I really, really doubt there is some genetic limit that prevents people from thinking. It's just a case of mindset. People who are coerced into rote memorization and 'surface learning' have just lost their curiosity and do not realize that thought is something you can do. I mean, we live in a post-industrial age. All throughout history most people 'did what they were told'.

People don't question because they don't think authority will like it.