National Geographic News
The black wolves that haunt scary stories would have been mere fiction were it not for domestic dogs.
A recent study surprised scientists by revealing that the gene for darker coats in gray wolves, at least in North America, originated in our best furry friends.
Although it's well known that dogs descended from wolves, the new finding implies that some genetic material moved backward in the evolutionary chain.
(From wolf to woof: see pictures of dogs' evolution from wolves.)
This isn't to say that darker wolves resemble dogs, said study co-author Greg Barsh, a geneticist at Stanford University in California.
"It's quite clear that black wolves are just as much wolf as a non-black wolf," Barsh said. But this small amount of dog genes may have given black-coated wolves a selective advantage.
Native American Dogs
Among the gray wolves in North America, the number of dark wolves in a given population can range from 10 to 70 percent. Worldwide, the only other wolves known to have darker coats are in Italy.
Scientists know there are particular gene receptors that cause dark colors in animals as diverse as birds, fish, and rabbits.
But when Barsh and colleagues looked at variations of those genes in wolves and coyotes, the researchers found that those variations didn't affect the color of the canines' fur.
Instead, a more unique gene that darkens fur in dogs was found in dark wolves and coyotes from Wyoming's Yellowstone National Park and the Canadian Arctic.
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