Man’s best friend was the first animal to be domesticated by man. But there is no clear dividing line when dogs diverge from wolves. Some of the ancient skeletons were clearly dogs, but there were many more ambiguous skeletons before that. Using the genes of modern and ancient dogs might reveal what once happened. But much of this analysis depends on what kind of wolf population you think dogs have diverged from. Now researchers have a clearer picture of how wolves have evolved over the past 100,000 years . The picture it paints is that despite being spread across the continents around the North Pole, wolves remain a single population, supplemented sporadically centered in Siberia. Many breeds of dogs originate from East Asian wolves. Other breeds of dogs have also received significant input from Middle Eastern populations – but it’s unclear whether it’s wolves or dogs.
The ability to sequence ancient DNA was critical to the new work, which extracted DNA from the skeletons of 66 wolves that spanned 100,000 years of evolution, including most of the most recent ice age. Wolves exist in the northern hemisphere, and the skeletons used for research tend to be closer to the Arctic (in part because DNA is well preserved in cooler environments). But these skeletons are widely distributed, represented by Europe, Asia and North America. The researchers also used five ancient wolf genomes that had been analyzed by others, as well as some modern wolf genomes.
Typically, you will find regional populations that do not frequently mix with more distant parent species. If you map the most closely related genomes, you’ll see that they usually cluster together. But that’s not the case with wolves. Instead the ancient wolf genomes were clustered in time. That is, a given wolf is most likely to be closely related to other wolves living at the same time—regardless of where on Earth those wolves live. Studies of modern wolves show that local populations developed after the last peak of the last ice age. But all of these populations were more similar to each other than the wolves before this Ice Age peak.
How do these animals maintain genetic continuity across the vast distances that separate them? Apparently through repeated expansions of Siberian populations. Somewhere 100,000 years ago, there was a distinct European wolf population. But the constant arrival of Siberian wolves gradually reduced the numbers of these ancient European wolves by 10 to 40 percent, depending on the population. In contrast, all wolves in North America today are mainly from Siberia, with the rest coming from interbreeding with coyotes. One consequence of a global population is the rapid spread of favorable mutations around the world. The researchers found that 24 regions of the genome appeared to carry useful adaptations, and they were present in all wolf populations covered in the study.
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