Ecology
Polar bears' past may affect their future. Genetic research has shown that polar bears living on Arctic ice interbred with brown bears after the two species separated from each other 5 million years ago. Climate change appears to have influenced this blood mixing, studies say, and they believe this is happening again.
“This may be a hint that in warmer climates, polar bears are beginning to change their lifestyle and come into contact with and even mate with brown bears,” says the researcher Stephan Schuster is a professor of biochemistry and molecular biology at the University of Pennsylvania.
Scientists estimate that polar and brown bears separated from their common ancestor sometime between 4 and 5 million years ago, after which they periodically encountered climatic fluctuations, including glacial ones periods and global warming.
Polar bears today are facing the effects of climate change, but these changes are now man-made. The Arctic ice on which bears live is disappearing at an enormous rate.
“If the trend continues, polar bears are likely to spend more time on land in the future, even during the breeding season, and therefore they will bond with brown bears bears are more common than usual,” the researchers said.
Wild hybrids and even their offspring have recently been discovered in the northern part of the Beaufort Sea, where populations of white bears and brown bears overlap, apparently due to the planet's warming climate.
Shuster and his colleagues isolated the genomes of three brown bears and a black bear and compared them with the genomes of polar bears, one modern species and one ancient bear that lived on planet 120 thousands of years ago.
Scientists have noticed, after studying the genetic codes of bears, that polar and brown bears separated around the same time that black bears became a separate species. After this separation, brown bears and polar bears lived in isolation from each other, so they accumulated genetic differences, but later these two species began to interbreed and have more in common.