Is 'Tamil' the oldest language ? தமிழ் தான் உலகின் மூத்த மொழியா ? சில சந்தேகங்கள்

 Is 'Tamil' the oldest language ?  Few logical (?) questions

1)  There were more than 1600 languages spoken in India. It's quite unbelievable that 'Tamil' is the mother language for all the 1600 languages that were spoken in India.  I am not sure how far this true or possible? 

2. I am not sure which one of the following is correct (a) or (b)

   (a)  There was no indian language at all when 'Tamil' was originated (or) developed

   (b)  There were NO Indian languages which had SCRIPT associated with them during the period when Tamil 'evolved' or 'orginated'

Let us consider the following scenario

As we all knew during the ancient days people used to live in small groups

Let's say a set-of-people (Group A) who spoke 'Tamil' lived in some region of TamilNadu.  And there was another set-of-people (Group B) lived in some region of 'Andhra'

As 'Tamil' is the mother language for all other 1600 Indian languages 'Group B' people should have used 'sign language' (సంకేత భాష or சைகை பாஷை) until a person from 'Group A' reached out to 'Group B' and taught them Tamil

P.S: Travelling from one region to another region was NOT that easy during the ancient days

I personally feel that at least 3-4 languages should have existed apart from 'Sanskrit' and 'Tamil' during the same period.  As languages were evolving they no longer exists and there's no evidence for us to prove that they existed