Photo by Alan Wilson via Wikimedia Commons.
A polar bear on Arctic ice - its diminishing habitat.
Polar Bears Older But Still Threatened
Author: Laura Komor
A recent analysis of polar bear genetics shows that polar bears originated much earlier than scientists previously believed. Prior to a new study, our best guess placed the great white beasts on Earth only 150,000 years ago. Frank Hailer of the Biodiversity and Climate Research Centre in Frankfurt, along with other colleagues, arrived at a new "first appearance" of approximately 600,000 years ago by studying polar bears’ nuclear DNA; the old approximation was based on mitochondrial DNA, which is only passed down the maternal line. This new information indicates that polar bears be much hardier than we imagine. The lineage of Ursus maritimus
managed to survive though past climate changes, including regular ice ages and periods of global warmings, which occurred in the early years of their existence. Perhaps this means that there is hope for polar bears and other species whose existence is threatened by global warming. At the moment, U. maritimus
’ Arctic habitat is being reduced by rising temperatures. Just this past year, Arctic ice levels were the second lowest since the United States Geological Survey began reporting ice levels in 1979. Despite this new starting point, and the new appreciation for polar bear survival through the eons, Hailer's analysis also confirms low genetic variation in polar bears - an evolutionary "bottleneck" caused by the deaths of many individuals during warm phases. In other words, a smaller population has less genetic variation than a large one. With these two strikes against polar bears, we hope that they can pull through once again.
More about polar bear evolution can be found at ScienceNews
Read the original study in the journal Science
Read about climate change and polar bears at National Wildlife Federation's global warming website