60-Second Science

Polar Bear Rapid Evolution Lets Them Be Fat Fit

Since diverging from a common ancestor with brown bears less than half a million years ago, polar bears have accumulated genetic changes that allow them to eat a superhigh-fat diet without suffering cardiovascular consequences. Karen Hopkin reports


A triple bacon cheeseburger seems like a heart attack on a plate. So how can polar bears thrive on their version, seal blubber? Turns out they’ve stocked up on genes that let them clear fats from their blood. That’s according to a study in the journal Cell. [Shiping Liu et al, Population Genomics Reveal Recent Speciation and Rapid Evolutionary Adaptation in Polar Bears]

Polar bears are well adapted to life on the sea ice. Up to half their body weight’s fat, which gives them extra insulation and buoyancy, and provides them with a ready source of energy.
But how can an animal so fat also be so fit? Researchers compared the genomes of polar bears with those of brown bears, and found that polar bears have accumulated genetic changes that boost their heart health and fat metabolism. One gene in particular, called ApoB, helps move cholesterol out of the blood—where it causes problems in humans—and into cells.
These genomic changes happened quickly, evolutionarily speaking. Polar bears and brown bears diverged from a common ancestor less than half a million years ago. But if that seems super speedy, the ability to digest lactose didn’t spread through human populations until we domesticated cows, just 10,000 years ago. A moooving testament to the power of natural selection.
—Karen Hopkin
[The above text is a transcript of this podcast.]

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