Alfred Russel Wallace was an English naturalist, explorer, geographer, anthropologist and illustrator. He independently conceived the theory of evolution through natural selection; his 1858 paper on the subject was published that year alongside extracts from Charles Darwin's writings on the topic. It spurred Darwin to set aside the "big species book" he was drafting and to quickly write an abstract of it, which was published in 1859 as On the Origin of Species.