Creepy wolves had a number of newfound celebrities with their looks in Game of Thrones, where they were portrayed as a far larger version of more worldly wolves. Here in the real world, only the largest populations of contemporary wolves are as large as the gloomy wolf that weighs almost 70 kg. These animals once shared North America ̵
Like smilodon and many other large North American mammals, the eerie wolf disappeared during a period of climate change and human arrival on the continent, even as gray wolves and coyotes survived. And with their departure, they left behind a bit of a mystery: what were they?
A new study uses ancient DNA from gloomy wolf skeletons to determine that they were not actually wolves and had been genetically isolated from them for millions of years.
Looks like a wolf, but …
When it comes to canids, species boundaries and their relationship to anatomy are unclear. Domestic dogs have incredibly different morphologies, yet they are part of a species and can still cross the gray wolves from which they originate. Gray wolves and coyotes can also cross each other. So the question of whether gray wolves and gloomy wolves are closely related, as indicated by their similar appearance, would also indicate whether the gloomy wolf has made genetic contributions to any current species.
The new work done by a large, international collaboration (full publication: I have climbed with one of the authors) started with the traditional means of trying to answer this question: by looking at the skeletons of gloomy wolves. However, this analysis, which involved over 700 individual skeletons, did not produce much. Although they differ enough that the two species could be consistently identified, there were no dramatic differences suggesting a significant evolutionary distance.
So the team turned to more modern methods. It is possible to isolate fragments of collagen, a protein that is a major component in bones and often has subtle differences between species. The sequence of gloomy wolf collagen had enough differences to suggest that gloomy wolves were distantly related to many other modern dog-like species. But the similarities among them all were high enough to prevent scientists from resolving the relationship between these species.
Then the team began isolating DNA from the remains and managed to get some from five samples originating from across the United States, from Idaho to Tennessee. The skeletons ranged in age from 13,000 to over 50,000 years old. An analysis of the shorter mitochondrial genome yielded results similar to collagen. It indicated that gloomy wolves were a distinct lineage distant from wolves and coyotes, but the analysis was confused both by small differences between species and the fact that some genera (such as wolves and coyotes) had inbred.
A distant relative
It left the assay depending on the order of the common nuclear genome. Due to the age of the samples, the DNA was very damaged and gave only a small part of the animals’ full genomes (only from 1 to 20 percent of the genome was obtained, depending on the sample). To fully explore the canid genus, the researchers also obtained the genome sequence from a North American wolf and two jackals – most of the other species on this branch of the evolutionary tree had been sequenced.
The tree based on these sequences indicates that the last fox branched off from the rest of the canids about 7 million years ago. The next branch, which took place about 6 million years ago, produced a branch that includes both jackal species and the gloomy wolf. Everything else, including African wild dogs, various wolf species, and coyotes, were all on a separate branch of the genus and are far more closely related to each other than to the gloomy wolf.
There is a great deal of uncertainty here, as there is typically in evolutionary sequence analyzes; The division between the gloomy wolf and the other great branch could have taken place from 4 to over 8 million years ago. But it is clear that despite their physical similarities, expensive wolves are part of a separate genus that is only distantly related to dogs.
Given that other dog species appear to have engaged in semi-regular inbreeding, the researchers checked for signs of this. This analysis showed that there was no clear indication that expensive wolves had mingled with either wolves or coyotes, despite sharing a continent for many thousands of years. There is a hint of a possibility that gloomy wolf fathers had mingled with the ancestors of wolves, coyotes and dholes somewhere about 3 million years ago, but the signal for this is somewhat weak.
Overall, this result is interesting as a fact. A few generations of Dungeons & Dragons the players have probably been told that a gloomy wolf is a really big wolf and we now know that it is wrong. But it will probably also make us go back and reconsider some fossils that we have had for years. We have a number from North America that has been interpreted under the view that all canids on the continent were part of a closely related cluster of species. Now that we know that there were two very different genera here, we can go back and try to determine if any of the older fossils are more closely related to one or the other genus.
Nature, 2021. DOI: 10.1038 / s41586-020-03082-x (About DOIs).