Have there been attempts to identify Chomsky's "language mutation" in humans?
The anthropologist Svante Pääbo is more recently famous for trying to track down the 'language gene'.  There isn't a lot of reference to Chomsky in his work as I've noticed, but it is to me the same intriguing idea.  

That being that the chimpanzee and the bonobo have 99+% identical to human genome sequences and we also have data from human variations as well from a few thousand individuals.  Using this data you could try to evaluate a small list of differences which might have led to the inborn trait human beings have to acquire language.  

Pääbo's work focused on FOXP2, which leads to language disorders in humans when it is damaged in human beings.  On the other hand its also known that primates can learn to speak rather well if they are trained their entire lives by the right people.  They can even reflect on abstract ideas such as life after death.  This is a typical result when looking for a single gene that causes something- it rarely leads to a conclusive result as a phenotype like verbality, or even height or body mass is the result of the action and fine tuning of many genes acting in concert.  

That is, if you introduced human FoxP2 into transgenic chimps its unlikely that they would be as verbal as human beings.  This current reference for instance talks about how important the slower development rate for human children is.  This is one of the most unusual thing about human beings - it takes 1/3 to 1/5 of the human lifetime before we are fully mature.  This phenotype is incredibly unlikely to be the result of FoxP2 alone, or any single gene. 

There has been recent work published (2012) where the unique human FOXP2 gene was put into transgenic mice.  They seem to have different sort of personality tendencies and are said to vocalize differently - brain activity profiles are also different.  Kinda exciting, but not the Secret of NIMH yet....