What Darwin discovered at the Galápagos Islands?

At the Galápagos Islands, Charles Darwin observed unique species that varied from island to island, which played a crucial role in the development of his theory of natural selection. He noted differences in the beak shapes of finches, adapted to different food sources, and the distinct characteristics of tortoises and marine iguanas. These observations led him to conclude that species evolve over time through the process of adaptation to their environments. This foundational work contributed to his groundbreaking book, "On the Origin of Species."