It's from the play The Captain of Köpenick, 'Der Hauptmann von Köpenick' by German playwright Carl Zuckmayer. In the scene in question, the government bureaucrat Dr. Obermüller, who has just been promoted from Vizefeldwebel (a senior NCO of the reserve-officer carreer track, roughly equivalent to a Fähnrich or Ensign) to Leutnant der Reserve, Lieutenant of the Reserves, has just entered the store of the uniform-tailor Wormser (since he will be needing a new uniform for his newly aquired rank), who is very efficious and eager:

WORMSER: Recht so. Muß'n schönes Gefühl sein, wenn man auf einmal mit Herr Leutnant angeredet wird, das schmeichelt den Gehörknöchelchen. Wissen sie, ich sage immer: vom Gefreiten aufwärts beginnt der Darwinismus. Aber der Mensch, der Mensch fängt erst beim Leutnant an, is nich so, is nich so?

'WORMSER: That's right. Must be a great feeling, when people start to call you 'Herr Leutnant', that pleases the ossicles. You know, I always say: Darwinism begins from the private upwards. But humanity, humanity begins only at the Lieutenant, doesn't it, doesn't it?'

The whole play is, of course, a satire on the German/Prussian glorification of the officers corps as almost superhuman. Based on a true story, in which Friedrich Wilhelm Voigt, an out-of-work shoemaker, in 1906 put on the uniform of a Captain, commandeered a troop of soldiers, occupied the city hall of Cöpenick, now a part of Berlin, and stole the city's funds. The play uncovered and satirized the total and utterly uncritical authoritarian affiliation and trust in its superiors of the German population in the Wilhelminic age and then again during the late stages of the Weimar Republic, with the upcoming National Socialist movement and its uniform fetishism - consequently, the play was much maligned by Goebbels. The play came out in 1931, and was forbidden in 1933, but until then, it had much success.

So, misattributed, yes.