Lithograph of Charles Darwin (1809-1882) with this signature. Darwin was an English naturalist and geologist. He established that all species of life have descended over time from common ancestors, and in a joint publication with Alfred Russel Wallace introduced his scientific theory that this branching pattern of evolution resulted from a process that he called natural selection, in which the struggle for existence has a similar effect to the artificial selection involved in selective breeding. This image has been colour enhanced.