Support WBURFungus Provides Clues To North American ExtinctionsPlay03:28Download AudioRichard HarrisNovember 20, 2009 ShareNorth America was once home to mammoths, mastodons (above) and beavers the size of black bears. (University of Wisconsin-Madison)
North America was once home to mammoths, mastodons (above) and beavers the size of black bears. (University of Wisconsin-Madison)