Rapid Polar Bear Adaptations; Golden Frog Not A Victim of Warming

After sequencing the mitochondrial DNA of an ancient polar bear, scientists have determined that the great Arctic bears probably split off from brown bears roughly 150,000 years ago, far more recently than previous estimates. The ancient bear’s DNA was decoded after scientists on Norway’s Spitzbergen Archipelago made a rare find of a polar bear jawbone estimated to be 110,000 to 130,000 old. By comparing the ancient bear’s DNA with that of two modern polar bears and four brown bears, researchers from the State University of New York at Buffalo estimated that polar bears split off from brown bears 150,000 years ago at a time when a colder climate made it advantageous for polar bears to specialize in Arctic living. Scientists say the research shows that polar bears — which can successful breed with brown bears — may survive in some form during the present era of warming by mating with brown bears. In a separate study, scientists have determined that Costa Rica’s golden tree frog, which went extinct in the late 1980s, was the victim of an outbreak of chytrid fungus exacerbated by extremely dry weather associated with an El Nino weather pattern. Some scientists have blamed the frog’s demise on global warming, but the recent study suggests warming was not the chief culprit. Both studies were published in the Proceedings of the National Academy of Sciences.