Estimates of when polar bears began to split from brown bears continue to change as geneticists look further into the polar bear genome. The most recent paper now puts the evolutionary time frame at around 400,000-500,000 years.
After beginning to branch off from brown bears, the polar bear's ancestors underwent a series of rapid evolutionary changes (less than 20,500 generations) in order to survive in the harsh conditions of the Arctic. The bears adapted to a life of hunting seals and surviving extreme cold. One of the most remarkable adaptations was the ability to thrive on a fat-rich diet without heart damage.
Interestingly, the research shows that after brown bears and polar bears separated, there were periods when they came into contact again, particularly with polar bear genes flowing into grizzlies.
What does this mean in the face of the current arctic warming now taking place?
- All these recent studies are interesting in terms of understanding how polar bears got to where they are today. But none really alter the risks polar bears face if we allow the climate to continue to warm.
- Whether polar bears are 150,000 years old or five million years old, unless we take action to curb greenhouse gas emissions, they face a future where the climate will continue to warm. And this warming will be unlike anything polar bears have survived before.