Ed Yong in The Atlantic:
Between 14,000 and 18,000 years ago, the ancestors of today’s Native Americans first entered the land where they now live. They came from Asia, walking east across a broad land bridge that connected the two continents, snaking south past a stretch of retreating glaciers, and eventually spreading across a new land. A few millennia later, dogs followed them.
The origin of those indigenous American dogs is unclear—as is their fate. Some say they were wiped out after European colonizers arrived in the 15th century, bringing their own dogs with them. Others believe their genes still exist in modern-day Chihuahuas and Xolos.
A team of researchers, led by Laurent Frantz, Greger Larson, and Elizabeth Murchison, has now settled the debate. By analyzing DNA from 71 archeological dog remains and comparing them to the genomes of modern breeds, the team showed that the indigenous dogs all but died out. There are tiny traces of their DNA in modern dogs, but that genetic legacy is so faint that it might not be real.
More here.