They say "pizzlies", but I like the OP's "grolar bear" much better.
They seem scandalized, or maybe robbed, by this. It's a survival tactic. It's working. Sheesh. Let them do what they do, the natural thing, instead of trying to preserve a too-small gene pool.
"Polar bears are interbreeding with grizzlies because their habitat is disappearing. This is tragic and the new bears are doomed because they are poorly adapted to polar bear habitat. This wouldn't be so bad if humans weren't at fault."
The species distinction is often made when two populations of otherwise compatible creatures do not reproduce due to time, location, or physiological factors. In this case, geography has historically kept Grizzlies and Polar Bears separate, so their physical features have diverged a great deal despite remaining sexually compatible.
In other cases, different mating seasons or physiological incompatibility might prevent breeding, even though the gametes are compatible. Coyotes and wolves and dogs can breed, for instance, but they usually don't and so they're considered separate species.
The mathematician in me hates this abuse of what should be an absolute and well-defined term, and the cynic wonders about eugenicists making a species distinction between the various human lineages.
"Polar bears assure survival with inter-species mating"
Wonder why people always want nothing to change? Seems like a strange thing found in folks of all religions and philosophies. This sounds like great news: life carries on. Such a great story and such a sucky title.
I am reminded of a cartoon in one of my environmental studies college texts. (IIRC:) The cartoon depicted a colony of bacteria on pre-historic earth having hissy fits and NIMBY-like protests that their off-gassing of oxygen was destroying the environment and would soon endanger the survival of their species if something wasn't done about it.
Two things:
Creationists (to which I believe the middle of the Posterous article was referring) shouldn't be upset at all. The Bible says kinds, not species, and that kinds can and do mate.
Two: why try to cull the mixing? If it's working (and isn't the operation of natural selection all about discouraging what doesn't work?) why try to put a human hand in the activity? Are we so desperately trying to retain what we define as species?
I assume the reason to stop is due to a feeling of guilt. Instead of considering human influence as a part of nature, many people consider it to be some sort of perversion. So instead of being amazed by the adaptability of life, people feel guilty about causing changes.
Plus there is the whole time scale thing. The fact that evolution took a really long time to differentiate polar and grizzly bears and in a few lifetimes you would see that split undone is concerning.
You are right, we shouldn't interfere with nature but to me if the polar bear is lost through interbreeding it would be a loss. It's like mixing two good perfumes or two good wines, the uniqueness of each is lost to get only one unique thing.
I suspect adaptation might be a better term. Mutations aren't causing this or doing anything (so far as I know) with this, it's merely two creatures breeding and their gene pools intermingling.
It's just a matter of changing genes to produce something new and then selecting the best outcomes. Whether the change happens randomly or because two organisms combined their DNA, is irrelevant.
