well-known secondary sex characteristics in humans are for men: low voice tone, facial hair (mustache and beard) and more muscular build, shoulders wider, bones heavier, hands and feet bigger, height taller. in women, those characteristics usually cited are more prominent breasts, lips, eyes, long/fast growing hair, no facial hair, wider hips, more fat, and a higher voice tone. faces, generally, make a big impact. it is the part other people interact with when meeting each other.