It comes back to data. A useful question helps, too.

“Which is the oldest language in the world?  Hebrew or Greek?”

“That’s a good question.  Neither is the oldest.  Certainly Egyptian in one form or another is older.  Abraham came from Sumeria, and headed for Canaan speaking some form of the Sumerian Language.  Possibly Hebrew came into being when the Abraham family were slaves in Egypt and were combining what they already spoke (some form of Sumerian plus one or more Canaanite dialects with what the Egyptians were saying.”

So went a Christmas conversation.  The answer is both correct (‘Neither”) and incorrect.  According to Answers.com (http://wiki.answers.com/Q/What_is_the_world's_oldest_language) Sanskrit predates all other known languages.  

On the other hand, Wikipedia (http://en.wikipedia.org/wiki/List_of_languages_by_first_written_accounts) asserts that Sumerian is the oldest written language.  

Buzzle.com suggests Mandarin (http://www.buzzle.com/articles/oldest-language-in-the-world.html).  

Searching for answers I find a lot of “I believe” answers -- but inadequate data.  Truth be told, we really don’t know.  There are sign languages that may be older than spoken and written languages.  In fact, to answer the question the person asking must constraing the quesion.  What is a language?  Written?  Spoken?  Sign?  Musical tones?  

It comes back to a usefully worded question and working with integrity with such data as we have.  In this case, we may not have definitive data.