Polar bears evolved recently and adapted quickly, reveals ancient DNA

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Washington, March 2 (ANI): New research indicates that a rare, ancient polar bear fossil discovered in Norway in 2004 has revealed that polar bears evolved recently and adapted quickly.

The research, by researchers at Penn State University, the University at Buffalo, the University of Oslo, and other institutions is filling in key pieces of the evolutionary history of polar bears and brown bears, including their response to past climate changes.

"Our results confirm that the polar bear is an evolutionarily young species that split off from brown bears some 150,000 years ago and evolved extremely rapidly during the late Pleistocene, perhaps adapting to the opening of new habitats and food sources in response to climate changes just before the last interglacial period," said Charlotte Lindqvist, research assistant professor in the UB Department of Biological Sciences.

In 2004, an Icelandic geologist found a rare, well-preserved, 110,000-to-130,000-year-old, fossil jawbone and canine tooth in the Svalbard archipelago of Norway.

Lindqvist, who was working at Oslo's Natural History Museum as a postdoctoral researcher, extracted DNA from the sample after drilling into the bone and tooth to obtain the powder to analyze.

When she arrived at UB in 2008, she obtained tissue samples from modern polar bears and brown bears and began analyzing them at UB's New York State Center of Excellence in Bioinformatics and Life Sciences after starting the collaboration with Schuster at Penn State.

This work resulted in the sequencing of the complete mitochondrial genome of the fossil.

The scientists then used that information to develop mitochondrial sequencing of the other bears and to construct phylogenies showing that the ancient polar bear evolved within the lineage of brown bears.

"Since the brown bears from Alaska's Admiralty, Baranof, and Chichagof Islands are the polar bears' closest relatives, it was crucial to include them in our study in order to more precisely date when polar bears appeared as a distinct species," Lindqvist explained.

"The fact that our ancient polar bear lies almost directly at the splitting point between this unique group of brown bears and polar bears, that is, close to their most recent common ancestor of the two species, was very intriguing. It provided an ideal opportunity to ultimately settle the time of polar bear origin," she added.

"This is, by far, the oldest mammal mitochondrial genome to be sequenced," said Stephan C. Schuster from Penn State's Center for Comparative Genomics and Bioinformatics.

Lindqvist and Schuster are seriously considering working on sequencing the nuclear genome of the ancient polar bear, work that they expect will reveal even more about polar bear evolution. (ANI)

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