Book excerpt: Easy, enlightening and mind-stretching, here are answers to the 20 biggest questions of evolution and what they tell us about life on Earth. The Big Questions series is designed to let renowned experts address the 20 most fundamental and frequently asked questions of a major branch of science or philosophy. Each 3,000-word essay simply and concisely examines a question that has eternally perplexed enquiring minds, and provides answers based on the latest research. This ambitious project is a unique distillation of humanity's best ideas. In The Big Questions: Evolution, Francisco Ayala answers the 20 key questions: What is evolution? Was Darwin right? What is natural selection? What is survival of the fittest? Is evolution a random process? What is a species? What are chromosomes, genes and DNA? How do genes build bodies? What is molecular evolution? How did life begin? What is the tree of life? Am I really a monkey? What does the fossil record tell us? What is the missing link? Is intelligence inherited? Will humans continue to evolve? Can I clone myself? Where does morality come from? Is language a uniquely human attribute? Is Creationism true?