The dangers of overinterpretation and oversimplification

In one of the forums recently, I came across another person asking the eternal question: is there a "talent" for learning languages?  In other words, are some people just better at learning languages than others?

One of the ideas that came up in the thread was the notion of the "blank slate" theory of psychology, which was essentially taken for granted for a long time, but is increasingly being shown to be overly simplistic through the identification of specialisation and variation in human brains.

The most famous work on this is Steven Pinker's book, which I have never read.  I have, however, watched his TED talk:


Now, setting aside that most TED talks are (as far as I am aware) made by people who have paid a lot of money to stand up on that stage, and therefore often little more than adverts for books, it is an interesting little talk.
One problem I have with it, though, is its failure to comment on the multiple dimensions of "blank slate", because the notion of a blank slate can mean two different things.
First of all, there is the classical notion of the brain as a content-agnostic calculation machine, as put forth by David Hume, and that the human "mind" is merely a collection of learned responses to stimulus.

This theory is thoroughly discredited by modern neuroscience as it is very clear that certain regions of the brain are very specialised, and as scanning technology improves, we're finding more and more specialisation at a finer and finer level.

The second notion is of individual differences -- he talks about the "blank slate" idea as being fashionable egalitarianism: we're all born "the same".  But this isn't the blank slate per se, because there is nothing to say that one blank slate can't be bigger than another, or easier to read than another, or quicker to write on than another.
The "blank slate" he's really talking about is something of a chimera -- he's accepting brain region specialisation as a given, but treating the individual regions as though these were slates.  It's something of a rather confused strawman, but it's deceptively appealing.
So yes, there is brain specialisation and yes, there are individual differences.  This shouldn't be controversial, so really the controversy must be in his extrapolations.  This makes for entertaining pop science, but as a scientific thesis intended to convince others, it's sorely lacking.

The biggest problem I have with Pinker's talk is its failure to state very clearly that its findings are irrelevant and inapplicable in any practical context.  Pinker's conclusions relate to the study of the brain, and it is important that future research accounts properly for the issues he discusses.  However, while the differences in individual brains exist and many abilities are strongly affected by heredity, we have no way of identifying and measuring these inherited differences beforehand.  Hermann Einstein's work as an electrification engineer may give some inkling of his son Albert's future career as a theoretical physicist, but what does it tell you about his daughter Maja's study of Romance languages and literature?

But that wouldn't sell a pop science book.  People want to read these books and then feel like they're part of this "new" knowledge.  They want to go out and apply the theory straight away.  They conclude that they're good at what they're good at simply because "the slate isn't blank".  But Pinker has never once claimed to be able to identify with certainty which abilities arise due to culture and peer group, which he says are important factors in the video itself.  If he can't, how can we? 

For now we must simply get on with teaching the best way possible, rather than trying to second guess the hows and whys.

Edit: How the hell did I manage to describe the father of relativity as a "chemist"?  I think I might be going senile already....