Fossilized Cavities Reveal Ancient Bear’s Sweet Tooth

Dentistry Today
Art by Mauricio Antón based on research of this paper and with input on plant community from Alice Telka.


Art by Mauricio Antón based on research of this paper and with input on plant community from Alice Telka.

Researchers from the Canadian Museum of Nature and the Natural History Museum of Los Angeles County (NHMLA) have identified the remains of a 3.5-million-year-old bear from a fossil-rich site in Canada’s High Arctic. Their study shows that the animal is a close relative of the ancestor of modern bears, tracing its ancestry to extinct bears of similar age from East Asia, and that it had a sweet tooth as determined by cavities in its teeth.

The researchers identified the bear as Protarctos abstrusus, which was previously only known from a tooth found in Idaho. Showing its transitional nature, the animal was slightly smaller than a modern black bear, with a flatter head and a combination of primitive and advanced dental characters. The researchers studied recovered bones from the skull, jaws, and teeth, as well as parts of the skeleton from two individuals.

“This is evidence of the most northerly record for primitive bears and provides an idea of what the modern ancestor of modern bears may have looked like,” said Xiaoming Wang, PhD, lead author of the study and head of vertebrate paleontology at NHMLA.

“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 diet, presumably from berries. This is the first and earliest documented occurrence of high-calorie diet in basal bears, likely related to fat storage in preparation for the harsh arctic winters,” said Wang.

The bones were discovered over a 20-year period by Canadian Museum of Nature scientists at a fossil locality on Ellesmere Island known as the Beaver Pond site. The peat deposits include fossilized plants indicative of a boreal-wetland forest and have yielded other fossils, including fish, beaver, small carnivores, deerlets, and a three-toed horse. The findings show that the Ellesmere Protarctos lived in a northern boreal-type forest habitat with 24-hour darkness in winter and six months of ice and snow.

“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,” said co-author Natalia Rybczynski, PhD, a research associate and paleontologist with the Canadian Museum of Nature.

“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,” said Rybczynski.

Wang analyzed characteristics of fossil bear remains from around the world to identify the Ellesmere remains as Protarctos and to establish its revolutionary lineage in relation to other bears. Modern bears are wide-ranging, found from equatorial to polar regions. Their ancestors, mainly found in Eurasia, date to about 5 million years ago.

Fossil records of ursine bears (all living bears plus their ancestors, except the giant panda, which is an early offshoot) are poor, and their early evolution is controversial. The new fossil represents one of the early immigrations from Asia to North America, but it is probably not a direct ancestor to the modern American black bear.

Also, the teeth of both Protarctos individuals show signs of well-developed dental cavities, which were identified following CT scans by Stuart White, DDS, PhD, a retired professor with the University of California Los Angeles School of Dentistry. The cavities underline that these ancient bears consumed large amounts of sugary foods such as berries. Berry plants also are found preserved in the same Ellesmere deposits as the bear remains.  

“We know that modern bears consume sugary fruits in the fall to promote fat accumulation that allows for winter survival via hibernation. The dental cavities in Protarctos suggest that consumption of sugar-rich foods like berries, in preparation for winter hibernation, developed early in the evolution of bears as a survival strategy,” said Rybczynski.

The study, “A basal ursine bear (Protarctos abstrusus) from the Pliocene High Arctic reveals Eurasian affinities and a diet rich in fermentable sugars,” was published by Scientific Reports.

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