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The polar bear has become a symbol for threatened wildlife, and its future in a warming world has created much controversy. The predator’s past is equally controversial. The evolutionary history of polar bears has been rewritten several times in recent years, complicated by an incomplete fossil record and a history of hybridization with brown bears, and a new study, published today in the Proceedings of the National Academies of Sciences, continues the trend.
Researchers from Pennsylvania State University have completed the most extensive genomic study of polar bears to date. By comparing its DNA to that of brown and black bears, the team calculated that polar bears arose between 4 and 5 million years ago, making them far older than anyone had suspected. And their genes carry the imprints of repeated interbreeding with brown bears during much of that history.
The team also started documenting the ...
