Which scientist first described natural selection alongside Darwin?

Alfred Russel Wallace, who worked it out independently while ill with fever in what is now Indonesia, and posted an essay describing it to Darwin in 1858 - to Darwin, of all people, asking whether it seemed worth publishing. Darwin had been sitting on the same idea for twenty years, terrified of the reaction, and wrote to a friend that he had never seen a more striking coincidence and that all his originality would be smashed.

The resolution was arranged by Darwin's friends: Wallace's essay and extracts from Darwin's earlier unpublished writing were read together at the Linnean Society, in the absence of both men - Wallace was still in the Malay Archipelago and had not been consulted. It was handled decently by the standards of the time and it did put Darwin first.

Wallace never complained, called it Darwinism himself, and remained on good terms - Darwin later helped secure him a government pension. He also went further in one direction and stranger in another: he was among the first to argue that human activity was changing the climate of whole regions, and he founded biogeography, but he also believed spiritualism explained the human mind and refused to accept that natural selection could account for it, which cost him credibility in his lifetime and has cost him position in the story since.