Polar Bears were once brown bears, may be again.
From Science News 7/8/11.
"An international team of scientists has discovered that the female
ancestor of all living polar bears was a brown bear that lived in the
vicinity of present-day Britain and Ireland just prior to the peak of
the last ice age -- 20,000 to 50,000 years ago. The research is expected
to help guide future conservation efforts for polar bears, which are
listed as threatened under the Endangered Species Act. Climate change
has forced polar and brown bears to share habitats. Occasionally, the
two species interbreed and produce hybrid bears.....
Polar and brown bears are vastly different species in terms of body
size, skin and coat color, fur type, tooth structure, and many other
physical features. Behaviorally, they are also quite distinct: Polar
bears are expert swimmers that have adapted to a highly specialized,
arctic lifestyle, while brown bears -- a species that includes Grizzlies
and Kodiaks -- are climbers that prefer the mountain forests,
wilderness regions, and river valleys of Europe, Asia, and North
America. "Despite these differences, we know that the two species have
interbred opportunistically and probably on many occasions during the
last 100,000 years," Shapiro said. "Most importantly, previous research
has indicated that the brown bear contributed genetic material to the
polar bear's mitochondrial lineage -- the maternal part of the genome,
or the DNA that is passed exclusively from mothers to offspring. But,
until now, it was unclear just when modern polar bears acquired their
mitochondrial genome in its present form."
Posted by Kathy Meeh