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Beagle, a Royal Navy surveying ship, he was an inexperienced, 23-yearold gentleman naturalist. He returned as one of the rising scientific stars of his generation. Many of Darwin’s experiences on this trip shaped his thinking, but none was more influential than the five weeks he spent in the Galapagos Islands. Since Darwin’s time, research on islands has continued to advance the understanding of the evolutionary process. Indeed, evolutionists have come to regard islands as laboratories of evolution because island geography lays before them the underlying mechanisms of species formation and adaptive radiation. But islands also vary in many ways, and the evolutionary proliferation of life has progressed much further on some islands than on others. The varied outcomes of evolution in island settings can indicate a great deal about how evolutionary and spatial processes have built biological diversity through the formation and differentiation of species. In this Review, we discuss what Darwin’s time in the Galapagos Islands taught him about evolution and explore what islands have shown about evolution since then. In particular, recent work on islands has demonstrated the importance of geographical isolation (allopatry) in the initial stages of species formation, the role of interactions between species in adaptive radiation, and the effects of both historical happenstance and deterministic factors in the outcome of evolution on islands. In addition, in recent years, there has been a widespread move to re construct phylogenetic trees for individual islands on the basis of molecular information. These phylogenies describe the history of island biotas and might provide a way to synthesize evolution and biogeography at scales that bridge single remote islands, archipelagoes and continents.