Fossil offers clues to bear migration

By The Associated Press

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CALGARY, Alberta — A fossilized jaw found in an Alberta gravel pit may have cleared up a mystery for researchers wondering how brown bears originally made it across North America.

They probably migrated from what's now Alaska and the Yukon before glaciers covered the region, thousands of years before previously believed.

The findings are discussed in today's issue of the journal Science.

"It's like finding the missing link," said Paul Matheus, lead author of the paper and a paleobiologist at the University of Alaska.

Matheus said the discovery could have interest to archaeologists trying to determine when humans first arrived in North America. The first appearance of large mammals in the region has been viewed as an indicator of when humans likely migrated south along the same route.

"One of the good litmus tests for habitability of that corridor and route down south has been, when do you actually see large mammal fossils show up, indicating there was a presence of game for people to eat?" Matheus said.

Matheus recognized the jaw bone as a brown bear's during a 2001 visit to the Provincial Museum of Alberta in Edmonton. Radiocarbon dating and DNA testing determined the fossil was about 26,000 years old and closely related to bears in Canada and the northern United States.

Scientists previously believed brown bears first made it to central Alberta about 13,000 years ago when an ice-free corridor opened up and large mammals began to move south.

"The mystery has been more or less solved — they walked through Alberta," said paleontologist Jim Burns, curator of ice-age fossils at the museum.

"This is the first evidence that shows they made the journey prior to the maximum glaciation when the passage was blocked," said Burns, the paper's co-author.

Brown bears migrated from Asia to North America through Siberia 50,000 to 100,000 years ago across the Bering Strait during times of low sea level.

Copyright © 2004 The Seattle Times Company

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