Charles Darwin was a British naturalist who lived from 1809 to 1882 and developed the theory of evolution by natural selection, which explains how species change over time. Darwin proposed that animals and plants aren't fixed forever but gradually adapt to their environments across many generations. Those with traits that help them survive are more likely to pass those traits to their offspring.

Darwin's famous voyage on HMS Beagle took him around the world for five years. During the trip, he observed finches on the Galápagos Islands that had different beak shapes suited to the foods available on each island. This observation helped him understand that species could change to fit their surroundings.

His groundbreaking book On the Origin of Species, published in 1859, transformed how scientists understand life on Earth. Before Darwin, most people believed that every species had been created exactly as it appeared and never changed. Darwin showed through careful observation and reasoning that life forms evolve gradually through a process he called natural selection: individuals with helpful traits survive and reproduce more successfully, passing those advantages to future generations.

Darwin's work sparked intense debate but eventually became the foundation of modern biology. Today, scientists study evolution to understand everything from why bacteria become resistant to antibiotics to how different animals developed their unique features. Darwin's patient observations and logical thinking changed humanity's understanding of the natural world.