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The history of the bears of the Alexander Archipelago is unusual in that these island populations carry polar bear DNA , presumably originating from a population of polar bears that was left behind at the end of the Pleistocene , but have since been connected with adjacent mainland populations through movement of males , to the point where their nuclear genomes are now more than 90 % of brown bear ancestry .
 Alexander Archipelago
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
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Text: {0} 
Answer:
 Alexander Archipelago