In the 1830s a scientist called Charles Darwin sailed round the world studying animals and plants from different countries. He gradually became convinced that all the living things he saw had resulted from evolution. Evolution is a slow and gradual change.

Darwin believed that life on earth started out with simple animals and plants and over millions of years they became more and more complex. At first people did not believe that evolution could be true but now there is a lot of evidence to suggest that evolution did take place and is still continuing today.