Why is it difficult for some people to shake their hips (when dancing)? (ANATOMIC fact or CULTURAL fact?)?

Hey, I'm impressed. You may be on to something here. I have done novice studies in cultures and anatomies. And I think you may be on to something here. Given some thought here I have to admit that some cultures seem to be more body-language expressive. And yes, I agree, are more adapt to hip movement. Other cultures like myself, who are ingrained with more subtle body language replacing it with verbal action, could never accomplish excessive hip movement as a form of expression - like trying to fly by flapping my arms - just isn't gonna work. I think you're right. But in a time of political correctness, we have to keep this between ourselves.