14 DAY TRIAL // According to a paper published in the April 20 issue of the top journal Science, it would appear that polar bears have been roaming Earth's ices for at least 600,000 years. This estimate pushes back the suspected age considerably.
Known as Ursus maritimus, the polar bear was initially thought to have evolved some 150,000 years ago. But the new investigation looked into the species' mitochondrial DNA, which was used to determine the animals' course of evolution.
What this discovery suggests is that polar bears were able to survive through a number of cold and warm climate spells, adapting as they went along. During the new study, their mitochondrial DNA was compared to similar genetic materials from brown and black bears.
Over the past 600,000 years, Ursus maritimus has gone through a number of genetic bottlenecks. A similar situation is happening now, but at an accelerated pace, on account of man-made global warming, Science News reports.