Physical depiction of emotions

Laughter, as a muscular response, seems to depict itself the same way in every culture.  How did man first equate positive feelings with chuckling, positioning jaws or curvature of mouth? Normally pleasure/happiness triggers smiling, even babies show intriguing behaviour towards positive conditions like comfort. A baby cant analyze and reply accordingly by prior experience so how does it exactly assign the action to stimulus? Is it copying the parents  handling  baby care by simultaneously matching gestures to actions? May be, but that also points out a child can be brought up with mismatched values and inappropriate responses. Fear or anger can be confronted calmly. Odd combinations may be created too, like shutting one eye twitching the other and clenching teeth when feeling curious. As straining as it seems, laughing or crying are no less of efforts for facial muscles. Take crying for instance, what an unusual case tearing is. Yawning?

Op is off the rez.
1st, humans didn't EQUATE positive emotions with chuckling. Chuckling resulted in positive emotions and the rest is history.
You are attempting to make a logical deductive conclusion based upon faulty perceptions, which is why you are wretched, nasty fail.
2nd, you forgot about progressive behavior and human conditions. Without an action there is no reaction, without awareness of choice; choice cannot be chosen. Rather, to Choose NOT to choose becomes the seemingly logical belief which is practiced. This is how illusions become reality and reality appears elusively unobtainable and loathed.
3rd, A human will think of what is a personally good thought and think of what action will promote that good feeling and express said thought; the repetition of this is human behavior.
4th, failing 1, 2, and 3 is autofailure. Go back to school or learn2learnBetter; your lack of intelligence is nails on chalkboard. :\