Polar bear evolution

Nell -  So the first one is about a polar bear evolution.  Now, everybody likes polar bears.  They're cute, they're fluffy.  What we're looking at here is how did polar bears evolve to be different from normal bears - brown bears, all kinds of bears that do not live in the Arctic.  Obviously, they're big, they're white, they can cope with cold so, clearly, they're quite different and it was actually confusing scientists because it didn't seem like they'd have enough time to evolve all these differences.  We previously believed that they evolved from a brown bear about 150,000 years ago.  It's when they split off from that heritage.  Now, they've looked at better samples of DNA, not just mitochondrial DNA, but the rest of the DNA code as well, and that suggests that they've actually evolved five times longer ago than we thought which explains why they've become so different over that longer period of time.

Kat -  So yeah, we thought they were some kind of evolutionary ninja that they changed really fast, but they've had 600,000 years to turn into polar bears.  I also thought it was quite interesting it picked up that it's very difficult to do evolutionary research on polar bears.  There aren't fossils because they tend to just die on the sea ice and then sink to the bottom of the sea.  So, it's quite good that they've managed to get enough samples and use new techniques to make sense of it because the polar bears are under a lot of pressure at the moment, and poor things.

Nell -  Yes, aren't they?

Kat -  Are they going to evolve out of it?  I don't know.

Nell -  Well, we'd hope so.  One thing they also found was that they're not very genetically diverse which is going to be a problem if they need to evolve to cope with less sea ice than there was before, encountering humans, putting up with pollution, all that kind of thing.  So hopefully, this might, maybe give us some ideas of how to help them do that if we need to in the future.