Researchers from the US and Canada have identified remains of a 3.5-million-year-old bear from a fossil-rich site on Ellesmere Island in Canada's High Arctic. The mammal had well-developed cavities, according to an article in the journal Scientific Reports.

"This is evidence of the most northerly record for primitive bears, and provides an idea of what the ancestor of modern bears may have looked like," says Dr. Xiaoming Wang of the Natural History Museum of Los Angeles County. "Just as interesting is the presence of dental caries, showing that oral infections have a long evolutionary history in the animals, which can tell us about their sugary diet."

Wang and his colleagues found further evidence that cavities have existed for many millions of years, studying the deposits of the Pliocene ‒ the last warm epoch in the geological history of the Earth ‒ formed on the Canadian Arctic's Ellesmere Island.

At that time, the climate of the Arctic was much milder than today: as scientists suggest, the Arctic was not yet covered with ice, but resembled a Siberian tundra or taiga free from snow in the summer and spring. Canadian scientists have been studying the flora and fauna of that time for two decades, excavating at the site of a dried swamp that existed on Ellesmere Island about 3.5 million years ago.

"It is a significant find, in part because all other ancient fossil ursine bears, and even some modern bear species like the sloth bear and sun bear, are associated with lower-latitude, milder habitats," says Natalia Rybczynski of the Canadian Museum of Nature in Ottawa. "So, the Ellesmere bear is important because it suggests that the capacity to exploit the harshest, most northern forests on the planet is not an innovation of modern grizzlies and black bears, but may have characterized the ursine lineage from its beginning."

The difficulties of adapting to the Arctic, according to the paleontologist, had the greatest impact on the teeth of this bear, named Protarctos abstrusus. As X-ray images of his jaws showed, his teeth had a lot of cavities. Scientists attribute this to the typical diet of modern and ancient bears.