Charles Darwin and Alfred Russel Wallace were two men in the 19th century who independently came up with the theory of natural selection. Their works created the basis for the modern theory of evolution and its related studies.
Darwin was born in 1809 and attended Edinburgh University and Cambridge with the intention of pursuing a medical career. In 1831, he joined an expedition, during which he explored scientific research about fossils and geology. This trip took him to the Galapagos Islands, where he did his famous research on finches and tortoises. His observations about finches became the starting point from which he developed his theory about natural selection. The theory states that individuals more suited to their environment are more likely to live and pass on their genes, including any mutations.
Wallace was born 14 years after Darwin and spent some time as a teacher. His scientific journey took him to Brazil and the Amazon rainforest, where he spent four years researching and collecting data. However, most of his research was lost when the ship caught on fire and sank during the return trip. It was his research in the Malay Archipelago that finally helped him come to the same conclusion as Darwin. He wrote to Darwin about his discoveries, and the older man's "The Origin of Species" became the trademark work about natural selection.