Final answer:
Charles Darwin published 'On the Origin of Species by Means of Natural Selection' in 1859, which outlined the theory of evolution by natural selection.
Step-by-step explanation:
The scientist who published 'On the Origin of Species by Means of Natural Selection' in 1859 was Charles Darwin. Darwin is renowned for developing and proposing the theory of evolution through natural selection, a revolutionary concept that changed the understanding of species development. While Alfred Russel Wallace also independently conceived of natural selection, it was Darwin's book that provided extensive detail and examples, such as the diversity of beak shapes among finches in the Galápagos Islands, to support the theory.