I bet you also know this argument. But isn't 30 or more years a long time? I am not even 30 years old so I cannot say how good you can remember something which happened 30 years ago. How can they be so sure that within 30 or 40 years the memory was still so intact that the people remembered everything? And on the other hand how many eye witnessed were still left after 30-40 years? How old did the people become back then?