Which island chain did Darwin visit that inspired his theory?

The island chain Darwin visited that helped inspire his theory of evolution was the Galápagos Islands. This volcanic archipelago lies in the Pacific Ocean about 1,000 kilometers west of mainland Ecuador, whose territory includes the islands.

Darwin visited the Galápagos in 1835 during the second voyage of HMS Beagle. He collected specimens and observed differences among mockingbirds, tortoises, and finches on separate islands. These island-by-island variations later became especially important in explaining how populations can diverge when they live in different environments.

The popular story that Darwin immediately invented natural selection in the Galápagos is too simple. He did not fully understand the significance of all his observations while there, and his notebooks and specimens required later comparison. His thinking was also shaped by geology, selective breeding, and Thomas Malthus's writing about population growth and competition.

Darwin's finches became a famous example, although the birds were not the sole or instant source of his theory. The Galápagos observations helped him recognize a broader pattern: related organisms can become different when separated geographically and exposed to distinct ecological pressures.