I am not sure how "Orthodox" my answer is, but at an OCF meeting a few years ago, I remember this question being posed to Abouna Mikhail, and he stated that at the occurrance of the Tower of Babylon, in addition to the mixing of language, there was a physiological change as well.
Perhaps Cleveland could shed some light on this subject, as he is familiar with Abouna Mikhail. By the way, I hope no one reads in my post that I am questioning Father Mikhail's legitimacy as a priest. I have a lot of respect for him. I am not sure whether this is a Coptic understaning, or universally accepted as Orthodox. On my own, I have not been able to find the answer to this question.