· I have another bit of hope for the polar bears, not mentioned elsewhere.
I’m an evolutionary biologist (among other things). One of the outcomes of polar bears being forced off the ice is the apparently increasing number of hybrid bears being found – part polar bear, part grizzly.
Usually this is seen as a “bad” thing; a potential “dilution” of the polar bear gene pool, leading to its disappearance.
NOT SO. Rather, this may be one way for the polar bear genes to survive a warm spell, until the ice comes back.
A polar bear is a collection of specific sets of genetic differences from their grizzly ancestors. Those genes CAN survive in the polar-grizzly hybrids; for generations. This would be easiest for us to see if some pure polar bears survived, and continued to contribute to the hybrids every once in a while- but in fact polar bear genes could survive for many generations entirely “submerged” in bears that look just like grizzlys.
When the ice habitat returns, someday- essentially the polar bear species could be “reconstituted” in a few generations from the hybrids; no need for eons of new selection from scratch. The genes will be there, just waiting for the selective pressures to bring them together again.
This is going to happen more and more as warming progresses- far from being abhorred, natural hybrids may be the best way for some species to adapt to the rapidly changing world. In some cases (not all) fervid attempts to maintain “pure” species may be seriously misguided.
— Posted by Greenpa