...I remembered where I read it and had the book on my desk at school...
This original sin, for Friedrich Nietzsche, was ressentiment, bad conscience, which developed due to our apmutation from our original condition as warriors, hunters, and "beasts of prey", in civilization. Civilization domesticated humanity, made us docile, "a household pet", although our inner nature continues to rebel against this deformation.
"Man, full of emptiness and torn apart with homesickness for the desert has had to create from within himself an adventure, a torture-chamber, an unsafe and hazardous wilderness-this fool, this prisoner consumed with longing and despair, became the inventor of 'bad conscience'"
Modern nihilim revaled "man's sickness of man himself" but this "forcible breach from his animal past" suggested, and pressed toward, new conditions of existence, "as though something were being announced through him, were being prepared, as though man were not an end but just a path, an episode, a bridge, a great promise..."