Understandably, we pay a lot of attention to attractiveness in our society. It's pretty biological, after all. Indeed, common signals of attractiveness are signs of health and resistance to disease that display themselves as bilateral facial symmetry, large bright pupils, full lips, youthful skin, and melanin-rich hair. Would you have figured all that?
Many of the things that make us attractive to other people are even less obvious. To find out what they are, click through this gallery.