How Did Dogs Get to North America?

The history of dogs and humans has been intertwined since ancient times. But how far back does that history go in the Americas, and which route did dogs, together with their humans, use to enter this part of the world?

Researchers are closer than ever to answering those questions thanks to a new study led by the University at Buffalo. The study reports that an ancient bone fragment excavated in Southeast Alaska belonged to a dog that lived in the region about 10,150 years ago, making it the oldest confirmed remains of a domestic dog in the Americas.

DNA evidence gathered by the researchers indicates that the animal belonged to a lineage of dogs whose evolutionary history diverged from that of Siberian dogs as early as 16,700 years ago. The timing of that split coincides with a period when humans may have been migrating into North America along a coastal route that included Southeast Alaska.

“Because dogs are a proxy for human occupation, our data help provide not only a timing but also a location for the entry of dogs and people into the Americas,” says Charlotte Lindqvist, an evolutionary biologist at UB and the project’s lead researcher. The discovery lends credence to the coastal corridor theory of migration, with Southeast Alaska possibly serving as a sort of ice-free waypoint along the journey.

The bone fragment, smaller than a dime, was originally thought to have come from a bear, but when the DNA was studied, the team realized it was actually from a dog.

After this surprise discovery, the scientists compared the bone’s mitochondrial genome to those of other ancient and modern dogs, finding that the Southeast Alaskan dog shared a common ancestor with canines that lived in the Americas before the arrival of Europeans. Mitochondrial DNA represents only a small fraction of an organism’s complete DNA; if a complete nuclear genome could be extracted, it might provide more clues.

“This all started out with our interest in how Ice Age climatic changes impacted animals’ survival and movements in this region,” Lindqvist explains. “And now, with our dog, we think that early human migration through the region might be much more important than some previously suspected.”