In "Lord of the Flies", why does Golding chose a parachutist who plays the role of a beast?

The parachutist is a handy convention because he represents the outside world and its war, thus what is wrong with mankind in general.  Also, the parachutist, because of the strings attached to the parachute and the parachute itself, can be made to physically resemble some sort of beast or animated being.  Golding wrote the book not long after the end of the second world war.  He felt that the war revealed the underlying savagery in all mankind.  The story begins with the boys fleeing that imperfect world of war.  The parachutist reminds the reader that the imperfect world still exists out there beyond the boys' microcosm of society.  The boys have been having nightmares, especially the little ones, of beasts.  When the parachutist is seen from a distance, the wind catches the parachute and causes the dead man's body to move as though under its own power.  This gives credence to the boys' fear that there is a tangible beast on the island.  This allows them to stop looking for the beast outside of themselves.