Polar bears are no new kids on the block

LONDON Thu Apr 19, 2012 2:29pm EDT

1 of 3. A large male polar bear feeds on the fin of a whale carcass in Holmiabukta Bay, northwestern Svalbard, in this undated handout photo.

Credit: Reuters/Florian Schulz/Handout

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LONDON (Reuters) - Polar bears evolved as a separate species far earlier than previously thought, according to a new genetic study, which adds to worries about their ability to adapt in a rapidly warming world.

Research published on Thursday found the Arctic's top predators split off from brown bears, their closest relatives, around 600,000 years ago - five times earlier than scientists had generally assumed.

The finding suggests polar bears took a long time to adapt to their icy world and may therefore struggle to adjust as the Arctic gets warmer and the sea ice melts, depriving them of vital hunting platforms.

Despite being a very different species in terms of body size, skin and coat color, fur type, tooth structure, and behavior, previous research had indicated that polar and brown bears diverged only recently in evolutionary terms.

That assumption was based on studying mitochondrial lineage - a small part of the genome, or DNA, that is passed exclusively from mothers to offspring.

But after studying a lot more DNA from inside the cell nucleus, using samples from 19 polar and 18 brown bears, Frank Hailer of Germany's Biodiversity and Climate Research Centre and colleagues reached a very different conclusion.

They found both polar and brown bears were much older, as species, according to a paper published in the journal Science on Thursday.

"Previous studies suggested that polar bears would have had to be evolving very rapidly, since they were so young," Hailer said in a telephone interview.

"Our study provides a lot more time for polar bears to adapt ... It makes more sense from an evolutionary standpoint that polar bears would be older."

His team's calculations put the moment when the two types of bears diverged in the Pleistocene period, when the climate record shows that global temperatures reached a long-term low.

That could be coincidental but it suggests that the planet's cooling may have triggered the split.

While the latest research implies that past polar bear adaptation was probably a slow process, it also means the animals have been through warming phases before.

"If they go extinct in this phase of warming, we're going to have to ask ourselves what our role in that process was," Hailer said.

"In previous warm phases between the ice ages polar bears were able to survive. The main difference this time is that humans are impacting polar bears as well."

Genetic studies are an important tool in researching the evolutionary history of polar bears, since the animals typically live and die on sea ice. As a result, their bodies sink to the sea floor, where they get ground up by glaciers or remain undiscovered, making fossils scarce.

(Editing by Maria Golovnina)

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Comments (12)
PseudoTurtle wrote:
As happens with most species, when a new habitat opens up they tend to expand into it, which sounds like what the polar bear did. For the most part this adaptation to their arctic environment has apparently been successful.

Unfortunately, there are no guarantees in the life of a species. Some specializations work out well, while others lead to a dead end.

The truth of the matter is that the earth is presently recovering from a massive ice age — which means what we are witnessing today is the earth still in an extremely abnormal period of cold temperatures (put simply, the earth should NOT have polar ice caps, nor glaciers) — and it was due primarily to changes in ocean currents due to the breakup of the supercontinent, Pangea, many million of years ago.

The breakup of Pangea into roughly the present continental configurations has been slowly forcing the earth’s temperature downwards below its long-term average for millions of years.

The final event that sealed the fate of the earth in terms of this particular ice age was the movement of South America northwards. When it collided with the North American continent, the Isthmus of Panama was formed. This cut off most of the normal ocean current (i.e. heat circulation and distribution) from working to keep the planet much warmer.

To add insult to injury, the northward movement of South America also opened up the Drake Passage (the narrow passage of water between South America and Antarctica). What this did was to allow a circumpolar flow of frigid conditions to begin around Antarctica, thus creating the ice sheets we see today. (Antarctica, for most of its history has had a climate much milder, and even dinosaur remains have been found there from its pre-ice age history.)

The “inconvenient truth” is that the polar bear (and penguins) made adaptive choices long before man was even a “sentient” being.

Man CANNOT protect either species, as long as the earth continues on this NORMAL recovery from an ice age.

In fact, Man CANNOT stop what is happening, since this is a NORMAL process of the earth moving its average global temperatures back to more normal conditions — which are MUCH warmer than today.

Man will be lucky to survive this natural event at all, if he does not adapt.

THAT is the real truth about what is happening all over the world in terms of melting glaciers, receding ice caps, and the Arctic Ocean opening up.

ANYONE who says otherwise — to put it very politely — either doesn’t understand the science involved, or is not telling the truth to force people to change their lifestyles by frightening them about global warming. Climate “scientists” are well-aware of continental drift, but choose to ignore it since it would provide evidence to refute their global warming theories.

In effect, it is a totally moot point as to whether man is adding to the effects of global warming or not — notice I did not say, causing it, because that would be a lie — because we do not have the technology to reverse an ice age.

Since the rate of change seems to be accelerating, if we don’t adapt our species to survive in the new ice-free environment, we will die off just like all other species who couldn’t adapt to their environment have done.

THAT is the lesson we should be learning from this, but we are being seriously misled by people who are disingenuous about their motives.

Apr 19, 2012 4:48pm EDT  --  Report as abuse
PseudoTurtle wrote:
I would like to address this one particular comment in the article:

——————————————————————————-

“If they go extinct in this phase of warming, we’re going to have to ask ourselves what our role in that process was,” Hailer said.

“In previous warm phases between the ice ages polar bears were able to survive. The main difference this time is that humans are impacting polar bears as well.”

———————————————————————————–

What Mr. Hailer forgot to mention is that one of the reasons polar bears are endangered is because we are still shooting them for sport.

If we wanted to do something to help them survive, how about forcing humans to stop killing them?

Apr 19, 2012 5:02pm EDT  --  Report as abuse
tmc wrote:
Thank you @psudoTurtle for your excellent commentary. I’m no scientist, but I am a history buff and I never believed this man made global warming stuff.
But as for polar bears, I very much like being the top of the food chain. As an old comedian once said, species come and species go. It’s our turn.

Apr 19, 2012 8:08pm EDT  --  Report as abuse
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