In researching this subject --- how we sense gravity/motion and whether it is inherited or learned --- I've run across an article which might interest y'all:
Graviperception and Graviresponse at the Molecular Level (pdf) The bottom line according to this article is that they don't know but they have a few ideas such as intracellular receptors, heavy cell organelles, ion channels. This is very fascinating to me. Even flagella seem to know up from down but they aren't really sure how. I'm particularly curious how evolution theory explains the rise of graviperception.
I'm hoping one of you may have a clue -- url, phrase, word or whatever --- to help me know where to look for more information.