In his poem "The Negro Speaks of Rivers," Langston Hughes juxtaposes diction related to ancient times with images of youth and vitality. His purpose is to show that though the African race is ancient and should be valued for its ancient roots which have endured the tests of time, it is also still a race full of youthfulness and vitality. Capturing the race's youthfulness and vitality serves to show that the ancient African race will continue to endure the tests of time and continue to be valuable, just as young and strong men, generally speaking, tend to continue to endure through life.
Two images of youth and vitality appear in his third paragraph stanza. The first image describes the speaker as bathing in the Euphrates in times so ancient that the "dawns were young," meaning that the earth was so young that the sunrises could also be considered young. The second image of youth and vitality describes the speaker as having "built [his] hut near the Congo." Since only a young man has the strength and vitality to build a hut, we know this image is meant to capture the strength and vitality of the speaker and thus of the African race.