Which archipelago in the Pacific Ocean did Darwin study that inspired his theory?

The Galápagos Islands were the Pacific archipelago Darwin studied during the voyage that helped shape his theory of evolution. He visited the islands for about five weeks in 1835 while traveling aboard HMS Beagle.

The Galápagos are a volcanic island group lying on the equator, roughly 1,000 kilometers west of mainland Ecuador. Darwin noticed that animals on different islands could resemble one another while still showing distinct differences. Galápagos mockingbirds and tortoises particularly influenced his thinking about how isolated populations might change over time.

Darwin did not suddenly formulate the complete theory of natural selection while standing on the islands. His ideas developed gradually after the voyage, as he compared his Galápagos observations with evidence from other regions, domesticated animals, fossils, geology, and earlier scientific writing. The islands supplied an especially vivid example of geographic variation.

A common misconception is that Darwin studied only finches there. The finches became famous later, but his observations also included mockingbirds, tortoises, marine iguanas, and other wildlife. The Galápagos helped him recognize that related species could diverge in different environments.