In a recent study posted in LA Times, scientist have found that the polar bears closest relative is the brown bear, but they are now trying to study when the two types diverged from each other. They are trying to figure this out to try to save polar bears, whose icy cold climates are melting away. In recent studies scientist have shown that polar bear and brown bears are closely related but are arriving at different dates of when the genes between the two species split. This is because the different blend of genes between the two are allowing for multiple dates of the two animals genetic histories.
The monkey wrench in this situation comes from one group of brown bears that live on the ABC islands in Alaska. Recent studies show that the original researchers misunderstood the gene history of these bears. These bears were first thought to be the ancestors the polar bear, but it seem they may not be anymore. Scientist now believe that instead of these brown bears being the ancestors of polar bears, that they are actually descendants of the the first female polar bears on earth. They think that the original inhabitants of the islands were in fact were female polar bears and that male brown bears actually swam to the islands and mated with them. The male brown bear gene's eventually over ran the polar bear DNA because there was more migrating male brown bears then original stranded female polar bears. Over the years the brown bear DNA took over but still has some polar bear DNA in the descendants of the original female polar bears.
This phenomena might have happened before with the now extinct Ireland brown bear. It was once thought that all polar bears descended from these Irish brown bears, but after studying the genomes of both the brown and polar bears' that polar bears have no brown bear ancestry. The only explanation of this the example of the ABC brown bear phenomena. This might lead to finding other examples of animals having this new island phenomena. More research is being done to find the polar bear ancestry and figure out the fate of the popular bears.
http://articles.latimes.com/2011/jul/08/science/la-sci-polar-bears-20110708
I found the article on the link between brown and polar bears to be fascinating. It would seem that there is a lot to be learned from the ABC island bears. I find it strange that there were enough female polar bears left behind on the island to mate with the male brown bears that swam to the island to alter the gene pool. Yet, there were not enough male polar bears to keep stronger linkages to the polar bears active upon the island. There is clearly much more work to be done in order to determine when the two species actually did split from each other, and must be done quickly in order to help save the polar bears from extinction due to the current climate.
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