On This Green Earth, Nell and Chris talk with author and National Geographic magazine contributor, Doug Chadwick. Chadwick's new book is titled, Four-Fifths a Grizzly - A New Perspective on Nature that Just Might Save Us All. The book takes a close look at our place in the natural world from a scientific angle, with the underlying message that humans aren't that much different from other creatures. He shows us the surprisingly close relationship between humans and grizzly bears, with whom we