Polar Bears Descended from Single Brown Bear

courtesy of Anchorage Daily News
by Amina Khan

All polar bears alive today are descended from a single female brown bear who most likely hailed not from Alaska — as widely presumed — but from Ireland, scientists said.

The discovery, reported online Thursday in the journal Current Biology, suggests that polar bears and various species of brown bears probably encountered each other many times over the last 100,000 years or so as climate change forced them into each others’ territory. On some occasions, those meetings produced hybrid offspring whose genetic signature lives on in polar bears today.

The findings were made by analyzing the mitochondrial DNA extracted from 242 bear lineages. Some of them were polar bears and some were brown bears. Some lived recently and others have been dead since the late Pleistocene, which ended nearly 12,000 years ago.

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