Media.
Media is pervasive in our lives and has been for centuries on end. It shapes and alters our perceptions of reality. There are people alive today who earnestly argue that the Pharoahs were white dudes.
Jesus Christ himself is almost invariably portrayed in paintings and movies as a white dude with high cheekbones, long wavy brown hair, and a close cut beard. And he has been since around 800AD.
From artwork to plays to handbills and penny dreadfuls on up to television and movies, media has had a huge impact on the world. And cross-cultural, too, thanks to England invading EVERYTHING. "The Sun Never Sets on the British Empire" was a saying for a reason. They imposed their cultural norms, language, and media on people from America to China (and not just across the Pacific, either, though it is a shorter distance!)
And yes, many cultures took what the British brought and adapted it to their culture, but few if any threw away everything the Brits brought, from Political Theory to Foreign Concepts. And it's not like it was -just- England, either. Spain, France, and Portugal all did the same thing and all of them were, to some degree or another, linked through shared media. Shakespeare's plays may only have played in the Globe Theatre in the late 1500s, but by the 1800s his plays were being performed across Europe and around the world, translated into half a dozen languages. And of those only England is nearly as bad as Rome was at creating a monoculture, since it wound up forming the basis for almost every European society moving forward with shared language, coinage, sharing of ideas and plays and poetry and stories...
Bring it forward into the 20th century and you've got three of the most pervasive forms of media available, to date, which are constantly surrounding people in what is now known as Western Culture, rather than specifically British or European. Because while there may be cultural differences, here or there, we share much of the same monoculture, these days, through Movies, TV, and the Internet.
The last one being the most egregious of the bunch. Not that it's bad, it's just that it's the one that does it the most effectively.
Media has been affecting our cultural perspectives across borders and oceans since before people thought that the four humors determined health.
Sorry. Didn't realize I didn't explain that all out in the thread. I did in the dozen PMs I got about this thread from several posters who were confused by what I meant.
We know for a fact that social pressures can drive sexual selection. It's why peacocks have big freaking tails that only serve to signal the male is a decent mate for a peahen. At some point the peahens started breeding more often with the peacocks who had the bigger, prettier, tail and evolution took it's course after that.
Could sexual selection based on age be a biological evolutionary trait encoded into half the population? Maybe, but it's doubtful. Because like we both noted evolution doesn't care.
Redheads are essentially endangered at this point. We're breeding them out. For many (mostly white) guys, though, Redheads are sexy as hell. It's obviously not an advantageous trait for sexual selection, since it's going extinct, but there are a hell of a lot of dudes who find it sexy as hell. Are they biologically predisposed to redheads or is it a social expectation?
Guys like tits, right? I mean, evolutionarily speaking. But there's so much variety in what shape or size that a given dude might be interested in. Same thing with skin tones, hair colors, eye colors, shape and size of the backside, and overall body type. How many of those are biological and if they're evolutionary preferences why is there so much variety? If it's biological then maybe what we're looking at is dozens or even hundreds of different evolutionary lines coming to the fore.
But regardless of evolutionary background all of these dudes wants women who are young. Regardless of their age relative to their partner's age, they want a 20-something.
If there is so much variety in sexual preference based on biology, why is the sexual preference unilateral on age? Shouldn't ALL men want women with a thick body type, wide hips, and large breasts for childrearing based on what is most evolutionary advantageous, preferably with dark skin and dark hair since that's the most common (and therefore successful) biological trait?
But they don't. They want body types that are relative to their cultural and social background with some level of homogeneity brought on by mass media linking many basic pieces of western culture which has been thoroughly integrated into every other society on some level or another.
As for evolution being handwavey and shouldershrugging... It really is when I'm discussing a social issue and the implications of it. Even if it's not intended to be, stating that the reasons behind this "Have evolution's fingerprints" all over it really does come across as being dismissive and reductive of the question posed about the sociological underpinnings.