Outraged people claimed that Darwin''s theory had made humans the relatives of monkeys. Scientists were sure that species changed over time, but no one could explain how. In the 1800s, Charles Darwin''s studies of thousands of specimens of living things showed that no two individuals of any species were exactly alike. He realized that over millions of years, some individuals had traits that gave them an edge to survive and reproduce. As they reproduced, the successful traits were inherited by later generations. This book explains Darwin''s theory. It shows how later discoveries in genetics provided more evidence that the theory of evolution works. Each year, scientists in many fields are making new discoveries that provide further proof of Darwin''s world-shaking ideas.