I want to clear up, in case people reading this get the wrong idea from your example of the 'mother tongue', that Latin and Greek are two language that share a common ancestor and, in fact, Greek contributed to the Latin language.  They are, of course, two separate languages and Latin did not evolve out of Greek.

Your essay reads well.  I don't know that it is widely disputed in the linguistic community whether or not human language is the result of evolutionary processes; it most certainly is.  That humans share similar linguistic traits with other organisms is not particularly remarkable from that perspective.  I do find problem in what you purpose are the two unique features of human language, because while writing and the duality of patterning to which you refer are unique, so is our consciousness as far as we know.  You actually touch on this when explaining the differences between certain similarities in human language and the types of communication undertaken by primates and bees.  The simple fact is that these modes of communication are only similar and that humans are the only organisms we know of that are capable of what we understand to be language, something that actually comprises a number of things unique in humans.