In chapter 5, Simon asks "what is the dirtiest thing there is?". What is he referring to and what does this reveal about human nature?

In chapter five of "The Lord of The Flies" the boys are at a meeting and Ralph is trying to get the boys to take things more seriously. Simon tries to make a point.  “Simon became inarticulate in his efforts to express mankind's essential illness.” He attempts to explain by asking what they believe is the dirtiest thing of all."  "As an answer Jack dropped into the uncomprehending silence that followed it the one crude expressive syllable." (pg 103). This means that Simon's "effort results in a crudely anonymous response, a one-syllable word referring to a bowel movement, and his point is not made." What this says about the human nature of man is what Golding was trying to say throughout the novel, and "It is Simon who recognizes Golding’s thesis, that mankind’s evil nature is inherent in man. Unfortunately, Simon is also acutely aware of his own defect, his inability to communicate his knowledge to the others. This arises from his terror of the true beast, one that is harder to fight than any physical beast: the evil nature of mankind." The idea that man is basically evil and will if put in the right circumstances act like an animal.