In the 1850s, on an island that would one day be part of Indonesia, a British naturalist named Alfred Russel Wallace came down with malaria. Perhaps during one of the fever dreams that are a symptom of the illness, Wallace had a profound realization: There wasn’t necessarily a supernatural force driving changes in living organisms.
Wallace had spent much of the early part of his life exploring in the tropics, observing the animals, plants and people who lived there, collecting specimens, and sending them back to England. Like most well-read English men and women of his time, Wallace was familiar with the evidence that the Earth and its life had evolved over time. Fossilized remains of strange plants and animals that no longer existed were being found all over the place. Sometimes, sea creatures were discovered embedded in rock on the tops of mountains, hundreds of miles from the coast.