I'd use evolutionary psychology as the subject. It's how certain traits of the opposite sex are relevant to attraction:
(obviously these don't ALWAYS apply, but usually do):
-Tall guys are intimidating to enemies, therefore attractive to females
-A confident man is more capable of survival
-A deep voice = higher testosterone = more muscle growth, ect.
-A more toned body obviously more fit for suvival
-Women tend to have a greater bond towards children because males would usually mate, stay until the child was old enough to be fully supported by the mother, then go off to the next mate
-A female's function is to seduce a male while the male's function is to prove genetic superiority to earn the priviledge to mate
Just google it up and I'm sure you'll find a ton more. Keep in mind most women would find some of it degrading, but if you want the truth, it's out there.