Scientists said Wednesday they had discovered the oldest remains of a domestic dog in the Americas dating back more than 10,000 years, suggesting the animals accompanied the first waves of human settlers.
Humans are thought to have migrated to North America from Siberia over what is today the Bering Strait at the end of the last Ice Age -- between 30,000 and 11,000 years ago.
The history of dogs has been intertwined with man since ancient times, and studying canine DNA can provide a good timeline for human settlement.
A new study led by the University at Buffalo analysed the mitochondrial DNA of a bone fragment found in Southeast Alaska.
The team initially thought the fragment belonged to a bear.
But closer examination revealed it to be part of a femur of a dog that lived in the region around 10,150 years ago, and that shared a genetic lineage with American dogs that lived before the arrival of European breeds.
"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," said Charlotte Lindqvist, an evolutionary biologist from the University at Buffalo and the University of South Dakota.
She said the findings, published in the journal Proceedings of the Royal Society B, supports the theory that humans arrived in North America from Siberia.
"Southeast Alaska might have served as an ice-free stopping point of sorts, and now -- with our dog -- we think that early human migration through the region might be much more important than some previously suspected," said Lindqvist.
A carbon isotope analysis of the bone fragment showed that the ancient Southeast Alaskan dog likely had a marine diet that consisted of fish and seal and whale scraps.
Lindqvist said dogs did not arrive in North America all at once. Some arrived later from East Asia with the Thule people, while Siberian huskies were imported to Alaska during the Gold Rush in the 19th century.
There is a long-standing contention about whether the first humans entered North America through a continental corridor that formed as the ice sheets receded or along with the North Pacific coast thousands of years earlier.
Previous age estimates of dog remains were younger than the fragment found by Lindqvist and the team, suggesting that dogs arrived in the continent during the later, continental migrations.
Lindqvist said her findings supported the theory that dogs in fact arrived in North America among the first waves of humans settlers.
"We also have evidence that the coastal edge of the ice sheet started melting at least around 17,000 years ago, whereas the inland corridor was not viable until around 13,000 years ago," she told AFP.
"And genetic evidence that a coastal route for the first Americans over 16,000 years ago seems most likely. Our study supports that our coastal dog is a descendant of dogs that participated in this initial migration."