Especially big and terrifying: The Canis dirus provided the template for the shadow wolves in the fantasy series “Game of Thrones”. But what was it really about these predators that roamed North America until 13,000 years ago? An analysis of fossil DNA now shows that the “direwolf” was surprisingly only distantly related to wolves and other dog-like animals and apparently could not mix with them either. According to the genetic characteristics, Canis dirus was the last member of an extinct lineage that split off from the canine group around six million years ago.
Until the end of the last ice age, North America was the empire of Canis dirusas evidenced by numerous fossil finds. The scientific name means “terrible dog” – it owes this name to its comparatively massive appearance. In the versions of the fantasy genre, the dimensions of the animals are usually clearly exaggerated, but Canis dirus was up to 65 kilograms in body weight significantly larger than a wolfCanis lupus) and also had a heavier set of teeth. It is possible that the Ice Age predators were specially adapted to hunt large prey such as bison.
Fossil DNA reveals secrets
Due to the anatomical similarities, it was previously assumed that Canis dirus was closely related to the wolf. But an international team of researchers wanted to know more: Using so-called paleogenomics techniques, they investigated the question of how the prominent predators of the Ice Age should be classified in the family tree of the representatives of the canids. As part of their study, they managed to find five, some more than 50,000 years old Canis-dirus– Extract and sequence the remains of fossil DNA. “This was made possible with the help of modern molecular biological methods for severely degraded materials,” explains co-author Alice Mouton from the University of California in Los Angeles.
The scientists were then able to compare the reconstructed genetic material with the genomes of numerous other wolf-like representatives of the canine species in order to uncover possible links. “It turned out that the story of Canis dirus is actually much more complicated than we previously thought, ”says co-author Angela Perri of the University of Durham. Although their anatomical features were similar to those of wolves, these animals were only distantly related to one another and the genetic distance to other representatives of canids such as coyotes, jackals or wild dogs was comparatively large.
Much more special than expected
Although their range in North America overlapped with that of coyotes and wolves for at least 10,000 years, the researchers found no evidence of crosses in the genome of Canis dirus. “It is actually assumed that hybridizations between canids occur very frequently,” says co-Auor Laurent Frantz from the Ludwig Maximilians University in Munich. “When we started this study, we thought that Canis dirus is just an enlarged wolf. We were very surprised that the genetic differences are so great that they probably couldn’t have crossed, ”said the scientist. His colleague Kieren Mitchell from the University of Adelaide added: “One might have guessed that Canis dirus and the gray wolf were similarly related to modern humans and the Neanderthals. However, our results show that these animals were more distant cousins - similar to humans and chimpanzees, ”said the scientist.
The researchers conclude that Canis dirus was the last member of an extinct lineage that split off from the canid family tree around six million years ago. The scientists’ results also suggest that, unlike other canids, the animals did not migrate back and forth between North America and Eurasia, but instead evolved exclusively in North America over millions of years. “To be so genetically different you have to Canis dirus have been isolated in North America for a very long time, ”says Frantz.
But why did the strong predators disappear about 13,000 years ago while the more delicate wolves survived? The researchers suspect that Canis dirus due to its profound evolutionary peculiarities, it could have been less equipped to adapt to the environmental changes at the end of the Ice Age.
Source: Durham University, Ludwig Maximilians University Munich, specialist article: Nature, doi: 10.1038 / s41586-020-03082-x