STOCKHOLM, SWEDEN—Mitochondrial DNA samples taken from living Asian, American, and European dogs, and from dog bones found at American archaeological sites, show that many American dog breeds, including Chihuahuas, Peruvian hairless dogs, and Arctic sled dogs, originated with dogs from East Asia and Siberia. Their canine ancestors probably crossed the land bridge linking East Asia and North America with the ancestors of Native Americans. “Our results confirm that American dogs are a remaining part of the indigenous American culture, which underscores the importance of preserving these populations,” said Peter Savolainen of the KTH Royal Institute of Technology.