What a disppointment. The author, a geologist, falls flat in this book. He strays into areas of expertise with grand claims and zero proof. He does not refer to his ideas as theories but as fact. Aside from the joy ride around good questions, the book is filled with extreme political correctness... Why are SUV's, Republicans, and present day humans always the ones that are to blame for extinctions that happened thousands of years ago (now you get an idea of what light that this book was written in). Pure rubbish as a science book. Great for "politically correctness" fans.