Charles Darwin proposed the theory of evolution by natural selection alongside Alfred Russel Wallace.
Darwin developed his ideas after observing organisms and fossils during the voyage of HMS Beagle, including distinctive species in the Galápagos Islands. He spent years collecting evidence before publishing his theory in On the Origin of Species in 1859.
Natural selection explains how inherited variations can become more common when they help organisms survive and reproduce in particular environments. Over many generations, this process can produce adaptation and the divergence of populations.
Wallace independently developed a similar theory and sent Darwin an essay in 1858. Their work was presented jointly at the Linnean Society in London. Darwin is often given primary credit because his book provided a much fuller explanation and a large body of supporting evidence.