All of language is a physical intervention. Moreover, language is the efficient consequence of a larger system in interaction between organisms. So how is it efficient and how are specific interventions selected for efficiency? We can imagine that there is some minimal efficiency required in the activity of language; otherwise gestures and grunts would be the favored approached in communicating. How is it then that gestural interventions gave way to mostly linguistic ones?
Every intervention is an exploitation. Naturally occurring phenomena serve our activities frequently. The application of launching a message into the flow of a stream, is such an example. More importantly it is the motion of the flow that is exploited and not so much the stream itself. The registering of that fact is exploited by extending it to other environments and creating alternatives. So if a stream is not present to carry the message, the function of motion is implemented in some other way, using a bird for example instead of creating a stream to carry a message which in fact would require a tremendous outpouring of kinetic energy for the simple task of carrying a message.