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Updated: March 2, 2010 18:47 IST

Climate change in past helped evolution of polar bear: Study

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The common ancestors of truly modern polar bears lived about 45,000 years ago, surviving population bottlenecks resulting from changing climate patterns. Photo: AP
The common ancestors of truly modern polar bears lived about 45,000 years ago, surviving population bottlenecks resulting from changing climate patterns. Photo: AP

Global warming may be threatening the survival of polar bears, but similar climactic changes in the past have played an important role in the evolution of the species, a new study has claimed.

Researchers at the State University of New York at Buffalo, who have sequenced the mitochondrial genome of an ancient polar bear’s jawbone, said that similar climactic sifts have played an important part in bringing the species into existence.

The 110,000 to 130,000 years old jawbone revealed that the species likely split from brown bears just 150,000 years ago, at a time when specialising in arctic living quickly became an advantage rather than a liability, they said.

Judging from comparisons of modern bear genetics, it is estimated that the common ancestors of truly modern polar bears lived about 45,000 years ago, surviving what may have been a population bottleneck resulting from changing climate patterns, journal Proceedings of the National Academy of Sciences said.

“From isotope analysis, we were able to get a good idea of its feeding ecology, and it fits very well at the top of the feeding chain of marine mammals like polar bears today,” lead author Charlotte Lindqvist said.

And even without the genetic revelations, the jawbone itself gives a few hints about the individual. “We can say it was probably a male adult polar bear of a size which can be found in modern polar bears and had a feeding ecology similar to today,” Ms. Lindqvist says.

“Just finding such an ancient fossil was pretty magnificent. Previous estimates of polar bear evolution had placed the split any where from 70,000 years ago to more than one million years ago,” the researcher was quoted as saying by the Scientific American.

The team sees the nuclear genome as their next step in tracking down polar bears’ past and possibly their future as a mitochondrial genome does not give away physiological secrets like the more complete nuclear genome.

A nuclear genome would give the researchers more crucial information about the polar bear’s physical characteristics, elucidating how the owner of the ancient jawbone was evolving to rule over its harsh landscape.

For example, Ms. Lindqvist says, “If we’re able to retrieve more of the nuclear genome, we’ll be able to get hold of at least some genes that are known to be in charge of coat colours in other mammals.”

The polar bear’s short history has already revealed itself to be one of nimble evolutionary moves. And the new findings present “another example of how rapidly-in evolutionary terms-species can evolve,” she added.

“This is just yet another very astonishing example that such a specialised species can evolve fairly rapidly to probably fill an opening of habitat - a new niche — in response to climate change.”

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