Evolution Evolution is change over time. The Theory of Evolution states that all organisms share a single common ancestor and have evolved over time. It also states that this has occurred largely due to changes in environmental conditions that have led to a necessity for organisms to change and adapt or go extinct. Darwin?s Theory of Natural Selection In 1831, Charles Darwin set sail on the HMS Beagle as the ship?s naturalist. His job was to collect biological and geological specimens. After traveling from England across the Atlantic and collecting specimens along the eastern and western coasts of South America, the ship landed in the Galapagos Islands. Darwin?s Theory of Natural Selection