Charles Darwin was the British naturalist who became famous for his theories of evolution and natural selection. Like several scientists before him, Darwin believed all the life on earth evolved over millions of years from a few common ancestors.

Born in Shrewsbury, Shropshire, England, on February 12, 1809，Darwin was the fifth child of a wealthy family. After graduating from the elite school at Shrewsbury in 1825, young Darwin went to the University of Edinburgh Medical School to study medicine. In 1827 he dropped out of medical school and entered the Christ’s College, Cambridge, in preparation for becoming a clergyman of the Church of England. There he met two stellar figures: Adam Sedgwick, a geologist, and John Stevens Henslow, a naturalist. Henslow not only helped build Darwin’s self-confidence but also taught him to be a meticulous and painstaking observer of natural phenomena and collector of specimens. After graduating from Cambridge in 1831，the 22-year-old Darwin was taken aboard the English survey ship Beagle, largely on Henslow's recommendation, as an unpaid naturalist on a scientific expedition around the world.

In South America Darwin found fossils of extinct animals that were similar to modern species. On the Galapagos Islands in the Pacific Ocean he noticed many variations among plants and animals of the same general type as those in South America. The expedition visited places around the world, and Darwin studied plants and animals everywhere he went, collecting specimens for further study.

Upon his return to London in 1836，Darwin conducted thorough research of his notes and specimens. Out of this study grew several theories: one, evolution did occur; two, evolutionary change was gradual, requiring thousands to millions of years; three, the primary mechanism for evolution was a process called natural selection; and four, the millions of species alive today arose from a single original life form through a process called “sperfation."

Darwin’s theory of evolutionary selection holds that variation within species occurs randomly and that the survival or extinction of each organism is determined by that organism's ability to adapt to its environment. He set these theories forth in his book called The Origin of Species (1859). After publication of Origin of Species, Darwin continued to write on botany, geology, and zoology until his death in 1882.