Bear ancestry gets new insight -- help for polar bears?

Biologists have recovered mitochondrial DNA from long-extinct cave bears, from about 30,000 years ago. Cave bears are sisters to modern grizzly (brown) and polar bears, which can still interbreed.

Using the mDNA found from the cave bear bones, and comparing that with the mDNA of grizzlies (which are the brown bear of Eurasia) and polar bears, the scientists extrapolated a common ancestor about 1.6 million years ago.

This information ma prove useful in a sad way, namely, to determine more of how grizzly and polar bears are different, and why, as polar bears near critically small numbers.