Laughter, "Powerful, Ancient and Crude"

Scientists explain how laughter originated.  What's So Funny?  Well, Maybe Nothing

“Laughter is an honest social signal because it’s hard to fake,” Professor Provine says. “We’re dealing with something powerful, ancient and crude. It’s a kind of behavioral fossil showing the roots that all human beings, maybe all mammals, have in common.
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Professor Panksepp thinks the brain has ancient wiring to produce laughter so that young animals learn to play with one another. The laughter stimulates euphoria circuits in the brain and also reassures the other animals that they’re playing, not fighting.

“Primal laughter evolved as a signaling device to highlight readiness for friendly interaction,” Professor Panksepp says. “Sophisticated social animals such as mammals need an emotionally positive mechanism to help create social brains and to weave organisms effectively into the social fabric.”

Apparently the lower you are on the status pole, the more you laugh.

Maybe that's why we all laugh at our bosses' lame jokes.