Tiny bone fragment helps scientists learn when dogs came to the Americas

Dogs and humans have lived side-by-side since the distant past. Scientists have wondered how far back the history of dogs spans in the Americas and what route dogs use to enter this part of the world. Researchers from the University at Buffalo have used a small bone fragment from a dog found in Southeast Alaska that lived in the region about 10,150 years ago to answer some of these questions.The bone fragment is a piece of the femur and represents the oldest confirmed remains of a domestic dog in the Americas. Researchers say that DNA inside the bone has clues about early canine history on this continent. The researchers analyzed the mitochondrial genome from the bone. They found the animal belongs to a line of dogs with an evolutionary history that diverged from that of Siberian dogs as early as 16,700 years ago.

The timing of that evolutionary divergence also matches up with the period when humans may have been migrating into North America along a coastal route that included Southeast Alaska. One researcher on the project says that since the team has genetic evidence from an ancient dog discovered along the Alaska coast. Since dogs are proxy for human occupation, the data provides timing and location for the entry of dogs and people into the Americas.

Evidence discovered by the team supports the theory that migration of people and dogs occurred just as coastal glaciers retreated during the last Ice Age. Before this study, the earliest ancient American dog bones that had DNA sequenced were discovered in the Midwest of the United States.

The bone fragment that was the center of the study was discovered among a collection of hundreds of bones excavated years before by scientists from other universities. Originally, the fragment was believed to have come from a bear, but researchers realized it was from a dog when the DNA was studied. The southeast Alaskan dog shared a common ancestor about 16,000 years ago with American canines that lived before the arrival of European colonizers.