It's all about perspective
This research project has so far produced a fair amount of media attention - but I guess anything examining human attractiveness is bound to have popular appeal! This particular line of research began with the inspiration that, since men are taller than women, the viewpoint that each sex has of the opposite sex's face is a little bit different (on average) and this may have had consequences for how evolution has shaped our faces and our preferences for which faces we like.
A simple tilt of the head
Since men taller than women, they tend to view women's faces from slightly above and women view men's faces from slightly below (and have done for 4.5 milliion or so years!). This difference in perspective corresponds to the physical differences between male and female faces - women have flatter eyebrows, larger foreheads and fuller lips (these features are exaggerated when the face is viewed from slightly above) while men have larger jaws and shorter foreheads (which are also exaggerated when viewed from slightly below). in this study we presented images of 3D computer generated models of faces at a range of different tilts and demonstrated that females are perceived as being more feminine and more attractive when viewed from above and males are perceived as more masculine when viewed from slightly below. (Have a look at the image to the right and see what you think!)
These data suggest that sexual dimorphism of human faces may have evolved as a consequence of males being taller than females and people choosing prospective mates based on features that accentuated their masculinity or femininity, respectively.