A lecture about the genetics of behaviour

I let the students in my genetics-pilot class choose a topic for me to teach about, and they chose The Genetics of Behaviour.  The class comes up next Monday (the second-last class of the term), so I need to get to work on it.  Of course I know nothing about this, but that's not a big problem - I can certainly learn.

The problem is that all I've found is various individual studies that connect particular behaviours with particular genotypes.  All very well, each reasonably good science about an interesting behaviour, but essentially just a series of anecdotes.  What I'm hoping to come up with is a lesson, or a take-away message, or some unifying principle.

What form might such a principle take?  That behaviour is a biochemical phenomenon?  That it isn't?  That we still have free will?  That we don't?   That nature and nurture interact to determine behaviour, as everything else? 

Maybe I should start the class by raising the big questions (after I start preparing for the class by finding out what these are).  What is consciousness?  No, too big.  Do we have 'free will'?  Also too big.  In fact, I think both these questions should be better handled by saying "What do we want the words 'consciousness' or 'free will' to mean?"  After we've settled on clear definitions we'll be in a better position to answer questions about them.

So I won't start with such big questions.  How about 'What can genetics teach us about why we behave the way we do?"  A bit vague.  Should I pick one behaviour that's been well studied and report on the findings?  Not if it's a boring behaviour like the ability of rats to remember the location of an underwater platform.  What about all those Drosophila vegetable mutants (rutabaga, cabbage, turnip, dunce)?

Sexual behaviour is much more interesting, especially to college kids.  And it's where natural selection/sexual selection has probably acted very strongly, but in complex ways.  Maybe the genetics of sexual orientation - review the studies, tell them whether there is any good data at all?  Wikipedia looks like a good starting point, but it tells me that there's very little good data, certainly not enough to base a whole lecture on.

What about human pheromones?  The whole question of whether we pick our mates partly because they have different HLA alleles than we do.  All those T-shirt-sniffing experiments are thought to be detecting genetic differences.  And there's that ocytocin study, and lots of sleazy marketing.  And then I could end with the new Drosophila study showing that the smells being used for mate choice can come from bacteria which come from the food source...