>>> My theory is that all animals have extensive defense mechanisms to prevent motor entrainment to external stimuli, since that would make one very vulnerable. Therefore, they only exhibit entrainment during ritualized mating, etc.

Wow, seems very reasonable! It made mi think about it in a bit different way: as other animals are thought as "following instinct" and "closer to nature" maybe this inhibition systems are way more advanced in humans than in other animals. It would make explaining dance harder, but would fit great to big literary topos "men vs nature".

Is it completely your theory or was it inspired by something that you could recommend?