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Polar bear and brown bears diverged much longer ago than previously retrieve , newfangled enquiry suggests .
Past estimation for this divergence come from dark-brown bears living on the Admiralty , Baranof and Chichagof ( ABC ) Islands in Alaska .
One geneticist has suggested that a relative of the polar bear may have given rise to the legend of the yeti, or Abominable Snowman.
But harmonize to a raw study , ABC Island bear are in reality the result ofmating between brown bear and frigid bearsin the last several thousand years , making the population useless for determine polar bear roots .
" If we really need to empathize the evolution of brown bear andpolar bear , we should snub them [ the ABC bears ] , " enounce study co - author Beth Shapiro , an evolutionary life scientist at the University of California Santa Cruz . " They are a especial case and they ’re not going to differentiate us anything about the origin of the polar bear . "
The finding were published today ( March 14 ) , in the journalPLOS Genetics .
ABC Island brown bears actually came from a population of polar bears that mated with male brown bears over thousands of years, new research suggests.
ABC bears
Just whenpolar bears and brown bearsdiverged has been an ongoing debate .
Past research revealed that brownish bears on the ABC Islands , off the southeast coast of Alaska , had mitochondrial DNA that looked just like glacial bear DNA . ( Mitochondrial DNA comes only from the mother and is carry in the cytoplasm in the cell ’s energy - defecate social organisation telephone mitochondria . )
That seemed to suggestpolar bears diverge from dark-brown bearsaround 150,000 year ago , Shapiro told LiveScience .
But that did n’t make sensation : The two majestic species have different deportment and physical appearances , and other factor studies suggest they split off from one another 4 million years ago . The unknown finding led research worker to propose gonzo theories to excuse the mystery story , Shapiro said , including intermix at least two disjoined times in their yesteryear .
migratory dads
To class out the confusion , Shapiro and her colleagues analyzed the desoxyribonucleic acid of seven polar bears , two brown bear ( one from ABC Islands ) and one black-market bear .
The team found that the ABC Islands ' bear shared more than 6 percent of the DNA in its 10 sex chromosome , but just 1 percent of its overall desoxyribonucleic acid , with diametric bears .
Because go - chromosomegenes get from the mothermost of the sentence , the findings suggest the icy bear DNA originally came from female bear . [ In Photos : 8 Bizarre Hybrid creature ]
To explain the findings , the researchers proposed a unknown scenario : The chocolate-brown bears of ABC Islands were once polar bear . But as the glacier melted grand of years ago , those polar bears became trap on their islands .
Further warming led to better conditions forbrown bearsto colonize the Alaskan mainland . Because male are the ones that disperse , they swam across the channel to the ABC Islands over a long menstruation of time , mating with the local female person ( arctic bear ) . As a result , the ABC bears finally came to wait and dissemble like chocolate-brown bears , while still maintaining traces of their diametric bear by in their mitochondrial deoxyribonucleic acid .
The genetic analytic thinking unwrap a blanket estimate for when browned bears and polar bears first depart , rank from hundreds of yard to billion of years ago .
The finding hint people should ignore ABC bear when attempt to sort out polar bear ' account , Shapiro said .
Unfortunately , scientist are n’t any closer to solve the mystery of opposite bear origins .
" pivotal bears live in a property that it is very unbelievable that they ’re going to leave fossils , " Shapiro said , mention to the fact that fogey do n’t live in the wintry , watery condition of the Arctic . That makes it unmanageable to trace their evolution from a common root with brown bear , she say .
