One of my points earlier was that people (not even just martial artists, but people) tend to try breaking things as kids. I used to break sticks. Sometimes with other sticks, sometimes by stomping on them, etc. I think as a young boy that was part of me testing out my abilities. I can't see how that would be unlikely to occur in any culture where wood or some similar substance exists, so it seems likely it existed - outside of martial arts - in China, Okinawa, and Japan as long as people have been there. Why would martial artists have been the ones NOT doing it?