from the begining what are the signs that show that the group might separate?

Right from the first election we see a split. Although Jack's hunters obediently vote for him, Jack is mortified to lose the popular vote. Ralph appeases Jack by giving him a title but this lasts only so long. Jack chips at Ralph's leadership for much of the novel. Jack disputes Ralph's orders or just does not carry them out. When a ship passes and Jack had made no signal fire, Ralph is furious. Although Jack is at fault, he is able to clearly manipulate the situation to gain respect and sympathy from most of the boys. This is a turning point in the play. Soon after Jack tries to pull a public coup de taunt during a meeting. Jack demands a re-vote for chief. Although the boys vote for Ralph, most of them slide into the forest to join Jack. The desertion goes on until Ralph is left with only Simon, Piggy and the twins.