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Climate Linked To Extinction of Alaska's Native Horses


November 14, 2003
Friday - 1:15 am

Alaska's native horses became extinct about 12,500 years ago. But before they did, they shrank, says R. Dale Guthrie, Institute of Arctic Biology researcher - a professor emeritus at the University of Alaska Fairbanks. This suggests, he says in this week's Nature, that climate change, not hunting, was to blame for their demise. Guthrie radiocarbon-dated bones from the forelimbs of two Alaskan horse species. Bones from the last days of the horses were about 12% shorter than those from the beginning of the period, about 27,000 years ago.

About 70% of North America's large mammals, including all the horse species, became extinct between 20,000 and 10,000 years ago. The reasons for this have been controversial - some researchers blame climate change, others the human hunters newly arrived in the Americas.

The timing of the horses' disappearance, and their size change, suggests that environmental change, not humans, were to blame, says Guthrie. The horses died out about 500 years before the first evidence of human settlement in Alaska. And their disappearance coincided with a shift in vegetation from grassland to tundra, which would have reduced their food supply. We may be mistaken in looking for blanket explanations for extinctions, Guthrie concludes: each species' disappearance probably results from a unique combination of influences and history.



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