Black Sheep

Borrowed Gene Blackens Wolves -- Pennisi 2009 (205): 4 -- ScienceNOW

Turns out North American wolves interbred with domestic dogs thousands of years ago:

"Black wolves are quite rare outside North America. So Barsh and his colleagues think that more than 10,000 years ago, black dogs migrating with people heading across the Bering Strait into North American interbred with wolves, introducing the K locus variant. "Typically, hybridization is thought to retard adaptation. However, every once in a while, [a variant] is introduced from one species into a second and is advantageous," says Hopi Hoekstra, an evolutionary biologist at Harvard University. "This is really an exceptional finding.""