Skip to comments.Polar bears' ancient roots pushed way back
Posted on 07/25/2012 6:22:06 PM PDT by SunkenCiv
...A new analysis of its DNA suggests that Ursus maritimus split from the brown bear between 4 million and 5 million years ago -- around the same time when, some scientists believe, the Arctic's thick sea ice first formed.
With such old origins, the creature must have weathered extreme shifts in climate, researchers report online July 23 in the Proceedings of the National Academy of Sciences. Simulations of how the DNA changed over time suggest that polar bear populations rose and fell with the temperature. After thriving during cooler times between 800,000 and 600,000 years ago, the bears seem to have suffered a genetic bottleneck and crashed after a warmer period that started about 420,000 years ago...
Lindqvist and colleagues had previously dated the emergence of the polar bear to no more than 150,000 years ago... But that research relied on a single fossil containing mitochondrial DNA, genetic material inherited from the mother. In April, the origin was pushed back to 600,000 years ago by Frank Hailer... His team examined more than 9,000 letters in nuclear DNA (derived from both parents) of modern bears.
The new study provides an even clearer picture, says Lindqvist, because it looks at the entire genetic blueprints of 23 modern polar bears... more than 2.5 billion letters in... nuclear DNA... more than 13 million points of comparison.
But the date in the new study was calibrated using the rate at which mutations appear in the DNA of primates, Hailer says...
Isolated brown bears living in Alaska's Admiralty, Baranof and Chichagof islands share between 5 and 10 percent of their DNA with polar bears, Lindqvist's team found. A previous study found that ancient brown bears in Ireland also shared much mitochondrial DNA with their comrades to the north.
(Excerpt) Read more at sciencenews.org ...
“Isolated brown bears living in Alaskas Admiralty, Baranof and Chichagof islands share between 5 and 10 percent of their DNA with polar bears”
The article goes on to say that polar bears and brown bears interbreed occasionally (much as coyotes and wolves occasionally do) and that this might be a “threat” to the polar bear in diluting what makes them unique.
In light of this I think what the journalist was ATTEMPTING to say is that these particular Brown bears are of 5 to 10% polar bear ancestry - much as some coyote populations are of 5 to 10% wolf ancestry.
So rather than being “SUNSABITCHES” that are “ALL GODDAM EFFING LIARS” - maybe the journalist was unclear in what they were attempting to say?
These are actually some Not-So-Great Auks, which are rare.
But grilling them for a while should take care of that.
That’s adorable. Of course, after the weight doubled, there weren’t any more games of that kind. ;’)
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