These are some of the points regarding this new paper by Miller et al. (2012, in press), on genetic evidence for the origin of polar bears, that I think deserve a critical look. See part 1, for my comments on Claim #1 (the fossil evidence)(see Doug Hoffman summary of the paper here).
In this post, I’ll elaborate on Claim #2. I’ve added one more to the original three listed.
Claim #1 Polar bears and brown bears (aka grizzlies) arose 4-5 million years old. [I countered with the fossil evidence]
Claim #2 Hybridization in both directions occurred repeatedly throughout the evolutionary history of polar bears and brown bears.
Claim #3 Svalbard may have been an important refugium for polar bears during warm interglacial periods.
Claim #4 Polar bear population numbers (population size estimates) over the last one million years tracked changes in climate (warmer/colder periods).
Claim #2 Hybridization in both directions occurred repeatedly throughout the evolutionary history of polar bears and brown bears [a claim also made in two other recent papers on polar bear evolution (Edwards et al. 2011; Hailer et al. 2012)].