Post by marchesarosa on Aug 5, 2012 11:09:27 GMT 1
From Lubos Motl
Polar bears may have been around for 4-5M years
Three days ago, we discussed the claim about palm trees in the Antarctica aproximately 52-53 million years ago. There's one more paper about a similar topic that was published in recent two weeks. The New York Times wrote the following story about it:
How Brown and Polar Bears Split Up, but Continued Coupling
See other articles that mention the study's co-author Charlotte Lindqvist.
The media reports refer to a paper in PNAS. The paper by Webb Miller et al (26 authors in total) is called
Polar and brown bear genomes reveal ancient admixture and demographic footprints of past climate change
They looked at DNA markers of polar bears as well as other bears. The main question is: When did polar bears separate as a new species?
As recently as a year ago, folks in that field would tell you that it was about 150,000 years ago: the polar bears were supposed to be a very modern invention, one that had to evolve very quickly. In April 2012, it was moved to 500,000 years ago. This new paper claims that the DNAs have apparently evolved independently for 4-5 million years.
This claim, if true, moves the separate life of the polar bears as a species before quaternary glaciation (also known as the Pleistocene glaciation or the current ice age) which began 2.58 million years ago and despite the screaming by the global warming fearmongers, it continues even today (by definition, that's because the Greenland has a permanent ice sheet).
I want you to appreciate the implications of this claim. The fearmongers have shamelessly tried to invent hundreds of bogus worrisome claims and identify tons of species endangered by the so-called global warming. They have failed miserably but there was still one charismatic species, the polar bears, for which it looked at least plausible that it could be endangered if there were some warming.
The world population of polar bears grew by a factor of four or five or so during the recent 50 years – from 5,000 to 20,000-25,000 – but despite this fact, you may still find it plausible to believe that they need chilly enough climate to thrive.
However, this new research seems to imply that the polar bears began to develop as a separate species in a significantly warmer world – a world in which the Greenland had no permanent ice sheets. And the same was arguably true about the Antarctica, too. Be sure that the Arctic Ocean was ice-free for a significant portion of the year. Nevertheless, the polar bears chose those warm epochs to establish themselves as a separate species.
Quite generally, I find it preposterous if someone believes that permanent ice creates the good – or even necessary – environment for any life form. Everyone whose body parts have ever frozen must understand what I am talking about. (I was once sliding on a Norwegian glacier for about 200 meters, using hands to decelerate, which was ultimately successful. I didn't feel them for 2 days.) Every organism contains water and if it freezes, life comes to a halt. Think about it.
Some species such as the polar bears may be more resilient than others so that they may tolerate more chilly conditions than what other species might withstand – and that gives them a "relative" advantage. They may even find it helpful if their prospective dinner is shaken and paralyzed by freezing conditions. But they don't really depend on it. They don't like those chilly, sub-freezing conditions in an absolute sense. No one does. There would be nothing wrong with a world that would come out of quaternary glaciation (and this is just a complete speculation because nothing indicates that we are approaching this geological event). Life on Earth – with pretty much the same composition of major species that we know today (including polar bears and some ancestors of humans) – has already tried it and the results were highly encouraging.
And that's the memo.
motls.blogspot.co.uk/2012/08/polar-bears-may-have-been-around-for-4.html
