Reconstruction of the mid-Pliocene Protarctos abstrusus in the Beaver Pond site area during the late summer. Credit: Art by Mauricio Antón.

Two 3.5-million-year-old bears had a sweet tooth for berries. Paleontologists have discovered ancient teeth with cavities that serve as evidence.

“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, lead author of the study and Head of Vertebrate Paleontology at the Natural History Museum of Los Angeles County (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 sugary 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.”

A rare glimpse into High Arctic life

The international team of researchers excavated the ancient bear fossils belonging to Protarctos abstrusus at the Beaver Pond site on Ellesmere Island, Canada. This site is one of the few where fossils have been found in the Arctic, especially mammal fossils.

Unlike other sites down south where scientists can chisel fossils out of rock, at Beaver Pond you have to pick your way through layers of peat. The bones are usually fragmented from all the repeated cycles of freezing and thawing, and appear brown or iridescent blue in color due to the presence of a mineral called vivianite.

The first pieces of a bears skulls’ were found in the 1990s. During excavations over the last 14 years, paleontologists have recovered more fragments of the skull, a jaw, and other skeleton fragments. When the researchers pieced together the fragments, they found the pieces belonged to two bears. One was five to seven years old and the other was older. Both didn’t seem to brush their teeth, judging from the cavities.

“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 co-author Dr. Natalia Rybczynski, 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.”

Digital reconstruction of the Canadian Arctic fossil bear, Protarctos abstrusus. Credit: Xiaoming Wang.

 

Along with the fossils, scientists have found remains of raspberry, blueberry, lingonberry and crowberry plants. Their sweet berries likely helped the ancient bears hibernate through the polar winter, just like their modern cousins.

While Canada’s High Arctic doesn’t look all that hospitable nowadays, three and a half million years ago Beaver Pond was home to a boreal forest. It provided a home to a variety of animals like beavers, deer, and three-toed horses, to name a few.

A view of the Beaver Pond fossil site, with a number of the animals and plants based on fossils recovered from the site. Credit: George “Rinaldinho” Teichmann.

In addition to being able to discern what some ancient bears had for breakfast — which is fascinating in its own right — scientists say the fossils also provide a missing link between primitive and modern bears. The findings suggest that bears were stuffing up on a high-sugar diet to hibernate very early in their evolutionary history. About 44 percent of modern black bears have cavities, which are very rare in other animals.

Protarctos abstrusus — a species first discovered in Idaho in 1970 — was able to reach up to 100 kilograms, making it a bit smaller than modern black bears. The two species are related but Protarctos abstrusus is not the direct ancestor of the black bear, which crossed into North America from Asia much later, during the last ice age.

Scientific reference: Xiaoming Wang et al, A basal ursine bear (Protarctos abstrusus) from the Pliocene High Arctic reveals Eurasian affinities and a diet rich in fermentable sugars, Scientific Reports (2017). DOI: 10.1038/s41598-017-17657-8.

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