If people were to be asked who developed the natural selection theory, almost always, Charles Darwin would be the name associated with it. But, Alfred Wallace is also the co-author or co-discoverer of the theory of evolution by natural selection. He was a naturalist that collected several species of plants and animals for experimental purposes. Both men actually published a joint paper arguing the theory of evolution and natural selection. But eventually Wallace faded when Darwin wrote the book the Origin of the Species.