Bear with us - news story - 24 Jul 2012
One of the icons of the battle to acknowledge and address climate change has been the polar bear. Concerns over the fate of Nanook due to the shrinking of the ice-cap might be allayed a little by the recent discovery that polar bears have been around far longer than we previously thought.
Until April, it had been thought polar bears, Ursus maritimus, had separated from their closest relative the brown bear (U.arctos) only about 150,000 years back, though there hadn't been much material evidence for this date. In April, further study of mitochondrial DNA shifted the date of the split back to at least 600,000 years. The waters are muddied by the ability of the two species (and they are considered distinct species) to produce viable offspring on ocassion. It's thought interbreeding at some stage will have complicated the DNA succession.
The latest update is that the divergence may have actually happened some 4-5 million years ago, which would indicate an ability of the species to survive prolonged periods of warmer climates. Possibly by getting on a little better with its cousin. You can read more by clicking here.