While Darwin explored and theorized about the origin of species, and destroyed the claim of those who actually belied that God created his world in 6 days, Nietzsche was not so much interested in where mankind came from, as in how it can overcome its problems and, to lead the way to some solution, create a super-man.
That Darwin would inspire Nietzsche in some way seems obvious in the sub-title of "The Origin of Species" which he called "The preservation of favoured races in the struggle for life" (Darwin, 1859 frontispiece). Nietzsche picks up on this thought (whether accidentally or not: "Our present-day Europe, the scene of a senseless, precipitate attempt at a radical blending of the classes, and consequently of racesais often sick to death of its will" (Nietzsche, 1952, p. 508).
Just as Darwin speaks of "from war of nature, from famine and death, the most exalted object we are capable of conceiving, namely, the production of higher animals, directly follows" (Darwin, 1859, p. 459). What is that "higher animal"- it is something which tends to thrive on cruelty, according to Nietzsche: "Cruelty is here revealed, for the first time, as one of the oldest and most indispensable elements in the foundations of culture (Nietzsche, 1952, p. 910).
While Darwin is obviously interested only in the origin and the various branching out of species, Nietzsche for one is not really interested in why things began or how they evolved as much as what the cultural and social and generic make-up of present society. His is a society of social strata, with the bottom eminently forgettable. Nietzsche is not interested in the ordinary worker, the one who supports the "super-man" and the philosopher. That is where Karl Marx comes into sharper focus.
Where Nietzsche was interested in superiority and its essentials, Marx was concerned with what we today would call the underdog, or the under-class. The bourgeoisie was Ni...