Whose Theory Explained the Origin of Species?

Charles Darwin published On the Origin of Species on 24 November 1859, arguing that species evolve over time through natural selection — organisms with traits better suited to their environment are more likely to survive and reproduce. Darwin developed the theory over two decades, partly based on observations from his 1831–1836 voyage on HMS Beagle, including the famous Galápagos finches. Alfred Russel Wallace independently conceived a similar theory, prompting Darwin to finally publish. The book sold out its first print run on day one.