In his story Heart of Darkness, Joseph Conrad paints a picture of the African Congo as a dark and mysterious place. Apart from the civilization that customarily binds we see a land where human nature is free to exert its natural self. Conrad's character Marlow is the orator for this tale, recounting the many things he saw on his long journey.
Throughout, Marlow's tale references Africa as a land of darkness. The natives are given a somewhat animalistic portrayal, but are still acknowledged to be human. Chinua Achebe, in his essay "An Image of Africa," attacked Conrad for his portrayal of Africa and its people. In fact, he goes as far as to say that "Conrad was a bloody racist." Most readers, however, would disagree with Achebe. Conrad uses Africa as a backdrop to his tale about the digression of human nature, merely setting the story where he does because in his time Africa is the only suitably unexplored continent. Achebe attacks this view as well, saying that "there is a preposterous and perverse kind of arrogance in thus reducing Africa to the role of props for the breakup of one petty European mind."
Conrad's story, however, is not about Africa. Conrad is writing a story about the fragile hold mankind has on civilization. Marlow's oration centers on the journey to reclaim a once highly renowned station manager from his post far up river. Marlow is introduced to this station manager by hearing of his wide range of refined skills and talents as a painter, speaker, and writer. Yet when they finally find their man, he is but a shadow of his former self. Free from intervention his mind has been completely able to throw off its inhibitions and has become utterly devoid of the civilization he had left. This process is evidenced in one of his writings, which, after spending its text on the study of how to civilize the African natives, ends with a scrawled postscript reading "Kill the brutes."
Achebe gives the contrasting portrayal of two women as an example of the racism inherent in Conrad's thinking. He points to how the native woman is "savage and superb, wild-eyed and magnificent" (103) while the European woman is "in mourning" with a "mature capacity for fidelity, for belief, for suffering." (126) What Achebe doesn't mention is the other aspect of the European woman's portrayal. When Marlow approaches her, he remarks that "The room seemed to have grown darker, as if all the sad light of the cloudy evening had taken refuge on her forehead." (126) Contrary to the derogatory description Achebe seems to find, the image of the African woman is sad, but proud, while the European is dark and eternally in mourning for the passing of her love.
Some of Conrad's views may now be considered racist, but it's unfair to him to pin this on him specifically. Conrad lived in a time when European nations were biased towards Africans as a whole, and so some of this popular sentiment is bound to be found in his work. At it's core, however, this is not a story about racism. Instead, the underlying theme is that civilization is merely superficial. Once taken away from the external physical and moral environments, human nature is quick to return to its primal roots.