a reader writes:

Given that Asperger Syndrome is much more frequent in monozygotic than fraternal twins, I think many brain doctors would say that it does have a genetic component.

It's true that they would. It's also true that they invariably become evasive when it is pointed out that by this definition of “have a genetic component”, being the victim of racist attacks also “has a genetic component”, as does being the beneficiary of favouritism due to one's looks.

It seems perfectly conceivable that there is simply a part of the brain that is not functioning, and that this is likely to be due to genes interacting with environment in ways that render a person unable to will themselves out this situation.

In view of the above, it is perfectly possible for a given behaviour to be 100% caused by “part of the brain not functioning … due to genes … [that] … render a person unable to will themselves out”, and yet also to be 100% due to the way other people have behaved towards that person, or 100% due to the person's own choices.

Therefore, even setting aside the philosophical complexities of the terms “conceivable” and “unable”, the idea that a behaviour is “due to genes” has essentially no content in the absence of some theory about what sort of “interaction with the environment” is deemed to be the mechanism through which the behaviour in question is “due to genes”.