About This Book This is not a book about evolution per se. That is, it is not about the theory by which life accumulates changes over time, so that simple, early organisms change over eons into more complex, advanced ones. It is not about the entire history of life on Earth either. Rather, this book has a narrower, yet crucial, focus. And it is within this context that the RTB Model is presented. This book is about the origin of life—the first appearances of living organisms on Earth. We address