The boars head on the stick symbolizes savagery and the loss of innocence.
In history the conch shell has been a symbol of order in multiple societies. In Lord of the flies this is also used as a symbol of order. By using the conch shell as a way to get people to listen to whoever is talking was a clever way to direct attention to what importance a person might have to say. This allowed there to be less chaos during meetings and discussions. People would now no longer talk over each other because only one person could have the conch at a time.
The boar's head represents savagery. A big indication of why the boar's head represents savagery is because Jack and his clan of boys let fear overcome them and let it absorb their actions of civilized humans and instead spit out savage behavior. Their actions snowball later in the book into murder but it all started from the fear of the beast and the creation of the boar's head on a stick which turned them savage and made them lose a majority of their innocence. These symbols show the two sides of the spectrum between civilization and savagery.