North America's rarest mammal was thought to have ... at odds with the local prairie dog population. The burrowing rodents were seen as pests, and vast numbers of them were killed to make way ...

The timing of human arrival in North America roughly coincides with the disappearance of these animals, adding weight to this hypothesis. Others believe that climate change was the primary factor.

North America used to be crawling with giant mammals, from dire wolves to big cats. Horses and camels evolved on the continent while others, like bison, crossed over from Asia. Most of these ...

most of North America's megafauna disappeared. How and why remains hotly contested. Some researchers believe the arrival of humans was pivotal. Maybe the animals were hunted and eaten, or maybe ...