not breed with them, as the researchers found no traces of genetic mixing. This is unusual, Perri says, since even such diverse species as dogs and coyotes can have offspring. It further indicates, she says, that distressed wolves were a very different animal than these other creatures.
However, Wang notes that the team could not get a complete genome from any of the samples. This may mean that genetic signatures are missing, which may indicate that distressed wolves do breed with these other animals, and may help to further classify the species. “We are gaining a lot of new insight into the relationship between distressed wolves and other dogs,” he says, “but there are still open questions.”
Why the wolves disappeared, scientists only know that they disappeared with other great ice age creatures. Perri suspects that climate change may have killed the large prey that the wolves that killed killed and that gray wolves and coyotes survived because they could stalk smaller animals. Human hunting for serious prey of wolves may also have played a role, as the wolves probably occupied North America with early Indians for thousands of years.
“These animals were not mythological animals,” Perri says. “They lived among us. Not so long ago, the world was full of creatures we would never see again. ”