Marlow tells the story of his travels up the Congo River. That makes the setting…the Congo. And more generally, Africa. Check out one of Marlow's descriptions of sailing up the river:
Going up that river was like traveling back to the earliest beginnings of the world, when vegetation rioted on the earth and the big trees were kings. An empty stream, a great silence, an impenetrable forest. The air was warm, thick, heavy, sluggish. There was no joy in the brilliance of sunshine. The long stretches of the waterway ran on, deserted, into the gloom of overshadowed distances. On silvery sand-banks hippos and alligators sunned themselves side by side. The broadening waters flowed through a mob of wooded islands; you lost your way on that river as you would in a desert, and butted all day long against shoals, trying to find the channel, till you thought yourself bewitched and cut off for ever from everything you had known once—somewhere—far away—in another existence perhaps. (2.5)
What's cool about this is the way that Marlow compares sailing up that river to going back in time. It's almost as though—hint, this is SUPER important, Shmoopers—he's making Africa into a version of Europe's past. Remember that Marlow is telling us this story on a different river, the English Thames. That makes the Thames into a parallel for the Congo. So, if the Thames is like the Congo, then England is like Africa, which means that … white men are like black men, with a key difference: white men used to be like black men.
Want more evidence? At the beginning of the novel, Marlow breaks the silence by saying, "And this also has been one of the dark places of the earth" [1.8]). In other words, England, too, was a place of "primitive darkness" until men from Rome (in this scenario, the noble, altruistic "civilized" people invading to do good) rode up and conquered it.
What we have here is allochronic discourse, a very fancy phrase for—well, actually, a complex idea: that Westerners often talk and write about other countries as though they exist in different times and are just trying to catch up with the West. You can hear that kind of thinking even in phrases like "developing countries": developing countries are countries that are stuck in a different time and are racing to get up to our time. (Does this idea get you excited? There's a whole book about it! Er, well, a whole library really—but that should be enough to get you started.)
But there's a major problem with thinking that way: Africa actually exists in the exact same time that Europe does. It's not really a prehistoric land that only serves to remind Europe about its past, and treating it that way sounds, well, a little (or a lot) racist. And that's the source of a major critique against Heart of Darkness: even though Conrad seems to be saying that Europeans can be just as bad by putting the "heart of darkness" on the Thames, he's still saying that Africans represent a primitive and savage stage of human development.
What do you think?