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（靠存活） 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 bears 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 Berkeleys 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 as百度竞价推广bled genome of the polar bear as the cover story in the May 8 issue of the journal Cell.
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1 previously adv.以前，先前（地） 参考例句： The bicycle tyre blew out at a previously damaged point.自行汽车轮胎在以前损毁过的地方又爆开了。 Let me digress for a moment and explain what had happened previously.让我岔开一会儿，讲解原先出了什么事。
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