I agree with the two previous posters and want to add a few more details about what there might be to appreciate in the Langston Hughes' poem "The Negro Speaks of Rivers."
The speaker is interesting. He (if he's a he?) is identified as "the negro" in the title of the poem, but he lives through centuries in a way that is impossible for humans. We may see details in the poem that suggest that he has been both a peasant (in a hut) and a pharoah. This last item is really interesting, I think. The speakers says: "I looked upon the Nile and raised the pyramids above it." He doesn't say "I made bricks and hauled them for some great leader." He seems to be the one occupying the vantage point and the high social position in this line.
The repetition of the word "human" is interesting, too, as is the choice of rivers. The Congo is in black Africa and the Mississippi can easily be connected (through slavery) to African American history, but the Euphrates doesn't fit if we see this poem as being about only black history. The Euphrates (along with the Tigris) is tied to the notion of very early human civilization. Maybe this poem is as much about blacks as it is about what humans in general share.
Finally, the colors in the poem are interesting. There's not just the implied "black" (from the word "negro"); there are also "muddy," "golden," and "dusky." These may refer to a range of skin tones as well as a range of ethnic groups.
The poem's enduring power, I think, lies in the way it can evoke so much. According to the autobiographical work The Big Sea, the poem was written when Hughes was a young man (maybe just turned 17), and it's ended being one of his best known pieces.
In the poem 'The Negro speaks of Rivers' by Langston Hughes, the poet is discussing Time - and he goes back a very long way, longer even than the history of Man himself. It is a very modern-thinking poem in some ways and remarkably insightful, given that Hughes was not privy to much of the research that has been done since on the origins of Man. He seems,in the poem, to sense that Man came from 'out of Africa' and that we are all 'dusky' or black under the skin, and that muddiness or blackness can be golden too - like a river in sunlight. Some readers may pick up a vibe that it is the black man who still carries the ancient soul of man - the timelessness of which Hughes portrays very well in a poem that itself seems primeval at times.
To me, this poem is a very early move towards what can be called "Afrocentrism." Here in the US, there are African American scholars who argue that the contributions of black people have been central to the history of the US and the world.
I also see the beginnings of the argument that black people have more "soul." This was the idea from the '60s and '70s that black people feel more things because of their experiences (thus we have soul music and soul food).
Hughes uses his image effectively to get this point across, speaking of his blood going back to the earliest days of civilization. The poem is evocative, but I do not think he effectively argues that any one race can claim that it is older and deeper than any other.
It's interesting because the analysis I used to answer a similar poem by Robert Frost is the same I would use here. So much of Hughes' work and its critical implications have to be experienced by the reader. His work is layered with thought, as he was aware of the importance and allusion of each line, word, and phrase. With such driven and focused attention, the critical appreciation of any of his work has to be done from an individual level. With that in mind, I think that one of the most interesting aspects of Hughes' poem is his attempt to articulate the condition of someone who has endured and seen much. The history of the Black person in the world context is where his focus seems to lie in the poem. Given the struggles of race in America at the time he is writing, Hughes might be positing the idea that while America is a nation, it is a young one and the history of the African in the world has outstripped it multiple times over. While the African- American might be experiencing something now at this moment in time, it is something that has been a part of the larger context and this might help to bring a sense of understanding to what is being endured at this time for the African in World History.