a well-dressed businessman suddenly pounds his chest and bares his teeth at his colleagues during a tense negotiation. He abandons his civilized demeanor and displays aggressive territorial behavior like his primitive ancestors. The stress of the meeting triggers his ancient fight-or-flight instincts to take over his modern rational thinking. His polished business suit contrasts sharply with his caveman-like posturing and intimidation tactics. Other suited colleagues step back in shock as they witness his sudden regression to primal behavior. the tendency to revert to something ancient or ancestral