What do the boys' attitudes and action (e.g. Ralph's joy at being free of "grownups," the vote for leader , Ralph's telling the other boys about Piggy's nickname) reveal about human nature?

The boys' reaction to the no grownups is that they are excited, which shows that they are made to oppose authoritative figures; Each boys constantly wants to be accepted and be part of the group, this shows that humans never want to be left out