Charles Darwin developed the theory of evolution, fundamentally challenging traditional views in the 19th century with his work "On the Origin of Species," published in 1859. His theory proposed that species evolve over time through a process known as natural selection, where adaptive traits become more common in successive generations. This concept contradicted the prevailing notion of fixed species, suggesting instead that all life shares a common ancestry. Darwin's ideas sparked significant debate in scientific, religious, and cultural circles, prompting discussions about human origins that continue to influence modern biology and social thought.