Researchers have found the genes of dogs in some North American wolves, linked to interbreeding some 15,000 years ago, reports Wired. The black fur of some forest-dwelling wolves is the result of the long-ago matings with dogs, likely kept as companions by American Indians. The dalliances may have strengthened the wolves' immune systems—and their camouflage abilities, researchers believe.
“This is pretty unique,” said a Stanford University biologist, lead author of the study. “Typically, you’d expect gene flow from domestic to wild animals would not be beneficial." There is no evidence of recent interbreeding between dogs and wolves, he noted.