I think we should look at this from a "Farmers and Foragers" perspective, as Robin Hanson often does. Foragers don't tolerate non-egalitarian relationships, and a young, vulnerable woman and an older, more-settled man have a wide gap in power. Farmers accepted marriages between young women and older men because they have more tolerance for power differences and less expectation of equality. More recently, we have switched back from farmer-style culture to forager culture, and these old-man/young-woman relationships are less tolerated.
I also think it is worth noting that women reach their peak fertility at around 23 years, not shortly after puberty. Your point still stands, because for long-term mating it is more valuable for the man to commit to a woman a few years before her fertility peak, so he can get more years of near-max fertility.
Farmers accepted marriages between young women and older men because they have more tolerance for power differences and less expectation of equality.
Or: Such asymmetric relationships worked well in farmer economies, where more established men had the resources to support (often several) wives, while younger men simply hadn't had the time and success yet to do so. In forager economies individuals couldn't accumulate so much private property as to make that difference. Farmer societies that developed an ideology that would support their economic success w...
Why don’t men go for younger women? That’s not quite accurate, because they do, but we seem to have a cultural norm against girls who have recently exited puberty, even though they are highly fertile. Some time in the last few hundred years, we reached a cultural norm that as a man gets older, it’s increasingly less appropriate for him to be with a sixteen year old. That’s not long enough to override thousands of years of evolution, so what could have contributed to it?
The best solution I’ve heard started by looking at who benefits from this norm [older women] and wondering whether they could have contributed to it. After all, the strength of this norm has been increased in the last sixty years or so, which coincides with the period in which women’s power has increased.
One alternative I heard recently is that it doesn’t make sense biologically to go for women who are recently post-pubescent, as they don’t make the best mothers. Instead, a slightly older woman [mid-twenties] makes sense to be the best mother. This is perfectly plausible.
Another, less plausible, suggestion I’ve heard is that it’s to do with mental capacity. I find this unconvincing because we have few objections to a high-status man dating a beautiful but low-intellect woman.
Thoughts?