Contrasting with the symbol of the conch is the symbol of the beast which comes to be associated with Jack as by the end of the novel he is almost devil worshipping it.
In an attempt to recreate the culture they left behind, they elect Ralph to lead, with the intellectual Piggy as counselor.
But Jack wants to lead, too, and one-by-one, he lures the boys from civility and reason to the savage survivalism of primeval hunters.
Jack chants “kill the pig, cut her throat, spill the blood”.
This suggests savagery as the boys are being violent and aggressive when killing the pig and they don’t care about it.