Perhaps the predominant theme in fable is also the oldest

Perhaps the predominant theme in fable is also the oldest. It can be found in the first recorded fable in the Aesopic fable tradition, from Hesiod’s Works and Days (which significantly pre-dates the supposed dates for Aesop’s life).

There is some disagreement about the lesson to be taken from this fable, but it seems clear that the opposition is between the strength of the hawk and the words of the nightingale, who has nothing but words to counter that strength. It is the classic statement of “might makes right,” and those who have little power of their own must necessarily learn this lesson quickly and well. In the poem, Hesiod goes on to claim that the exercise of unjust power is wrong and that Zeus will punish it. 

Whether or not this is true, it is clear that the thought of future divine punishment will not necessarily deter the strong or protect the weak.