The sweat soaked gladiator looks up to thewho will make the call--cut the throat of his downed opponent or let him live. The crowd yells and makes dramatic hand gestures, trying to sway the stony-faced editor.(Let him go!) scream some.(Kill him!) roar others.The editor extends his hand and dramatically lifts his thumb. Will the downed gladiator live or die?Most Americans say, "He will live!" After all, the thumbs-up sign is a positive thing. It's how we encourage our friends and silently show approval. But to the ancient Romans, a thumbs up mimicked the upward thrust of a sword through the heart. It meant,A thumbs-down meant "put your sword down."So where did this confusion about thumbs come from? Many blame the painter Gerome, whose(1873) painting (above) still has the power to capture our imaginations. But look closer:Gerome wrongly interpreted Juvenal's description of the killing sign as thumbs, confusing the rest of us ever since.In the meantime, that painting is pretty remarkable, isn't it? I love Gerome's work so I give his paintings a thumbs-up. Oh, wait. I mean, a thumbs-down.Oh, never mind!