Arguing the age of polar bears

Dr. Danovi:: The first story comes from a scientist at Pennsylvania State University and the University of Buffalo in the US. And it's basically about when in history polar bears started evolving out from other types of bear.

Kat:: Because we covered this couple of months ago and there had been some new research that have suggested that maybe polar bears and brown bears split about 600,000 years ago. But actually, this new data is now putting this much, much earlier.

Dr. Danovi:: Absolutely, I mean what a difference a few months make. So at the moment, they're saying this current data is suggesting that polar bears and brown bears split about 4 to 5 million years ago so it's a massive, massive difference. And I suppose the difference is just down to the techniques that they have used. This new study has done whole genome sequencing of the nuclear genome whereas the last study just looked at various points in the genome. So I guess the devil is really in the detail.

Kat:: And what's quite interesting as well, is the people are looking back at what the earth was like 4 to 5 million years ago and saying, well you know, it's obvious you can see about 600,00 years ago there were ice floes and the polar bears had separated geographically. But much further back than that, brown bears and polar bears were co-existing so actually it throws up the idea that maybe there was hybridisation, there was breeding between them and the situation is a lot more murky when we look at the evolution of these bears.

Dr. Danovi:: Absolutely and I think that the data is being contested by another group based in Frankfurt in Germany who are arguing that the ice sheets weren't around 4 to 5 million years ago. So what was the selective pressure that caused polar bears to split? So I suppose this isn't the end of the story. But seriously, who knew that polar bears can be so controversial?

Kat:: And some people are saying, maybe as the ice sheets are vanishing, we'll see polar bears coming back onto the land mass. Maybe could they start to breed with land bears again?

Dr. Danovi:: We might be seeing the emergence of a beige bear.

Kat:: Certainly an interesting thought.