Hello. You did not inform the myth to which this question refers, which makes it impossible for it to be answered accurately. However, I will try to help you in the best possible way.
It is only possible to know the central theme of a myth by reading it. In this case, when reading the myth, you must show the tension in the subject, in the most discussed idea during the narrative. This idea rules the whole story, establishing itself as the central idea. In the case of the myth mentioned in the question above, this idea has to be related, in some way to life and its elements, in a direct or subjective way.
