Well lets use the bible, lets consider the ludicris stories of a global flood and the tower of Babel were true, how much time is there between the two? about 100 years? I can't remember exactly, but the idea that shortly after the flood the earth had enough population of inbreeds to support and build a city?
The truth is many cultures all over the world have their own explanations on how language came about. The bible bible version is just another myth to explain something from a small limited point of view.
The human genome and the movement of people around the world should disprove not only the flood but the babel story without these silly debates over little details. Think about all the other civilizations thriving and growing during this supposed time of mass global genocide, Egypt, China, India... they never got the memo I guess.