I'd like to expound briefly on a long-held theory of mine...

...to the effect that the reason many folksongs are so atrocious some women are considered sexually attractive is that they're mannish.

Okay, not really.

But I've noticed that when we're talking about pure sexual attractiveness (as opposed to beauty, which is related but not required) many women who men consider sexy have in common features that are *male* secondary sex characteristics:
- stronger facial features: heavier eyebrows, cheekbones, chin
- larger eyes, mouth, teeth
- wider shoulders
- more height

My theory is that this might unconsciously suggest more testosterone, which would suggest stronger sex drive (ie, more sexuality).

Examples off the top of my head:
* Cindy Crawford
* Pamela Anderson
* Courtney Love
* Cameron Diaz
* Eva Mendes
* Selma Hayek

Certainly there's lots more to it that that, and there are lots of exceptions and counter-examples (why aren't mustaches on women more of a turn-on?), but look how few women in this random google result for "sexiest woman" have small mouths/teeth or faint eyebrows or small eyes.

There's a sort-of-related pseuodo-scientific article about this in the Telegraph.

Your mileage may vary, of course. It's just a theory...