[Inspired by a few of the science bits in HP:MOR, and far more so by the discussions between Draco and Harry about "social skills". Shared because I suspect it's an insight some people would benefit from.]
One of the more prominent theories on the evolution of human intelligence suggests that humans involved intelligence, not to deal with their environment, but rather to deal with each other. A small intellectual edge would foster competition, and it would result in the sort of recursive, escalating loop that's required to explain why we're so SUBSTANTIALLY smarter than every other species on the planet.
If you accept that premise, it's obvious that intelligence should, naturally, come with a desire to compete against other humans. It should be equally obvious from looking at human history that, indeed, we seem to do exactly that.
Posit, then, that, linked to intelligence, there's a trait for politics - using intelligence to compete against other humans, to try and establish dominance via cunning instead of brawn.
And, like everything that the Blind Idiot God Evolution has created, imagine that there are humans who LACK this trait for politics, but still have intelligence.
Think about the humans who, instead of looking inwards at humanity for competition, instead turn outwards to the vast uncaring universe of physics and chemistry. Other humans are an obtainable target - a little evolutionary push, and your tribe can outsmart any other tribe. The universe is not nearly so easily cowed, though. The universe is, often, undefeatable, or at least, we have not come close to mastering it. Six thousand years and people still die to storms and drought and famine. Six thousand years, and we have just touched on the moon, just begun to even SEE other planets that might contain life like ours.
I never understood other people before, because I'm missing that trait.
And I finally, finally, understand that this trait even exists, and what it must BE like, to have the trait.
We are genetic, chemical beings. I believe this with every ounce of myself. There isn't a soul that defies physics, there is not a consciousness that defies neurology. The world, even ourselves, can be measured. Anger comes from a part of this mixture, as does happiness and love. They are not lesser for this. They are not!
This is not an interlude. It is woven in to the meaning of what I realized. If you have this trait, then part of your values, as fundamental to yourself as eating and breathing and drinking, is the desire for status, to assert a certain form of dominance. Intelligence can almost be measured by status and cunning, and those who try to cheat and use crass physical violence are indeed generally condemned for it.
I don't have this trait. I don't value status in and of itself. It's useful, because it lets me do other things. It opens doors. So I invest in still having status, but status is not a goal; Status is to me, as a fork is to hunger - merely a means to an end.
So I have never, not once in my life, been able to comprehend the simple truth: 90% of the people I meet, quite possibly more, value status, as an intrinsic thing. Indeed, they are meant to use their intelligence as a tool to obtain this status. It is how we rose to where we are in the world.
I don't know what to make of this. It means everything I'd pieced together about people is utterly, utterly wrong, because it assumed that they all valued truth, and understanding - the pursuits of intelligence when you don't have the political trait.
I am, for a moment, deeply, deeply lost.
But, I notice, I am no longer confused.
I suppose "no sex before marriage" really depends on culture. If the most reliable way to get ANY sex is such a commitment, then you're probably right.
Outside of such a culture, though... well, the women with higher sex drives are presumably LESS likely to want to wait until marriage, so by waiting you both delay gratification AND probably end up with a partner who has below-average sex drive. AND you've made it more difficult for yourself to change partners.
Of course, whether the average male believes this to be true is another matter entirely :)
Suffice to say, if sex is a terminal value and you're able to move cities, this is blatantly the incorrect strategy. So either "no sex before marriage" is used by people who don't know better, or there's some other factor that has a higher priority :)
I can't think of any real gain to "no sex before marriage" beyond the status/reputation aspect, so I'd be forced to conclude that it is indeed an aspect of trading sex -> status/reputation
"No sex before marriage" could make casual dating less expensive, meaning you're more likely to find somebody more compatible with you. Polyamory is of course another solution, but is socially expensive.