The main evolutionary significance of humor is that it gets us from the closed mode to the open mode quicker than anything else.
John CleeseWe all operate in two contrasting modes, which might be called open and closed. The open mode is more relaxed, more receptive, more exploratory, more democratic, more playful and more humorous. The closed mode is the tighter, more rigid, more hierarchical, more tunnel-visioned. Most people, unfortunately spend most of their time in the closed mode.
John Cleese