Book excerpt: How did life emerge on Earth? Is there life on other worlds? These questions, until recently confined to the pages of speculative essays and tabloid headlines, are now the subject of legitimate scientific research. This book presents a unique perspective--a combined historical, scientific, and philosophical analysis, which does justice to the complex nature of the subject. The book's first part offers an overview of the main ideas on the origin of life as they developed from antiquity until the twentieth century. The second, more detailed part of the book examines contemporary theories and major debates within the origin-of-life scientific community. Topics include: Aristotle and the Greek atomists' conceptions of the organism Alexander Oparin and J.B.S. Haldane's 1920s breakthrough papers Possible life on Mars?