A professor of animal genetics at the University of Alaska Fairbanks School of Natural Resources and Extension has estimated when and how brown, black and polar bears diverged — and that data offers some hope for polar bears’ survival as the earth’s climate warms.
At one point, all three bears were the same species. Matthew Cronin, at UAF, and colleagues at the University of California Davis and Delta G Co., used genetic data to estimate that 2.3 million years ago, black bears diverged from the polar bear/brown bear population. About 1.2 million years ago, polar bears and brown bears diverged from each other.
This means polar bears have been a distinct species through previous periods of global warming, Cronin said.
Other studies, including some he’s been involved in, he said, have found similar results as to brown, black, and polar bears’ divergence. The timing of the divergence is what various studies estimate differently.
One other study placed polar bears as a unique species for 4 to 5 million years. A German study estimated it at around 600,000 years, he said.
“There are too many unknowns to be an exact date,” Cronin said. “The ‘molecular clock’ is not a very accurate clock … However, studies … suggest polar bears are a fairly old lineage.”
The oldest polar bear fossil, he said, is around 120,000 years old.
Cronin said he’d like to work with geologists who study glacial maximums and warming periods to determine how past glacial warming periods might compare to the current one and its effect on the bears.
“It seems logical that if polar bears survived previous warm, ice-free periods, they could survive another. This is of course speculation, but so is predicting they will not survive, as the proponents of the endangered species act listing of polar bears have done,” he said in a press release from UAF.
Cronin has written against some aspects of the Endangered Species Act. A 2006 article in Range Magazine called “An Act of Deception” questions why subspecies and animals whose endangerment is location-specific are listed. Range Magazine focuses on “the cowboy spirit on America’s Outback.”
“I do DNA stuff,” he said. “It’s a simple observation (that polar bears have been around for previous periods of warming.) What does this mean for your predictions? I’m trying to be dispassionate. It’s a simple question to which I’d like an answer.”
Cronin’s team and another research team simultaneously, and unbeknownst to each other, mapped out the bears’ genomes, finding about 2.5 billion base pairs, he said.
Cronin’s current research, which he said is close to completion, looks at how Southeast Alaskan wolves differ from dogs, coyotes, and other populations of wolves.