In a new study published Tuesday in the journal Proceedings of the Royal Society B, researchers at the University of Buffalo and the University of South Dakota discuss how a serendipitous finding offered another piece to the puzzle in the complex history of humans’ relationships with canines.
The finding in question occurred when a team of scientists, led by lead author Charlotte Lindqvist, an associate professor of biological sciences in the UB College of Arts and Sciences, were studying a collection of fossils excavated in southeast Alaska. These fossils were obtained by a team of researchers, including Timothy Heaton, professor of earth sciences at the University of South Dakota.
While performing DNA sequencing on the b.on.es, the scientists noticed a suspicious f.e.m.ur fragment that at first appeared to be from a bear. It was later discovered to have belonged to an ancient dog, which analysis confirmed would have lived there approximately 10,150 years ago.
Researchers analyzed the dog’s mitochondrial genome, and concluded 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.
“We now have genetic evidence from an ancient dog found along the Alaskan coast. 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. Our study supports the theory that this migration occurred just as coastal glaciers retreated during the last Ice Age,” says Lindqvist, PhD, associate professor of biological sciences in the UB College of Arts and Sciences. “There have been multiple waves of dogs migrating into the Americas, but one question has been, when did the first dogs arrive? And did they follow an interior ice-free corridor between the massive ice sheets that covered the North American continent, or was their first migration along the coast?”
After this surprise discovery, the scientists compared the b.on.e’s mitochondrial genome to those of other ancient and modern dogs. This analysis showed that the Southeast Alaskan dog shared a common ancestor about 16,000 years ago with American canines that lived before the arrival of European colonizers, Lindqvist says. (Mitochondrial DNA, inherited from the mother, represents a small fraction of an organism’s complete DNA, so sequencing a complete nuclear genome could provide further details if that material can be extracted.)
Of interest, carbon isotope analysis on the b.on.e fragment indicates that the ancient Southeast Alaskan dog likely had a marine diet, which may have consisted of foods such as fish and scraps from seals and whales.
The research adds depth to the layered history of how dogs came to populate the Americas. As Lindqvist notes, canines did not arrive all at once. For example, some Arctic dogs arrived later from East Asia with the Thule culture, while Siberian huskies were imported to Alaska during the Gold Rush.
The new study sharpens the debate on dog and human migration into the Americas.
Fossil records show that once the Europeans arrived with their domesticated dogs, existing dogs in the Americas started d.y.ing in large numbers. Scientists hypothesize that colonists may have k.i.l.led them to avoid mixing b.lo.o.dlines with their dogs bred specially for h.u.nting and herding, or perhaps resorted to hunting them for food when resources were scarce. Though the most likely explanation is d.i.s.e.a.s.e.s introduced by the c.o.lo.ni.zers’ arrival.