In "The Nature of the Beast," you'll join scientists to explore the puzzling question of how dinosaurs originated, and how these amazingly diverse and successful animals came to dominate the entire planet for over 140 million years. Traveling to the high plateaus of Argentina, you'll glimpse the recently discovered remains of the earliest known dinosaur. In Nova Scotia, you'll learn of a cataclysmic prehistoric extinction that destroyed the dinosaurs' competition and ushered in the age of the Terrible Lizards. And, in the American West, you'll encounter the maiasauras, or "good mother lizards" --creatures that radically changed our concept of the nature of dinosaurs by showing that some of them lived in nesting colonies where they fed and protected their young.