A CAT scan of pivotal bear DNA has shown that icy bears came into existence far earlier than previously assumed . Working with fossil alone , scientists had call up that glacial bear , after blend with brown bears , made their first snow-white white show anywhere between 60,000 to 600,000 years ago . But a genetic analysis now shows that they first emerge considerably in the first place — as much as 4 - 5 million years ago .
The subject , which was deport by Penn State University and the University at Buffalo , indicates that polar bears are not a late spinoff of dark-brown bears , and are instead a species that ebbed and flow over the millennia accord to changing climatic conditions — produce in universe during cool periods , and shrinking in warmer times .
And fascinatingly , it was during these warmer periods that polar bear would immingle with their browned full cousin . Writing in the New York Times , James Gormans explains :
The progress of mintage establishment , at least in this case , is a bit like a long , ambivalent divorce in which the two parties separate but occasionally decrease back into bed even after the official fiat .
Dr. [ Charlotte ] Lindqvist , said the DNA demo grounds of intermittent hybridizing between brownish and polar bears from the time of the split until the present – most probable during periods of thaw , when dark-brown bear moved north and polar bears were forced onto landed estate .
In most brown stick out the percentage of genetic stuff trackable to gelid bears is 2 pct . But on the Alexander Archipelago , a 300 - mile - foresightful train of islands off the southeast coast of Alaska , the brown bears have 5 to 10 percentage arctic bear DNA , suggest more frequent interbreeding .
The microscope of whole - genome studies and comparison also give glimpse into the adaptation of polar bears to the Arctic environment , including gene for high rich content in milk and for fatness accumulation .
Quite plain , this study has implication for our understanding of what will happen to frigid bear given the current point of climate change . It ’s enticing to suggest that today ’s polar bears , like their ancient predecessors , will go this current thaw tendency . But as the authors of the study warn , the berth is considerably dissimilar this time . Not only is climate modification happening at a much more rapid stride , but the diversity of bear bear in warmer areas has been drastically diminished . Consequently , polar bears may be in a bit of difficulty as they look for potential match down south .
Check out theentire studyin PNAS .
Top figure of speech viaShutterstock.com/Anita Gilden . Inset image fromTree Hugger .
BiologyClimate changeGeneticsGlobal warmingZoology
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