The gene responsible for dark coat color in American Gray Wolves and coyotes is a fairly recent addition to these animals’ genomes and most likely arrived through mating with domestic dogs—according to a paper published online in Science Express . The bigger surprise is that the mutation (spread through hybridization) may be helping wolves adapt and survive. Wolves living on the tundra tend to be light-colored, while forest-dwellers are dark. As tundra habitat decreases, a lighter coat is a disadvantage. Listen to a podcast  with one of the authors.