With Arctic ice predicted to shrink to another record low this summer, the threat to the polar bear population is increasing, scientists say.

But at least one expert believes evolution — or in this case, devolution — could provide the means for their survival.

Christian Sonne, a scientist with the Danish National Environmental Research Institute, says the reduction in sea ice habitat will have a major effect on polar bears' feeding habits, and he believes the population will drop over time.

But the environmental change that is reducing their hunting grounds doesn't necessarily mean the bears are headed for extinction, Sonne said.

Polar bears are believed to have evolved from brown bears, including grizzlies, that were trapped by glaciers in the mid-Pleistocene age, between 100,000 to 250,000 years ago, fossil records and DNA samples suggest.

The bears "may just need a few generations to … go more on the terrestrial environment," Sonne said.

Scott Schliebe, a scientist with the U.S. Fish and Wildlife Service in Anchorage, Alaska, disagrees.

"That terrestrial habitat is already occupied by another bear species, and the food supply that's on land would not be adequate to compensate for the loss of ring seals [one of polar bears' major food sources]," Schliebe said.

Polar bears are larger animals than grizzlies, Schliebe said, and the changes in their environment are happening too fast for them to successfully return to their brown bear roots.

The first case in the wild of a polar-grizzly offspring was documented two years ago on Banks Island, the westernmost island in the Canadian Arctic archipelago. However, scientists say it's just one case, and it's too soon to say what that might mean.