Actually, we humans aren't as symmetrical as we think. Our legs and arms are of slightly different lengths. Most people's dominant side feet and hands are slightly larger than their mates. (A ring that fits my left hand is too small for my right hand.) It's almost unheard of for a woman to have perfectly symmetrical natural breasts. Most men have one testicle that dangles a bit lower than its mate. And the two sides of our faces are so different that photographs created using mirror-image substitution come out looking like two entirely different people. So why worry about slightly lopsided ears? They're just par for the course.