A new paper out in the journal PLoS Genetics proposes that a hybridization event between female polar bears and male brown bears (aka grizzlies) occurred in Southeast Alaska at the end of the last ice age. I’ll get to a discussion of the paper itself (coming in a day or two) but first I have a few things to say about the global warming hyperbole generated by the people promoting the paper. I found it simply mind-boggling.
While the paper itself (Cahill et al. 2013: “Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution”) contains only one short phrase that could possibly be interpreted as linking the results to future scenarios of catastrophic global warming, some of the co-authors have made statements (for the press release and in media interviews) that spin the global warming mantra right over the top. Continue reading
Posted in Advocacy, Evolution, Sea ice habitat
Tagged ABC bears, Beth Shapiro, brown bears, Cahill, climate, Ed Green, global warming hype, hybridization, ice age, polar bear evolution, polar bear spin, sea ice extent, sea ice models
Most people would not question the species status of the polar bear (Ursus maritimus). While it is true that polar bears – under certain circumstances – have successfully interbred with brown bears (aka ‘grizzlies,’ Ursus arctos)[see previous post on hybridization], there are many characteristics that distinguish each of these species as unique entities (see diagram below).
Now, new genetic evidence adds weight to the balance on this issue. In this post, I’ll discuss very briefly the implications of this new paper:
Cronin, M. A. and MacNeil, M. D. 2012. Genetic relationships of extant brown bears (Ursus arctos) and polar bears (Ursus maritimus). Journal of Heredity 103 (6): 873-881. doi:10.1093/jhered/ess090 http://jhered.oxfordjournals.org/content/103/6/873.abstract
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)].