The bone was found below a layer that contained material from the Pleistocene period when the last ice age was thought to have occurred. The archaeologists identified the bison using an upper molar, which is thought to be representative of a Bison antiquus, a direct ancestor of the American bison that roamed North America until it became extinct. Because bison was a grassland-adapted animal, nearly 100 percent of their bones disintegrated after death unless they were preserved in some way. "This finding is especially significant because of the meticulous documentation that has been involved," said James M. Adovasio, Ph.D., principal...