Top O' The Mornin' To You, Mrs. Polar Bear!

Image by Wildyles at B3ta.





Science provides the answers to questions you hadn't even thought to ask:

All polar bears alive today are descended from a female brown bear that 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 other's territory. On some occasions, those meetings produced hybrid offspring whose genetic signature lives on in polar bears today.

...Based on fossil evidence and genetic analysis, scientists had thought that polar bears' closest relatives were the brown bears living on islands off the coast of Alaska.

Although members of the two species can, and have, met and mated — as evidenced by the occasional "grolar bear" hybrid popping up in the Canadian Arctic — those couplings are extremely rare and thought to be brought on by global warming, as melting glaciers force polar bears into brown bears' habitat and brown bears encroach northward into polar bears' Arctic refuge.

So imagine study leader Ceiridwen Edwards' surprise when she analyzed mitochondrial DNA in the bones of extinct brown bears collected from Irish caves and discovered that it most closely resembled the DNA of modern polar bears.

...The researchers think that during colder times, the glacial ice sheet would have extended all the way south into Ireland, allowing polar bears to roam into brown bear territory and making cross-species hybridization possible. One of the resulting female cubs probably went on to become a polar bear matriarch, and the descendants of all other matriarchal lines died off.