The majority of the novel is set on a fictional island in the Pacific Ocean, off the coast of South America. Doctor Moreau moves to the island after being forced to discontinue his vivisection practices in England. The lush island is reminiscent of the Garden of Eden: it is a place where Doctor Moreau goes to start over and create a new world, with a new kind of people and a new set of rules. Here, he is allowed to practice vivisection without interference from people who believe it is unethical. The way he makes himself king or even god of his own island is also reminiscent of Daniel Defoe's novel Robinson Crusoe, in which a younger son of a middle-class Englishman is shipwrecked on an island and lives out his fantasy of ruling over his own property.
As isolated as Moreau tries to be, Montgomery still must leave the island regularly to engage in trade that is connected to the British empire. The impossibility of complete disentanglement from Victorian England reflects the state of the colonial world at the end of the 19th century. For some time, the world has been a place where Europeans, real and fictional, could "discover" new frontiers far away from home. By the 1890s, though, Europeans had the sense that the world was shrinking. Steam ships and railroads had made it possible for passengers to circumnavigate the globe. This was the subject of Jules Verne's 1872 novel, Around the World in 80 Days. The popularization of the telegraph also made quick long-distance communication possible. Starting over on a distant island far away from society is truly a fantasy by the time Doctor Moreau tries to do it, and he fails spectacularly at recreating an Edenic paradise.
In fact, although Doctor Moreau's island is geographically far from England itself, this distance actually strengthens Wells's overall point about Victorian England and its hypocrisy. Wells is interested in the use of Darwinian evolution as a justification for the claim that people of color are less evolved than white people, a claim that was being used to prop up ongoing English colonization around the world. By having Moreau, Montgomery, and even Prendick behave monstrously on the island, he suggests that Europeans are less evolved than they would like to believe. Wells is not so radical as to mount a clear defense of human rights, but the novel's setting helps convey the sense that the world is small and that there is nowhere to go where humans are beyond committing horrifying acts of violence against one another.