Prehistoric animals once roamed — and ruled — planet Earth. Some of them, like the giant sloth or the woolly rhino, were generally gentle. Others, like the saber-toothed tiger and the dire ...

This world is ancient. Scientists believe the world is billions of years old — with the exact number believed to be 4.5 billion years old. In that time, there have been many creatures roaming Earth.

Are wild horses truly “wild,” as an indigenous species in North America, or are they “feral weeds”—barnyard escapees, far removed genetically from their prehistoric ancestors? The question at hand is, ...