A team of scientists from Pennsylvania State University and the University at Buffalo, sequenced the genomes of polar and brown bears and speculate that polar bears evolved into a distinct species some four or five million years ago. But they’re really observing a recent phenomenon. “Maybe we’re seeing a hint that in really warm times, polar bears changed their life style and came into contact, and indeed interbred, with brown bears,” says Stephan Schuster of Penn State.
Schuster and colleagues sequenced the genomes of three brown bears and a black bear and compared them with the genomes of polar bears, one modern and the other obtained from remains from a prehistoric polar bear.
As shown in this image, the nuclear genomes of bears (black outline), suggest that occasional exchange of genes between the two species (shaded gray areas) takes place. Results from maternally inherited mitochondrial DNA (dotted line) indicates extinction (marked with an “X”) and replacement of polar bear mitochondrial DNA in the past due to interbreeding between the two species.
Hybridization between the two species has continued to this day. As Arctic sea ice upon which they live recedes ever more and polar bears become forced to spend increasingly more time on land, this trend is set to intensify.
“Recently, wild hybrids and even second-generation offspring have been documented where the ranges of brown bears and polar bears appear to overlap, perhaps as a recent response to climatic changes,” the researchers write.
That’s pretty much the original article, but we add the following comments: First, global warming isn’t killing the polar bears. Rather they seem to be taking advantage of the warm weather by making whoopee with the brown bears. Second, we should be skeptical about the dates. The difference between polar bears and brown bears is no more profound than the difference between Scandinavian and Africans humans. No evolutionist would propose the human divergence more than a few thousands of years ago. So why should bears take so long? Evolutionary dating is a house of cards that doesn’t operate on consistent sound reasoning.