Charles Darwin wasn't an inventor; he was a naturalist and geologist. His theories about the way biological populations change over time revolutionized biological science. He published two books, "On the Origin of Species" and "The Descent of Man."
As a young naturalist and geologist, Darwin spent almost five years on a round-the-world voyage aboard a ship called the "Beagle." During that voyage, Darwin collected specimens and made observations that led him to conclude that all species descended from common ancestors and that the gradual change in biological populations resulted from a process he called "natural selection." This process explains the struggle for existence as survival traits are passed down. As a result, new species emerged.