Instinct

A quick note before I dash of on holiday. 

I was just reading the Wikipedia entry on Instinct, and was surprised to read that there is a "hot debate" on whether or not humans have instinct. And the reason this is an issue at all is because - after having coined a very useful term (albeit one that does not really explain anything) - people sat down and wrote a definition that made the term completely useless.  

There are a lot of things wrong with the definition, but my main objection is a more general one: almost every single criterion is an absolute. To be considered instinctive, behavior must be automatic, irresistible, and unmodifiable. But there are many examples of behavior that most people would label instinctive, but that can be and is suppressed under certain circumstances. This may occur more often in humans (for the simple reason that we think too much), but it definitely not unique. As for "unmodifiable", the definition itself is contradictory: after having established unmodifiable as a criterion, it goes on to mention that "the organism may profit from experience and to that degree the behavior is modifiable". I don't want too be accused of being too categoric myself, but I fail to see a middle ground here: behavior is either modifiable or unmodifiable. It cannot be both at the same time.   

Of course, I understand why people like the idea of denying that humans have instinct: it makes them exempt of innate behavior, which is almost like getting carte blanche on your own destiny. But that is an illusion, I fear: free will is not quite as free as some people would like. If humans are electrons, free will is our ability to jiggle our trajectory. Only a few of us will succeed in jumping from one electron shell to another, and some might even escape the atom completely, but that is about as far as we can go. 

Irrespective of the in-fighting about definitions, the big question remains: how is innate behavior possible at all? It has to be hard-coded or hard-wired somewhere, but where and how? (Any input on this is welcome.)