What does Buck conclude about human beings in "Call of the Wild"?
Although page numbers vary from edition to edition of the story (in my version, the text ends of page 83), I am assuming you are talking about Buck's conclusions about human beings after the death of John Thornton, when he returns completely to the wild. Buck contemplates the carcasses of the Yeehats he has vanquished, and experiences " pride greater than any he had yet experienced". In the established hierarchy of things, man is "the noblest game of all", yet Buck had killed man wantonly, even "in the face of the law of club and fang". Buck is surprised that the men "had died so easily...it was harder to kill a husky dog than them".
Buck concludes that man is not so powerful after all. In fact, if "it were not for their arrows and spears and clubs", they would be completely insignificant in the scheme of the unwritten laws of the wild. From now on, he will "be unafraid of them except when they bore in their hands their arrows, spears, and clubs". Most importantly, though, Buck now understands that the ascendancy of civilization over the wild is not absolute. It is true that man is much more of an opponent to be feared when he is armed, but even then, Buck now knows that man is not invincible (Chapter 7).