The dogs of the earliest Native Americans or of European immigrants probably contributed to the genetic variability of their wild counterparts, researchers from Stanford University and the University of Calgary found in a study published in the journal Science.
Most canine geneticists believe that North American dogs today are all descended from European dogs, the study said.
"Although it happened by accident, black wolves are the first example of wolves being genetically-engineered by people," said study co-author Marco Musiani, a University of Calgary professor and wolf expert.
"Domestication of dogs has led to dark-colored coats in wolves, which has proven to be a valuable trait for wolf populations as their arctic habitat shrinks," Musiani said.
A darker coat helps wolves hide when chasing their prey in forested areas, where the black wolves make up about 62 percent of the wolf population. Wolves gray with age, and coats vary from white to gray to black.
Lighter-colored wolve