The use of the 'rib' to create eve is to indicate that Man and Woman should be 'of a single flesh'. It is basically a symbolic way of showing that it is desireable for marriage to last a lifetime, rather, than like the beasts, go from mate to mate to mate.
This concept can be further expanded upon by the choice of the name 'EVE'. In Hebrew, the name is related to the word 'life'. It also means 'mother of all things'.
Also, the word 'rib' is also the hebrew word for 'side'. This signfies that a man and wife shoudl be 'side by side'.. as
Because of the generic meanings of the names, ADAM and EVE are the archtypical 'every man' and 'every woman'.
Because of the meanings of the words, it is obvious that the story of Genesis was not literal, but was an allegory.