A comparison of the genomes of polar bears and brown bears reveals that the polar bear is a much younger species than previously¹ believed, having diverged² from brown bears less than 500,000 years ago. The analysis also uncovered several genes³ that may be involved in the polar bears' extreme adaptations to life in the high Arctic. The species lives much of its life on sea ice, where it subsists⁴ on（靠……生存） a blubber-rich diet of primarily marine⁵ mammals.

 

The genes pinpointed⁶ by the study are related to fatty acid metabolism⁷ and cardiovascular function, and may explain the bear's ability to cope with a high-fat diet while avoiding fatty plaques⁸ in their arteries⁹ and the cardiovascular diseases that afflict¹⁰ humans with diets rich in fat. These genes may provide insight into how to protect humans from the ill effects of a high-fat diet.

 

The study was a collaboration¹¹ between Danish researchers, led by Eske Willerslev and including Rune Dietz, Christian¹² Sonne and Erik W. Born, who provided polar bear blood and tissue samples; and researchers at BGI in China, including Shiping Liu, Guojie Zhang and Jun Wang, who sequenced the genomes and analyzed¹³ the data together with a team of UC Berkeley researchers, including Eline Lorenzen, Matteo Fumagalli and Rasmus Nielsen. Nielsen is a UC Berkeley professor of integrative biology and of statistics.

 

"For polar bears, profound obesity¹⁴ is a benign¹⁵ state," said Lorenzen, one of the lead authors and a UC Berkeley postdoctoral fellow. "We wanted to understand how they are able to cope with that."

 

"The promise of comparative genomics is that we learn how other organisms deal with conditions that we also are exposed to," said Nielsen, a member of UC Berkeley's Center for Theoretical Evolutionary¹⁶ Genomics. "For example, polar bears have adapted genetically¹⁷ to a high fat diet that many people now impose on themselves. If we learn a bit about the genes that allows them to deal with that, perhaps that will give us tools to modulate¹⁸ human physiology¹⁹ down the line."

 

The findings accompany the publication of the first assembled genome of the polar bear as the cover story in the May 8 issue of the journal Cell.

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