How did dogs get into the Americas? An ancient bone fragment contains clues

The history of dogs has been intertwined since ancient times with that of people who tamed them.

But how far back does history in the Americas go, and what path did dogs take to enter this part of the world?

A new study led by the University of Buffalo provides insight into these questions. The research reports that a bone fragment found in southeast Alaska belongs to a dog that lived in the region about 10,150 years ago. Scientists say that the remains – a piece of a femur – represent the oldest confirmed remains of a domestic dog in America.

DNA from the bone fragment contains clues about the early history of dogs in this part of the world.

Researchers analyzed the mitochondrial genome of the dog and concluded that the animal belongs to a genus of dogs whose evolutionary history differs from that of Siberian dogs as early as 16,700 years ago. The timing of this rift coincides with a period in which people may have migrated to North America along a coastal route that includes southeast Alaska.

The research will take place on 24 February in the Proceedings of the Royal Society B. Charlotte Lindqvist, an evolutionary biologist from the UB, was senior author of the study, which included scientists from the UB and the University of South Dakota. The findings contribute to a growing body of knowledge about the migration of dogs to the Americas.

“We now have genetic evidence of an ancient dog found off the Alaska coast. Because dogs are a proxy for human occupation, our data provides not only a timing, but also a place for dogs to enter. and our people in the Americas. Our study supports the theory that this migration occurred just when coastal glaciers retreated during the last ice age, “says Lindqvist, Ph.D., associate professor of biological sciences at the UB College of Arts and Sciences. “There have been several waves of dogs migrating to America, but one question was when did the first dogs arrive? And did they follow an ice-free passage between the massive ice sheets that covered the North American continent, or was their first trek? along the coast? ‘

“The fossil record of ancient dogs in the Americas is incomplete, so new remains found provide important clues,” said Flavio Augusto da Silva Coelho, a doctor at UB. student in biological sciences, and one of the first authors of the paper. “Before our study, the earliest ancient American dog bones with their DNA sequence were found in the American west.”

A surprising finding from a large collection of bones

Lindqvist’s team did not want to study dogs. The scientists came across the femur fragment as they sequenced DNA from a collection of hundreds of bones excavated years ago in southeastern Alaska by researchers, including Timothy Heaton, Ph.D., professor of earth sciences at the University of South Dakota.

“It all started with our interest in how climate change during the ice age affected the survival and movements of animals in this region,” says Lindqvist. “Southeast Alaska may have served as a sort of ice-free stop, and now – with our dog – we think early human migration through the region may be far more important than previously thought.”

The bone fragment, which was originally from a bear, was quite small, but when the DNA was studied, the team realized it was from a dog, Lindqvist says.

After this surprising discovery, the scientists compared the mitochondrial genome of the bone with that of other ancient and modern dogs. This analysis showed that the Southeast Alaska dog shared a common ancestor about 16,000 years ago with American dogs that lived before the arrival of European colonizers, Lindqvist says. (Mitochondrial DNA, inherited from the mother, represents a small fraction of the complete DNA of an organism, so that the sequence of a complete nuclear genome can provide further details if it can extract material.)

Importantly, carbon isotope analysis on the bone fragment suggests that the ancient Southeast Alaska dog probably had a marine diet, which may have consisted of foods such as fish and pieces of seals and whales.

The research adds depth to the low history of how dogs came to populate the Americas. As Lindqvist notes, dogs did not arrive at the same time. For example, some Arctic dogs later arrived with the Thule culture from East Asia, while Siberian huskies were imported to Alaska during the Gold Rush. Other dogs were brought to America by European colonizers.

The new study intensifies the debate over the migration of dogs and humans to the Americas.

“Our early dog ​​from southeast Alaska supports the hypothesis that the first migration of dogs and humans occurred along the Northwest Pacific Coast Route instead of the central continental corridor, which presumably only became viable about 13,000 years ago,” says Coelho.