Polar bears split from their ancient ancestors more than 4 million years ago, according to ancient DNA maps of multiple bears in a study that was published in the Proceedings of the National Academy of Sciences journal.
USA Today reports that the new polar bear genome finding contradicts earlier gene studies that suggest an earlier split of within 600,000 years, because polar bears and grizzly bears are still able to mate and produce viable offspring.
The study, led by Penn State’s Webb Miller, begins by saying:
“Although polar bears ( Ursus maritimus) and brown bears (Ursus arctos) are considered separate species, analyses of fossil evidence and mitochondrial sequence data have indicated a recent divergence of polar bears from within brown bears.”
Miller also states in the study that:
“A whole-genome analysis of the polar bear may provide a more complete picture of its evolutionary history, possible signatures of admixture, and clues about the genetic basis of adaptive phenotypic features facilitating life in the Arctic, all of which are imperative for gaining a better understanding of possible responses to current and future climatic changes,” says the study.
According to The Christian Science Monitor, the study also shows that despite their split, brown and polar bears have interbred multiple times since then. They believe that climate change was the cause of the bears interbreeding, and also believe it may be happening again.
Study researcher Stephan Schuster, a professor of biochemistry and molecular biology at Pennsylvania State University, and a research scientist at Nanyang Technological University in Singapore, in a statement that:
“Maybe we’re seeing a hint that in really warm times, polar bears changed their lifestyle and came into contact, and indeed interbred, with brown bears.”
Eureka Alert notes that Charlotte Lindqvist, the study’s senior author and an assistant professor of biology at UB, stated that the split of 5 million years means “polar bears definitely persisted through warming periods during Earth’s history.” She cautions, however, that just because the ice-dwelling bears were able to survive warmer temperatures in the past, this does not mean they will be able to survive in the future, because the current climate change is occurring faster than they have experienced before.
Knowing that polar bears were able to adapt and survive to previous global warming times, do you think they will be able to survive this time, even if the climate change is happening faster?