Fossils reveal bisons' secrets

January 13, 2005, vol. 32, no. 1
By Marianne Meadhal

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Studies of DNA from bison fossils show that the development of ice sheets over most of Canada in the last ice age cut off southern varieties of bison from their relatives to the north.

"This separation resulted in different evolutionary paths for the northern and southern populations," says SFU archaeologist Jonathan Driver, part of an international team of scientists who studied fossilized bison bones from Canada, Siberia, China and the U.S.

Led by Beth Shapiro and Alan Cooper at Oxford University, the group's findings were published in the journal Science in late November.

Driver says when the ice melted, the northern bison began to move south, while the southern bison began to move north.

The only place in North America where there is a record of these two populations meeting is at Charlie Lake cave in northeast B.C., which has been excavated by teams from SFU led by archaeologists Knut Fladmark and Driver.

"Our analysis of the stone tools at the site suggested that there were similarities to both northern and southern artifacts, so it is interesting that the bison tell the same story of people and animals moving from different directions into newly created landscapes," he says.

Driver says analysis of the ancient DNA allows researchers to model the overall size of the bison population.

"This analysis suggests that the bison populations began to decline well before humans entered the new world," he notes. "This suggests that large animal species in the Americas were affected by climatic change during the ice age. Many of these large animals (although not the bison) became extinct. Some have blamed this on human over-hunting. Others have blamed climate.

"This study strengthens the climate hypothesis," Driver adds, "although I believe that there is still enough evidence for human involvement in the extinction of the mammoth."

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