Gentlemen Prefer Blondes. WHY?

According to another stereotype about blondes – they are highly appreciated by gentle(and not too gentle)men. This stereotype was successfully sealed with a movie with the same name starring Marilyn Monroe. As we have figured out already, many men really are into blond women, even if it suggests the latter ones' stereotypically dumb (lack of) intelligence and behaviour patterns – whines, pink, gold-diggingness, silliness, tastelessness implied (according to the stereotype that is).
What are the stable reasons of such phenomenon? Aren't there any at least close-to-scientific reasons why men are so fond of blondes? There sure are. As we all know, both natural and artificial blonde hair image goes hand in hand with sexual attractiveness and beauty.
A research has been conducted last year which concluded in the fact that cavemen directed their preferences towards fair-haired soul mates because blond hair was connected with the idea of a much higher level of fertility and female hormones.
Oh well, we have slightly 'grown up' since the cave-period but looks like most males' preferences are still the same – God bless cavemen! So much for the idea of gentlemen – looks like men's spirit of cavemen scarcely evolved into something strikingly different!