Polar bears have seen hard times

摘要

The polar bear, furry face of wildlife at risk from climate change, now looks as if it may have been around long enough to have survived past warm spells. Just how long remains to be seen, but two genetic studies published this year push the species' origins back beyond the start of the most recent ice age. That's a big rewrite of polar bear history that has people thinking about the bears' future; even if the bears survived several past warm periods, that's no guarantee they will survive this one. Until the genetic analyses this year, polar bears' history as a species was thought to be short. Afossil jawbone and tooth from Norway, the oldest well-documented polar bear remnants, date back only 110,000 to 130,000 years. And preliminary genetic studies by Charlotte Lindqvist of the University at Buffalo and her colleagues traced the female polar bear line back only about 150,000 years to a junction with the brown bear lineage.