Remains Show Ancient Horses Were Hunted for Their Meat

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Unexplained Extinction

As the ice began to retreat on the North American continent 14,000 to 12,000 years ago, humans made their way to the New World. A massive extinction of megafauna—animals weighing more than 100 pounds (45 kilograms)—occurred in North America about 10,000 years ago. The role of humans in the extinction is the subject of debate among scientists.

"Retreating ice would cause changes in temperature, vegetation bands and probably a patchiness in vegetation and loss of habitat," said Paul McNeil, a Ph.D. candidate in paleontology at the University of Calgary who has been working the site. "This would stress the animal populations, and it wouldn't take much to push them over the edge to extinction."

"Environment and climate change were definitely factors in the extinction event, but there had been numerous instances of glaciers advancing and retreating during the Pleistocene, and this is the only time we see a megafaunal extinction. The arrival of humans is the only real new factor," he said.

The lakebed where the footprints, animal skeletons and artifacts were found is usually flooded. Currently, however, the region is undergoing a drought. St. Mary's reservoir is expected to fill with water again, perhaps soon, so the scientists are working feverishly—sometimes in the midst of brutal sandstorms—to document the tracks and continue the archaeological excavations.

From a preservation standpoint, McNeil noted, the tracks are better protected under water. "One of the results of glaciations is a denuded countryside, with lots of dust and sand and silt. So when the wind blows it can be fierce enough to erode meters at a time," he said.

The researchers are excited by their discoveries at the site and how they are helping to fill in details of the past. "It's an amazing sight, like a snapshot of what life was like in the late Pleistocene, 10,000 years ago," said McNeil.

"The tracks represent living animals and a living ecosystem. In your mind you can see the animals cohabitating, gathering in the same place," he said. "We've found the only camel tracks we know of in North America—at one place you can see where five of them were walking next to each other."

Threatened by the filling of the lake, Kooyman said: "Right now we're just scrambling to do the really critical things."

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