24 Jul 2012:
Evolution of Polar Bear
Followed Changes in Climate, Study Says
An analysis of sequenced polar bear genomes provides new insights into how climate change and interbreeding with brown bears led to the evolution of the modern-day polar bear
. In an analysis of the
nuclear genomes of 28 brown, black, and polar bears, an international team of researchers found evidence that polar bear populations fluctuated with climate shifts over the last million years, with populations increasing during cooler periods and declining during periods of warmer temperatures. Their findings also suggest that during periods of glacial retreat, polar bears came into greater contact with brown bears as their ranges overlapped. “Maybe we’re seeing a hint that in really warm times, polar bears changed their life style and came into contact, and indeed interbred, with brown bears,” said Stephan Schuster, a scientist at Pennsylvania State University and co-lead author of the study, published in the Proceedings of the National Academy of Sciences
. While earlier research indicated that polar bears have only existed for about 600,000 years, the new research suggests that the polar bear may have evolved into a distinct species 4 to 5 million years ago.
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A look at how acidifying oceans could threaten the Dungeness crab, one of the most valuable fisheries on the U.S. West Coast. Watch the video.
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An aerial view of why Europe’s per capita carbon emissions are less than 50 percent of those in the U.S. View the photos.
An indigenous tribe’s deadly fight to save its ancestral land in the Amazon rainforest from logging. Learn more.
video series looks at the staggering amount of food wasted in the U.S. – a problem with major human and environmental costs. Watch the video.
Residents of the Chocó Rainforest in Ecuador are choosing to plant cacao over logging in an effort to slow deforestation.
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Tribal people and ranchers join together to stop a project that would haul coal across their Montana land. Watch the video.