Charles Darwin (1809?1882) was an English naturalist, geologist, and biologist, widely known for his contributions to the science of evolution. His five-year voyage aboard the HMS Beagle provided him with the critical geological and biological observations that formed the basis of his theories. In 1859, he published On the Origin of Species, introducing the scientific theory that populations evolve over generations through a process called natural selection. His work completely revolutionized the life sciences and remains the foundational framework of modern biology.