Polar bears' ancient roots pushed way back

New analysis of polar bear DNA suggests that they branched off from brown bears much earlier than previously thought.  The new study dates the split back to the formation of the thick sea ice in the Arctic between 4 and 5 million years ago.  This new date of origin suggests that the polar bears were exposed to extremely variable weather and suffered a genetic bottleneck during the warm period 420 thousand years ago.  Today we are again facing a warm period in the earth’s history and it is questionable as to whether or not the polar bear will be able to survive it.



Charlotte Lindqvist and her colleagues at the University of Buffalo developed genetic blueprints of 23 modern polar bears.  However, they used the rate of mutation appearance in the DNA of primates to calibrate the polar bear DNA and come up with a date of origin.  This assumes that polar bears evolve at the same pace as primates, which could prove false.  There is also evidence of polar bears mating with brown bears, most likely during warm periods.  This hybridization is potentially dangerous for the continued separation of bear species.

This article was very interesting given its present implications regarding our warming environment.  Polar bears are a species of concern due to the reduction of their natural habitat.  I have heard of polar bears and brown bears mating as their environments begin to merge and am curious as to what would happen when this occurs.  Obviously the interbreeding would be detrimental to both species specific genetic uniqueness, but to what extent?  I hope scientists will be able to determine the answer to this question before the polar bear becomes extinct.