Long before humans developed language skills, we found ways to communicate with one another. Even in the absence of recognizable words, we were highly attuned to nonverbal clues (think: lots of grunts and hand gestures). We had to be if we wanted to survive.
Of course, language eventually came along on the evolutionary scale—but we still trust what we see and sense even more than the actual words we hear.
Marvin E. Smith 