he is the last word, since Star Wars is his baby. That's only your opinion. So many more people other than GL have contributed to SW.
It is ridiculous, if you take it as a scientific fact. If there's a genetic trait that makes you a head-bumper, that'd mean that the person would bump his head constantly.
but then in an interview Lucas start spewing BS and says that Anakin Skywalker was born in Bozeman, Montana, which explanation are you going to accept?
Movies may override books, but how can what he says off-screen do that? They're not even PART of the SW continuity.
The events of the movies are tied with the EU.
There are stormtroopers who have their own history.
You can't use such trivial, circumstantial, and coincidential evidence. The head-bumping thing was a coincidence or a result of helmets that cuts down on the wearer's field of vision.
Btw, we don't know for sure that Padme is the mother of Luke/Leia.
the guy in ANH is a clone.