Dire wolves had an explosion of modern fame with their appearances Game of Thrones, where they were represented as a much larger version of small wolves. Here in the real world, only the largest numbers of wolves today get as big as the upright wolf, which weighed nearly 70 kilograms. These animals once shared North America – and perhaps prey – with predators like the smilodon, a cat with saber teeth. Before humans, wolves were far more common than regular wolves, as can be seen in the remains of La Brea ‘s tar shoots, where they outnumber gray wolves by a factor of around 100.
Like the smilodon and many other large mammals in North America, the wolf disappeared during climate change and when humans came to the continent, even as gray wolves and coyotes survived. And when they left, they left a bit of a mystery: what were they?
A new study uses ancient DNA from a wolf’s skeleton to discover that they were not wolves and that they were genetically separated from them for millions of years.
Looks like a wolf, but …
When it comes to canids, the boundaries of species and their relationship to anatomy are fuzzy. Domestic dogs have a very diverse morphology but are all part of one species and can still interact with the greyhounds from which they are descended. Gray wolves and coyotes can also interbreed. So the question of whether gray wolves and closely related wolves, as suggested by similar appearances, would also suggest whether the wolf has just made genetic contributions to sex any custom.
The new work, done by a large, international collaboration (full publication: I have been rock climbing with one of the authors) began with the traditional methods for answering this question: by looking at the skeleton of wolves. But this analysis, which included more than 700 individual skeletons, did little. Although they differ enough that the two species could be consistently identified, there were no striking differences indicating a large evolutionary rate.
So the team turned to newer modes. It is possible to separate pieces of collagen, a protein that is a major component of bone and often has small differences between species. There were enough variations in the wolf collagen series just to suggest that wolves were terribly related to many other dog-like species. But their similarities were high enough to keep the researchers from resolving the relationships among these species.
Next, the team began separating DNA from debris and obtained some from five samples, which came from all over the United States, from Idaho to Tennessee. The skeletons were between 13,000 and over 50,000 years old. Examination of the shortest mitochondrial genome yielded collagen-like results. He pointed out that straight wolves were a distinct line that was far removed from wolves and coyotes, but the analysis was confused both with small differences between species and because some lines (like wolves and coyotes) interconnected.
Distant relationship
That made the analysis dependent on the sequence of the regular nuclear genome. Due to the age of the samples, the DNA was severely damaged and produced only a small fraction of the full genomes of the animals (only 1 to 20 percent of the genome was found, according to the sample). To fully examine the canal line, the researchers also obtained the genome sequence from a North American wolf and two jackals – most other species went on this branch of the middle tree. -growth to follow.
The tree based on these lines reveals that the last fox species disappeared from the rest of the canals about 7 million years ago. The next branch, which occurred about 6 million years ago, bore a branch that includes both the jackal species and the upright wolf. Everything else, including African wild dogs, various species of wolf, and the coyote, were all on a separate branch of the line and are far more closely connected than the wolf. just.
There is a degree of uncertainty here, as is usual in evolutionary order studies; the separation between the upright wolf and the other main branch could have occurred anywhere from 4 to over 8 million years ago. But it is clear that, despite their physical similarities, wolves are just part of a particular line that only applies to dogs.
Since other canid species appear to have been involved in semi-regular interfaith, the researchers studied for signs here. This analysis showed that there was no clear indication that wolves had just interacted with wolves or coyotes, despite sharing a continent for thousands of years. There is a theory that the ancestors of wolves were just intertwined with the ancestors of wolves, coyotes, and teenagers somewhere around 3 million years ago, but the indication for this is somewhat weak.
Overall, this result is interesting as a fact in itself. A generation or two of Dungeons & Dragons players seem to have been told that a wolf is a giant wolf, and we now know that that is wrong. But it is also likely that we will look back and rethink some of the fossils we have had in recent years. Several of us from North America have been explained under the notion that the canals on the continent were part of a collection of closely related species. Now that we know that there were two very specific lines here, we can go back and try to find out if any of the older fossils are more closely related to one or the other line.
Nature, 2021. DOI: 10.1038 / s41586-020-03082-x (Mu DOIs).