‘Jumping genes’: how polar bears are rewiring their DNA to survive the warming Arctic

Polar bears are leaping through their evolution in real time as rising temperatures threaten their habitat. A population of bears was found in a climate warmer than one in which they usually exist and showed genetic differences from their colder-weather counterparts. Those differences could be key to the survival of the species, as well as show how other animals and humans could evolve in the future.

Hot and cold

An isolated colony of polar bears found in southeast Greenland “inhabits a warmer climate zone, akin to the predicted future environments of polar bears with vastly reduced sea ice habitats,” said a study published in the journal Mobile DNA. The subpopulation is particularly interesting as it may have had a “200-year start on developing advantageous genetic changes for survival in this shifting landscape,” said Popular Mechanics.

Researchers analyzed blood samples from polar bears located in northeastern and southeastern Greenland. The results showed that “some genes linked to heat-stress, aging and metabolism” were “behaving differently” in the southern bears compared to the northern ones, Alice Godden, a co-author of the study, said in an article for The Conversation.

This difference can be attributed to “jumping genes,” or transposons, which are “mobile pieces of a gene that can move around to influence how other genes work,” said Popular Mechanics. “By comparing these bears’ active genes to local climate data, we found that rising temperatures appear to be driving a dramatic increase in the activity of jumping genes within the southeastern Greenland bears’ DNA,” Godden said in a statement.

Jumping genes are like “puzzle pieces that can rearrange themselves, sometimes helping animals adapt to new environments,” said Godden. In this case, researchers “found active jumping genes in parts of the genome that are involved in areas tied to fat processing,” which is “important when food is scarce.” This could mean that the southern polar bears are “slowly adapting to eating the rougher plant-based diets that can be found in the warmer regions,” while the “northern populations of bears eat mainly fatty seals.” The polar bear genome comprises approximately 38.1% jumping genes, compared to 45% in humans.

Up and down

Because of climate change, more than two-thirds of polar bears are predicted to be extinct by 2050, and total extinction is expected by 2100. Arctic Ocean temperatures are also “continuing to rise, reducing vital sea ice platforms that the bears use to hunt seals, leading to isolation and food scarcity,” said the statement. Scientists believe this is the “first documented case of rising temperatures driving genetic change in a mammal,” said NBC News.

While the genetic changes “provide a genetic blueprint for how polar bears might be able to adapt quickly to climate change,” it “does not mean that polar bears are at any less risk of extinction,” Godden said. It is still required that we “do more to mitigate our carbon emissions to help provide and extend this window of opportunity to help save this wonderful, vital species.” Since humans also have transposons in their genome, our DNA sequence also has the potential to change and evolve, “but environmental stress, such as warmer climates, can accelerate this process,” said the statement.