Isn't it a counter-argument ? If they had innate grammatical capabilities, they wouldn't need to acquire them in their early childhood. That seems justly to confirm my idea that language need to be learnt (even unconsciously) but human contacts. I don't see the see for... QUOTE]
No, it is NOT a counter-argument. Children are born with an innate ability to naturally acquire language, or with a language faculty, to use Chomsky's term. But (as far as I know)this ability/faculty must be activated (just like a forum account must!). The activation is the exposure to natural language. I think Chomsky calls it 'parameter setting'.