https://www.scientificamerican.com/article/ancient-dog-dna-reveals-close-relationship-with-contagious-cancer/

By analyzing dog DNA from archaeological remains, researchers last week pinned down the evolutionary history of domesticated dogs in North America. Dogs are thought to have first populated the Americas alongside humans via the Bering Land Bridge more than 10,000 years ago. These early arrivals disappeared following the introduction of European breeds, leaving little genetic trace among modern dogs, according to the new study. But the researchers found a relative of America’s original dogs that persists in a bizarre form: a sexually transmitted cancer descended from the tumor of single dog that lived thousands of years ago.

Dogs played a key role in ancient Native American societies, according to Laurent Frantz, a geneticist at Queen Mary University of London and a co-author of the study. “These cultures didn’t have access to any other domestic animals, so dogs were really important,” says Frantz, who notes dogs may have aided in transportation and hunting. Both the origin and fate of these ancient American dogs have been hotly debated. So his team set out to establish where these dogs came from and what happened to them following the arrival of European breeds.